JP2006324387A - Plasma processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma CVD apparatus which can manufacture various types of thin films of high quality. <P>SOLUTION: The plasma CVD apparatus 1 comprises a processing chamber 11, wherein a processed substrate 10 is set up, a gas supply 16a, a gas pressure controller 16b, and a plasma discharge generator 13 which is so arranged as to face the processed substrate 10. The plasma discharge generator 13 includes an anode electrode 19, a first cathode electrode 20a, and a second cathode electrode 20b. The anode electrode 19, the first cathode electrode 20a, and the second cathode electrode 20b are so arranged such that the distance between the anode electrode 19 and the first cathode electrode 20a, and the distance between the anode electrode 19 and the second cathode electrode 20b are different, and according to the gas pressure, plasma can be generated between the anode electrode 19 and the first cathode electrode 20a and/or between the anode electrode 19 and the second cathode electrode 20b. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plasma processing apparatus. Specifically, the present invention relates to an apparatus for manufacturing a thin film transistor (TFT) substrate used for a display device.

  Conventionally, a plasma-excited chemical vapor deposition method (hereinafter abbreviated as a plasma CVD method) is known as a method for forming a semiconductor film or the like using plasma. An example of a plasma process apparatus for forming a film on a substrate to be processed by plasma CVD is a parallel plate type apparatus. Hereinafter, a conventional parallel plate type plasma processing apparatus will be described with reference to FIGS.

  FIG. 13 is a schematic perspective view showing a main part of a conventional parallel plate type plasma processing apparatus 100.

  FIG. 14 is a cross-sectional view showing a parallel plate type plasma processing apparatus 100 during film formation.

  The parallel plate type plasma processing apparatus 100 includes a processing chamber 105, which is a vacuum vessel, and a cathode electrode 102a (discharge electrode) and an anode electrode 102b arranged in parallel inside the processing chamber 105.

  The cathode electrode 102 a is fixedly supported on an electrode support portion 122 provided in the processing chamber 105. The anode electrode 102b is provided above the cathode electrode 102a. A power supply circuit 101 that applies a voltage for generating plasma 111 is connected to the cathode electrode 102a. As the power supply circuit 101, high-frequency electrical energy having a normal frequency of, for example, 13.56 MHz is generally used. On the other hand, the anode electrode 102b is electrically grounded.

  A substrate 104 to be processed such as silicon or glass, which is a processing target, is mounted on the lower surface of the anode electrode 102b. A plurality of gas introduction holes 106 are formed in the cathode electrode 102a. The material gas supplied from the gas supply unit 113 is supplied to the space between the cathode electrode 102a and the anode electrode 102b via the gas introduction hole 106. A vacuum pump 110 is connected to the processing chamber 105.

  When a predetermined voltage is applied to the cathode electrode 102a by the power supply circuit 101, an electric field is generated between the electrodes 102a and 102b. Plasma 111 which is a glow discharge phenomenon is generated by the dielectric breakdown phenomenon of the generated electric field. A portion where a relatively large electric field is formed in the vicinity of the cathode electrode 102a is referred to as a cathode sheath portion. At the cathode sheath part or in the vicinity thereof, electrons in the plasma 111 are accelerated, and radicals are generated by promoting dissociation of the material gas supplied from the gas supply part 113. As shown by an arrow R in FIG. 14, the radicals are diffused toward the substrate to be processed 104 attached to the anode electrode 102 b at the ground potential and deposited on the surface of the substrate to be processed 104 to form a film.

  During film formation, the inside of the processing chamber 105 is depressurized by the vacuum pump 110. An electric field having a certain level is also formed in the vicinity of the anode electrode 102b. The vicinity thereof is called an anode sheath portion.

For example, when amorphous silicon (a-Si) is formed on the surface of the substrate to be processed 104, SiH ₄ gas can be used as a material gas. Then, radicals containing Si such as SiH ₃ radicals are generated by glow discharge plasma. An amorphous silicon thin film is formed on the substrate to be processed 104 by the generated radicals.

  As described above, the parallel plate type plasma process apparatus is excellent in simplicity and operability, and thus is preferably used for manufacturing various electronic devices such as integrated circuits, liquid crystal displays, organic electroluminescence elements, and solar cells. It has been. For example, in a manufacturing process of an active drive type liquid crystal display, a thin film transistor (TFT) which is a switching element is formed using a plasma process apparatus. In the TFT, a semiconductor film composed of an amorphous silicon thin film, silicon nitride, or the like plays a particularly important role. For this reason, in order to realize a high-quality TFT, it is indispensable to form a semiconductor film with high accuracy.

  For example, in order to manufacture an organic electroluminescence element, it is necessary to form a transparent insulating film with high accuracy as a protective film for protecting a surface exposed to the atmosphere after forming an organic thin film.

  Similarly, in order to produce a solar cell, it is important to form a high-quality protective film that protects the surface exposed to the atmosphere after the solar cell layer is formed.

  However, in the parallel plate type plasma processing apparatus 100, since the substrate to be processed 104 is provided on the ground electrode (anode electrode) 102b, an anode sheath portion of an electric field is always formed on the surface of the substrate to be processed 104. Become. Since ions in the plasma are accelerated in the anode sheath portion, ion bombardment (ion damage) is applied to the film formation surface of the substrate to be processed 104. Therefore, the conventional parallel plate type plasma processing apparatus 100 has a problem that it is difficult to manufacture the semiconductor film and the like with sufficiently high quality.

