Solid state imaging device and electronic apparatus

0001The present disclosure relates to a back-illuminated solid-state image sensor and an electronic device.

0002In recent years, a back-illuminated solid-state image sensor that irradiates light from the side opposite to the side on which the wiring layer is formed on the substrate has been proposed (see Patent Document 1 below). In the back-illuminated solid-state image sensor, since no wiring layer or circuit element is formed on the light irradiation side, the aperture ratio of the light receiving portion formed on the substrate can be increased, and the incident light is reflected by the wiring layer or the like. Since it is incident on the light receiving portion without any light, the sensitivity can be improved. The solid-state image sensor of Patent Document 1 is provided with a light-shielding film at the pixel boundary in order to reduce optical color mixing.

<p num="0003"><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2010-186818</text></patcit></p>

<p num="0004"> In such a solid-state image sensor, further improvement in characteristics such as reduction of optical color mixing is required.</p><p num="0005"> The present disclosure provides a solid-state image sensor with further improved characteristics such as reduction of optical color mixing. Further, an electronic device using the solid-state image sensor is provided.</p>

<p num="0006"> The solid-state imaging device of the present disclosure includes a substrate and a plurality of photoelectric conversion units formed on the substrate, and the plurality of photoelectric conversion units include a first photoelectric conversion unit and a second photoelectric conversion unit. The first photoelectric conversion unit and the second photoelectric conversion unit are formed adjacent to each other, have a first groove portion between the first photoelectric conversion unit and the second photoelectric conversion unit, and have a first groove portion. It has a first insulating film having a fixed charge formed so as to cover the inner wall surface of the groove portion and the light incident surface side of the first photoelectric conversion portion and the second photoelectric conversion portion, and is cut in the light incident direction. In a certain cross section, a semiconductor composed of a first conductive type on the light incident surface side of a region in contact with the periphery of the first groove portion, a charge storage region of the first photoelectric conversion portion, and a charge storage region of the second photoelectric conversion portion. A region is formed, and the charge storage region of the plurality of photoelectric conversion units is formed by a semiconductor region made of a second conductive type.</p><p num="0007"> The electronic device of the present disclosure includes an optical lens, the above-mentioned solid-state imaging device in which light focused on the optical lens is incident, and a signal processing circuit for processing an output signal output from the solid-state imaging device.</p>

<p num="0008"> According to the present disclosure, in a solid-state image sensor, characteristics such as reduction of color mixing can be further improved. Further, by using the solid-state image sensor, an electronic device with improved image quality can be obtained.</p>

0009<figref num="1">It is a figure which shows the whole structure of the solid-state image sensor which concerns on 1st Embodiment of this disclosure.</figref><figref num="2">It is a figure which shows the cross-sectional structure of the main part of the solid-state image pickup apparatus which concerns on 1st Embodiment of this disclosure.</figref><figref num="3">It is a plane layout of the solid-state image sensor according to the first embodiment of the present disclosure.</figref><figref num="4">4A and 4B are diagrams showing a method of manufacturing a solid-state image sensor according to the first embodiment of the present disclosure.</figref><figref num="5">4C and 4D are diagrams showing a method of manufacturing a solid-state image sensor according to the first embodiment of the present disclosure.</figref><figref num="6">It is a potential distribution diagram of the main part of the solid-state image sensor and the conventional solid-state image sensor according to the first embodiment of the present disclosure.</figref><figref num="7">It is a plane layout of the solid-state image sensor according to the first modification of the first embodiment.</figref><figref num="8">It is a plane layout of the solid-state image sensor according to the second modification of the first embodiment.</figref><figref num="9">It is a figure which shows the cross-sectional structure of the main part of the solid-state image pickup apparatus which concerns on 2nd Embodiment of this disclosure.</figref><figref num="10">10A to 10C are diagrams showing a method of manufacturing a solid-state image sensor according to a second embodiment of the present disclosure.</figref><figref num="11">It is a figure which shows the cross-sectional structure of the main part of the solid-state image pickup apparatus which concerns on 3rd Embodiment of this disclosure.</figref><figref num="12">It is a figure which shows the cross-sectional structure of the main part of the solid-state image sensor which concerns on 4th Embodiment of this disclosure.</figref><figref num="13">13A and 13B are diagrams showing a method of manufacturing a solid-state image sensor according to a fourth embodiment of the present disclosure.</figref><figref num="14">FIG. 14C is a diagram showing a method of manufacturing a solid-state image sensor according to a fourth embodiment of the present disclosure.</figref><figref num="15">It is a figure which shows the cross-sectional structure of the main part of the solid-state image sensor which concerns on 5th Embodiment of this disclosure.</figref><figref num="16">It is a figure which shows the cross-sectional structure of the main part of the solid-state image pickup apparatus which concerns on 6th Embodiment of this disclosure.</figref><figref num="17">It is a figure which shows the cross-sectional structure of the main part of the solid-state image sensor which concerns on 7th Embodiment of this disclosure.</figref><figref num="18">18A and 18B are diagrams showing a method of manufacturing a solid-state image sensor according to a seventh embodiment of the present disclosure.</figref><figref num="19">It is a figure which shows the cross-sectional structure of the main part of the solid-state image sensor which concerns on 8th Embodiment of this disclosure.</figref><figref num="20">20A and 20B are diagrams showing a method of manufacturing a solid-state image sensor according to an eighth embodiment of the present disclosure.</figref><figref num="21">It is a figure which shows the cross-sectional structure of the main part of the solid-state image sensor which concerns on a modification.</figref><figref num="22">It is a schematic block diagram of the electronic device which concerns on 9th Embodiment of this disclosure.</figref>

0010The present inventors have discovered the following problems in the solid-state image sensor of Patent Document 1.

0011In the back surface type solid-state image sensor, the semiconductor layer on which the photodiode is formed is formed thinner than that of the surface-illuminated solid-state image sensor. For this reason, in the conventional front-illuminated solid-state imaging device, the signal charge overflowing with the photodiode overflows in the depth direction (longitudinal direction) of the semiconductor layer, but the back-illuminated solid-state imaging device , It is not possible to overflow in the depth direction of the semiconductor layer. Therefore, in the back-illuminated solid-state image sensor, the electrons overflowing with the photodiode are configured to flow to the floating diffusion (so-called lateral overflow).

0012When the lateral overflow structure is adopted, whether the electrons overflowing from the photodiode flow to the floating diffusion side or the adjacent photodiode side is determined by the potential in the substrate. Therefore, by setting the potential between the photodiode and the floating diffusion higher than the potential between the adjacent photodiodes during charge accumulation, the overflowing electrons can be transferred to the floating diffusion at any time. Therefore, in the case of a configuration in which the overflowing electrons can be transferred to the floating diffusion, a decrease in the saturated charge amount (Qs) becomes a big problem. On the other hand, when the saturated charge amount is increased, the signal charge overflowing from the white point pixel leaks to the adjacent pixel during long-term storage, which causes blooming, which contributes to the deterioration of resolution and image quality. .. Further, in the structure in which the light-shielding film is provided at the pixel boundary, it is not possible to completely suppress the color mixing that occurs under the light-shielding film when oblique light enters. In the embodiment of the present disclosure, a solid-state image sensor capable of reducing color mixing, suppressing blooming, and improving saturation characteristics will be described.

0013Hereinafter, an example of the solid-state image sensor, its manufacturing method, and an electronic device according to the embodiment of the present disclosure will be described with reference to FIGS. 1 to 22. The embodiments of the present disclosure will be described in the following order. The present disclosure is not limited to the following examples. 1. First embodiment: Solid-state image sensor (example of sharing one floating diffusion unit with 4 pixels) 1-1 Overall configuration of solid-state image sensor 1-2 Composition of key parts 1-3 Manufacturing method of solid-state image sensor 1-4 Modification 1 1-5 Modification example 2 2. Second embodiment: Solid-state image sensor (example in which a light-shielding film is formed in the element separation part) 3. Third embodiment: Solid-state image sensor (example in which only the end portion of the element separation portion on the back surface side of the substrate is in contact with the p-type semiconductor region) 4. Fourth embodiment: Solid-state image sensor (example in which the element separation part penetrates the substrate) 5. Fifth embodiment: Solid-state image sensor (example in which a light-shielding layer formed in an element separation portion is connected to a wiring layer) 6. Sixth embodiment: Solid-state image sensor (example of forming two layers of fixed charge film in the element separation part) 7. Seventh embodiment: Solid-state image sensor (example in which the element separation part has a hollow structure) 8. Eighth embodiment: Solid-state image sensor (example in which the element separation part has a hollow structure) 8-1 Modification example 9. Ninth embodiment: Electronic device

0014&lt;1. First Embodiment: Solid-state image sensor&gt; [1-1 Overall configuration of solid-state image sensor] FIG. 1 is a schematic configuration diagram showing the entire CMOS type solid-state image sensor according to the first embodiment of the present disclosure. The solid-state image sensor 1 of the present embodiment has a pixel region 3 having a plurality of pixels 2 arranged on a substrate 11 made of silicon, a vertical drive circuit 4, a column signal processing circuit 5, a horizontal drive circuit 6, and an output. It is configured to have a circuit 7 and a control circuit 8 and the like.

0015The pixel 2 is composed of a photoelectric conversion unit composed of a photodiode and a plurality of pixel transistors, and a plurality of pixels 2 are regularly arranged in a two-dimensional array on the substrate 11. The pixel transistors constituting pixel 2 are a transfer transistor, a reset transistor, a selection transistor, and an amplifier. It may be four MOS transistors composed of a transistor, or may be three transistors excluding a selection transistor.

