JP5585294B2 - Plasma processing apparatus and thin film manufacturing method using the same - Google Patents

Description

  The present invention relates to a plasma processing apparatus that suppresses the influence of unnecessary substances generated in plasma, and a thin film manufacturing method using the same.

  In recent years, solar power generation has attracted attention due to increasing environmental awareness, and various types of solar cells have been developed and put into practical use. In particular, the production scale of thin-film silicon solar cells, which use less silicon raw materials and are suitable for mass production, is being expanded. However, thin-film silicon solar cells have an unsolved problem of so-called photodegradation in which power generation efficiency decreases with time due to light irradiation, and further improvements for improving energy conversion efficiency are required.

A hydrogenated amorphous silicon (a-Si: H) thin film used for a thin film silicon type solar cell is often formed by a plasma CVD method using silane gas (SiH ₄ ) as a raw material. Silane gas is decomposed in the plasma, SiH ₃ radicals, which are the main film formation species, are generated, and the film formation species reaches the substrate to form a thin film. However, unnecessary substances such as higher-order silane (Si _m H _n , m ≧ 4) and particles are also generated in the plasma in addition to the film-forming species such as SiH ₃ radicals. It is said that such unnecessary substances are mixed into the film and cause photodegradation. When such an unnecessary substance is mixed in the film, the number of silicon atoms bonded to two hydrogen atoms and two silicon atoms increases per one silicon atom having four bonds. That is, the so-called Si—H ₂ bond concentration increases in the film. According to Non-Patent Document 1, there is a correlation between the Si—H ₂ bond concentration in the film and the degree of photodegradation, and in order to prevent photodegradation, it is necessary to reduce the Si—H ₂ bond concentration in the film. ing. Therefore, in order to prevent photodegradation, it is necessary to devise a method for preventing unnecessary substances such as higher order silane and particles from being mixed into the film.

  FIG. 10 is a schematic sectional view of a conventional general parallel plate type plasma CVD apparatus. Inside the vacuum vessel 1, the cathode electrode 3 and the ground electrode 22 are arranged to face each other, and the inside of the vessel is kept at a low pressure by the vacuum exhaust device 6 connected to the vacuum vessel 1. The cathode electrode 3 is provided with a showerhead-like gas supply port 8, and after supplying a raw material gas such as silane gas from the gas supply port 8 into the vacuum vessel 1, power is supplied by a power source 10 connected to the cathode electrode 3. Then, plasma 2 is generated. A thin film is formed on the substrate 4 held on the ground electrode 21 by using a film-forming species generated by decomposing the source gas by the plasma 2.

  In the case of a general parallel plate type plasma CVD apparatus as shown in FIG. 10, the plasma 2 spreads to the vicinity of the surface of the substrate 4 placed on the ground electrode 22. Since unnecessary substances such as higher-order silane and particles described above are mainly generated inside the plasma, the frequency with which unnecessary substances are mixed into the film increases. For this reason, improvements have been made so far, such as keeping the plasma away from the vicinity of the substrate surface and quickly exhausting the generated unwanted substances.

  For example, Patent Document 1 has a configuration in which a mesh electrode having a ground potential is disposed between a cathode electrode and a substrate, and plasma is confined between the cathode electrode and the mesh electrode. Thereby, no plasma exists in the vicinity of the substrate, and ion bombardment to the substrate by positive ions from the plasma can be avoided, so that the quality of the obtained thin film can be improved. Furthermore, it is possible to avoid mixing unnecessary substances generated in the plasma into the film. Further, in Patent Document 2, a plurality of recesses are provided on the substrate side of the cathode electrode, and the recesses are configured by spot-type recesses arranged in a predetermined pattern and groove-type recesses that communicate the spot-type recesses with each other. The structure in which both the holes and the holes for exhausting the gas are provided is described. As a result, spot-like high-density plasma is generated in the vicinity of each spot-type recess on the electrode surface, while the plasma in the vicinity of the substrate surface becomes weak, so that contamination of unnecessary substances into the film can be reduced. Further, unnecessary substances can be removed by the flow of gas to the gas exhaust hole of the cathode electrode.