Thus, for example, Patent Documents 1 and 2 disclose a composite electrode type plasma process apparatus in which a plurality of anode electrodes and cathode electrodes for generating discharge plasma are alternately arranged at positions facing a substrate to be processed. Proposed. In this composite electrode type plasma process apparatus, since the substrate to be processed is provided separately from the anode electrode, ions in the plasma are not accelerated toward the surface of the substrate to be processed. As a result, the influence of ion bombardment (ion damage) on the anode electrode with respect to the film formation surface is suppressed, so that a high-quality thin film can be formed as compared with a parallel plate type plasma process apparatus.
JP 2001-338885 A JP 2004-158839 A

  For example, when a silicon nitride thin film or the like used for an insulating film of a TFT is formed, it is preferable that ions reach the substrate to be processed. This is because an ion assist effect can be obtained by allowing ions to reach the substrate to be processed, so that a high-quality thin film can be formed. However, as described above, in the conventional composite electrode type plasma processing apparatus, the arrival of ions to the surface of the substrate to be processed is suppressed. For this reason, the ion assist effect cannot be obtained, and there is a problem that it is difficult to form a high-quality insulating film or the like.

  The present invention has been made in view of the above points, and an object of the present invention is to realize a plasma process apparatus capable of manufacturing various types of thin films with high quality.

  The plasma processing apparatus according to the present invention is an apparatus for performing plasma processing on a substrate to be processed. A plasma processing apparatus according to the present invention includes a processing chamber in which a substrate to be processed is loaded, a gas supply unit that supplies gas into the processing chamber, a gas pressure adjustment unit that adjusts the pressure of the gas in the processing chamber, and a processing chamber. A plasma discharge generator provided to face the loaded substrate to be processed.

  The plasma discharge generator includes an anode electrode, a first cathode electrode that generates an electric field substantially parallel to the plate surface of the substrate to be processed inserted between the anode electrode, and a processing target that is inserted from the anode electrode. A second cathode electrode provided apart from the substrate and generating an electric field in a direction intersecting with a plate surface of the substrate to be processed inserted between the anode electrode and the substrate;

  The anode electrode, the first cathode electrode, and the second cathode electrode are different from each other in the distance between the anode electrode and the first cathode electrode and the distance between the anode electrode and the second cathode electrode. It is installed so as to generate plasma between the anode electrode and the first cathode electrode and / or between the anode electrode and the second cathode electrode according to the pressure.

  In the plasma processing apparatus according to the present invention, the cathode electrode is composed of a first cathode electrode and a second cathode electrode. Further, the distance between the anode electrode and the first cathode electrode and the distance between the anode electrode and the second cathode electrode are different. Furthermore, a gas pressure adjusting unit for adjusting the gas pressure in the processing chamber is provided. Therefore, by adjusting the gas pressure in the processing chamber, according to Paschen's law, either the anode electrode and the first cathode electrode or the anode electrode and the second cathode electrode are used as the main plasma generation site. Can be selectively determined.

  According to Paschen's law, the voltage V at which discharge is started is a function of the product of the surrounding gas pressure P and the discharge path length d (that is, V = f (P × d)). For this reason, when the gas pressure P increases in a state where the voltage V is constant, the discharge path length d increases. As described above, Paschen's law is generally a law relating to the discharge start condition, but it is empirically known that the same tendency is also observed for the sustained discharge. For example, when the distance between the anode electrode and the first cathode electrode is shorter than the distance between the anode electrode and the second cathode electrode, and the first cathode electrode and the second cathode electrode are at the same potential, the gas pressure By making P relatively small, it is possible to generate mainly plasma between the anode electrode and the first cathode electrode. Conversely, plasma can be mainly generated between the anode electrode and the second cathode electrode by relatively increasing the gas pressure P.

  By the way, in the plasma processing apparatus according to the present invention, an electric field is generated between the second cathode electrode and the anode electrode in a direction intersecting the plate surface of the substrate to be processed (for example, an obtuse angle). Further, the plasma discharge generating part is separated from the installation position of the substrate to be processed. For this reason, when plasma is mainly generated between the second cathode electrode and the anode electrode, as in the case of using a conventional composite electrode type plasma process apparatus, ion damage received by the substrate to be processed is effectively reduced. Can be reduced. Accordingly, a semiconductor thin film such as a silicon thin film can be manufactured with high quality.

  On the other hand, an electric field substantially parallel to the plate surface of the substrate to be processed is generated between the first cathode electrode and the anode electrode. In this case, plasma can be generated at a position closer to the substrate to be processed as compared with the case where an electric field is generated between the second cathode electrode and the anode electrode. For this reason, when plasma is mainly generated between the first cathode electrode and the anode electrode, ions can reach the substrate to be processed, so that an ion assist effect can be obtained. Therefore, an insulating thin film such as a silicon nitride thin film can be manufactured with high quality.

  As described above, according to the plasma processing apparatus of the present invention, it is preferable to form the film in a mode (mode in which ion damage is suppressed) in which the arrival of ions to the substrate to be processed is suppressed by adjusting the gas pressure. Both the thin film and the thin film which are preferably formed in such a manner that ions reach the substrate to be processed can be produced with high quality.

  In the present specification, the distance between the anode electrode and the first (second) cathode electrode refers to the shortest distance between the anode electrode and the first (second) cathode electrode.

