JP4672436B2 - Plasma processing equipment - Google Patents

Description

The present invention is, in particular, to a plasma treatment MakotoSo location that may be used to uniformly form a thin film on a large area substrate for use in liquid crystal art.

  In recent years, as the demand for large-screen, high-quality, low-cost liquid crystal displays and organic electroluminescence display panels increases, the increase in the size of the mother glass used for production thereof has been accelerated.

  Today, the demand for large-sized, high-quality, low-priced liquid crystal displays and organic electroluminescence display panels is increasing, and the increase in the size of the mother glass used for production thereof is accelerating. Along with this, in the process of manufacturing devices on a substrate, in the process steps such as film formation around the plasma, etching, surface modification, etc., increasing the processing area and in-plane uniformity of processing performance are important issues. ing.

  Conventionally, in order to form a thin film transistor, amorphous silicon (a-Si), silicon nitride (SiNx), silicon oxide (SiOx), silicon oxynitride (SiOxNy), n-doped amorphous silicon (n + a) are formed by high-frequency plasma CVD. A method of depositing -Si) on a substrate has been employed.

  When these thin films are formed on the substrate, the film forming gas is turned into plasma using high frequency power in a plasma CVD apparatus. However, the larger the size of the electrode that supplies high-frequency power with an increase in the size of the substrate, the more the standing wave generated on the electrode affects the in-plane uniformity of the plasma density, resulting in a non-uniform deposition film thickness. It is known to cause sexual deterioration.

  Conventionally, in order to form a thin film transistor, amorphous silicon, a silicon nitride film, and n-doped amorphous silicon are deposited on a substrate by a high-frequency plasma CVD method. There's a problem. On the other hand, low-damage film formation is desirable for a thin film forming a thin film transistor. For this purpose, film formation at a frequency higher than the industrial frequency of 13.56 MHz is desirable. However, since the influence of the standing wave is more susceptible to a shorter distance as the frequency increases, a method such as cathode division has been proposed to use a higher frequency, but this also has a problem.

  More specifically, since the voltage distribution is generated in the electrode plane than the influence of the standing wave, the plasma intensity is distributed. Therefore, distribution occurs in the film quality and film thickness of the deposited thin film.

  At the same time, the larger the size of the substrate used, the larger the size of the electrode, the larger the vacuum chamber in which the electrode and the substrate holder are arranged, and the higher the high-frequency power supplied to the plasma. Since the relative size is reduced, it is also known that the influence of plasma on the current distribution flowing from the substrate holder on which the substrate is placed to the ground potential via the vacuum chamber wall cannot be ignored.

  FIG. 17 of the accompanying drawings shows an example of a conventional plasma CVD apparatus. In FIG. 17, A is a vacuum chamber, and a substrate holder B and an electrode C are disposed inside the vacuum chamber A so as to face each other. The substrate holder B is attached to the bottom wall of the vacuum chamber A, has a heater D inside, and a substrate E is placed on the upper surface.

The electrode C is attached to the top of the vacuum chamber A through an insulating member F, and is connected to a film forming gas introduction system (not shown) through a film forming gas supply port G.
Although not shown, the electrode C is not shown, but is connected to a high frequency power source, and the vacuum chamber A is provided with an evacuation system.

 In the conventional apparatus configured as described above, a high-frequency power source having a frequency of 13.56 MHz or 27.12 MHz is usually used as the high-frequency power source. When the size of the substrate E is 1 m × 1 m or less, the film thickness distribution obtained can be made ± 10% or less by optimizing the film formation conditions according to the type of film to be deposited.

 However, when the substrate size is 1 m × 1 m or more, the desired uniformity of the film thickness distribution cannot be ensured for the reasons described above.

 In order to solve such problems, conventionally, an electrode for supplying high-frequency power is divided into a central portion and a peripheral portion, and the distance between the electrode and the substrate holder in the central portion and the peripheral portion of the electrode can be adjusted to make plasma. A plasma CVD apparatus has been proposed in which the distribution is adjusted and the film thickness distribution is made uniform (see Patent Document 1).

 Further, the electrode is divided into a plurality of small electrodes so that the distance between the electrode and the substrate holder is continuous at the boundary between the divided electrodes, and the high-frequency power supplied to each small electrode is adjusted, thereby A plasma processing apparatus that makes the thickness distribution uniform has also been proposed (see Patent Document 2).

Further, in the plasma forming apparatus, the conductive region and the insulating region are alternately formed on the boundary surface facing the one discharge space of the pair of electrodes that define the discharge space therebetween, so that the charge on the surface of the insulating region is reduced. It has also been proposed in the past to locally enhance the electric field in the vicinity of the surface by accumulation of electrons, thereby emitting electrons uniformly over the entire surface and improving the uniformity and stability of the plasma (patent) Reference 3).
Japanese Patent Laid-Open No. 10-289881 JP 2003-68651 A JP 2005-63973 A

  However, the apparatus described in Patent Document 1 has a problem that plasma becomes unstable and a thin film cannot be formed uniformly because the boundary between the central part and the peripheral part of the electrode is discontinuous.

