Plasma processing method and manufacturing method of electronic device

The present invention relates to a plasma processing method for processing an object to be processed such as a semiconductor substrate and a liquid crystal display substrate by oxidation, nitriding, oxynitriding, etc., and a manufacturing method for manufacturing an electronic device such as a semiconductor device using the plasma processing method. ..

As a conventional plasma processing apparatus, an apparatus as described in Patent Document 1 is used. As described in Patent Document 1, the plasma processing apparatus includes a radial line slot antenna that emits microwaves in a processing chamber, a slow-phase plate that compresses the wavelength of microwaves emitted from the antenna, and the slow-phase plate. It is composed of a cover plate arranged at intervals with respect to the cover plate and a dielectric material placed directly under the cover plate. Further, at the lower part of the dielectric, structures provided with a large number of gas outlets are arranged at intervals.

Gas for plasma generation is supplied to the vacuum vessel, and when microwaves are applied from the antenna in this state, high-density plasma is generated in the space between the dielectric and the structure. The plasma device is guided to a processing space for processing a semiconductor wafer via a structure. In such a configuration, the processing gas discharged from the gas outlet of the structure is excited by the high-density plasma formed in the lower part of the dielectric.

In this case, the flange constituting the processing container is formed with a plasma gas supply passage communicating with the plasma gas supply port provided on the outer wall of the processing chamber, and plasma excitation of Ar, Kr, etc. is formed from the plasma gas supply port. Gas is supplied to the supply passage in the flange. Further, the excitation gas is introduced into the treatment chamber through the supply passage and the gas discharge port of the flange.

In the plasma processing apparatus provided with the above-mentioned radial line slot antenna, a uniform high-density plasma is formed in the space directly under the dielectric.

<patcit num="1"><text>Japanese Unexamined Patent Publication No. 2001-500327</text></patcit>

<p> Conventionally, the oxynitriding treatment of a substrate is performed at a high temperature of 600 ° C to 800 ° C, but it is known that the dopant is re-diffused due to this high temperature treatment.</p><p> Therefore, as is known in Japanese Patent Application Laid-Open No. 2000-294550, there is a plasma nitriding treatment that promotes oxynitriding by plasma at a low temperature in order to prevent rediffusion. However, at the same time, it is known that the plasma treatment causes damage to the object to be treated.</p><p> According to the experiments of the present inventors, it has been found that the leakage current increases on the low electric field side by introducing the oxynitriding process gas inside in the plasma nitriding treatment.</p><p> An object of the present invention is to investigate the causes of various defects associated with the above-mentioned oxynitriding treatment and to provide a method capable of alleviating these defects.</p><p> A specific object of the present invention is to provide a plasma process capable of achieving high quality oxynitriding.</p><p> As a result of investigating the cause of the above-mentioned defect, the present inventor promotes excessive dissociation by introducing nitrous oxide into the plasma, and N2 ions are generated to damage the formed oxynitride film. A problem was found that gave it.</p><p> From this, the present invention proposes a manufacturing method using a plasma processing apparatus that reduces the generation of ions that damage the insulating film and enables uniform and efficient supply of oxynitride species into the plane of the substrate to be processed. To do.</p>