  In the plasma processing apparatus according to the present invention, the first cathode electrode and the second cathode electrode may be at the same potential. The first cathode electrode and the second cathode electrode may be integrally formed. Further, the first cathode electrode and the second cathode electrode may be insulated so that the first cathode electrode and the second cathode electrode can be controlled to different potentials.

  In the plasma processing apparatus according to the present invention, the second cathode electrode is formed in a plate shape, an insulating layer is provided on the surface of the second cathode electrode on the substrate to be processed, and the anode electrode is formed on the insulating layer. The first cathode electrode may be electrically connected to the second cathode electrode, and may be formed as a protrusion on the surface of the second cathode electrode on the substrate to be processed.

  In the plasma processing apparatus according to the present invention, the tip of the first cathode electrode may be closer to the substrate to be processed than the anode electrode.

  In the plasma processing apparatus according to the present invention, the insulating layer includes a plurality of wall-like insulating portions extending in parallel with each other, the first cathode electrode is provided between the plurality of adjacent wall-like insulating portions, and the plurality of wall-like insulating portions are provided. A line electrode extending in parallel with the insulating portion may be included.

  In the plasma processing apparatus according to the present invention, the insulating layer may have an opening that opens to the second cathode electrode, and the first cathode electrode may be provided in the opening.

  As described above, according to the present invention, a thin film that is preferably formed in a mode that suppresses the arrival of ions to the substrate to be processed (a mode that suppresses ion damage), and a mode that allows ions to reach the substrate to be processed. Both of the thin films that are preferably formed by high-quality can be produced with high quality.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiment.

  (First Embodiment) FIG. 1 is a perspective view schematically showing a plasma CVD apparatus 1 according to the first embodiment.

  FIG. 2 is a cross-sectional view schematically showing the plasma CVD apparatus 1 according to the first embodiment.

  A plasma CVD apparatus 1 as a plasma process apparatus includes a processing chamber (vacuum container) 11 into which a substrate 10 to be processed is charged, a gas inlet 12 for introducing a material gas into the processing chamber 11, And a plasma discharge generating part 13 provided in the. Typically, a substrate holder 14 that holds the substrate to be processed 10 is provided in the processing chamber 11, and the substrate to be processed 10 is placed on the substrate holder 14.

  Outside the processing chamber 11, a high-frequency power source 15 for supplying electric power to the plasma discharge generator 13, in other words, applying electric energy, and a material gas (hereinafter also simply referred to as “gas”) inside the processing chamber 11. A gas supply unit 16 that supplies gas to the gas chamber, a gas discharge unit 17a that discharges the gas in the processing chamber 11, and a gas pressure adjustment unit 17b that adjusts the gas pressure in the processing chamber 11 are provided. The gas supply unit 16 can be configured by a gas cylinder or the like. The gas pressure adjusting unit 17b can be configured by a gas pressure adjusting valve or the like. For example, a mechanical booster pump or a rotary pump is used as the gas discharge unit 17a. The high frequency power supply 15 is connected to the plasma discharge generator 13 via the wiring 18. The frequency of the high frequency power supply 15 can be set to 13.56 MHz, for example.

  The plasma discharge generator 13 is provided in the processing chamber 11 so as to be separated from the substrate 10 to be processed and to face the substrate 10 to be processed. The plasma discharge generator 13 includes an anode electrode (anode) 19, a first cathode electrode (first cathode) 20 a, a second cathode electrode (second cathode) 20 b, and an interelectrode insulating layer 21. The second cathode electrode 20b is provided in a plate shape so as to face the substrate 10 to be processed. On the second cathode electrode 20b, a plurality of inter-electrode insulating layers 21 having a substantially rectangular cross section are provided at equal intervals so as to extend in parallel with each other. The anode electrode 19 is provided so as to cover the upper end surface of the interelectrode insulating layer 21. That is, the anode electrode 19 is also provided (in a stripe shape) so as to extend in parallel with each other. The first cathode electrode 20 a is provided in a stripe shape between the adjacent inter-electrode insulating layers 21. The first cathode electrode 20a is integrally formed on the plate-like second cathode electrode 20b in a protruding shape, and the first cathode electrode 20a and the second cathode electrode 20b are at the same potential.

  The second cathode electrode 20b is provided with a gas inlet 12 that penetrates the second cathode electrode 20b in the thickness direction. The gas supplied from the gas supply part 16 a once stays in the gas retention part 22, then passes through the gas introduction port 12 and is introduced into the processing chamber 11. Thus, a plurality of grooves 23 having a concave cross section are formed in the plasma discharge generator 13 by the anode electrode 19, the first cathode electrode 20a, and the second cathode electrode 20b.

  Each gas inlet 12 is provided at the center position of the groove 23 in the groove width direction. The position where the gas inlet 12 is provided is preferably on the cathode electrodes 20a, 20b side as shown in FIGS. In the plasma CVD apparatus 1 according to the first embodiment, the second cathode electrode 20 b is farther from the substrate to be processed 10 than the anode electrode 19. Therefore, by introducing the gas from the second cathode electrode 20b side, the gas flows smoothly toward the substrate 10 to be processed.