  However, in the method of Patent Document 1, it is inevitable that a film adheres to the mesh electrode between the cathode electrode and the substrate, and the adhered film peels off and drops, causing abnormal discharge, or contamination of the substrate with foreign matter. It may cause a problem. Further, if the mesh electrode has an excessively high aperture ratio, plasma confinement becomes insufficient, so that the mesh electrode cannot have a very large aperture ratio. For this reason, there has been a problem that the film forming speed is limited, and the film forming speed is further lowered due to film adhesion to the mesh electrode. Further, in the method of Patent Document 2, the plasma is not completely confined in the vicinity of the electrode, and the plasma is generated although it is weak in the vicinity of the substrate. Therefore, it is possible to completely prevent an unnecessary substance from being mixed into the film. could not.

  Therefore, as a result of intensive studies, as shown in FIGS. 11 and 12, the anode electrode 14 is provided between the cathode electrode 3 and the substrate 4, and the cathode electrode 3 having a plurality of recesses 23 or a plurality of exhaust holes 18 is provided. And the anode electrode 14 provided with the through hole 15 at a position facing the concave portion 23 or the exhaust hole 18 of the cathode electrode 3 in close proximity to each other, and the plasma 2 is stably formed inside the concave portion 23 or the exhaust hole 18. As a result, it has been found that a state in which the plasma 2 is generated only in the vicinity of the cathode electrode 3 and no plasma is generated in the vicinity of the substrate 4 can be realized. FIG. 11 shows the case where the cathode electrode 3 is provided with the recess 23, and FIG. 12 shows the case where the cathode electrode 3 is provided with the exhaust hole 18. As a result, it has become clear that the plasma 2 can be localized inside the recess 23 or the exhaust hole 18 by the action of the anode electrode 3, and there is an effect of reducing unnecessary substances in the film. However, a problem has arisen that it is difficult to light plasma uniformly in all the recesses 23 or all the exhaust holes 18 provided in the cathode electrode 3 with good reproducibility. The same problem is also taken up in Patent Document 2, and in Patent Document 2, an attempt is made to solve the problem by connecting the spot-type concave portions to each other by the groove-type concave portions. When such a groove-type recess is used to connect the recesses or the exhaust holes, the uniformity of the plasma lighting state to the recesses or the exhaust holes is slightly improved, It was difficult.

Japanese Patent Laid-Open No. 6-49648 JP 2007-214296 A

Applied Physics Vol. 71, No. 7 (2002), p. 823-832

  An object of the present invention is to generate plasma only in the vicinity of a cathode electrode having a plurality of recesses or a plurality of exhaust holes, to suppress the generation of plasma in the vicinity of the substrate, and to be uniform in all the recesses or all the exhaust holes of the cathode electrode. An object of the present invention is to provide a plasma processing apparatus capable of generating plasma and a method of manufacturing a thin film using the same.

In order to achieve the above object, the present invention provides a cathode electrode, a substrate holding mechanism for holding a substrate facing the cathode electrode, and a substrate holding mechanism in a vacuum container equipped with an evacuation device that holds the inside at a reduced pressure. A plasma processing apparatus comprising an anode electrode between a cathode electrode and the substrate holding mechanism, wherein a power source is connected to the cathode electrode, wherein the cathode electrode has a plasma holding portion opened to a film formation substrate side and the plasma holding unit The anode electrode has a through hole formed at a position facing the plasma holding portion of the cathode electrode, and the cathode electrode and / or the anode electrode is between the two electrodes. distance have a movable mechanism to increase or decrease, the movable mechanism is spread distance between the cathode electrode and the anode electrode during plasma ignition, the plasma processing cathode electrode and an anode To provide a plasma processing apparatus which is a movable mechanism which is disposed in close proximity to pole.

  Moreover, according to the preferable form of this invention, the said plasma holding | maintenance part provides the plasma processing apparatus which is the concave shape opened only to the film-forming substrate side.

  According to a preferred embodiment of the present invention, the cathode electrode is hollow, the plasma holding part is in a cylindrical shape communicating with the hollow part, and the vacuum exhaust device is connected to the hollow part of the cathode electrode. A plasma processing apparatus is provided.

  Further, according to a preferred embodiment of the present invention, a deposition target substrate is disposed on the substrate holding mechanism of any of the plasma processing apparatuses, and a gas is introduced into a vacuum vessel to keep the cathode electrode and the anode electrode away from each other. A method for producing a thin film is provided in which the cathode electrode and the anode electrode are brought close to each other after the plasma is ignited in a heated state.

