Image sensor and manufacturing method of image sensor

Image sensor and manufacturing method of image sensor

<p>Embodiments relate to image sensors and methods of manufacturing the image sensors.</p>

<p>An image sensor is a semiconductor device that converts an optical image into an electrical signal, and is largely a charge coupled device (CCD) and a CMOS (Complementary Metal Oxide Silicon) image sensor. sensor).</p><p>The CMOS image sensor uses a CMOS technology that uses a control circuit and a signal processing circuit as peripheral circuits to form MOS transistors corresponding to the number of unit pixels on a semiconductor substrate, thereby increasing the output of each unit pixel by the MOS transistors. It is a device employing a switching method that detects sequentially.</p><p>1 is a top plan view showing the structure of a CMOS image sensor, and FIG. 2 is a side cross-sectional view showing the structure of the CMOS image sensor.</p><p>1 and 2 , the image sensor is largely divided into a photodiode region 12 and a transistor region A. The transistor region A shows only a transfer transistor among a plurality of transistors, and the gate 14 , a gate insulating film 15 and a spacer 16 .</p><p>In addition, the photodiode 12 and the ion implantation layer 13 for converting light incident from the outside into an electric signal are formed in the active region of the substrate 10 defined by the device isolation region 11 . A floating diffusion layer 17 is formed on the other side of the transistor A in which the photodiode 12 is not formed.</p><p>The electric signal generated by the photodiode 12 is transferred to the floating diffusion layer 17 through the channel region under the gate 14, and the floating diffusion layer 17 transmits the electric signal to the following transistors. Before receiving the next signal, it is switched to the initialization state to minimize unnecessary signals generated by the photodiode 12 .</p><p>However, the floating diffusion layer 17 is adjacent to the substrate 10 and the device isolation region 11 , and is influenced by defects formed on the surfaces of the substrate 10 and the device isolation region 11 . As a result, leakage current or unnecessary signals are generated in the floating diffusion layer 17 , thereby deteriorating the operational reliability of the image sensor.</p>

<solutionproblem><p>The embodiment provides an image sensor and a method of manufacturing an image sensor capable of improving the current characteristics of a photodiode and securing operational reliability by preventing unnecessary signals from being generated in the floating diffusion layer due to the influence of surface defects in the substrate or device isolation region provides</p></solutionproblem><meansproblemsolution><p>An image sensor according to an embodiment includes a semiconductor substrate on which an isolation region is formed; a gate insulating film formed on the semiconductor substrate to a predetermined depth; a gate formed on the gate insulating layer and formed from the inside of the semiconductor substrate to the surface of the substrate; a photodiode formed on the semiconductor substrate at one side of the gate; and a floating diffusion layer formed on the semiconductor substrate at the other side of the gate and spaced apart from the surface of the semiconductor substrate and formed inside the semiconductor substrate.</p><p>According to an embodiment, a method of manufacturing an image sensor includes forming a trench in a semiconductor substrate in which an isolation region is formed, and forming the gate insulating layer on the semiconductor substrate under the trench; forming a gate to be exposed from above the gate insulating layer to a surface of the semiconductor substrate; forming a photodiode on the semiconductor substrate at one side of the gate; and forming a floating diffusion layer on the semiconductor substrate at the other side of the gate, wherein the floating diffusion layer is spaced apart from a surface of the semiconductor substrate and formed inside the semiconductor substrate.</p></meansproblemsolution><effectiveness><p>According to the embodiment, the following effects are obtained.</p><p>First, by forming the floating diffusion layer inside the substrate and spaced apart from each other, the influence generated from the surface defects of the substrate and the device isolation region can be minimized.</p><p>Second, since the influence of surface defects of the substrate and the device isolation region can be minimized, it is possible to suppress the occurrence of leakage current and unnecessary signals in the floating diffusion layer, and it is possible to improve the operational reliability of the image sensor.</p></effectiveness>