0016The pixel region 3 has a plurality of pixels 2 regularly arranged in a two-dimensional array. The pixel area 3 is an effective pixel area that actually receives light, amplifies the signal charge generated by photoelectric conversion, and reads it out to the column signal processing circuit 5, and black for outputting optical black that serves as a reference for the black level. It is composed of a reference pixel area (not shown). The black reference pixel region is usually formed on the outer peripheral portion of the effective pixel region.

0017The control circuit 8 generates a clock signal, a control signal, etc. that serve as a reference for the operation of the vertical drive circuit 4, the column signal processing circuit 5, the horizontal drive circuit 6, etc., based on the vertical synchronization signal, the horizontal synchronization signal, and the master clock. To do. Then, the clock signal, the control signal, and the like generated by the control circuit 8 are input to the vertical drive circuit 4, the column signal processing circuit 5, the horizontal drive circuit 6, and the like.

0018The vertical drive circuit 4 is composed of, for example, a shift register, and sequentially selects and scans each pixel 2 in the pixel area 3 in the vertical direction in units of rows. Then, the pixel signal based on the signal charge generated in the photodiode of each pixel 2 according to the amount of light received is supplied to the column signal processing circuit 5 through the vertical signal line.

0019The column signal processing circuit 5 is arranged for each column of pixel 2, for example, and outputs a signal output from pixel 2 for one row for each pixel string in a black reference pixel area (not shown, but around an effective pixel area). Signal processing such as noise removal and signal amplification is performed by the signal from). A horizontal selection switch (not shown) is provided between the output stage of the column signal processing circuit 5 and the horizontal signal line 10.

0020The horizontal drive circuit 6 is composed of, for example, a shift register, and by sequentially outputting horizontal scanning pulses, each of the column signal processing circuits 5 is sequentially selected, and a pixel signal is output from each of the column signal processing circuits 5 as a horizontal signal line. Output to 10.

0021The output circuit 7 processes and outputs signals sequentially supplied from each of the column signal processing circuits 5 through the horizontal signal line 10.

0022[1-2 Composition of key parts] FIG. 2 shows a cross-sectional configuration in the pixel region 3 of the solid-state image sensor 1 of the present embodiment, and FIG. 3 shows a planar layout of the pixel region 3 of the solid-state image sensor 1 of the present embodiment. The solid-state image sensor 1 of the present embodiment is an example of a back-illuminated CMOS-type solid-state image sensor, and has a so-called 4-pixel sharing in which necessary pixel transistors are shared by four photoelectric conversion units. This is an example of a unit. Further, in the following description, the first conductive type will be described as p-type, and the second conductive type will be described as n-type.

0023As shown in FIG. 2, the solid-state image sensor 1 of the present embodiment includes a substrate 12 having a plurality of pixels, a wiring layer 13 formed on the surface side of the substrate 12, and a support substrate 31. Further, an insulating film (hereinafter, fixed charge film) 20 having a fixed charge, which is sequentially formed on the back surface side of the substrate 12, an insulating film 21, a light-shielding film 25, a flattening film 26, a color filter layer 27, and the like. Further equipped with an on-chip lens 28.

0024The substrate 12 is made of a semiconductor substrate made of silicon, and is formed with a thickness of, for example, 1 μm to 6 μm. In the pixel region 3 of the substrate 12, a plurality of pixels composed of a photoelectric conversion unit 40 composed of a photodiode and a plurality of pixel transistors (Tr1 to Tr4) constituting a pixel circuit unit are formed in a two-dimensional matrix. ing. The adjacent photoelectric conversion units 40 are electrically separated by the element separation unit 19. Further, although not shown in FIG. 2, a peripheral circuit portion is configured in the peripheral region of the pixel region formed on the substrate 12.

0025The photoelectric conversion unit 40 includes a first conductive type (hereinafter, p-type) semiconductor region 23, 24 formed on the front surface side and the back surface side of the substrate 12, and a second conductive type (hereinafter, n-type) semiconductor region formed between them. It is composed of 22. In the photoelectric conversion unit 40, a main photodiode is composed of a pn junction between the p-type semiconductor regions 23 and 24 and the n-type semiconductor region 22. The photoelectric conversion unit 40 generates a signal charge according to the amount of incident light and stores it in the n-type semiconductor region 22. Further, the electrons that cause the dark current generated at the interface of the substrate 12 are absorbed by the holes, which are the majority carriers of the p-type semiconductor regions 23 and 24 formed on the front surface and the back surface of the substrate 12, so that the dark current is generated. Is suppressed. Further, each photoelectric conversion unit 40 is electrically separated by a pixel separation layer 18 formed of a p-type semiconductor region and an element separation unit 19 formed in the pixel separation layer 18.

0026In the present embodiment, the pixel transistor is composed of four transistors, a transfer transistor Tr1, a reset transistor Tr2, an amplification transistor Tr3, and a selection transistor Tr4, as shown in FIG.

0027As shown in FIG. 3, the transfer transistor Tr1 is composed of a floating diffusion unit 30 formed at the center of four photoelectric conversion units 40 formed in 2 rows and 2 columns, and a transfer gate electrode 16. As shown in FIG. 2, the floating diffusion portion 30 is an n-type semiconductor region formed by implanting n-type impurities at a high concentration into the p-well layer 29 formed on the surface side of the substrate 12. Consists of. Further, the transfer gate electrode 16 is formed on the surface side of the substrate 12 between the photoelectric conversion unit 40 and the floating diffusion unit 30 via the gate insulating film 17.

0028Among the pixel transistors, the reset transistor Tr2, the amplification transistor Tr3, and the selection transistor Tr4 are formed for each of the four photoelectric conversion units 40 that share the floating diffusion unit 30. As shown in FIG. 3, these pixel transistors are arranged on one side of the group composed of the four photoelectric conversion units 40.

0029The reset transistor Tr2 is composed of a pair of source / drain regions 35 and 36 and a reset gate electrode 32 formed between the source / drain regions 35 and 36. The amplification transistor Tr3 is composed of a pair of source / drain regions 36 and 37 and an amplification gate electrode 33 formed between the source / drain regions 36 and 37. The selection transistor Tr4 is composed of a pair of source / drain regions 37 and 38 and a selection gate electrode 34 formed between the source / drain regions 37 and 38.

0030Although the cross-sectional configuration of the reset transistor Tr2, the amplification transistor Tr3, and the selection transistor Tr4 is not shown, these pixel transistors have the same configuration as the transfer transistor Tr1. That is, the source / drain regions 35 to 38 are composed of n-type high-concentration impurity regions formed in the p-well layer 29 on the surface of the substrate 12, similar to the floating diffusion portion 30. Further, the reset gate electrode 32, the amplification gate electrode 33, and the selection gate electrode 34 are formed on the surface side of the substrate 12 via the gate insulating film 17.

0031The element separation portion 19 is composed of a fixed charge film 20 formed by sequentially embedding in a groove portion 39 formed in the depth direction from the back surface side of the substrate 12 and an insulating film 21, and a pixel formed on the substrate 12. It is carved and formed in the separation layer 18. That is, the element separating portions 19 are formed in a grid pattern so as to surround the pixels as shown in the figure. When a pixel transistor is formed between the adjacent photoelectric conversion unit 40 and the photoelectric conversion unit 40, it is arranged so as to overlap the floating diffusion unit 30 and the source / drain region.

0032Further, the element separation portion 19 is formed at a depth that reaches the p-well layer 29 on which the pixel transistor is formed, and is formed at a depth that does not reach the floating diffusion portion 30 or the source / drain region. Assuming that the depth of the floating diffusion portion 30 and the source / drain region is less than 1 μm, the element separation portion 19 can be formed to a depth of about 0.25 to 5.0 μm from the surface of the substrate 12. In the present embodiment, the depth reaches the p-well layer 29 of the pixel transistor, but if the end of the element separation portion 19 on the back surface side of the substrate 12 is formed so as to be in contact with the p-type semiconductor layer. Well, it does not necessarily have to be deep enough to reach the p-well layer 29. When it is formed in the pixel separation layer 18 made of the p-type semiconductor layer as in the present embodiment, the effect of insulation separation can be obtained even in a configuration that does not reach the p-well layer 29.

0033Further, the fixed charge film 20 formed in the groove 39 is formed on the inner peripheral surface and the bottom surface of the groove 39, and is formed on the entire back surface of the substrate 12. In the following description, the inner peripheral surface and the bottom surface of the groove 39 will be combined and described as an "inner wall surface". As the fixed charge film 20, it is preferable to use a material capable of generating a fixed charge by depositing on a substrate such as silicon to strengthen pinning, and a high refractive index material film having a negative charge or a high high refractive index film 20. A dielectric film can be used. As a specific material, for example, an oxide or a nitride containing at least one element of hafnium (Hf), aluminum (Al), zirconium (Zr), tantalum (Ta) and titanium (Ti) is applied. Can be done. Examples of the film forming method include a chemical vapor deposition method (hereinafter referred to as CVD (Chemical Vapor Deposition) method), a sputtering method, and an atomic layer deposition method (hereinafter referred to as ALD (Atomic Layer)). Deposition) method) and the like. By using the ALD method, a SiO2 film that reduces the interface state during film formation can be simultaneously formed to a film thickness of about 1 nm. Materials other than the above include lantern (La), placeodium (Pr), cerium (Ce), neodymium (Nd), promethium (Pm), samarium (Sm), ytterbium (Eu), gadolinium (Gd), and terbium. Examples thereof include oxides or nitrides containing at least one element of (Tb), dysprosium (Dy), formium (Ho), yttrium (Tm), ytterbium (Yb), lutetium (Lu) and yttrium (Y). .. Further, the fixed charge film can be formed of a hafnium oxynitride film or an aluminum oxynitride film.