  According to the present invention, as described below, plasma is generated only in the vicinity of the cathode electrode to suppress the generation of plasma in the vicinity of the substrate, thereby preventing unwanted substances from being mixed into the film. Since plasma can be generated stably and uniformly, a plasma processing apparatus and a thin film manufacturing method capable of forming a thin film with excellent uniformity can be obtained.

It is a schematic sectional drawing which shows an example of the plasma processing apparatus of this invention. It is a top view which shows an example of the cathode electrode in the plasma processing apparatus of this invention. It is a schematic sectional drawing which shows another example of the plasma processing apparatus of this invention. It is a schematic sectional drawing which shows operation | movement of an example of the plasma processing apparatus of this invention. It is a schematic sectional drawing which shows operation | movement of another example of the plasma processing apparatus of this invention. It is a schematic sectional drawing which shows another example of the plasma processing apparatus of this invention. It is a schematic sectional drawing which shows operation | movement of another example of the plasma processing apparatus of this invention. It is a schematic sectional drawing which shows another example of the anode electrode position variable mechanism in the plasma processing apparatus of this invention. It is a schematic sectional drawing which shows operation | movement of another example of the anode electrode position variable mechanism in the plasma processing apparatus of this invention. It is a schematic sectional drawing of the conventional common parallel plate type plasma CVD apparatus. It is a schematic sectional drawing of the conventional plasma CVD apparatus which has a structure which equips a cathode electrode with a recessed part and provides an anode electrode between a cathode electrode and a board | substrate. It is a schematic sectional view of a conventional plasma CVD apparatus having a configuration in which an exhaust hole is provided in a cathode electrode and an anode electrode is provided between the cathode electrode and a substrate.

  Hereinafter, examples of the best mode of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic sectional view showing an example of the plasma processing apparatus of the present invention. The plasma processing apparatus of the present invention includes a cathode electrode 3 for generating plasma 2 and a substrate holding mechanism 5 for holding the substrate 4 so as to face the cathode electrode 3 inside the vacuum vessel 1. An evacuation device 6 is connected to the vacuum vessel 1 so that the inside of the vacuum vessel 1 can be held at a reduced pressure. The source gas supplied from the gas supply pipe 7 is supplied to the inside of the vacuum vessel 1 from the gas supply port 8 provided in the cathode electrode 3. The cathode electrode 3 is fixed by being electrically insulated from the vacuum vessel 1 by an insulator 9. A power source 10 is electrically connected to the cathode electrode 3, and plasma 2 is generated by the power supplied to the cathode electrode 3 by the power source 10.

  An anode electrode 14 is provided between the cathode electrode 3 and the substrate holding mechanism 5. A plasma holding portion 13 opened to the substrate 4 side is formed in the cathode electrode 3, and a through hole 15 is formed in the anode electrode 14 at a position facing the plasma holding portion 13 of the cathode electrode 3. The plasma holding unit 13 has a role of generating and holding the plasma 2 in a space formed by the through hole 15 of the anode electrode 14 (hereinafter simply referred to as “inside the plasma holding unit”). During the plasma processing, the cathode electrode 3 and the anode electrode 14 are disposed close to each other, so that the plasma 2 can be localized in a state where it enters the plasma holding portion. That is, it is possible to generate the plasma 2 only in the vicinity of the cathode electrode 3 and suppress the generation of plasma in the vicinity of the substrate 4. However, when the cathode electrode 3 and the anode electrode 14 are arranged close to each other, there arises a problem that it is difficult to uniformly generate the plasma 2 in all the plasma holding portions at the time of plasma ignition. Therefore, the present invention solves this problem by changing the distance between the cathode electrode 3 and the anode electrode 14 during plasma ignition. That is, at the time of plasma ignition, the distance between the cathode electrode 3 and the anode electrode 14 is increased, and a single plasma is generated between the cathode electrode 3 and the anode electrode 14, and then the cathode electrode 3 and the anode electrode 14. , The plasma 2 enters all of the plasma holding units, and finally the plasma 2 is held in a dispersed state in each plasma holding unit.