  The plasma discharge generator 13 generates a discharge (plasma) 24 according to a voltage (potential difference) applied between the anode electrode 19 and the cathode electrodes 20a and 20b. The gas supplied to the plasma discharge generator 13 is decomposed and dissociated to generate radicals. 2 in FIG. 2 indicates the flow of radicals. The generated radicals diffuse to the substrate 10 to be processed, and adhere to and deposit on the surface of the substrate 10 to be processed held by the substrate holder 14. That is, a film grows on the surface of the substrate to be processed 10 to form a thin film.

  The generated radicals successively reach the surface of the thin film and the thickness of the thin film increases. After the voltage is continuously applied until the set film thickness is reached, the voltage application between the cathode electrodes 20a, 20b and the anode electrode 19 (power supply to the plasma discharge generator 13) is stopped. In this manner, the plasma processing is performed on the surface of the substrate 10 to be processed. Thereafter, when the substrate 10 to be processed is removed from the substrate holder 14 and taken out of the processing chamber 11, a thin film-formed substrate on which a thin film is formed is obtained.

  The distance L1 between the anode electrode 19 and the first cathode electrode 20a is different from the distance L2 between the anode electrode 19 and the second cathode electrode 20b (see FIG. 1). Specifically, the distance L1 is shorter than the distance L2. For this reason, in the plasma CVD apparatus 1 according to the first embodiment, by adjusting the gas pressure in the processing chamber 11 according to Paschen's law, or between the anode electrode 19 and the first cathode electrode 20a, or the anode electrode 19 Between the first cathode electrode 20b and the second cathode electrode 20b can be selectively determined as a main plasma generation location.

  According to Paschen's law, the voltage V at which discharge is started is a function of the product of the gas pressure P in the processing chamber 11 and the discharge path length d (that is, V = f (P × d)). The voltage V has a minimum value with respect to the product of the gas pressure P and the discharge path length d. For this reason, when the gas pressure P increases while the voltage V is constant, the discharge path length d decreases. For example, when the distance L1 between the anode electrode 19 and the first cathode electrode 20a is shorter than the distance L2 between the anode electrode 19 and the second cathode electrode 20b as in the first embodiment, the gas pressure P is compared. By making the size small, plasma can be mainly generated between the anode electrode 19 and the first cathode electrode 20b. On the contrary, plasma can be mainly generated between the anode electrode 19 and the second cathode electrode 20a by making the gas pressure P relatively large.

  By the way, when the interelectrode insulating layer 21 does not exist between the second cathode electrode 20b and the anode electrode 19, the surface of the anode electrode 19 on the second cathode electrode 20b side and the surface of the second cathode electrode 20b on the anode electrode 19 side are also plasma. Functions as a discharge surface. When plasma is mainly generated between the second cathode electrode 20b and the anode electrode 19 in this state, main discharge is performed on the surface of the second cathode electrode 20b on the anode electrode 19 side and on the second cathode electrode 20b side of the anode electrode 19. Occurs between the surface. However, even if the material gas is dissociated by the plasma generated in the space, many of the dissociated radicals adhere to the surface of the anode electrode 19 on the second cathode electrode 20b side as a film. Therefore, the film forming speed cannot be increased as intended, so that the throughput of the apparatus is limited.

  On the other hand, in the plasma CVD apparatus 1 of the present embodiment, the plasma discharge surface of the second cathode electrode 20b and the plasma discharge surface of the anode electrode 19 do not face each other. Therefore, most of the radicals dissociated between the second cathode electrode 20b and the anode electrode 19 can be effectively led to the substrate 10 to be processed.

  By the way, in the case of the conventional parallel plate type apparatus shown in FIGS. 13 and 14, the distance between the anode electrode and the cathode electrode is structurally determined. It becomes the length of the path itself, and the material gas pressure at which plasma is likely to be generated is determined within a certain range. This is because it is governed by the aforementioned Paschen's law.

  On the other hand, in the structure shown in FIGS. 1 and 2, since the electrode surfaces of the second cathode electrode 20b and the anode electrode 19 do not face each other, the path length of the discharge generated between them is relatively high due to the level of the material gas pressure. Change flexibly.

  Hereinafter, the thin film formation process on the to-be-processed substrate 10 using the plasma CVD apparatus 1 is demonstrated in detail. First, a case where a semiconductor thin film or the like that is preferably formed in a mode in which the arrival of ions to the substrate to be processed 10 is suppressed will be described. In addition, the specific numerical value shown below has shown only the case of one Example of this invention, and does not limit this invention at all.

For example, a case where a silicon thin film is formed on the substrate 10 as a semiconductor thin film will be described as an example. When forming a silicon thin film, silane (SiH ₄ ) gas, hydrogen (H ₂ ) gas, or the like can be used as a material gas. The pressure in the processing chamber 11 can be set to 50 Pa to 300 Pa, for example. When forming a silicon thin film, it is preferable to heat the processing chamber 11 to about 300 ° C., for example.

  In the case of forming a silicon thin film, it is preferable that ions reach the substrate 10 to be processed. For this reason, it is preferable to mainly generate plasma between the anode electrode 19 and the second cathode electrode 20b. The main plasma generation position can be adjusted by changing the gas pressure or the like as described above.

  FIG. 3 is a diagram showing a discharge path when a discharge occurs between the anode electrode 19 and the second cathode electrode 20b.

  Actually, discharge occurs between the anode electrode 19 and the second cathode electrode 20b, and discharge also occurs somewhat between the anode electrode 19 and the first cathode electrode 20a. However, for convenience of explanation, it is assumed in FIG. 3 that discharge occurs only between the anode electrode 19 and the second cathode electrode 20b.