0034Silicon (Si) or nitrogen (N) may be added to the material of the fixed charge film 20 described above as long as the insulating property is not impaired. The concentration is appropriately determined as long as the insulating property of the film is not impaired. By adding silicon (Si) and nitrogen (N) in this way, it becomes possible to increase the heat resistance of the membrane and the ability to prevent ion implantation in the process.

0035In the present embodiment, since the fixed charge film 20 having a negative charge is formed on the inner wall surface of the groove 39 and the back surface of the substrate 12, an inversion layer is formed on the surface in contact with the fixed charge film 20. As a result, the silicon interface is pinned by the inversion layer, so that the generation of dark current is suppressed. Further, when the groove portion 39 is formed on the substrate 12, physical damage may occur on the side wall and the bottom surface of the groove portion 39, and pinning detachment may occur in the peripheral portion of the groove portion 39. In response to this problem, in the present embodiment, the pinning is prevented from coming off by forming the fixed charge film 20 having a large amount of fixed charges on the side wall and the bottom surface of the groove 39.

0036The insulating film 21 is embedded in the groove 39 in which the fixed charge film 20 is formed, and is formed on the entire back surface side of the substrate 12. The insulating film 21 is preferably formed of a material having a refractive index different from that of the fixed charge film 20, and for example, silicon oxide, silicon nitride, silicon oxynitride, resin, or the like can be used. Further, a material having a feature of having no positive fixed charge or having a small positive fixed charge can be used for the insulating film 21.

0037Then, by embedding the groove portion 39 in the insulating film 21, the photoelectric conversion unit 40 constituting each pixel is separated via the insulating film 21. As a result, the signal charge is less likely to leak to the adjacent pixels, so that when a signal charge exceeding the saturated charge amount (Qs) is generated, the overflowed signal charge is less likely to leak to the adjacent photoelectric conversion unit 40. be able to. Therefore, electron color mixing can be suppressed.

0038Further, the two-layer structure of the fixed charge film 20 and the insulating film 21 formed on the back surface side of the substrate 12 on the incident surface side has a role of an antireflection film due to the difference in the refractive index. As a result, the substrate 12 Reflection of light incident from the back surface side on the back surface side of the substrate 12 is prevented.

0039The light-shielding film 25 is formed in a desired region on the insulating film 21 formed on the back surface of the substrate 12, and in the pixel region, the light-shielding film 25 is formed in a grid pattern so as to open the photoelectric conversion unit 40. That is, the light-shielding film 25 is formed at a position corresponding to the element separation portion 19. The material constituting the light-shielding film 25 may be any material that blocks light, and for example, tungsten (W), aluminum (Al), or copper (Cu) can be used. The flattening film 26 is formed on the entire surface of the insulating film 21 including the light-shielding film 25, whereby the back surface side of the substrate 12 is flattened. As the material of the flattening film 26, for example, an organic material such as a resin can be used.

0040The color filter layer 27 is formed on the upper surface of the flattening film 26, and is formed for each pixel, for example, corresponding to R (red), G (green), and B (blue). In the color filter layer 27, light having a desired wavelength is transmitted, and the transmitted light is incident on the photoelectric conversion unit 40 in the substrate 12.

0041The on-chip lens 28 is formed on the upper surface of the color filter layer 27. In the on-chip lens 28, the irradiated light is condensed, and the collected light is efficiently incident on each photoelectric conversion unit 40 through the color filter layer 27.

0042The wiring layer 13 is formed on the surface side of the substrate 12, and is configured to have wiring 15 laminated in a plurality of layers (three layers in the present embodiment) via an interlayer insulating film 14. The pixel transistor Tr constituting the pixel 2 is driven via the wiring 15 formed in the wiring layer 13.

0043The support substrate 31 is formed on a surface of the wiring layer 13 opposite to the side facing the substrate 12. The support substrate 31 is configured to secure the strength of the substrate 12 at the manufacturing stage, and is composed of, for example, a silicon substrate.

0044In the solid-state image sensor 1 having the above configuration, light is irradiated from the back surface side of the substrate 12, and the light transmitted through the on-chip lens 28 and the color filter layer 27 is photoelectrically converted by the photoelectric conversion unit 40 to obtain a signal charge. Is generated. Then, the signal charge generated by the photoelectric conversion unit 40 is output as a pixel signal by the vertical signal line formed by the desired wiring 15 of the wiring layer 13 via the pixel transistor formed on the surface side of the substrate 12. To.

0045[1-3 Manufacturing method of solid-state image sensor] Next, a method of manufacturing the solid-state image sensor of the present embodiment will be described. 4 and 5 are cross-sectional views showing a manufacturing process of the solid-state image sensor of the present embodiment.

0046First, as shown in FIG. 4A, after forming the photoelectric conversion unit 40, the pixel transistor, and the pixel separation layer 18 on the substrate 12, wiring is performed by alternately forming the interlayer insulating film 14 and the wiring 15 on the surface of the substrate 12. Form layer 13. Impurity regions such as the photoelectric conversion unit 40 formed on the substrate 12 are formed by ion-implanting desired impurities from the surface side of the substrate 12.

0047Subsequently, a support substrate 31 (see FIG. 4B) made of a silicon substrate is adhered to the uppermost layer of the wiring layer 13 and inverted. The manufacturing process up to this point is the same as that of a normal back-illuminated solid-state image sensor. Although not shown, in general, after the substrate 12 is inverted, the substrate 12 is polished from the back surface side to reduce the thickness to a desired thickness.

0048Next, as shown in FIG. 4B, it is desired to selectively etch the boundary of each pixel of the substrate 12, that is, the portion where the pixel separation layer 18 is formed, from the back surface side of the substrate 12 in the depth direction. A groove 39 having a depth of 3 is formed.

0049In the step of forming the groove portion 39, a hard mask (not shown) having a desired opening is formed on the back surface of the substrate 12, and the groove portion is formed by etching through the hard mask. Considering the spectral characteristics, the depth of the groove 39 is preferably 0.2 μm or more, more preferably 1.0 μm or more from the back surface of the substrate 12. Further, the width of the groove 39 is preferably 0.02 μm or more depending on the spectral characteristics. By setting the width of the groove 39 wider, it becomes easier to process the groove 39, but the wider the groove 39, the lower the spectral characteristics and the amount of saturated charge, so the width of the groove 39 should be about 0.02 μm. More desirable.

0050In this embodiment, as shown in FIG. 4B, a groove portion 39 having a depth that reaches the p-well layer 29 of the pixel transistor and does not reach the floating diffusion portion 30 or the source / drain region is formed. The step of forming the groove 39 can be performed in common with other substrate penetration steps, and when shared, the number of steps can be reduced.

0051Next, the hard mask used for processing the groove 39 is removed, and as shown in FIG. 5C, the side wall, the bottom surface of the groove 39, and the back surface of the substrate 12 are covered by the CVD method, the sputtering method, ALD, or the like. A fixed charge film 20 is formed on the film. After that, the insulating film 21 is formed by embedding the insulating film 21 in the groove 39 by using a CVD method or the like, and the insulating film 21 is also formed on the upper surface of the fixed charge film 20 on the back surface side of the substrate 12.

0052Next, a light-shielding material layer is formed on the entire upper surface of the insulating film 21, and then the light-shielding material layer is patterned into a desired shape. As a result, as shown in FIG. 5D, the photoelectric conversion unit 40 is opened to form a light-shielding film 25 that blocks light between adjacent pixels. After that, the solid-state image sensor 1 shown in FIG. 2 is completed by forming the color filter layer 27 and the on-chip lens 28 by a usual method.

0053As described above, the solid-state image sensor 1 in which the pixels are separated by the element separation unit 19 formed by embedding the insulating film 21 in the substrate 12 is formed. In the solid-state image sensor 1 of the present embodiment, the photoelectric conversion unit 40 of each pixel is separated by the element separation unit 19 formed by embedding the insulating film 21 in the groove portion 39. Therefore, the leakage of the signal charge accumulated in the photoelectric conversion unit 40 to the adjacent photoelectric conversion unit 40 side can be reduced as compared with the case where the signal charge is separated only in the impurity region. As a result, when the photoelectric conversion unit 40 generates a signal charge equal to or larger than the saturated charge amount, it can be swept out to the floating diffusion unit 30 side more efficiently. As a result, the occurrence of blooming is suppressed.

0054FIG. 6 shows the potential distribution at the time of charge accumulation, and is a diagram for explaining the horizontal overflow structure (lateral overflow structure). FIG. 6 shows a potential distribution diagram of the two adjacent photoelectric conversion units 40 of the solid-state image sensor 1 of the present embodiment and the substrate 12 in the portion where the transfer transistor Tr1 is formed. Further, in FIG. 6, as a comparative example, the potential of the substrate in the part where the photoelectric conversion part and the transfer transistor of the conventional solid-state imaging device are formed in which the adjacent photoelectric conversion parts are separated only by the element separation region 100 formed by ion implantation. The distribution map is also shown. In FIG. 6, the parts corresponding to FIG. 2 are designated by the same reference numerals.