  The substrate holding mechanism 5 may include a substrate heating mechanism 11 such as a heater. Further, it is preferable to provide a ground shield 12 on the side surface of the cathode electrode 3 with a space of about 1 mm from the cathode electrode. By providing the earth shield 12, unnecessary plasma generation on the side surface of the cathode electrode 3 can be prevented. The power source 10 may be an arbitrary power source such as a high frequency power source, a pulse power source, or a DC power source, and an arbitrary frequency may be selected when the high frequency power source is used. This is suitable because it is easy to generate a plasma having an electron temperature and a high density. Further, pulse modulation or amplitude modulation may be applied to the output of the high frequency power source.

  FIG. 1 shows an example in which the cathode electrode 3 is made of a flat conductor and the plasma holding part is formed by a plurality of through holes provided in the cathode electrode 3. FIG. 2 is a plan view showing an example of the cathode electrode 3. As shown in FIG. 2, the cathode electrode 3 includes a plasma holding unit 13 that is open to the substrate 4 side and a connecting unit 21 that connects the plasma holding unit 13. The opening shape of the plasma holding unit 13 may be an arbitrary shape such as an ellipse, a square, a rectangle, or a spiral, in addition to a circle as shown in FIG. In the case of FIG. 1, the plasma holding unit 13 includes a through hole having an opening on the substrate 4 side. However, the shape is not limited to such a shape as long as the opening is provided on the film formation substrate side. The connecting portion 21 is a portion other than the plasma holding portion 13 on the substrate 4 side of the cathode electrode 3.

  Further, in the present invention, as shown in FIG. 3, it is preferable that the plasma holding unit 13 has a concave shape opened only on the deposition substrate side. By adopting such a shape, unnecessary plasma generation on the opposite side of the cathode electrode 3 from the deposition target substrate can be prevented, and stable plasma generation state can be maintained in the plasma holding unit. . The shape of the plasma holding unit 13 is preferably a cylindrical recess having a circular cross-sectional shape from the viewpoint of ease of processing and stable generation of discharge, but the cross-sectional shape of the plasma holding unit 13 is a polygon such as a triangle or a quadrangle, or an elliptical shape. Or any other shape such as a star shape. Further, the cross-sectional shape of the plasma holding unit 13 may be different in the depth direction of the plasma holding unit 13. For example, when the shape of the plasma holding unit 13 is cylindrical, the inner diameter of the plasma holding unit 13 is preferably 2 mm or more and 30 mm or less, more preferably 5 mm or more. 20 mm or less is good. From the viewpoint of generating the plasma 2 stably and uniformly in the plasma holding unit, it is not preferable that the inner diameter of the plasma holding unit 13 is too small because the plasma 2 does not enter the plasma holding unit, and the inner diameter of the plasma holding unit 13 is too large. It is not preferable because it is difficult to uniformly generate the plasma 2 inside the plasma holding unit 13. Further, if the depth of the plasma holding portion 13 is too shallow, the plasma 2 does not enter the plasma holding portion, and if it is too deep, the electrode size becomes too large. Therefore, it is preferably 5 mm or more and 30 mm or less, more preferably 10 mm or more. 20 mm or less is good. Although any arrangement of the plasma holding units 13 can be selected, the plasma holding unit 13 is formed in a square lattice shape as shown in FIG. Although not, it is preferable to arrange them equally in an equilateral triangular lattice. In addition, in order to adjust the uniformity of the plasma 2 in the surface of the cathode electrode 3, the arrangement of the plasma holding unit 13 may be intentionally nonuniform.

  An anode electrode 14 is provided between the cathode electrode 3 and the substrate holding mechanism 5. The anode electrode 14 is preferably electrically grounded. If the thickness of the anode electrode 14 is too thin, it is not preferable because warpage occurs during use or plasma localization is insufficient, and if it is too thick, the active species necessary for the plasma treatment are sufficient for the substrate. Since it is not supplied, it is not preferable. Therefore, the thickness of the anode electrode 14 is 3 mm or more and 15 mm or less, preferably 5 mm or more and 10 mm or less. The anode electrode 14 is disposed substantially parallel to the cathode electrode 3 and the substrate holding mechanism 5. A through hole 15 is formed in the anode electrode 14 at a position facing the plasma holding portion 13 of the cathode electrode 3. The cross-sectional shape of the through hole 15 formed in the anode electrode 14 may be the same as the cross-sectional shape of the plasma holding unit 13 of the cathode electrode 3, but may be different. Further, the cross-sectional shape of the through hole 15 may be the same or changed in the thickness direction of the anode electrode 14. In the plasma processing apparatus of the present invention, the plasma 2 generated in the plasma holding unit can be localized by arranging the cathode electrode 3 and the anode electrode 14 close to each other during the plasma processing. At this time, if the anode electrode 14 is set to the ground potential, the high-frequency electric field from the cathode electrode 3 is shielded by the anode electrode 14, so that it is possible to prevent the plasma 2 from being generated in the space between the anode electrode 14 and the substrate 3. ,preferable.