  As shown in FIG. 3, when a discharge occurs between the anode electrode 19 and the second cathode electrode 20b, plasma is generated only in the vicinity of the plasma discharge generator 13. That is, the plasma is generated only at a position relatively far from the substrate 10 to be processed. The generated ions are attracted to the anode electrode 19. For this reason, in this case, ions in the plasma are effectively suppressed from reaching the substrate 10 to be processed. Therefore, since it is possible to effectively suppress the silicon thin film to be subjected to ion damage, a high-quality silicon thin film can be formed.

  Next, a case where an insulating thin film or the like that is preferably formed in a mode that allows ions to reach the substrate to be processed 10 will be described.

For example, a case where a silicon nitride (SiNx) thin film is formed on the substrate 10 as an insulating thin film will be described as an example. When forming a silicon nitride thin film, silane (SiH ₄ ) gas, nitrogen (N ₂ ) gas, hydrogen (H ₂ ) gas, or the like can be used as a material gas. The pressure in the processing chamber 11 can be set to 50 Pa to 300 Pa, for example. In addition, when forming a silicon nitride thin film, it is preferable to heat the processing chamber 11 to about 300 ° C., for example.

  When a silicon nitride thin film is formed, it is preferable that ions reach the substrate 10 to be processed. For this reason, it is preferable to mainly generate plasma between the anode electrode 19 and the first cathode electrode 20a. The main plasma generation position can be adjusted by changing the gas pressure or the like as described above.

  FIG. 4 is a diagram showing a discharge path when a discharge occurs between the anode electrode 19 and the first cathode electrode 20a.

  Actually, a discharge occurs between the anode electrode 19 and the first cathode electrode 20a, and a discharge also occurs somewhat between the anode electrode 19 and the second cathode electrode 20b. However, for convenience of explanation, it is assumed in FIG. 4 that discharge occurs only between the anode electrode 19 and the first cathode electrode 20a.

  As shown in FIG. 4, when a discharge occurs between the anode electrode 19 and the first cathode electrode 20a, plasma is generated in a region relatively close to the substrate 10 to be processed. In addition, since the anode electrode 19 does not exist between the first cathode electrode 20a and the substrate 10 to be processed, ions generated in the plasma easily reach the substrate 10 to be processed. For this reason, in this case, ions in the plasma can easily reach the substrate 10 to be processed, and an ion assist effect can be easily obtained. Therefore, a high-quality silicon nitride thin film can be formed.

  As described above, according to the plasma CVD apparatus 1 according to the first embodiment, a thin film that is preferably formed in a mode in which the arrival of ions to the substrate 10 to be processed (a mode in which ion damage is suppressed) is preferable. Both a semiconductor thin film and the like, and a thin film (insulating thin film, etc.) that are preferably formed in such a manner that ions reach the substrate to be processed can be produced with high quality.

  In the first embodiment, the distance from the tip of the first cathode electrode 20a to the substrate to be processed 10 is substantially the same as the distance from the tip of the anode electrode 19 to the substrate to be processed 10. However, the present invention is not limited to this configuration. The tip of the first cathode electrode 20 a may be closer to the substrate to be processed 10 than the tip of the anode electrode 19.

  FIG. 5 is a diagram showing a discharge path between the anode electrode 19 and the second cathode electrode 20 b when the tip of the first cathode electrode 20 a is closer to the substrate 10 to be processed than the tip of the anode electrode 19.

  As shown in FIG. 5, by setting the discharge path length to a distance longer than L1 and shorter than L2, plasma can be generated even in a region very close to the substrate 10 to be processed. For this reason, a larger ion assist effect can be obtained. Therefore, a higher quality insulating film or the like can be formed.

  FIG. 6 is a diagram schematically showing the connection between the high-frequency power source 15 and the anode electrode 19.

  In the plasma CVD apparatus 1 according to the first embodiment, as shown in FIG. 6A, each of the plurality of rod-like anode electrodes 19 is connected to the high frequency power supply 15 via the wiring 18 at the end. However, the apparatus of the present invention is not limited to this configuration. For example, as shown in FIG. 6B, one end of a plurality of rod-shaped anode electrodes 19 may be connected with a rod made of the same material, and a wiring 18 from the high frequency power supply 15 may be connected to the connected rod. Alternatively, as shown in FIG. 6C, both end portions of the plurality of rod-shaped anode electrodes 19 may be connected with the same material rod, and the wiring 18 from the high frequency power supply 15 may be connected to the connected rod.

  Second Embodiment FIG. 7 is a perspective view schematically showing a plasma CVD apparatus 30 according to the second embodiment.

  FIG. 8 is a cross-sectional view schematically showing the plasma CVD apparatus 30 according to the second embodiment.

  FIG. 9 is a partially enlarged view of FIG.

  The plasma CVD apparatus 30 according to the second embodiment will be described with reference to FIGS. In the following description, components having substantially the same function as the plasma CVD apparatus 1 of Embodiment 1 are denoted by the same reference numerals, and the description thereof is omitted.

  The plasma CVD apparatus 30 of the second embodiment is that the plasma discharge surface of the second cathode electrode 20b is concave, and the plasma discharge surface of the second cathode electrode 20b is flat. And different.