0055As shown in FIG. 6, in a conventional solid-state image sensor, the potential of the transfer gate is set between two adjacent photoelectric conversion units 40 in order to laterally overflow the signal charge exceeding the saturated charge amount at the time of charge accumulation. Set deeper than the potential of the element separation region 100. By doing so, the signal charge exceeding the saturated charge amount of the photoelectric conversion unit 40 does not flow in the direction of the adjacent photoelectric conversion unit 40, but is swept out to the floating diffusion unit 30 through the transfer gate, thereby blooming. Is suppressed.

0056As described above, when the lateral overflow is adopted in the conventional solid-state image sensor, it is necessary to set the potential of the transfer gate deeper than the potential of the element separation region 100 between the two adjacent photoelectric conversion units 40. is there. Therefore, it is necessary to supply a predetermined potential to the transfer gate electrode at the time of charge accumulation to deeply set the potential of the transfer gate, and the saturated charge amount (Qs) is lowered by that amount.

0057On the other hand, in the solid-state image sensor 1 of the present embodiment, the adjacent photoelectric conversion unit 40 is separated by the element separation unit 19. As a result, at the time of charge accumulation, even if the potential of the transfer gate is shallow, the signal charge exceeding the saturated charge amount of the photoelectric conversion unit 40 does not flow in the direction of the adjacent photoelectric conversion unit 40, and the floating diffusion unit Sweeped to 30.

0058In the solid-state image sensor 1 of the present embodiment, by separating the photoelectric conversion unit 40 by the element separation unit 19 composed of the insulating film 21, the potential of the element separation unit 19 becomes shallower by Δx1 as compared with the conventional case. Therefore, it is not necessary to deepen the potential of the transfer gate at the time of charge accumulation. As shown in FIG. 6, the potential of the transfer gate can be made shallower by Δx2 as compared with the conventional one, and as a result, the solid-state image sensor 1 of the present embodiment can increase the saturated charge amount as compared with the conventional one. it can. That is, in the solid-state image sensor 1 of the present embodiment, the saturated charge amount can be improved while suppressing blooming. Further, it is not necessary to raise the electric field in the photoelectric conversion unit 40 to improve the saturation characteristics, and the density of the n-type semiconductor region constituting the photoelectric conversion unit 40 can be set low, so that the white point can be maintained at a low level. It is possible.

0059Further, in the solid-state image sensor 1 of the present embodiment, a fixed charge film 20 having a negative charge is formed in the groove 39. Therefore, the generation of the interface state can be suppressed by the negative bias effect of the fixed charge film 20, and the generation of dark current due to the interface state can be suppressed. Further, an inversion layer (p-type) is formed on the surface in contact with the fixed charge film 20, and a positive charge is induced. Therefore, even if the p-well layer 29 and the pixel separation layer 18 composed of the p-type semiconductor region are formed with a p-type impurity concentration that is about an order of magnitude lower than that of the conventional solid-state image sensor, the pixel separation function and the pixel separation function can be achieved. The effect of suppressing dark current can be fully exerted.

0060Further, in the present embodiment, since the p-well layer 29 and the pixel separation layer 18 can be formed with an impurity concentration lower than that of the conventional solid-state image sensor, the n-type semiconductor region 22 constituting the photoelectric conversion unit 40 is p-type. It does not erode the semiconductor region. As a result, the saturated charge amount can be improved. Further, since the p-type impurity concentration of the p-well layer 29 and the pixel separation layer 18 can be set low, the generation of a strong electric field is suppressed in the p-well layer 29 and the pixel separation layer 18, and the generation of noise is suppressed. can do.

0061Further, since the element separating portion 19 is formed so as to be in contact with the p-well layer 29 which is the ground potential, the inversion layer (p type) formed around the element separating portion 19 is fixed to the ground potential. It is pinned, which suppresses the generation of dark currents.

0062Further, in the solid-state image sensor 1 of the present embodiment, the element separation unit 19 can be formed in a region where the pixel transistor and the light are overlapped in the incident direction. Therefore, the element separation unit 19 can be formed without affecting the layout of the pixel transistor, and it is not necessary to separately provide a region for the element separation unit 19, so that the pixel area does not increase.

0063In the above, an example in which 4-pixel sharing in which the required pixel transistors are shared by the four photoelectric conversion units 40 is set as one unit has been described, but the present invention is not limited to this, and 2-pixel sharing is set as one unit. Various configurations are possible, for example, when the pixel transistors are not shared.

0064[1-4 Modification 1] As a solid-state image sensor according to the first modification of the present embodiment, an example will be described in which two pixel sharing in which the required pixel transistors are shared by two photoelectric conversion units is set as one unit. FIG. 7 is a planar layout of the solid-state image sensor according to the first modification. In FIG. 7, the parts corresponding to FIG. 3 are designated by the same reference numerals, and duplicate description will be omitted.

0065In the first modification, as shown in FIG. 7, the transfer transistor is composed of a floating diffusion unit 30 formed at the center of two photoelectric conversion units 40 formed in rows and columns, and a transfer gate electrode 16. Has been done. Further, among the pixel transistors, the reset transistor Tr2, the amplification transistor Tr3, and the selection transistor Tr4 are formed for each of the two photoelectric conversion units 40 that share the floating diffusion unit 30. These reset transistor Tr2, amplification transistor Tr3, and selection transistor Tr4 are arranged on one side of the group composed of two photoelectric conversion units 40. Further, even in the case of sharing two pixels, the element separation unit 19 is formed in a grid pattern so as to surround the photoelectric conversion unit 40 of each pixel, and in the region where the pixel transistor is formed, the region overlaps the pixel transistor. Have been placed.

0066Further, the cross-sectional configuration including the transfer transistor Tr1 of the solid-state image sensor according to the first modification is also the same as that in FIG. Even in such a solid-state image pickup device in which two pixel sharing is used as one unit, since the photoelectric conversion unit 40 of each pixel is insulated by the element separation unit 19, the signal charges generated by each photoelectric conversion unit 40 are adjacent to each other. It is difficult to leak into the photoelectric conversion unit 40 of the pixel. As a result, the same effects as those of the present embodiment can be obtained, such as suppressing blooming while maintaining the saturation characteristics.

0067[1-5 Modification 2] As a solid-state image sensor according to the second modification of the present embodiment, an example in which a pixel transistor is formed for each photoelectric conversion unit 40 of each pixel will be described. FIG. 8 is a planar layout in the pixel region of the solid-state image sensor according to the second modification. In FIG. 8, the parts corresponding to FIG. 3 are designated by the same reference numerals, and duplicate description will be omitted.

0068In the second modification, the transfer transistor Tr1, the reset transistor Tr2, and the amplification transistor Tr3 are formed for each pixel, and the selection transistor is not formed. The pixel transistors formed in each photoelectric conversion unit 40 are formed in one direction of the photoelectric conversion unit 40. Further, the element separation unit 19 is formed in a grid pattern so as to surround the photoelectric conversion unit 40 of each pixel, and is partially arranged in a region overlapping the pixel transistor.

0069Further, although the cross-sectional configuration of the solid-state image sensor according to the modified example 2 is not shown, in the solid-state image sensor in the modified example 2, one floating diffusion unit 30 is formed for each photoelectric conversion unit 40. .. Also in the second modification, since the photoelectric conversion unit 40 of each pixel is insulated by the element separation unit 19, the signal charge generated by each photoelectric conversion unit 40 is unlikely to leak to the photoelectric conversion unit 40 of the adjacent pixel. As a result, the same effects as those of the present embodiment can be obtained, such as suppressing blooming while maintaining the saturation characteristics.

0070As described above, even in the solid-state image pickup devices having different layouts, the configuration of the element separation unit 19 with respect to the photoelectric conversion unit 40 can be the same.

0071&lt;2. Second embodiment: solid-state image sensor&gt; Next, the solid-state image sensor according to the second embodiment of the present disclosure will be described. Since the overall configuration of the solid-state image sensor of this embodiment is the same as that shown in FIG. 1, the illustration is omitted. FIG. 9 is a cross-sectional configuration diagram of a main part of the solid-state image sensor 52 of the present embodiment. In FIG. 9, the parts corresponding to FIG. 2 are designated by the same reference numerals, and duplicate description will be omitted.

0072The solid-state image sensor 52 of the present embodiment is an example in which the configuration of the element separation unit 49 is different from that of the first embodiment. In the solid-state image sensor 52 of the present embodiment, the element separation unit 49 is composed of a fixed charge film 20, an insulating film 48, and a light-shielding layer 50, which are sequentially embedded in the groove 39. The light-shielding layer 50 is formed in the depth direction in the groove 39 in which the fixed charge film 20 and the insulating film 48 are formed, and is connected to the light-shielding film 25 formed on the back surface side of the substrate 12. There is.

007310A to 10C are cross-sectional views showing a manufacturing process of the solid-state image sensor 52 of the present embodiment. In the present embodiment, the steps up to the formation of the groove 39 are the same as the steps described with reference to FIGS. 4A and 4B, and thus the subsequent steps will be described.