<p> According to the uniform state of the present invention, when nitrous oxide is used as the oxynitriding process gas, the electron temperature in the plasma in the conventional plasma process is about 3.0 eV. On the other hand, in nitrous oxide, the binding energy between the nitrogen molecule and the oxygen atom is about 2.24 eV.</p><p> Therefore, if nitrous oxide is introduced into a plasma having an electron temperature lower than the binding energy of nitrous oxide, it is possible to reduce excessive dissociation.</p><p> Further, not limited to nitrous oxide, it is possible to reduce the generation of N2 ions and improve the characteristics of the oxynitriding film by suppressing excessive dissociation in other oxynitriding process gases such as ammonia. ..</p><p> According to the uniform state of the present invention, in a plasma processing method in which plasma is generated using a gas for exciting plasma and a processing gas is introduced into the plasma to process an object to be processed, the processing gas is subordinate. A plasma treatment method comprising nitrogen oxide gas and introducing the nitrous oxide gas into a plasma having an electron temperature of less than 2.24 eV can be obtained.</p><p> In the plasma treatment method, for example, the plasma excitation gas is introduced from the upper shower plate into the treatment chamber, the plasma is generated at the lower part of the upper shower plate, and the plasma is provided at the lower part of the upper shower plate. In a plasma with an electron temperature of less than 2.24 eV, the nitrous oxide gas is introduced from the lower shower plate into the plasma below the lower shower plate so as to pass through the lower shower plate and reach the untreated product. The treatment using the above-mentioned nitrous oxide gas becomes possible.</p><p> In the present invention, it is possible to obtain a method for manufacturing an electronic device, which comprises a step of performing acid nitriding treatment of an object to be treated by using the above plasma treatment method.</p><p> Further, a manufacturing method for manufacturing a semiconductor device, a liquid crystal display device, or an organic EL display device product, which is characterized in that plasma treatment is performed using these plasma treatment methods, can be obtained.</p>

<p> As described above, according to the present invention, it has become possible to suppress the generation of ions that damage the oxynitride film by suppressing dissociation. In addition, it has become possible to efficiently generate oxynitride species.</p><p> The present invention is particularly effective for oxynitriding using nitrous oxide, and enables the formation of a high-quality oxynitriding film. However, the film is not limited to this nitrous oxide, and a high-quality oxynitriding film can be formed by suppressing dissociation in other oxynitriding processes such as ammonia.</p><p> In the present invention, it has been found that the leakage current can be reduced by forming a high-quality oxynitride film, which is extremely effective in improving the holding characteristics of a memory or the like.</p>

FIG. 1 is a side sectional view of a plasma process apparatus according to an embodiment of the present invention. The plasma process apparatus according to the embodiment includes a vacuum vessel 101, a dielectric 102, a gas supply port 103 for plasma excitation, a gas introduction path 104 for plasma excitation, a gas discharge port 105 for plasma excitation, an O-ring 106, 107, 108, and a radial line. It has a slot antenna 109, a grid-like shower plate 110, a process gas supply port 111, a process gas discharge port 112, a stage 113, and an exhaust port 114. The plasma-treated substrate 115 is placed on the stage 113. Further, the stage 113 has a heating mechanism in order to raise the substrate temperature.

A radial line slot antenna 109 that radiates microwaves for plasma excitation is installed on the surface of the dielectric 102 opposite to the vacuum vessel 101. In the radial line slot antenna 109, a slow waveguide 120 made of alumina is sandwiched between a 0.3 mm thick copper plate and an aluminum plate 121 in which a large number of slits 119 are opened, and a coaxial guide for supplying microwaves to the center. The structure is such that the waveguide 116 is arranged. The 2.45 GHz microwave generated from the microwave power supply (not shown) is supplied to the coaxial waveguide 116 via an isolator / matching device (neither is shown), and 120 in the slow wave plate is supplied from the center. Microwaves are radiated to the dielectric 102 side substantially uniformly from the early slit 119 toward the periphery. The radiated microwave is introduced into the processing chamber 117 via the dielectric 102, and a high-density plasma is generated by ionizing the plasma excitation gas.

In this embodiment, the vacuum vessel 101 is made of aluminum and the dielectric 102 is made of aluminum nitride. The frequency of the plasma excitation microwave is 2.45 GHz. The substrate 115 is a silicon substrate having a diameter of 200 mm. Microwaves emitted from the radial line slot antenna 109 installed in the atmosphere pass through the plasma excitation gas discharge port 105 and are introduced into the vacuum vessel 101, and ionize the gas in the vacuum vessel 101 to generate plasma. Generate.