  However, when the cathode electrode 3 and the anode electrode 14 are arranged close to each other, it is difficult to uniformly generate the plasma 2 in all the plasma holding portions when trying to ignite the plasma in that state, and a part of the plasma holding The plasma 2 is not generated in the part, or the emission intensity of the plasma 2 varies depending on the position. Therefore, the plasma processing apparatus according to the present invention includes an anode electrode position varying mechanism 16 for changing the distance between the cathode electrode 3 and the anode electrode 14. The anode electrode position varying mechanism 16 can be applied to the present invention as long as the position of the anode electrode 14 can be moved between the cathode electrode 3 and the substrate 4. For example, as shown in FIG. Furthermore, the anode electrode 14 is fixed to the shaft of the linear introduction mechanism using the bellows, and is driven using a linear motion mechanism using an air cylinder or a ball screw (not shown) to change the position of the anode electrode 14. be able to. If such an anode electrode position varying mechanism 16 is provided, uniform plasma generation can be realized by the method described below.

  In order to make the plasma uniform in all plasma holding portions, first, in the case of the apparatus of FIG. 1, the anode electrode 14 is moved away from the cathode electrode 3 as shown in FIG. (In the case of the apparatus shown in FIGS. 3, 6, and 8, FIGS. 5, 7, and 9 correspond to FIG. 4 in the case of the apparatus shown in FIG. 1, respectively.) The same for). At this time, the distance between the anode electrode 14 and the cathode electrode 3 at the time of plasma ignition is preferably 5 mm or more, preferably 10 mm or more from the viewpoint of plasma uniform ignition. When the plasma is generated in a state where the cathode electrode 3 and the anode electrode 14 are separated from each other, the plasma is in a single connected state in the space between the cathode electrode 3 and the anode electrode 14. Since the plasma is not in an individually divided state, the plasma is generated in an autonomously uniformed state. Thereafter, the anode position varying mechanism 16 is operated to bring the distance between the cathode electrode 3 and the anode electrode 14 closer as shown in FIG. At this time, the distance between the cathode electrode 3 and the anode electrode 14 is 0.5 mm or more and 3 mm or less, more preferably 0.7 mm or more and 2 mm or less. This is preferable from the viewpoint of localization in a space formed by the portion 13 and the through-hole 15 of the anode electrode 14. In order to ensure that the anode electrode 14 is electrically grounded even in a movable state, the anode electrode 14 is connected by a flexible grounding member 17 that electrically connects a fixed ground potential surface such as a vacuum vessel wall surface and the anode electrode. This is more preferable.