0074After forming the groove 39 in the region surrounding the photoelectric conversion unit 40, the fixed charge film 20 is formed so as to cover the inner wall surface of the groove 39 and the back surface side of the substrate 12, as shown in FIG. 10A. The fixed charge film 20 is formed in the same manner as in the first embodiment. Next, the insulating film 48 is formed in the groove 39 and on the back surface side of the substrate 12 so as to cover the fixed charge film 20. At this time, the insulating film 48 formed in the groove 39 is formed to have a thickness that does not completely embed the inside of the groove 39. The insulating film 48 can be formed by, for example, a sputtering method.

0075Next, as shown in FIG. 10B, the inside of the groove 39 is completely embedded, and the light-shielding material layer 24a is formed so as to cover the back surface side of the substrate 12. The light-shielding material layer 24a can be formed in the same manner as in the first embodiment, but it is particularly preferable to use a material having good embedding property.

0076Next, as shown in FIG. 10C, the light-shielding material layer 24a is patterned so that the light-shielding material layer remains at the boundary between adjacent pixels. As a result, the light-shielding layer 50 embedded in the groove 39 and the light-shielding film 25 electrically connected to the light-shielding layer 50 are formed. Then, the solid-state image sensor 52 of the present embodiment is completed by forming the flattening film 26, the color filter layer 27, and the on-chip lens 28 in this order using a normal manufacturing method.

0077In the solid-state image sensor 52 of the present embodiment, a ground potential or a negative potential is supplied to the light-shielding film 25 and the light-shielding layer 50. By supplying a ground potential or a negative potential to the light-shielding film 25 and the light-shielding layer 50, the effect of hole pinning on the surface of the element separation portion 19 can be stabilized. Further, when a negative potential is supplied to the light-shielding film 25 and the light-shielding layer 50, an inversion layer is likely to be formed on the 12 surfaces of the substrate in contact with the element separation portion 19, and the effect of suppressing dark current can be enhanced.

0078Further, in the present embodiment, since the light-shielding layer 50 is formed in the groove 39, it is possible to prevent the obliquely incident light from entering the adjacent photoelectric conversion unit 40, and the optical color mixing is suppressed. Other than that, the same effect as that of the first embodiment can be obtained.

0079&lt;3. Third Embodiment: Solid-state image sensor&gt; Next, the solid-state image sensor according to the third embodiment of the present disclosure will be described. Since the overall configuration of the solid-state image sensor of this embodiment is the same as that shown in FIG. 1, the illustration is omitted. FIG. 11 is a cross-sectional configuration diagram of a main part of the solid-state image sensor 55 of the present embodiment. In FIG. 11, the parts corresponding to FIG. 2 are designated by the same reference numerals, and duplicate description will be omitted.

0080The solid-state image sensor 55 of the present embodiment is an example in which the pixel separation layer 18 composed of the p-type semiconductor region formed on the substrate 12 is not formed in the solid-state image sensor 1 according to the first embodiment. That is, in the solid-state image sensor 55 of the present embodiment, the photoelectric conversion unit 56 is separated for each pixel only by the element separation unit 19. However, also in this case, the end portion on the surface side of the element separation portion 19 is formed so as to be in contact with the p-well layer 29 of the pixel transistor.

0081In the solid-state image sensor 55 of the present embodiment, the photoelectric conversion unit 56 is formed of a p-type semiconductor region 23 formed on the front surface side of the substrate 12 and from the lower portion of the p-type semiconductor region 23 to the back surface side of the substrate 12. It is composed of an n-type semiconductor region 51. That is, in the present embodiment, the n-type semiconductor region 51, which is the charge storage region of the photoelectric conversion unit 56, is larger than the n-type semiconductor region 22 which is the charge storage region of the photoelectric conversion unit 40 in the first embodiment. It is formed. Therefore, the saturated charge amount can be further improved.

0082In the present embodiment, the pixel separation layer that separates the photoelectric conversion unit 56 of each pixel in the p-type impurity region and the p-type semiconductor region for suppressing dark current are not formed on the back surface side of the substrate 12. However, since the insulating film 20 having a negative fixed charge is formed in the element separating portion 19, an inversion layer is formed on the surface in contact with the fixed charge film 20, and the generation of dark current can be suppressed. it can. As described above, if at least the end portion of the element separation portion 19 on the surface side of the substrate 12 is in contact with the p-type semiconductor region such as the p-well layer 29 that electrically separates the adjacent n-type semiconductor regions 51 from each other. The leakage of electric charge between the photoelectric conversion units 56 can be sufficiently suppressed. Other than that, the same effect as that of the first embodiment can be obtained.

0083&lt;4. Fourth Embodiment: Solid-state image sensor&gt; Next, the solid-state image sensor according to the fourth embodiment of the present disclosure will be described. Since the overall configuration of the solid-state image sensor of this embodiment is the same as that shown in FIG. 1, the illustration is omitted. FIG. 12 is a cross-sectional configuration diagram of a main part of the solid-state image sensor 57 of the present embodiment. In FIG. 12, the parts corresponding to FIG. 2 are designated by the same reference numerals, and duplicate description will be omitted.

0084The solid-state image sensor 57 of the present embodiment is an example in which a part of the element separation portions 59 penetrates the substrate 12. As shown in FIG. 12, the element separation portion 59 is formed through the substrate 12 in a region that does not overlap with the pixel transistor (the floating diffusion portion 30 of the transfer transistor Tr1 in FIG. 12). That is, the element separation portion 19 in the region that does not overlap with the pixel transistor is composed of the fixed charge film 20 and the insulating film 21 that are sequentially embedded in the groove portion 60 formed through the substrate 12.

0085On the other hand, in the region overlapping the pixel transistor, the end portion on the surface side of the element separation portion 19 is formed so as to be in contact with the p-well layer 29 of the pixel transistor, as in the first embodiment. At this time, the end portion on the surface side of the element separation portion 19 is formed so as not to reach the floating diffusion portion 30 and the source / drain region constituting the pixel transistor.

008613 and 14 are cross-sectional views showing a manufacturing process of the solid-state image sensor 57 of the present embodiment. In the present embodiment, the steps before forming the groove portions 39 and 60 are the same as the steps described with reference to FIG. 4A, and thus the steps after that will be described.

0087In the present embodiment, the substrate 12 on which the wiring layer 13 and the support substrate 31 are formed is inverted and thinned to a predetermined thickness, and then grooves 39, 60 having different depths are formed as shown in FIG. 13A. .. In the region where the element separation portion 59 penetrating the substrate 12 is formed, the groove portion 60 penetrating the substrate 12 is formed, and in the region where the element separation portion 19 which does not penetrate is formed, the depth reaches the p-well layer 29 of the pixel transistor. A groove 39 is formed in the groove 39. The grooves 39 and 60 having different depths can be formed by performing an etching process divided into a plurality of stages.

0088Next, as shown in FIG. 13B, the fixed charge film 20 and the insulating film 21 are formed in the grooves 39 and 60 having different depths in the same manner as in FIG. 5C, so that the element separating portions 19 and 60 having different depths are formed. 59 can be formed.

0089Then, a light-shielding material layer is formed on the entire upper surface of the insulating film 21, and then the light-shielding material layer is patterned into a desired shape. As a result, as shown in FIG. 14C, the photoelectric conversion unit 40 is opened to form a light-shielding film 25 that blocks light between adjacent pixels. Then, the color filter layer 27 and the on-chip lens 28 are formed by a usual method to complete the solid-state image sensor 57 shown in FIG.

0090In the solid-state image sensor 57 of the present embodiment, since the element separation unit 59 is formed through the substrate 12 in the region other than the region overlapping the pixel transistors, the signal charge leakage between the adjacent photoelectric conversion units 40 is further increased. It can be reduced. Thereby, the effect of suppressing blooming can be enhanced. In addition, the same effect as that of the first embodiment can be obtained.

0091&lt;5. Fifth Embodiment: Solid-state image sensor&gt; Next, the solid-state image sensor according to the fifth embodiment of the present disclosure will be described. Since the overall configuration of the solid-state image sensor of this embodiment is the same as that shown in FIG. 1, the illustration is omitted. FIG. 15 is a cross-sectional configuration diagram of a main part of the solid-state image sensor 64 of the present embodiment. In FIG. 15, the parts corresponding to FIG. 2 are designated by the same reference numerals, and duplicate description will be omitted.

0092The solid-state image sensor 64 of the present embodiment has an element separation unit 62 that penetrates the substrate 12 in a part (for example, an edge) of a pixel region in the solid-state image sensor 52 according to the second embodiment. This is an example of forming a light-shielding layer 63 exposed on the surface side of the substrate 12 in the separation portion 62.

0093The element separation portion 62 penetrating the substrate 12 is composed of a groove portion 60 formed through the substrate 12 and a fixed charge film 20, an insulating film 48, and a light-shielding layer 63 sequentially formed in the groove portion 60. The light-shielding layer 63 is formed so as to be exposed on the surface side of the substrate 12. The light-shielding layer 63 formed so as to be exposed on the surface side of the substrate 12 is connected to the desired wiring 15 via the contact portion 61 formed in the interlayer insulating film 14 constituting the wiring layer 13. By supplying a ground potential or a negative potential from the wiring 15 to the light-shielding layer 63, a ground potential or a negative potential is supplied to the light-shielding layer 50 and the light-shielding film 25 formed in the pixel region. ..