<p>An image sensor and a method of manufacturing the image sensor according to an embodiment will be described in detail with reference to the accompanying drawings.</p><p>Hereinafter, in describing the embodiments, it is determined that detailed descriptions of related well-known functions or configurations may unnecessarily obscure the gist of the present invention, so only key components directly related to the technical idea of the present invention will be mentioned. .</p><p>In the description of the embodiment according to the present invention, each layer (film), region, pattern or structure is "on" or "under" the substrate, each layer (film), region, pad or patterns. )", "on" and "under" include both "directly" or "indirectly" formed through another layer. do. In addition, the reference for the upper / upper or lower of each layer will be described with reference to the drawings.</p><p>3 is a side cross-sectional view schematically illustrating components of an image sensor according to an embodiment.</p><p>Referring to FIG. 3 , the image sensor according to the embodiment includes an isolation region 110 defining an active region, a photodiode 120 , an ion implantation layer 122 formed on the photodiode 120 , and a gate 132 . , a gate insulating layer 131 , a spacer 133 , and a floating diffusion layer 140 .</p><p>The gate 132 , the gate insulating layer 131 , and the spacer 133 constitute a transfer transistor Tx for accumulating the electrical signal generated by the photodiode 120 in the floating diffusion layer 140 . A reset transistor Rx for applying power to the floating diffusion layer 140, a gate potential changes as an electrical signal is stored in the floating diffusion layer FD, and an access transistor Ax and an access transistor Ax for applying an electrical signal ), a selector transistor Sx for outputting the applied electrical signal may be further formed.</p><p>In this case, the reset transistor Rx, the access transistor Ax, and the selector transistor Sx may be connected to the floating diffusion layer 140 in a vertical direction passing through the drawing.</p><p>The select transistor Sx, the access transistor Ax, the transfer transistor Tx, and the reset transistor Rx have substantially the same configuration. is described as an example.</p><p>According to this embodiment, the floating diffusion layer 140 is formed deep inside the substrate 100 so as to be spaced apart from the surfaces of the substrate 100 and the device isolation region 110, and thus the substrate 100 and It is possible to minimize the influence from the surface defects of the device isolation region 110 .</p><p>4 is a side cross-sectional view showing the shape of the image sensor after the first photoresist pattern 151 is formed according to the embodiment.</p><p>A trench is formed in the semiconductor substrate 100 and an oxide is buried in the trench to form a plurality of isolation regions 110 .</p><p>Next, as shown in FIG. 4 , a first photoresist pattern 151 is formed on the semiconductor substrate 100 on which the device isolation region 110 is formed, and the first photoresist pattern 151 is applied as an etch mask. The trench T1 is formed by performing an etching process using</p><p>When the trench T1 is formed, an insulating layer is stacked on the bottom of the trench T1 to form the gate insulating layer 131 .</p><p>Thereafter, the first photoresist pattern 151 is removed.</p><p>5 is a side cross-sectional view illustrating the shape of the image sensor after the second photoresist pattern 152 is formed according to the embodiment.</p><p>After the first photoresist pattern 151 is removed, a polysilicon layer 132a is formed on the semiconductor substrate 100 by filling the trench T1, and the polysilicon layer 132a is formed on the polysilicon layer 132a. 2 A photoresist pattern 152 is formed.</p><p>The second photoresist pattern 152 is formed at a position corresponding to the trench T1 .</p><p>6 is a side cross-sectional view showing the shape of the image sensor after the third photoresist pattern 153 is formed according to the embodiment.</p><p>Next, the polysilicon layer 132a is etched using the second photoresist pattern 152 as an etch mask to form a gate 132 as shown in FIG. 6 .</p><p>Thereafter, the second photoresist pattern 152 is removed.</p><p>When the gate 132 is formed, a third photoresist pattern 153 is formed from the device isolation region 110 formed on one side of the gate 132 to the gate 132 , and the third photoresist pattern is applied thereto. The photodiode 120 is formed by doping the semiconductor substrate 100 with an N-type conductive impurity at a low concentration using an ion implantation mask.</p><p>Next, the ion implantation layer 122 is formed by doping a P-type conductive impurity on the surface of the semiconductor substrate 100 using the third photoresist pattern 153 as an ion implantation mask.</p><p>Thereafter, the third photoresist pattern 153 is removed.</p><p>7 is a side cross-sectional view showing the shape of the image sensor after the fourth photoresist pattern 154 is formed according to the embodiment.</p><p>After the third photoresist pattern 153 is removed, spacers 133 are formed on both sidewalls of the gate 132 , and the gate ( 132) to cover the ion implantation layer 122, a fourth photoresist pattern 154 is formed.</p><p>Next, the floating diffusion layer 140 is formed by implanting P-type impurity ions, for example, P+-type ions, using the fourth photoresist pattern 154 as an ion implantation mask.</p><p>At this time, by increasing the ion implantation energy by 2 to 3 times as compared to the conventional case in which the floating diffusion layer is formed on the surface of the semiconductor substrate, the floating diffusion layer 140 is formed deeply and spaced apart from the surface of the semiconductor substrate 100 . can be</p><p>For example, when an ion implantation energy of 40 keV to 60 KeV is supplied, the floating diffusion layer 140 may be formed to a depth near the bottom surface of the gate 132 .</p><p>Thereafter, although not shown in the drawings, one or more interlayer insulating layers including a contact plug and a metal wiring are formed on the semiconductor substrate 100 including the ion implantation layer 122 and the gate 132 .</p><p>In addition, a color filter layer and a protective layer are sequentially formed on the interlayer insulating layer, and a micro lens is formed on the protective layer perpendicular to the photodiode 120 , thereby completing the image sensor according to the embodiment.</p><p>According to this embodiment, since the electric signal generated by the photodiode 120 is transferred to the floating diffusion layer 140 through the gate 132 from a deep part of the substrate unlike the conventional one, the semiconductor substrate 100 ), an electron movement path spaced apart from the interface of the device isolation region 110 is formed, thus preventing unnecessary signals or leakage currents from being generated in the floating diffusion layer 140 .</p><p>In the above, the present invention has been mainly described with respect to the preferred embodiments thereof, but this is merely an example and does not limit the present invention, and those of ordinary skill in the art to which the present invention pertains within a range that does not deviate from the essential characteristics of the present invention It can be seen that various modifications and applications not exemplified above are possible. For example, each component specifically shown in the embodiment of the present invention can be implemented by modification. And the differences related to these modifications and applications should be construed as being included in the scope of the present invention defined in the appended claims.</p>