This device has a structure that allows plasma excitation gas and process gas to be discharged from different inlets. The plasma excitation gas is discharged into the vacuum vessel 101 by the plasma excitation gas discharge port 105. On the other hand, the process gas is supplied from the process gas supply port 111, passes through the inside of the grid-like shower plate 110, and is discharged from the plurality of process gas discharge ports 112 to the substrate 115 side.

In the illustrated plasma processing apparatus, a grid-like shower plate 110 is arranged in the processing chamber 101 between the dielectric 102 and the substrate 115 to be processed. The lattice-shaped shower plate 110 is formed with a large number of process gas outlets 112 for supplying processing gas from an external processing gas source through a processing gas passage 118 formed in the processing chamber. Each of the process gas discharge ports 112 of the grid-like shower plate 110 discharges the supplied processing gas into the space between the grid-like shower plate 110 and the substrate 115 to be treated. The lattice-shaped shower plate 110 is formed with an opening having a size that allows the plasma formed in the space 117 to efficiently pass through by diffusion between the adjacent process gas discharge port 112.

In such a structure, when the plasma excitation gas is discharged into the vacuum vessel 101 from the plasma excitation gas discharge port 105, the discharged plasma excitation gas is excited by the high-density plasma formed in the space. However, the plasma excitation gas from the plasma excitation gas discharge port 105 is between the lattice-like shower plate 110 and the substrate 115 to be processed from the space between the plasma excitation gas discharge port 105 and the lattice-shaped shower plate 110. Since the processing gas flows toward the space, there are few components for the processing gas to return to the space between the plasma excitation gas outlet 105 and the latticed shower plate 110, and the decomposition of gas molecules due to excessive dissociation due to exposure to high-density plasma is carried out. Since there are few, high quality substrate processing is possible.

An experiment was conducted in which a silicon substrate was nitrided using the plasma process apparatus shown in Fig. 1. Kr gas and O2 gas are introduced into the vacuum vessel for plasma excitation from the plasma excitation gas outlet 105, and nitrous oxide gas is introduced into the vacuum vessel 101 from the lattice-shaped shower plate 110, and the output is 2.0 kW and the frequency is 2.45. Plasma was generated at GHz. The pressure inside the vacuum vessel 101 is about 5 Pa (0.04 Torr), and the flow rates are all 100 cc. Figure 2 shows the measurements of NO radicals and N2O radicals in the plasma state in this process. In the conventional configuration, the generation of NO radicals and N2O radicals that contribute to oxynitriding was hardly detected. This is because the nitrous oxide gas is excessively dissociated in the plasma due to the excitation of the plasma, and N2 and O2 are generated. As shown in Fig. 3, it is clear that most of the nitrous oxide gas is dissociated into N2 and O2 even in the actual plasma emission measurement.

On the other hand, in the present invention, by introducing nitrous oxide from the grid-like shower plate 110, N2O radicals and NO radicals which are oxynitride species can be confirmed. This is because, unlike the conventional configuration, the lattice-shaped shower plate 110 and the substrate to be processed 115 form a plasma diffusion region, so that the electron temperature is very low and excessive dissociation is suppressed.

Here, according to the measurement, it has been found in the prior art that the electron temperature between the dielectric and the substrate to be processed is about 3.0 eV when plasma is generated in the vacuum vessel. On the other hand, when plasma is generated using a grid-like shower plate that emits process gas, it has been found that the electron temperature in the space between the substrate and the substrate to be processed is about 1.0 eV. In nitrous oxide, the binding energy of the nitrogen molecule and the oxygen atom is about 2.24 eV, so that excessive dissociation can be suppressed by introducing the process gas from the process gas outlet of the lattice-shaped shower plate.

Along with this, the generation of N2 and O2 due to the excessive dissociation of nitrous oxide gas is suppressed, and NO radicals and N2O radicals that contribute to oxynitriding can be efficiently generated. This is because, as shown in FIG. 4, in the Fourier transform infrared spectrophotometer, the introduction of nitrous oxide gas is dissociated by almost 99% with respect to 100 cc in the conventional technique, but in the present invention, the dissociation rate is It is 96%, and it can be seen that there is a difference of about 4 times in the undissociated nitrous oxide gas existing in the plasma. This indicates that dissociation is suppressed and NO radicals and N2O radicals are likely to be generated.