 In addition, in the invention described in Patent Document 2, in practice, it is difficult to stabilize plasma at the boundary between divided small electrodes, abnormal discharge is likely to occur, and a condition for uniformizing the thin film is found. There is a problem that is difficult. Further, the reaction product easily adheres to and peels from the interface between the electrodes, so that it becomes a source of particles in the apparatus and a source of abnormal discharge, resulting in a problem that the yield of the product is lowered.

  Furthermore, in the invention described in Patent Document 3, since the electrode surface has a step between the conductive region and the insulating region and is not flat, abnormal discharge occurs at the step portion between the conductive region and the insulating region. There is a problem that it is easy to maintain a stable plasma formation. Also, as shown in FIGS. 4a and 4c of Patent Document 3, when the dielectric has a rectangular shape such as a rectangular shape, an electric field is locally generated at the corner particularly in a discharge using a high frequency. As a result, the discharge concentrates on the metal-dielectric boundary on the surface, thereby causing dust due to the melting phenomenon of the metal portion. There is also a problem that the reaction product adheres to the step boundary and is easily peeled off.

Accordingly, the present invention is to solve the above problems associated with the prior art, uniform and stable plasma can be formed, film formation can be a plasma treatment MakotoSo location with uniform thickness and quality distributions on a large area substrate The purpose is to provide.

In order to achieve the above object, according to the first invention of the present invention,
A substrate placed on the substrate holder, placed in the vacuum chamber, with a substrate holder and an electrode facing each other, introducing a gas into the vacuum chamber and supplying high-frequency power to the electrode. In a plasma processing apparatus using capacitively coupled glow discharge for performing plasma processing on
The electrode is composed of a metal electrode body and a plurality of dielectrics embedded in the surface of the metal electrode body facing the substrate holder,
The surface of the electrode facing the substrate holder is flat;
End surfaces of a plurality of dielectrics embedded in the surface are located in the same plane as the surface of the electrode;
When the wavelength of the frequency of the high-frequency power supplied to the electrode is λ, in the first circular region in which the diameter centered on the center of the electrode is set in the range of λ / 8 to λ / 4, the surface of the electrode The ratio of the surface area of the metal to the surface area of the dielectric is 7: 3 to 5: 5 .

In the plasma processing apparatus according to the first aspect of the present invention, when the surface of the electrode facing the substrate holder is flat and the wavelength of the frequency of the high-frequency power supplied to the electrode is λ, the electrode is outside the first circular region. In the second circular region in which the diameter around the center of the electrode is set in the range of λ / 4 to λ / 3 , the ratio of the surface area of the metal to the surface area of the dielectric on the surface of the electrode is 8: 2 to 7: 3. In the third circular region where the diameter centered on the center of the electrode outside the second circular region is set in the range of λ / 3 to λ / 2 , the surface area of the metal and the dielectric on the surface of the electrode The surface area ratio may be approximately 8: 2.

  Each dielectric may be a columnar structure having an elliptical or circular cross section.

  When each dielectric is on a cylinder, each of the plurality of cylindrical dielectrics embedded in the surface of the electrode facing the substrate holder can be dimensioned in a range of 5-20 mm in diameter and 5-20 mm in height. .

  A plurality of dielectrics embedded in the surface of the electrode facing the substrate holder are arranged at equal intervals on the surface of the electrode, and the diameter of each dielectric embedded in the center of the surface of the electrode is embedded in the peripheral part of the electrode Can be larger than the diameter of the dielectric

  The number of the plurality of dielectrics embedded in the surface of the electrode facing the substrate holder can be large at the center portion of the electrode and small at the peripheral portion.

  Instead, a columnar dielectric having a high height may be embedded in the center of the surface of the electrode facing the substrate holder, and a columnar dielectric having a low height may be embedded in the peripheral portion of the surface of the electrode.

  A plurality of dielectrics embedded in the surface of the electrode facing the substrate holder may be concentrically arranged on the surface of the electrode.

  A plurality of dielectrics embedded in the surface of the electrode facing the substrate holder may be arranged at equal intervals on the surface of the electrode.

  Each dielectric may be made of a material selected from the group comprising ceramics such as alumina, A1N, macerite, and combinations thereof.

  The electrode is made of aluminum and its alloy as a base material, and can be subjected to any surface treatment of alumite, alumina spraying, Y2O3 spraying.

  The electrode may be composed of a shower head and a shower plate that are integrally formed.

  In the present specification, the term “large area substrate” means a substrate having an arbitrary shape having a size of 1 m × 1 m or more in length and width and a length of a long side or a long diameter of 1 m or more.