  In the plasma CVD apparatus 30 of Embodiment 2, as shown in FIGS. 7 to 9, the interelectrode insulating layer 21, the anode electrode 19, and the cathode electrode 20 (in this specification, the cathode electrode 20 is the first cathode electrode 20a). The second cathode electrode 20b in the groove 23 formed by (2) and the second cathode electrode 20b) has a pair of inclined surfaces extending obliquely upward outward from the vicinity of the gas introduction port 12. Yes. In other words, the lower portion of the groove 23 is configured in a wedge shape that increases from the gas inlet 12 toward the substrate 10 to be processed. The pair of opposed inclined surfaces constitutes the plasma discharge surface of the second cathode electrode 20b.

  By adopting such a configuration, it is possible to achieve a higher film forming speed than the plasma CVD apparatus 1 according to the first embodiment. In particular, it is possible to improve the deposition rate when plasma is generated mainly between the second cathode electrode 20b and the anode electrode 19. The reason why the film formation rate has increased can be explained as follows.

  In the plasma CVD apparatus 1 according to Embodiment 1, the surface of the interelectrode insulating layer 21 for insulating between the anode electrode 19 and the second cathode electrode 20b is perpendicular to the surface of the second cathode electrode 20b. . For this reason, plasma particles and radical particles generated on the surface of the second cathode electrode 20b easily collide with the interelectrode insulating layer 21 and disappear. On the other hand, in the plasma CVD apparatus 30 according to the second embodiment, for example, by the presence of an aluminum rod having a triangular cross section, the surface of the interelectrode insulating layer 21 and the inclined surface of the second cathode electrode 20b form an obtuse angle. Preferably, the angle can be approximately 180 °. Therefore, the probability that plasma particles or radical particles generated on the surface of the second cathode electrode 20b collide with the interelectrode insulating layer 21 and disappear is reduced. Further, since the cross-sectional shape of the plasma discharge surface of the second cathode electrode 20b is concave, a hollow cathode effect is also produced. Therefore, by making the plasma discharge surface of the second cathode electrode 20b concave, the throughput of the apparatus can be improved while maintaining other performance such as film quality.

  In the first and second embodiments, the case where the plasma process apparatus of the present invention is applied to a plasma CVD apparatus has been described. However, the plasma process apparatus of the present invention is not limited to the plasma CVD apparatus. The present invention can be used for plasma processing apparatuses in general that perform plasma processing such as thin film formation and processing using plasma, and can be suitably used for, for example, dry etching apparatuses and asher apparatuses.

For example, when applied to a dry etching apparatus, an etching gas such as CF ₄ , SF ₆ , Cl ₂ , HCl, BCl ₃ , or O ₂ can be used as a gas introduced into the processing chamber 11. In general, in a dry etching apparatus, not only radicals generated by plasma discharge but also ion bombardment to a surface to be processed of a substrate to be processed may be used for an etching operation. When ion bombardment is used for the etching operation, it is preferable to generate plasma between the anode electrode 19 and the first cathode electrode 20a. Thereby, a relatively large ion bombardment can be realized.

  In the first and second embodiments, the case where the gas inlet 12 is provided on the second cathode electrode 20b side has been described, but the formation position of the gas inlet 12 is not limited to this. For example, the gas inlet 12 may be provided so as to be positioned between the plasma discharge generating unit 13 and the substrate to be processed 10. In this case, the gas is introduced into the processing chamber 11 from the gas inlet 12 along the surface direction of the substrate 10 to be processed.

(Example 1) As Example 1, an amorphous silicon thin film was formed by using the plasma CVD apparatus 30 shown in FIGS. Silane (SiH ₄ ) gas and hydrogen (H ₂ ) gas were used as material gases. The flow rates of silane gas and hydrogen gas were 100 sccm, respectively. In this specification, “sccm” is a gas flow rate in units of cubic centimeters flowing every minute at 0 ° C.

  The pressure in the processing chamber 11 was 200 Pa, and the temperature during film formation was 300 ° C. The distance between the plasma discharge generating part 13 and the substrate to be processed 10 was 27 mm.

  Under the above conditions, when a voltage was applied between the anode electrode 19 and the cathode electrode 20, a discharge was generated between the second cathode electrode 20 b and the anode electrode 19.

After film formation, the ratio of Si—H ₂ to Si—H (Si—H ₂ / Si—H) of the amorphous silicon thin film was measured. Here, Si—H ₂ / Si—H is a parameter indicating the film quality of the amorphous silicon thin film, and it can be evaluated that the smaller the Si—H ₂ / Si—H, the higher the quality of the amorphous silicon thin film. In this specification, a JIR-7000 Fourier transform infrared spectrophotometer manufactured by JEOL Ltd. was used for the measurement of Si—H ₂ / Si—H. FIG. 10 shows the ratio of Si—H ₂ to Si—H (Si—H ₂ / Si—H) of the amorphous silicon thin film formed in Example 1. In this specification, “power” refers to an output value of a high-frequency power source.

Comparative Example 1 As Comparative Example 1 corresponding to Embodiment 1, an amorphous silicon thin film was formed using a conventional parallel plate type plasma CVD apparatus 100 shown in FIGS. Similar to Example 1, silane (SiH ₄ ) gas and hydrogen (H ₂ ) gas were used as material gases. The flow rates of silane gas and hydrogen gas were 100 sccm, respectively.