  FIG. 6 is a schematic sectional view showing another example of the plasma processing apparatus in the present invention. The cathode electrode 3 is hollow, and an exhaust chamber 19 is formed by this hollow space. The plasma holding unit 13 has a cylindrical shape communicating with the exhaust chamber 19. Further, the vacuum exhaust device 6 is connected to a hollow portion of the cathode electrode 3, that is, an exhaust chamber 19. At this time, the shape of the plasma holding unit 13 is preferably a cylindrical shape with a circular cross-sectional shape from the viewpoint of ease of processing and stable generation of discharge, but the cross-sectional shape of the plasma holding unit 13 is a polygon such as a triangle or a quadrangle, An arbitrary shape such as an elliptical shape or a star shape may be used. Further, the cross-sectional shape of the plasma holding unit 13 may be different in the depth direction of the plasma holding unit 13. For example, when the shape of the plasma holding unit 13 is cylindrical, the inner diameter of the plasma holding unit 13 is preferably 2 mm or more and 30 mm or less, more preferably 5 mm or more. 20 mm or less is good. From the viewpoint of stably and uniformly generating the plasma 2 in the plasma holding unit, it is not preferable that the inner diameter of the plasma holding unit 13 is too small because the plasma 2 does not enter the plasma holding unit. Further, if the inner diameter of the plasma holding portion 13 is too small, the exhaust conductance becomes small and the exhaust capability from the cathode electrode 2 is lowered, which is not preferable. Further, if the inner diameter of the plasma holding portion 13 is too large, it is difficult to uniformly generate the plasma 2 within the surface of the cathode electrode 3, which is not preferable. If the depth of the plasma holding unit 13 is too shallow, the plasma 2 may enter the exhaust chamber 19 and the wall surface inside the exhaust chamber 19 may become dirty or the loss of power supplied from the power supply 10 may increase. In addition, if the depth of the plasma holding unit 13 is too deep, the exhaust conductance of the plasma holding unit 13 becomes small, the exhaust capacity is lowered, and the size of the cathode electrode 3 becomes too large. Therefore, the depth of the plasma holding part 13 is preferably 8 mm or more and 40 mm or less, more preferably 13 mm or more and 30 mm or less. Arbitrary arrangements can be selected for the arrangement of the plasma holding unit 13, but from the viewpoint that the plasma 2 can be generated uniformly in the plane of the cathode electrode 3, the plasma holding unit 13 is evenly arranged in a square lattice shape or an equilateral triangular lattice shape. It is preferable to arrange. Moreover, in order to adjust the in-plane uniformity of the plasma 2 at the cathode electrode 3, it is possible to intentionally make the arrangement of the plasma holding portions 13 non-uniform.

  The plasma holding part 13 is formed on the cathode electrode 3, and the plasma 2 is formed in the plasma holding part (a space formed by the plasma holding part 13 of the cathode electrode 3 and the through hole 15 of the anode electrode 14). It is a preferable configuration from the viewpoint of preventing unwanted substances from being mixed into the film so that the unnecessary substances generated in step 1 can be quickly discharged from the vacuum container 1 by the exhaust flow toward the plasma holding unit 13.

  The plasma processing apparatus shown in FIG. 6 also includes an anode electrode position varying mechanism 16 for changing the distance between the cathode electrode 3 and the anode electrode 14. The anode electrode position varying mechanism 16 makes it possible to achieve uniform plasma generation in the following manner. In order to generate the plasma 2 uniformly in all the through-holes 15, first, the anode electrode 14 is moved away from the cathode electrode 3 as shown in FIG. 7, and the distance between the cathode 3 and the anode 14 is increased. The distance between the anode electrode 14 and the cathode electrode 3 during plasma ignition is preferably 5 mm or more, and more preferably 10 mm or more from the viewpoint of plasma uniform ignition. When the plasma is generated in a state where the cathode electrode 3 and the anode electrode 14 are separated from each other, the plasma 2 becomes a single connected state in the space between the cathode electrode 3 and the anode electrode 14. Since the plasma 2 is not in an individually divided state, the plasma 2 is generated in an autonomously uniformed state. Thereafter, the anode position varying mechanism 16 is operated to bring the distance between the cathode electrode 3 and the anode electrode 14 closer as shown in FIG. At this time, the distance between the cathode electrode 3 and the anode electrode 14 is 0.5 mm or more and 3 mm or less, and more preferably 0.7 mm or more and 2 mm or less, so that the plasma 2 is localized in the plasma holding portion of the cathode electrode 3. It is preferable from the viewpoint of being present. A flexible ground member that electrically connects the fixed ground potential surface such as the wall surface of the vacuum vessel 1 and the anode electrode 14 in order to ensure that the anode electrode 14 is electrically grounded even in the movable state. 17 is more preferable.

  8 and 9 are schematic sectional views showing another example of the anode electrode position varying mechanism 16 in the plasma processing apparatus of the present invention. The electrode position varying mechanism 16 in FIGS. 1 and 3 to 7 has a structure that supports the anode electrode 14 from the direction of the cathode electrode 3, but supports the anode electrode 14 from the direction of the substrate 4 as shown in FIG. 8, for example. It may be a structure. FIG. 8 shows a state in which the cathode electrode 3 and the anode electrode 14 are brought close to each other, and FIG. 9 shows a state in which the cathode electrode 3 and the anode electrode 14 are moved away from each other. The electrode position varying mechanism 16 is not limited to such a configuration.