As described above, in the apparatus according to the first aspect of the present invention, the electrode includes the metal electrode main body and the plurality of dielectrics embedded in the surface of the metal electrode main body facing the substrate holder. By configuring, uniform plasma is formed on a large-area substrate even at a high frequency of 27.12 MHz by controlling a plasma current which is one of the factors controlling the plasma, and the film quality and film are formed within the substrate surface. A film having a uniform thickness distribution can be obtained.

  Further, the surface of the metal electrode body facing the substrate holder is flat, and the end surfaces of the plurality of dielectrics embedded in the surface are positioned in the same plane as the surface of the metal electrode body. As a result, the electric field is not concentrated locally at the junction between the dielectric and the metal, so that the occurrence of abnormal discharge is suppressed, so that the discharge does not concentrate at the boundary between the metal and the dielectric on the surface. Generation of dust due to a melting phenomenon or the like can be prevented.

  Further, in the plasma processing apparatus according to the first aspect of the present invention, each dielectric has a columnar structure with an elliptical or circular cross-sectional shape, so that an electric field is locally concentrated particularly in a discharge using a high frequency. Abnormal discharge can be prevented because there are no corners to prevent the discharge from concentrating on the boundary between the metal on the surface and the dielectric, and the melting phenomenon of the metal part that causes dust can be prevented.

  In the plasma processing apparatus according to the first aspect of the present invention, when each dielectric is on a cylinder, a plurality of columnar dielectrics embedded in the surface of the electrode facing the substrate holder are provided with a diameter of 5 Dimensioning in a range of ˜30 mm and a height of 5-20 mm facilitates handling when a dielectric is embedded in a metal electrode, and is particularly a standard film formation in a plasma CVD method in which a thin film transistor is formed on glass. When growing on the substrate depending on the conditions, it is possible to prevent a significant difference between the deposition area at the dielectric exposure portion and the deposition area at the metal exposure portion, and the voltage distribution equalization effect is further improved.

  In the plasma processing apparatus according to the first aspect of the present invention, the number of the plurality of dielectrics embedded in the surface of the electrode facing the substrate holder is increased at the central portion of the electrode and decreased at the peripheral portion. , Increase the impedance per unit area at the center of the electrode (corresponding to resistance when considered in terms of direct current), decrease the plasma current at the center of the electrode, decrease the plasma intensity, This has the effect of increasing the plasma intensity and increasing the plasma intensity.

 Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 shows a plasma CVD apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a vacuum chamber, and a substrate holder 2 that functions as an anode and an electrode 3 that functions as a cathode are disposed inside the vacuum chamber 1 so as to face each other. The substrate holder 2 is attached to the bottom wall of the vacuum chamber 1, includes a heater 4 inside, and a large area substrate 5 is placed on the upper surface of the substrate holder 2. The electrode 3 is made of aluminum and its alloy as a base material, and is subjected to any surface treatment of alumite, alumina spraying, or Y2O3 spraying. All metal substrate and the surface treatment used is required to have corrosion resistance to NF ₃ or F ₂ or CF-based gas used during the self-cleaning. Note that the present invention is not limited to the plasma CVD apparatus, and can be similarly applied to an etching process or a plasma process for surface modification.

  The substrate holder 2 can be moved up and down by a lifting mechanism (not shown), whereby the distance from the electrode 3 can be adjusted, and the distance between the substrate holder 2 and the electrode 3 can be changed during film formation and cleaning. To be. In this case, the lifting mechanism also carries a large-area substrate 5 to be processed from the outside to the inside of the vacuum chamber 1 and a transfer operation when the processed large-area substrate 5 is unloaded from the inside of the vacuum chamber 1 to the outside. It can also be used for raising and lowering the substrate.

  The electrode 3 is attached to the top of the vacuum chamber 1 via an insulating member 6. The surface of the electrode 3 facing the substrate holder 2 is formed in a flat shape. Further, the outer dimension of the electrode 3 is configured to be larger than the outer dimension of the large area substrate 5 placed on the substrate holder 2.

  The electrode 3 includes an electrode base 7, an integrally configured shower head 8, and a shower plate 9 that forms a metal electrode body. The shower head 8 and the shower plate 9 are integrally configured. A cylindrical dielectric 10 having the same thickness and height is embedded in the shower plate 9, and the exposed end surface of each cylindrical dielectric 10 is in the same plane as the surface of the shower plate 9 facing the substrate holder 2. Is located. As shown in the figure, the cylindrical dielectric 10 is embedded at a high density in the central portion of the shower plate 9 and at a low density in the peripheral portion of the shower plate 9.

  The material of the dielectric 10 is selected from the group consisting of ceramics such as alumina, AlN (aluminum nitride), macerite, etc., which have corrosion resistance to NF3, F2 or CF gas used for self-cleaning, and combinations thereof. Is done.