0094When manufacturing the solid-state image sensor 64 of the present embodiment, first, grooves 39 and 60 having different depths are formed in the same manner as in FIG. 13A, and then insulated from the fixed charge film 20 in the same manner as in FIG. 10A. It forms a film 48. After that, only the fixed charge film 20 and the insulating film 48 formed on the bottom surface of the groove portion 60 penetrating the substrate 12 are removed by etchback. Then, with the wiring layer 13 exposed on the bottom surface of the groove portion 60 penetrating the substrate 12, a light-shielding material is embedded in the grooves 39 and 60, and a light-shielding material is formed on the back surface side of the substrate 12 to pattern the substrate 12 into a desired shape. As a result, the light-shielding layers 50 and 63 and the light-shielding film 25 are formed. As a result, the light-shielding layer 50 penetrating the substrate 12 can be pulled out to the wiring layer 13 side, and a desired potential can be supplied to the light-shielding layer 50 from the wiring 15 of the wiring layer 13. In the present embodiment, in the step of forming the wiring layer 13, the contact portion 61 connected to the light-shielding layer 63 is formed in advance.

0095In the solid-state image sensor 64 of the present embodiment, the light-shielding layer 63 can be pulled out to the wiring layer 13 side of the substrate 12 by forming a part of the element separation portions 62 so as to penetrate the substrate 12. Further, since the electrical connection between the light-shielding film 25 and the light-shielding layers 50 and 63 and the wiring 15 and the production of the element separation portions 19 and 62 can be performed in the same process, the number of steps can be reduced. In addition, the same effect as that of the solid-state image sensor according to the first and second embodiments can be obtained.

0096&lt;6. Sixth Embodiment: Solid-state image sensor&gt; Next, the solid-state image sensor according to the sixth embodiment of the present disclosure will be described. Since the overall configuration of the solid-state image sensor of this embodiment is the same as that shown in FIG. 1, the illustration is omitted. FIG. 16 is a cross-sectional configuration diagram of a main part of the solid-state image sensor 41 of the present embodiment. In FIG. 16, the parts corresponding to FIG. 2 are designated by the same reference numerals, and duplicate description will be omitted.

0097The solid-state image sensor 41 of the present embodiment has a different element separation unit 42 from the first embodiment. In the present embodiment, the element separating portion 42 includes a first fixed charge film 43, a second fixed charge film 44, a first insulating film 45, and a second insulating film 46 formed by sequentially embedding in the groove portion 39. In this embodiment, the side surface of the groove 39 is tapered so that the opening diameter becomes smaller in the depth direction of the substrate 12. Hereinafter, each film formed in the groove 39 and on the back surface of the substrate 12 will be described together with the manufacturing method thereof.

0098The first fixed charge film 43 is formed so as to cover the inner wall surface of the groove 39 and the back surface of the substrate 12, and is formed by using the CVD method or the ALD method. As the material for forming the first fixed charge film 43, the same material as the material of the fixed charge film 20 in the first embodiment can be used.

0099When the first fixed charge film 43 is formed by using the CVD method or the ALD method, a SiO2 film that reduces the interface state is simultaneously formed during the film formation. The SiO2 film is preferably formed with a thickness of about 1 nm. When the thickness of the SiO2 film formed at the substrate interface is excluded, the first fixed charge film 43 is preferably formed with a thickness of 3 nm or more, and for example, preferably 3 nm or more and 20 nm or less. ..

0100The second fixed charge film 44 is formed in the groove 39 and on the back surface of the substrate 12 so as to cover the first fixed charge film 43, and is formed by, for example, using the PVD (Physical Vapor Deposition) method. As for the material forming the second fixed charge film 44, the same material as the material of the fixed charge film 20 in the first embodiment can be used as in the case of the first fixed charge film 43. Further, the second fixed charge film 44 may be formed of the same material as the first fixed charge film 43, or may be formed of a different material.

0101The second fixed charge film 44 is preferably formed on the back surface of the substrate 12 with a film thickness of, for example, 40 nm or more and 60 nm or less. By forming the second fixed charge film 44 to a film thickness of 40 nm or more and 60 nm or less, the effect of pinning on the back surface side of the substrate 12 and the effect of the antireflection film described later can be obtained more reliably.

0102The first insulating film 45 is formed in the groove 39 and on the back surface of the substrate 12 so as to cover the second fixed charge film 44, and is an anisotropic oxide film formed by the PVD method or the CVD method, for example, TEOS. It is formed of an oxide film containing (Tetra Ethyl Ortho Silicate) material and silane material. The first insulating film 45 is preferably formed on the back surface of the substrate 12 with a film thickness of, for example, 0 nm or more and 600 nm or less.

0103The second insulating film 46 is formed in the groove 39 and on the back surface of the substrate 12 so as to cover the first insulating film 45, and in the present embodiment, the isotropic film formed by using the ALD method or the CVD method. It is formed of an oxide film, for example, a silicon oxide film or the like. In the present embodiment, the entire groove 39 is embedded by the second insulating film 46. The second insulating film 46 is preferably formed on the back surface of the substrate 12 with a film thickness of, for example, 0 nm or more and 300 nm or less, and the combined film thickness of the first insulating film 45 and the second insulating film 46 is 10 nm. It is formed so as to be 900 nm or more, preferably 50 nm or more and 700 nm or less, and more preferably 100 nm or more and 500 nm or less.

0104Further, the laminated film composed of the first fixed charge film 43, the second fixed charge film 44, the first insulating film 45 and the second insulating film 46 formed on the back surface side of the substrate 12 and the inside of the groove 39 is an antireflection film. It also plays a role. In the present embodiment, the case of forming the two-layer insulating film of the first insulating film 45 and the second insulating film 46 is described, but the present disclosure is not limited to this, and the first and second insulating films are not limited to this. Either 45 or 46 may be formed. Further, although the case where the anisotropic oxide film is formed as the first insulating film 45 and the isotropic oxide film is formed as the second insulating film 46 is described, the opposite case may be used. Further, even if the inner peripheral surface of the groove 39 has a structure in which all or part of the first fixed charge film 43, the second fixed charge film 44, the first insulating film 45, and the second insulating film 46 are laminated. , The structure may be such that none of the above films are laminated.

0105&lt;7. Seventh Embodiment: Solid-state image sensor&gt; Next, the solid-state image sensor according to the seventh embodiment of the present disclosure will be described. Since the overall configuration of the solid-state image sensor of this embodiment is the same as that shown in FIG. 1, the illustration is omitted. FIG. 17 is a cross-sectional configuration diagram of a main part of the solid-state image sensor 47 of the present embodiment. In FIG. 17, the parts corresponding to FIG. 2 are designated by the same reference numerals, and duplicate description will be omitted.

0106The solid-state image sensor 47 of the present embodiment is different from the first embodiment in that the element separation portion 53 has a hollow structure. In the present embodiment, as shown in FIG. 17, the element separating portion 53 includes a fixed charge film 20 and an insulating film 54 formed by sequentially embedding the fixed charge film 20 and the insulating film 54 formed in the groove 39 formed in the depth direction from the back surface side of the substrate 12. A hollow portion (so-called void) 58 is formed inside the groove portion 39.

0107The insulating film 54 is formed so as to cover the fixed charge film 20 formed on the inner wall surface of the groove 39 and the back surface of the substrate 12. Further, in order to form the hollow portion 58 in the groove portion 39, the insulating film 54 is formed with a film thickness that does not completely embed the groove portion 39 inside the groove portion 39, and is formed so as to close the groove portion 39 at the open end of the groove portion 39. ing. The insulating film 54 can be formed of the same material as the material of the insulating film 21 used in the first embodiment.

010818A and 18B show the manufacturing process of the solid-state image sensor 47 of the present embodiment. Since the steps up to the step of forming the groove 39 are the same as those in the first embodiment, duplicate description will be omitted. After forming the groove 39, as shown in FIG. 18A, a fixed charge film is used to cover the inner peripheral surface, the bottom surface of the groove 39, and the back surface of the substrate 12 by using a CVD method, a sputtering method, an ALD method, or the like. 20 is deposited.

0109Next, as shown in FIG. 18B, the insulating film 54 is formed so as to cover the fixed charge film 20 formed on the inner wall surface of the groove 39 and the back surface of the substrate 12 by using a CVD method, a sputtering method, a coating method, or the like. A film is formed. In the film forming step of the insulating film 54, the film forming conditions are set so that the opening end side of the groove 39 is closed before the inside of the groove 39 is completely embedded with the insulating film 54. By optimizing the film forming conditions in this way, it is possible to form the element separation portion 53 having the hollow portion 58 as shown in FIG. 18B.

0110The inside of the hollow portion 58 formed in the element separation portion 53 may be filled with air or may be in a vacuum state. Further, in order to prevent light from being mixed in the portion close to the incident side, it is more preferable that the hollow portion exists from the silicon surface on the back surface (the interface between the substrate 12 and the fixed charge film 20) to the upper part (light incident side).

0111After that, the solid-state image sensor 47 of the present embodiment shown in FIG. 17 is completed by the same process as that of the first embodiment. In the present embodiment, since the refractive index of the hollow portion 58 is 1 and the refractive indexes of the fixed charge film 20 and the insulating film 54 are both 1 or more, light is likely to be reflected at the element separation portion 53 and the optical color is mixed. Can be suppressed. Thereby, in the present embodiment, the optical light-shielding property can be improved in the element separation unit 53. Further, also in this embodiment, the same effect as that in the first embodiment can be obtained.

0112In the present embodiment, the fixed charge film 20 is formed in the element separating portion 53, but the fixed charge film 20 may not be formed. In this case as well, an insulating material having a refractive index of more than 1 is used as the material for forming the insulating film, and the insulating film is formed so as to form a hollow portion inside the groove 39, thereby optically blocking light. It is possible to improve the property and suppress optical color mixing.