The pressure in the processing chamber 11 was 80 Pa, and the temperature during film formation was 300 ° C. The distance between the anode electrode 19 and the cathode electrode was 30 mm. After film formation, the ratio of Si—H ₂ to Si—H (Si—H ₂ / Si—H) of the amorphous silicon thin film was measured.

  In both Example 1 and Comparative Example 1, the highest film formation rate was obtained when the power was 300 W. When the power was 300 W, the film formation rate in Example 1 was almost equal to the film formation rate in Comparative Example 1.

As shown in FIG. 10, at about 200W or more regions, Si-H ₂ / Si-H of Example 1 was a value smaller than the Si-H ₂ / Si-H of the Comparative Example 1. In particular, the 300W showed the highest deposition rate, Si-H ₂ / Si-H of Example 1 became even smaller about 70% than the Si-H ₂ / Si-H of the Comparative Example 1.

  As described above, it was found that by using the plasma CVD apparatus 30 according to the second embodiment, a high-quality amorphous silicon thin film can be formed as compared with the case where a conventional parallel plate type plasma CVD apparatus is used. .

(Example 2) As Example 2, a silicon nitride thin film used as an insulating thin film was formed by using the plasma CVD apparatus 30 shown in FIGS. Silane (SiH ₄ ) gas, ammonia (NH ₃ ) gas, nitrogen (N ₂ ) gas, and hydrogen (H ₂ ) gas were used as material gases. The flow rates of silane (SiH ₄ ) gas, ammonia (NH ₃ ) gas, nitrogen (N ₂ ) gas, and hydrogen (H ₂ ) gas were 55 sccm, 125 sccm, 350 sccm, and 500 sccm, respectively. The pressure and temperature in the processing chamber 11 were adjusted so that the film formation rate was 40 Å / sec. Specifically, the pressure in the processing chamber 11 was 225 Pa, and the temperature during film formation was 300 ° C. The distance between the plasma discharge generating part 13 and the substrate to be processed 10 was 30 mm.

  When a voltage was applied between the anode electrode 19 and the cathode electrode 20 under the above conditions, a discharge was generated between the first cathode electrode 20a and the anode electrode 19. The refractive index, etch rate, and hydrogen concentration of the silicon nitride thin film obtained in Example 2 were measured.

  An M-220 ellipsometer manufactured by JASCO Corporation was used for refractive index measurement. The refractive index of the obtained silicon nitride thin film was 1.87.

  The etch rate was measured by evaluating the speed of etching with a buffered solution of hydrofluoric acid (hydrofluoric acid: ammonium fluoride = 1: 10). The etch rate can be used as one measure for evaluating the denseness of the silicon nitride thin film. It can be evaluated that the lower the etch rate, the closer the film. The etch rate of the silicon nitride thin film obtained in Example 2 was 120 Å / min.

For measurement of the hydrogen concentration, a JIR-7000 Fourier transform infrared spectrophotometer manufactured by JEOL Ltd. was used. Similarly to the etch rate, the hydrogen concentration can also be used as a measure for evaluating the denseness of the silicon nitride thin film. It can be evaluated that the lower the hydrogen concentration is, the closer the film is. The hydrogen concentration of the obtained silicon nitride thin film was 0.75 × 10 ⁻²¹ cm ⁻³ .

  Comparative Example 2 FIG. 11 is a perspective view schematically showing a plasma CVD apparatus 200 according to Comparative Example 2.

  FIG. 12 is a cross-sectional view schematically showing a plasma CVD apparatus 200 according to Comparative Example 2.

  The plasma CVD apparatus 200 represented by FIGS. 11 and 12 has the same configuration as the plasma CVD apparatus according to the second embodiment except for the structure of the anode electrode and the cathode electrode and the interelectrode insulating layer. In the plasma CVD apparatus 200 according to Comparative Example 2, the cathode electrode 20 is configured only by the second cathode electrode 20b. In other words, the first cathode electrode 20a is not formed. An interelectrode insulating layer 21 is formed in a stripe shape on the plate-like second cathode electrode 20 b, and an anode electrode 19 is formed on the interelectrode insulating layer 21.

  In Comparative Example 2, a silicon nitride thin film was formed using this plasma CVD apparatus 200.

Silane (SiH ₄ ) gas, ammonia (NH ₃ ) gas, nitrogen (N ₂ ) gas, and hydrogen (H ₂ ) gas were used as material gases. The flow rates of silane (SiH ₄ ) gas, ammonia (NH ₃ ) gas, nitrogen (N ₂ ) gas, and hydrogen (H ₂ ) gas were 100 sccm, 200 sccm, 500 sccm, and 200 sccm, respectively. The pressure and temperature in the processing chamber 11 were adjusted so that the film formation rate was 40 Å / sec. Specifically, the pressure in the processing chamber 11 was 150 Pa, and the temperature during film formation was 300 ° C. The distance between the plasma discharge generating part 13 and the substrate to be processed 10 was 30 mm.

  In the same manner as in Example 2, the refractive index, etch rate, and hydrogen concentration of the silicon nitride thin film obtained in Comparative Example 2 were measured.

The obtained silicon nitride thin film had a refractive index of 1.87, which was the same as in Example 2. The etch rate was 480 kg / min. The hydrogen concentration was 1.20 × 10 ⁻²¹ cm ⁻³ .

  The results of Example 2 and Comparative Example 2 are summarized in Table 1 below.