  The present invention can be applied to an apparatus that performs various plasma treatments such as film formation, etching, and surface treatment. However, it is particularly effective in a process in which unnecessary by-products are formed during the treatment. For example, in dry etching using a halogen gas, there is a film peeling during processing or generation of particles due to deterioration of internal structures, which adversely affects the process. However, it is particularly suitable to apply to a plasma CVD apparatus. In plasma CVD, it is difficult to limit the reaction of active species generated in the plasma to only the film-forming surface, and a binding reaction of active species in the gas phase occurs, and unnecessary substances such as fine particles are likely to be generated. Under such circumstances, when the plasma is generated only in the vicinity of the cathode electrode and the generation of the plasma in the vicinity of the substrate is suppressed as in the present invention, the effect of preventing the mixing of unnecessary substances into the film becomes prominent. Conceivable.

Example 1
Next, the case where the plasma processing apparatus described above is applied to the formation of an amorphous silicon thin film by plasma CVD will be described.

An amorphous silicon thin film was formed using the apparatus shown in FIGS. In the cathode electrode 3 provided with a plurality of plasma holding portions 13, the shape of the plasma holding portion 13 was a cylindrical recess, the inner diameter of the plasma holding portion 13 was 10 mm, and the depth was 15 mm. The anode electrode 14 having a thickness of 10 mm was used, and through holes 15 were provided at positions facing the plurality of plasma holding portions 13 of the cathode electrode 3 on the surface of the anode electrode 14. The inner diameter of the through hole 15 was 10 mm. A glass substrate was placed as the substrate 4 on the substrate holding mechanism 5, and the distance between the cathode electrode 3 and the surface of the substrate 4 was 45 mm. A silane gas of 30 sccm as a source gas was supplied to the inside of the vacuum vessel 1 from the gas supply port 8 provided in the cathode electrode 3 through the gas supply pipe 7, and the pressure inside the vacuum vessel 1 was adjusted to 30 Pa. The power supply 10 was a high frequency power supply having a frequency of 60 MHz. First, as shown in FIG. 2, the gap between the cathode electrode 3 and the anode electrode 14 was increased using the anode electrode position varying mechanism 16, and the gap was set to 30 mm. When electric power of 50 W was supplied to the cathode electrode 3, plasma 2 was formed in the space between the cathode electrode 3 and the anode electrode 14. Thereafter, the gap between the cathode electrode 3 and the anode electrode 14 was narrowed by using the anode electrode position varying mechanism 16, and the gap was set to 1 mm. At this time, the plasma 2 changes so as to enter and disperse in a large number of independent spaces formed by the plasma holding portion 13 of the cathode electrode 3 and the through holes 15 of the anode electrode 14, and all the plasma holding Plasma 2 could be generated uniformly and stably in the part.
(Example 2)
An amorphous silicon thin film was formed using the apparatus shown in FIGS. In the cathode electrode 3 provided with a plurality of plasma holding portions 13, a hollow exhaust chamber 19 is provided inside the cathode electrode 3, and the shape of the plasma holding portion 13 is a cylindrical shape communicating with the exhaust chamber 19. The inner diameter was 10 mm and the depth was 15 mm. The anode electrode 14 having a thickness of 10 mm was used, and through holes 15 were provided at positions facing the plurality of plasma holding portions 13 of the cathode electrode 3 on the surface of the anode electrode 14. The inner diameter of the through hole 15 was 10 mm. A glass substrate was placed on the substrate holding mechanism 5 as the substrate 4, and the distance between the cathode electrode 3 and the substrate 4 was 45 mm. A silane gas of 30 sccm as a source gas was supplied to the inside of the vacuum vessel 1 from the gas supply port 8 provided in the cathode electrode 3 through the gas supply pipe 7, and the pressure inside the vacuum vessel 1 was adjusted to 30 Pa. The power supply 10 was a high frequency power supply having a frequency of 60 MHz. First, as shown in FIG. 2, the gap between the cathode electrode 3 and the anode electrode 14 was increased using the anode electrode position varying mechanism 16, and the gap was set to 30 mm. When electric power of 50 W was supplied to the cathode electrode 3, plasma was formed in the space between the cathode electrode 3 and the anode electrode 14. Thereafter, the gap between the cathode electrode 3 and the anode electrode 14 was narrowed by using the anode electrode position varying mechanism 16, and the gap was set to 1 mm. At this time, the plasma 2 changes so as to enter and disperse in a large number of independent spaces formed between the plasma holding portion 13 of the cathode electrode 3 and the through hole 15 of the anode electrode 14. It was possible to generate plasma uniformly and stably in all plasma holding portions.
(Comparative example)
An amorphous silicon thin film was formed using the apparatus shown in FIG. In the cathode electrode 3 provided with a plurality of recesses 23, the shape of the recesses 23 was cylindrical, the inner diameter of the recesses 23 was 10 mm, and the depth was 15 mm. The anode electrode 14 having a thickness of 10 mm was used, and through holes 15 were provided at positions facing the plurality of recesses 23 of the cathode electrode 3 on the surface of the anode electrode 14. The inner diameter of the through hole 15 of the anode electrode 14 was 10 mm. A glass substrate was placed on the substrate holding mechanism 5 as the substrate 4, and the distance between the cathode electrode 3 and the substrate 4 was 45 mm. A silane gas of 30 sccm as a source gas was supplied to the inside of the vacuum vessel 1 from the gas supply port 8 provided in the cathode electrode 3 through the gas supply pipe 7, and the pressure inside the vacuum vessel 1 was adjusted to 30 Pa. The power supply 10 was a high frequency power supply having a frequency of 60 MHz. The interval between the cathode electrode 3 and the anode electrode 14 is fixed at 1 mm. When power of 50 W is supplied to the cathode electrode 3, the plasma enters and disperses in a number of independent spaces formed between the recesses 23 of the cathode electrode 3 and the through holes 15 of the anode electrode 14. Occurred. However, plasma was not lit in some through holes 15. I tried to give fluctuations such as changing the electric power and changing the pressure, but when the pressure was finally returned to 30 Pa and electric power 50 W, it was impossible to form plasma uniformly in all the recesses 23 and the through holes 15. could not.