0113&lt;8. Eighth embodiment: solid-state image sensor&gt; Next, the solid-state image sensor according to the eighth embodiment of the present disclosure will be described. Since the overall configuration of the solid-state image sensor of this embodiment is the same as that shown in FIG. 1, the illustration is omitted. FIG. 19 is a cross-sectional configuration diagram of a main part of the solid-state image sensor 65 of the present embodiment. In FIG. 19, the parts corresponding to FIG. 2 are designated by the same reference numerals, and duplicate description will be omitted.

0114The solid-state image sensor 65 of the present embodiment is the same as the seventh embodiment in that the element separation unit 66 has a hollow structure, but the film structure of the element separation unit 66 and the film forming method thereof are different. In the present embodiment, as shown in FIG. 19, the element separating portions 66 are formed by sequentially embedding the element separating portions 66 in the groove portions 39 formed in the depth direction from the back surface side of the substrate 12, and the first film 67 and the second film 67 are formed. It has a film 68, and a hollow portion 58 is formed inside the groove portion 39.

0115The first film 67 is formed so as to cover the inner wall surface of the groove 39 and the back surface of the substrate 12, and the second film 68 is laminated on the first film 67 to cover the inner wall surface of the groove 39 and the substrate. It is formed on the back surface of 12. Then, in the groove portion 39, the open end side of the groove portion 39 is closed by the first film 67 and the second film 68 in a state where the hollow portion 58 is formed inside.

0116As will be described later, the first film 67 is formed by an anisotropic film forming method, and is provided so as to narrow the opening diameter on the opening end side of the groove 39. On the other hand, the second film 68 is formed by an isotropic film forming method, and is provided so as to close the open end of the groove 39 narrowed by the first film 67.

0117The first film 67 and the second film 68 can be formed by using, for example, an insulating material such as silicon oxide, silicon nitride, silicon oxynitride, or resin. Further, the first film 67 and the second film 68 may be formed of the same material or may be formed of different materials. When the first film 67 and the second film 68 are formed of different materials, the film stress of the first film 67 is smaller than the film stress of the second film 68, and the first film 67 It is preferable to select each material under the condition that the refractive index of the second film 68 is larger than the refractive index of the second film 68. In this embodiment, as an example, a case where both the first film 67 and the second film 68 are formed of silicon oxide will be described.

011820A and 20B show the manufacturing process of the solid-state image sensor 65 of the present embodiment. Since the steps up to the step of forming the groove 39 are the same as those in the first embodiment, duplicate description will be omitted. After forming the groove 39, as shown in FIG. 20A, a first film 67 made of silicon oxide is formed. The first film 67 is formed by using an anisotropic film forming method, for example, a plasma CVD method or a PVD method.

0119Since the first film 67 is formed anisotropically, the film thickness of the first film 67 on the bottom surface of the groove 39 and the back surface of the substrate 12 is the same as that of the first film 67 on the inner peripheral surface of the groove 39. It becomes thicker than the film thickness. Therefore, as shown in FIG. 20A, the first film 67 has an overhang shape on the open end side of the groove 39 due to the difference in the film formation rate between the back surface of the substrate 12 and the inner peripheral surface of the groove 39. The opening diameter on the opening end side is smaller than the opening diameter on the bottom surface side of the groove 39. Here, the first film 67 is formed with a film thickness that does not completely block the groove 39.

0120Next, as shown in FIG. 20B, a second film 68 made of silicon oxide is formed. The second film 68 is formed by an isotropic method, for example, the ALD method. Since the second film 68 is formed isotropically, the second film 68 is formed on the inner wall surface of the groove 39 and the back surface of the substrate 12 with almost the same film thickness on the upper part of the first film 67. Be filmed.

0121Further, the second film 68 is formed to have a film thickness that closes the groove 39 on the opening end side of the groove 39. In the present embodiment, the opening diameter on the opening end side of the groove 39 is narrower than the opening diameter on the bottom surface side of the groove 39 by the first film 67. Therefore, the second film 68 closes the open end side while maintaining the hollow structure of the groove 39. As a result, the hollow portion 58 is formed in the groove portion 39. Further, even if the first film 67 is replaced with an isotropic film formation and the second film 68 is replaced with an anisotropic film formation, the open end side can be closed while maintaining the hollow structure of the groove 39. Also in this embodiment, in order to prevent light from being mixed in the portion close to the incident side, a hollow portion exists from the silicon surface on the back surface (the interface between the substrate 12 and the first film 67) to the upper part (light incident side). Is more preferable.

0122After that, the solid-state image sensor 65 of the present embodiment shown in FIG. 19 is completed by the same process as that of the first embodiment. Also in this embodiment, since the hollow portion 58 is formed in the element separating portion 66, the same effect as that of the seventh embodiment can be obtained.

0123In the present embodiment, the element separation portion 66 is formed of two layers of the first film 67 and the second film 68, but may be formed of three or more layers if necessary. .. When the element separation portion 66 is formed of two or more films as in the present embodiment, the stress of the material to be formed first is lower than the stress of the material to be formed later. , The stress on the substrate 12 can be suppressed, and the generation of dark current and white spots due to the stress can be suppressed. Further, by setting the refractive index of the material to be formed later to be lower than the refractive index of the material to be formed earlier, it is possible to suppress the optical color mixing.

0124Further, also in the present embodiment, a film having a negative fixed charge (corresponding to the fixed charge film 20 in FIG. 2) may be formed between the first film 67 and the substrate 12. As the fixed charge film, the same material as in the first embodiment can be used.

0125Further, the second film 68 may be formed of a metal material such as tungsten (W), aluminum (Al), titanium (Ti), or an oxide or nitride thereof. When the second film 68 is made of a metal material, it is necessary to remove the metal material film formed on the light incident side of the photoelectric conversion unit 40. Hereinafter, as a modification, a case where the first film 67 is formed of silicon oxide and the second film 68 is formed of a metal material will be described.

0126[8-1 Modification example] FIG. 21 is a cross-sectional configuration diagram of the solid-state image sensor 70 according to the modified example. In FIG. 21, the parts corresponding to FIG. 19 are designated by the same reference numerals, and duplicate description will be omitted. In the solid-state imaging device 70 according to the modified example, the second film 71 constituting the element separation unit 72 is different from the present embodiment.

0127In the modified example, the second film 71 is formed of, for example, tungsten (W) so as to cover the first film 67 in the inner wall surface of the groove 39 and the light-shielding region on the back surface side of the substrate 12. Is formed in. That is, on the back surface side of the substrate 12, the second film 71 is formed in a region corresponding to the position where the light-shielding film 25 is formed, and is provided in a grid pattern so as to open the photoelectric conversion unit 40.

0128Also in the modified example, the second film 71 is formed on the surface of the first film 67 by using an isotropic film forming method as in the present embodiment. Then, on the back surface side of the substrate 12, a light-shielding material layer to be a light-shielding film 25 is formed on the entire upper surface of the second film 71, and then the light-shielding material layer and the second film 71 are simultaneously patterned. The second film 71 on the upper part of the photoelectric conversion unit 40 is removed. After that, the solid-state image sensor 70 shown in FIG. 21 can be manufactured by the same steps as in the first embodiment.

0129As shown in the modified example, when the film formed in the groove 39 is formed by using a metal material, photoelectric conversion is performed by patterning at the same time as the patterning step of the light-shielding film 25 formed on the back surface side of the substrate 12. The metal material on the upper part of part 40 can be removed. Further, in the modified example, the light-shielding film 25 is formed, but if sufficient light-shielding is possible only with the second film 71, the light-shielding film 25 may not be provided separately. In this case, since the number of laminated films formed on the light incident surface side of the substrate 12 can be reduced, the distance between the surface of the on-chip lens 28 and the substrate 12 can be shortened, and the sensitivity can be improved. Can be planned.

0130Further, the solid-state image sensor 70 according to the modified example may also be configured to supply a ground potential or a negative potential to the second film 71 made of a metal material, as in the second embodiment. By supplying a ground potential or a negative potential to the second film 71, the effect of hole pinning on the surface of the element separation portion 72 can be stabilized, and dark current can be suppressed.

0131In the seventh and eighth embodiments, the open end side of the groove 39 is blocked by the film formed in the groove 39, but the film formed on the back surface side of the substrate 12 is hollow in the groove 39. It suffices if the part 58 can be closed. Therefore, the open end side of the groove 39 does not necessarily have to be blocked by the film formed in the groove 39.

0132In the solid-state image sensor according to the first to eighth embodiments described above, the CMOS-type solid-state image sensor has been described as an example, but it can also be applied to the back-illuminated CCD-type solid-state image sensor. Also in this case, the element separating portion for electrically separating the photoelectric conversion portion is formed by embedding an insulating film in the groove formed from the surface opposite to the light incident surface, thereby forming the first to fifth elements described above. An effect similar to the effect in the embodiment can be obtained.

0133Further, in the solid-state image pickup apparatus according to the first to eighth embodiments, the lateral overflow structure is configured to overflow the signal charge overflowing in the floating diffusion portion. However, the present disclosure is not limited to such a configuration, and may be a configuration that overflows into the source / drain region of another pixel transistor. For example, the signal charge overflowing in the region to which the VDD potential is supplied, such as the drain region of the reset transistor, may be overflowed.