  As shown in Table 1, the etch rate in Example 2 was 120 Å / min, whereas in Comparative Example 2, the etch rate was 480 Å / min. Thus, according to Example 2, it can be seen that a thin film having a low etch rate, that is, a dense film can be formed.

The hydrogen concentration in Example 2 was 0.75 × 10 ⁻²¹ cm ⁻³ , whereas in Comparative Example 2, the hydrogen concentration was 1.20 × 10 ⁻²¹ cm ⁻³ . Thus, according to Example 2, it can be seen that a thin film having a low hydrogen concentration, that is, a dense film can be formed.

  From the above, it can be seen that the plasma CVD apparatus according to the second embodiment can form a dense and high-quality silicon nitride thin film.

  In Example 2 and Comparative Example 2, the flow rate of each gas was adjusted so that the film formation rate was about 40 liters / min. As a result, in Example 2, the gas flow rate was smaller than the gas flow rate in Comparative Example 2. For this reason, the silicon nitride thin film could be formed in Example 2 at a lower cost than in Comparative Example 2.

1 is a perspective view schematically showing a plasma CVD apparatus 1 according to Embodiment 1. FIG. 1 is a cross-sectional view schematically illustrating a plasma CVD apparatus 1 according to Embodiment 1. FIG. It is a figure which shows the discharge path | route in case discharge generate | occur | produces between the anode electrode 19 and the 2nd cathode electrode 20b. It is a figure which shows the discharge path | route in case discharge generate | occur | produces between the anode electrode 19 and the 1st cathode electrode 20a. 4 is a diagram showing a discharge path between the anode electrode 19 and the second cathode electrode 20b when the tip of the first cathode electrode 20a is closer to the substrate 10 to be processed than the tip of the anode electrode 19. FIG. FIG. 3 is a diagram schematically showing connection between a high-frequency power supply 15 and an anode electrode 19. It is a perspective view which shows typically the plasma CVD apparatus 30 which concerns on Embodiment 2. FIG. It is sectional drawing which shows typically the plasma CVD apparatus 30 which concerns on Embodiment 2. FIG. It is the elements on larger scale of FIG. It is a graph showing the correlation between the power and the Si-H ₂ / Si-H of the high-frequency power source in Example 1 and Comparative Example 1. 10 is a perspective view schematically showing a plasma CVD apparatus 200 according to Comparative Example 2. FIG. 6 is a cross-sectional view schematically showing a plasma CVD apparatus 200 according to Comparative Example 2. FIG. It is a schematic perspective view which shows the principal part of the conventional parallel plate type plasma process apparatus 100. FIG. It is sectional drawing which shows the parallel plate type plasma process apparatus 100 at the time of film-forming.

Explanation of symbols

1,30 Plasma CVD equipment
10 Substrate
11 Processing chamber
12 Gas inlet
13 Plasma discharge generator
14 Substrate holder
15 High frequency power supply
16 Gas supply section
17a Gas discharge part
17b Gas pressure adjustment part
18 Wiring
19 Anode electrode
20a First cathode electrode
20b Second cathode electrode
21 Insulating layer between electrodes
22 Gas retention part
23 groove

Claims (6)

A plasma processing apparatus for performing plasma processing on a substrate to be processed,
A processing chamber in which a substrate to be processed is charged; and
A gas supply unit for supplying gas into the processing chamber;
A gas pressure adjusting unit for adjusting the pressure of the gas in the processing chamber;
A plasma discharge generator provided so as to be opposed to the substrate to be processed placed in the processing chamber;
Have
The plasma discharge generator includes an anode electrode, a first cathode electrode that generates an electric field substantially parallel to the plate surface of the substrate to be processed inserted between the anode electrode and the anode electrode. A second cathode electrode that is provided apart from the substrate to be processed and generates an electric field in a direction intersecting with the plate surface of the substrate to be processed inserted between the anode electrode and the anode electrode,
The anode electrode, the first cathode electrode, and the second cathode electrode have the same distance between the anode electrode and the first cathode electrode and the distance between the anode electrode and the second cathode electrode. Unlikely, the plasma process is arranged to generate plasma between the anode electrode and the first cathode electrode and / or between the anode electrode and the second cathode electrode according to the pressure of the gas apparatus. The plasma processing apparatus according to claim 1, wherein
A plasma processing apparatus, wherein the first cathode electrode and the second cathode electrode have the same potential. The plasma processing apparatus according to claim 1, wherein
A plasma processing apparatus in which the first cathode electrode and the second cathode electrode are integrally formed. The plasma processing apparatus according to claim 1, wherein
The second cathode electrode is formed in a plate shape,
An insulating layer provided on the substrate-side surface of the second cathode electrode;
The anode electrode is provided on the insulating layer;
The plasma processing apparatus, wherein the first cathode electrode is electrically connected to the second cathode electrode, and is formed on a surface of the second cathode electrode on the substrate side to be processed. The plasma processing apparatus according to claim 4, wherein
The plasma processing apparatus, wherein the tip of the first cathode electrode is closer to the substrate to be processed than the anode electrode. The plasma processing apparatus according to claim 4, wherein
The insulating layer includes a plurality of wall-like insulating portions extending in parallel with each other,
The plasma processing apparatus, wherein the first cathode electrode is provided between adjacent wall-like insulating parts of the plurality of wall-like insulating parts, and includes a line-like electrode extending in parallel with the plurality of wall-like insulating parts.

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