The present invention is not limited to the plasma CVD apparatus among the plasma processing apparatuses, but can be applied to other apparatuses such as a plasma etching apparatus and a plasma surface modification apparatus, but the application range is limited thereto. It is not a thing.

DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Plasma 3 Cathode electrode 4 Substrate 5 Substrate holding mechanism 6 Vacuum exhaust apparatus 7 Gas supply pipe 8 Gas supply port 9 Insulator 10 Power supply 11 Substrate heating mechanism 12 Earth shield 13 Plasma holding part 14 Anode electrode 15 Through-hole 16 Anode Electrode position variable mechanism 17 Flexible grounding member 18 Exhaust hole 19 Exhaust chamber 20 Exhaust piping 21 Connecting portion 22 Ground electrode 23 Recessed portion

Claims (4)

Inside a vacuum vessel equipped with a vacuum exhaust device that holds the inside at a reduced pressure, a cathode electrode, a substrate holding mechanism that holds the substrate facing the cathode electrode, and an anode between the cathode electrode and the substrate holding mechanism And a plasma processing apparatus having a power source connected to the cathode electrode,
The cathode electrode includes a plasma holding portion opened to the film formation substrate side and a connecting portion for connecting the plasma holding portion, and the anode electrode has a through hole formed at a position facing the plasma holding portion of the cathode electrode. and said cathode electrode and / or the anode electrode have a moving mechanism for increasing or decreasing the distance between the electrodes, wherein the movable mechanism is spread distance between the cathode electrode and the anode electrode during plasma ignition, the plasma processing cathode The said plasma processing apparatus which is a movable mechanism which arrange | positions an electrode and an anode electrode closely . The plasma processing apparatus according to claim 1, wherein the plasma holding unit has a concave shape in which only the deposition substrate side is opened. The cathode electrode is hollow, and the plasma holding part is in a cylindrical shape communicating with a hollow part,
The plasma processing apparatus according to claim 1, wherein the vacuum exhaust apparatus is connected to a hollow portion of the cathode electrode. A plasma deposition substrate is disposed in the substrate holding mechanism of the plasma processing apparatus according to any one of claims 1 to 3 and gas is introduced into a vacuum vessel so that the cathode electrode and the anode electrode are separated from each other. After igniting, the cathode electrode and the anode electrode are brought close to each other.

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