0134Further, in the solid-state image pickup apparatus according to the first to eighth embodiments, the configuration when a negative charge (electrons) is used as a signal charge is shown, but also when a positive charge (hole) is used as a signal charge. This disclosure is applicable. When the hole is used as a signal charge, a material having a positive fixed charge may be used as the fixed charge film, and the p-type region and the n-type region in the substrate may be formed in reverse. That is, a material having the same charge as the signal charge as a fixed charge may be used as the fixed charge film.

0135Further, as the element separation portion, a fixed charge film is formed in the groove portion and an insulating film is further embedded, but the configuration of the present disclosure is also valid as a configuration in which only the fixed charge film is embedded in the groove portion. It is also possible to appropriately combine the first to eighth embodiments. Further, in the first to eighth embodiments, the element separation portion is formed in a grid pattern surrounding the photoelectric conversion portion, but the element separation portion does not have to be in a grid pattern, and various configurations are possible.

0136Further, the present disclosure is not limited to application to a solid-state image sensor that detects the distribution of the amount of incident light of visible light and captures it as an image, but is a solid that captures the distribution of the amount of incident light such as infrared rays, X-rays, or particles as an image. It can also be applied to an image sensor. In a broad sense, it can be applied to all solid-state image sensors (physical quantity distribution detection devices) such as fingerprint detection sensors that detect the distribution of other physical quantities such as pressure and capacitance and capture images as images.

0137Further, the present disclosure is not limited to a solid-state image sensor that sequentially scans each unit pixel in the pixel region in line units and reads out a pixel signal from each unit pixel. It is also applicable to an XY address type solid-state image sensor that selects an arbitrary pixel in pixel units and reads a signal from the selected pixel in pixel units. The solid-state image sensor may be formed as a single chip, or may be a modular form having an image pickup function in which a pixel region and a signal processing unit or an optical system are packaged together. Good.

0138Further, the present disclosure is not limited to application to a solid-state image sensor, and is also applicable to an image sensor. Here, the image pickup device refers to a camera system such as a digital still camera or a video camera, or an electronic device having an image pickup function such as a mobile phone. The modular form mounted on the electronic device, that is, the camera module may be used as the image pickup device.

0139&lt;9. Ninth embodiment: electronic device&gt; Next, the electronic device according to the ninth embodiment of the present disclosure will be described. FIG. 22 is a schematic configuration diagram of the electronic device 200 according to the ninth embodiment of the present disclosure.

0140The electronic device 200 according to the present embodiment includes a solid-state image sensor 203, an optical lens 201, a shutter device 202, a drive circuit 205, and a signal processing circuit 204. The electronic device 200 of the present embodiment shows an embodiment when the solid-state image sensor 1 in the first embodiment of the present disclosure described above is used as the electronic device (camera) as the solid-state image sensor 203.

0141The optical lens 201 forms an image light (incident light) from the subject on the image pickup surface of the solid-state image pickup device 203. As a result, the signal charge is accumulated in the solid-state image sensor 203 for a certain period of time. The shutter device 202 controls the light irradiation period and the light blocking period of the solid-state image sensor 203. The drive circuit 205 supplies a drive signal that controls the transfer operation of the solid-state image sensor 203 and the shutter operation of the shutter device 202. The signal transfer of the solid-state image sensor 203 is performed by the drive signal (timing signal) supplied from the drive circuit 205. The signal processing circuit 204 performs various signal processing. The video signal after signal processing is stored in a storage medium such as a memory or output to a monitor.

0142In the electronic device 200 of the present embodiment, the solid-state image sensor 203 suppresses blooming and improves the saturation characteristics, so that the image quality can be improved.

0143The electronic device 200 to which the solid-state imaging device 1 can be applied is not limited to a camera, but can be applied to an imaging device such as a digital still camera and a camera module for mobile devices such as mobile phones.

0144In the present embodiment, as the solid-state image sensor 203, the solid-state image sensor 1 in the first embodiment is used as an electronic device, but the solid-state image sensor manufactured in the second to eighth embodiments described above is used. You can also do it.

0145The present disclosure may also have the following structure. (1) With the board A plurality of photoelectric conversion units formed on the substrate, Have, The plurality of photoelectric conversion units include a first photoelectric conversion unit and a second photoelectric conversion unit. The first photoelectric conversion unit and the second photoelectric conversion unit are formed adjacent to each other. A first groove portion is provided between the first photoelectric conversion unit and the second photoelectric conversion unit. It has a first insulating film having a fixed charge formed so as to cover the inner wall surface of the first groove portion and the light incident surface side of the substrate. In a cross section cut in the light incident direction, a region in contact with the periphery of the first groove portion and a semiconductor region made of a first conductive type are formed on the light incident surface side of the substrate. Solid-state image sensor. (2) In a cross section in a light incident direction, a semiconductor region made of a first conductive type is formed between the first photoelectric conversion portion and the first groove portion. A semiconductor region made of a first conductive type is formed between the second photoelectric conversion portion and the first groove portion in a cross section in a light incident direction. The solid-state image sensor according to (1). (3) The bottom of the first groove is formed so as to be in contact with a semiconductor region made of the first conductive type in a cross section in a light incident direction. The solid-state image sensor according to (1) or (2). (Four) A part of the first groove portion was formed by being embedded in a semiconductor region made of a first conductive type. The solid-state image sensor according to any one of (1) to (3). (Five) The charge storage region of the plurality of photoelectric conversion units is formed by a semiconductor region composed of a second conductive type, which is an opposite conductive type to the first conductive type. The solid-state image sensor according to any one of (1) to (4). (6) A second insulating film was formed so as to cover the first insulating film. The solid-state image sensor according to any one of (1) to (5). (7) The first insulating film was formed containing a hafnium oxide. The solid-state image sensor according to any one of (1) to (6). (8) The second insulating film was formed containing any one of silicon oxide, silicon nitride, and silicon oxynitride. The solid-state image sensor according to (6). (9) The plurality of photoelectric conversion units include a third photoelectric conversion unit. The third photoelectric conversion unit is formed adjacent to the second photoelectric conversion unit. A second groove is provided between the second photoelectric conversion unit and the third photoelectric conversion unit. It has a first insulating film having a fixed charge formed so as to cover the inner wall surface of the second groove portion, and has a fixed electric charge. In the second groove portion, a semiconductor region made of a first conductive type is formed so as to be in contact with the periphery of the second groove portion in a certain cross section cut in the light incident direction. The first groove and the second groove were formed at different depths in the light incident direction. The solid-state image sensor according to any one of (1) to (8). (Ten) An interlayer insulating film and a plurality of wiring layers were formed on the side of the substrate opposite to the light incident surface. The solid-state image sensor according to any one of (1) to (9). (11) The interlayer insulating film and the plurality of wiring layers were formed on the side opposite to the light incident surface of the substrate with respect to the plurality of photoelectric conversion portions. The solid-state image sensor according to (10). (12) A pixel transistor was formed on the side of the substrate opposite to the light incident surface. The solid-state image sensor according to (10) or (11). (13) The pixel transistor was formed in a region overlapping the first groove portion in the light incident direction. The solid-state image sensor according to (12). (14) The second groove is formed to a depth that reaches the interlayer insulating film. The solid-state image sensor according to any one of (10) to (13). (15) A light-shielding film was formed above the light incident surface side of the first groove. The solid-state image sensor according to any one of (1) to (14). (16) A floating diffusion was formed below the light incident surface of the first groove on the opposite side. The solid-state image sensor according to any one of (1) to (15). (17) The first insulating film was formed on the light incident surface side of the first photoelectric conversion unit and the second photoelectric conversion unit. The solid-state image sensor according to any one of (1) to (16). (18) The second insulating film was formed by being embedded in the first groove. The solid-state image sensor according to any one of (6) to (17). (19) A third insulating film was formed on the light incident surface side of the substrate. The solid-state image sensor according to any one of (1) to (18). (20) With an optical lens The solid-state image sensor according to any one of (1) to (19) and A signal processing circuit that processes the output signal output from the solid-state image sensor, and Electronic equipment including.

01461, 52, 55, 57, 64 ... Solid-state imaging device, 2 ... Pixels, 3 ... Pixel region, 4 ... Vertical drive circuit, 5 ... Column signal processing circuit, 6 ... Horizontal drive circuit, 7 ... output circuit, 8 ... control circuit, 10 ... horizontal signal line, 11, 12 ... board, 13 ... wiring layer, 14 ... interlayer insulating film, 15 Wiring, 16 Transfer gate electrode, 17 Gate insulating film, 18 Pixel separation layer, 19 Element separation part, 20 Fixed charge film, 21 Insulation Film, 22 ... n-type semiconductor region, 23, 24 ... p-type semiconductor region, 25 ... light-shielding film, 26 ... flattening film, 27 ... color filter layer, 28 ... on Chip lens, 29 ... p-well layer, 30 ... floating diffusion part, 31 ... support substrate, 32 ... reset gate electrode, 33 ... amplification gate electrode, 34 ... selective gate electrode , 35, 36, 37 ... source / drain region, 39, 60 ... groove, 40 ... photoelectric conversion, 48 ... insulating film, 49 ... element separation, 50 ... shading Layer, 51 ... n-type semiconductor region, 51 ... light-shielding material layer, 52 ... solid-state imaging device, 200 ... electronic device, 201 ... optical lens, 202 ... shutter device, 203 ... Solid-state imaging device, 204 Signal processing circuit, 205 Drive circuit