Next, as shown in FIG. 5, the substrate was nitrided using the plasma processing apparatus of FIG. 1, and its electrical characteristics were measured. In the present invention, it has been found that the leakage current density of the oxynitriding film is low, especially in an electric field of 6.5 MV / cm2 or less. This is because N2 ions are generated in association with the generation of N2 in the substrate treatment of the prior art, and these ions reach the substrate during the treatment, causing deterioration of the film quality.

However, by processing the substrate according to the present invention, the generation of N2 due to excessive dissociation is suppressed, so that the generation of N2 ions can be suppressed accordingly, and the deterioration of the substrate during processing can be reduced. It has become possible.

On the other hand, the same experiment was conducted for nitric oxide using the same equipment as this configuration. As shown in Fig. 6, measurements were performed on NO radicals and N2O radicals in the plasma under the same conditions as nitrous oxide.

In the case of nitric oxide as well, it was found that by introducing gas from the grid-like shower plate, both were reduced as compared with the prior art. This is because the binding energy of oxygen molecule and nitrogen molecule is 6.46 eV in nitric oxide, so it can be seen that excessive dissociation does not occur in plasma even in the prior art. However, by further changing the introduction of oxygen gas to a grid-like shower plate, the generation of N2O radicals can be suppressed and almost only NO radicals can be selectively generated. This is known to be effective in forming a homogeneous oxynitride film because NO radicals have the same number of oxygen atoms and nitrogen molecules.

Reducing the leakage current value in these low electric field regions is very effective in improving the holding characteristics of the memory and the like.

7 to 12 are process cross-sectional views for explaining a method of manufacturing a cell transistor in a flash memory device.

FIG. 7 is a cross-sectional view of a P-type Si substrate whose elements are separated by STI. For example, a tunnel insulating film having a film thickness of 7 nm is formed by the oxynitride film forming method of the present invention. At this time, for example, Kr / O2 mixed gas is introduced into the plasma excitation region (electron temperature of about 7 eV) in the chamber by 1000 sccm / 30 sccm, respectively, and N2O or N2O or N2O or NO and NH3 gases are introduced, and a microwave-excited plasma is generated at a pressure of 133 Pa (1 torr) in the chamber to form an insulating film. The insulating film formed by the present invention has a characteristic that nitrogen is localized at the insulating film / silicon interface and the insulating film surface, and this nitrogen is an insulating film generated when electric charges are tunneled in the insulating film. It has the effect of suppressing the deterioration of the electric charge. Then, a 90 nm polycrystalline silicon film is formed on the entire surface of the substrate by using the CVD method. Further, the insulating film to be formed on the polycrystalline silicon film is formed by the oxynitride film forming method of the present invention. At this time, the insulating film is formed by using the oxynitriding method described above. Since the present invention can form an insulating film by a low temperature process of 400 ° C. or less, the insulating film can be formed without changing the surface state of the polycrystalline polysilicon film. Then, a second layer polycrystalline polysilicon film is formed at 150 nm by the CVD method.

Next, an interlayer insulating film is formed on the entire surface of the substrate, contact holes connecting to the source / drain region are opened, and then these contact holes are embedded with, for example, tungsten (FIG. 12). Then, after forming the wiring layer to be connected to the tungsten plug, a surface protective film is formed on the entire surface of the substrate.

13 to 18 are process cross-sectional views for explaining a method of manufacturing a cell transistor in a flash memory device.

FIG. 13 is a cross-sectional view of a P-type Si substrate whose elements are separated by STI. For example, a tunnel insulating film with a film thickness of 7 nm is formed in two stages. In this two-step forming method, an oxide film formed by, for example, a thermal oxidation method at 900 ° C or, for example, a microwave-excited plasma using a Kr / O2 mixed gas is formed at 6.5 nm, and then the oxynitride film of the present invention is formed. An oxynitride film of 0.5 nm is formed by the forming method.

In the formation of the oxynitride film of the present invention, for example, Kr / O2 mixed gas is introduced into the plasma excitation region (electron temperature of about 3 eV) in the chamber by 1000 sccm / 30 sccm, respectively, and the lattice is formed in the plasma diffusion region (electron temperature of about 1.0 eV). N2O or NO, NO gas is introduced using a state shower plate, and microwave excited plasma is generated at a pressure of 133 Pa (1 torr) in the chamber to form an insulating film.

The insulating film formed in these two steps has a feature that the nitrogen concentration can be arbitrarily controlled at the insulating film / silicon interface and the insulating film surface depending on the formation conditions of the oxynitride film. By performing oxynitriding according to the present invention after forming a thermal oxide film or a plasma oxide film, which is a conventional technique, it is possible to mix nitrogen at the interface at a low temperature without damaging the insulating film.

The nitrogen at the interface of the insulating film has an effect of suppressing the deterioration of the insulating film that occurs when the electric charge tunnels in the insulating film. Then, a 90 nm polycrystalline silicon film is formed on the entire surface of the substrate by using the CVD method. Further, in the present invention in which the insulating film to be formed on the polycrystalline silicon film is formed by the oxynitride film forming method described above, the insulating film can be formed by a low temperature process of 400 ° C. or less. Therefore, the insulating film can be formed without changing the surface state of the polycrystalline polysilicon film.

Next, an interlayer insulating film is formed on the entire surface of the substrate, contact holes connecting to the source / drain region are opened, and then these contact holes are embedded with, for example, tungsten (FIG. 18). Then, after forming the wiring layer to be connected to the tungsten plug, a surface protective film is formed on the entire surface of the substrate.

As described above, in the examples of the present application, by using the plasma treatment method of the present invention, a method for manufacturing an electronic device having an oxynitride film uniformly and efficiently can be obtained.

<figref num="1">It is sectional drawing of the plasma process apparatus in embodiment of this invention.</figref><figref num="2">It is a measurement result of radical in the embodiment of this invention.</figref><figref num="3">This is the spectrum according to the embodiment of the present invention.</figref><figref num="4">This is the spectrum according to the embodiment of the present invention.</figref><figref num="5">It is a leak current measurement result in embodiment of this invention.</figref><figref num="6">It is a measurement result of radical in the embodiment of this invention.</figref><figref num="7">It is sectional drawing of the device in Example 1 of this invention.</figref><figref num="8">It is sectional drawing of the device in Example 1 of this invention.</figref><figref num="9">It is sectional drawing of the device in Example 1 of this invention.</figref><figref num="10">It is sectional drawing of the device in Example 1 of this invention.</figref><figref num="11">It is sectional drawing of the device in Example 1 of this invention.</figref><figref num="12">It is sectional drawing of the device in Example 1 of this invention.</figref><figref num="13">It is sectional drawing of the device in Example 2 of this invention.</figref><figref num="14">It is sectional drawing of the device in Example 2 of this invention.</figref><figref num="15">It is sectional drawing of the device in Example 2 of this invention.</figref><figref num="16">It is sectional drawing of the device in Example 2 of this invention.</figref><figref num="17">It is sectional drawing of the device in Example 2 of this invention.</figref><figref num="18">It is sectional drawing of the device in Example 2 of this invention.</figref>

Code description

101: Vacuum vessel 102: Dioxide 103: Plasma excitation gas supply port 104: Plasma excitation gas introduction path 105: Plasma excitation gas discharge port 106, 107, 108: O ring 109: Radical line slot antenna 110: Lattice shower plate 111: Process gas supply port 112: Process gas discharge port 113: Stage 114: Exhaust port 115: Substrate 116: Coaxial waveguide 117: Processing chamber 118: Processing gas passage 119: Slit 120: Slow wave plate 121: Plate