  Although not shown in FIG. 1, the shower plate 9 is provided with a large number of gas discharge holes 11 at portions other than the columnar dielectric 10 as shown in FIG. 2. Thereby, the film forming gas supplied from the film forming gas supply source (not shown) to the inside of the shower head 8 through the film forming gas supply port 12 is diffused and mixed inside the shower head 8, and the shower plate 9 from a large number of gas discharge holes 11 toward the large area substrate 5 on the substrate holder 2.

  FIG. 3 shows zoning on the surface of the shower plate 9. The first zone A is a first circle whose diameter centered on the center of the electrode 3 is set in a range of 1/8 to 1 / 4λ when the wavelength of the frequency of the high frequency power supplied to the electrode 3 is λ. The second zone B is a second circular region whose diameter centered around the center of the electrode outside the first zone A is set to a range of ¼ to ３λ, and the third zone C is a third circular region having a diameter outside the second zone B and having a diameter of about 1/3 to 1 / 2λ centered on the center of the electrode.

  Note that the zoning is not limited to three, but can be two or four or more according to the size of the electrode. Further, the shape of the electrode need not be rectangular, and other shapes such as a circle can be similarly applied.

  Although not shown, the electrode 3 is supplied with high frequency power from a high frequency power source via a matching unit. The vacuum chamber 1 and the substrate holder 2 are connected to the ground potential.

  Although not shown, the vacuum chamber 1 has a film formation gas introduction system for introducing a film formation gas into the vacuum chamber 1 from an external film formation gas supply source, and vacuum exhaust and film formation gas in the vacuum chamber 1. An evacuation system for evacuating the air is provided.

  FIG. 4 shows a plasma CVD apparatus according to another embodiment of the present invention. In FIG. 4, corresponding parts in the apparatus of FIG. As in the case of the apparatus of FIG. 1, a substrate holder 2 that functions as an anode and an electrode 3 that functions as a cathode are arranged inside the vacuum chamber 1 so as to face each other. The substrate holder 2 is attached to the bottom wall of the vacuum chamber 1, includes a heater 4 inside, and a large area substrate 5 is placed on the upper surface of the substrate holder 2.

  The substrate holder 2 can be moved up and down by a lifting mechanism (not shown), whereby the distance from the electrode 3 can be adjusted, and the distance between the substrate holder 2 and the electrode 3 can be adjusted during film formation and cleaning. To be changed. In this case, the lifting mechanism also carries a large-area substrate 5 to be processed from the outside to the inside of the vacuum chamber 1 and a transfer operation when the processed large-area substrate 5 is unloaded from the inside of the vacuum chamber 1 to the outside. It can also be used for raising and lowering the substrate.

  The electrode 3 includes an electrode base 7, an integrally configured shower head 8, and a shower plate 9 that forms a metal electrode body. The shower head 8 and the shower plate 9 are integrally configured. A cylindrical dielectric 10 having the same thickness is embedded in the shower plate 9, and the exposed end surface of each cylindrical dielectric 10 is located in the same plane as the surface of the shower plate 9 facing the substrate holder 2. Yes. As shown in FIG. 5, a cylindrical dielectric 10 having a high height is embedded in the center of the shower plate 9, and a cylindrical dielectric 10 having a low height is embedded in the periphery of the shower plate 9. It is.

  As in the case of the embodiment shown in FIG. 1, although not shown, the shower plate 9 is provided with a large number of gas discharge holes 11 at portions other than the columnar dielectric 10 as shown in FIG. It has been. Thereby, the film forming gas supplied from the film forming gas supply source (not shown) to the inside of the shower head 8 through the film forming gas supply port 12 is diffused and mixed inside the shower head 8, and the shower plate 9 from a large number of gas discharge holes 11 toward the large area substrate 5 on the substrate holder 2.

  The arrangement pattern of the columnar dielectrics 10 on the surface of the shower plate 9 is the same as the example shown in FIG. 3. In this case, the diameter of the dielectrics 10 and the interval between the dielectrics 10 are fixed, and the first In the zone A, a cylindrical dielectric 10 having a diameter of 10 mm and a length of 10 mm is concentrically embedded in the zone A, and in the second zone B, the dielectric 10 having a distance of 10 mm and a length of 7 mm is embedded concentrically. In the third zone C, a dielectric 10 having a length of 4 mm and an interval of 10 mm is concentrically embedded.

 Although not shown, the vacuum chamber 1 is provided with an evacuation system for evacuating the vacuum chamber 1 and evacuating the film forming gas. Further, the outer dimension of the electrode 3 is configured to be larger than the outer dimension of the large area substrate 5 placed on the substrate holder 2.

  In the operation of the apparatus of FIG. 1 and FIG. 4 configured as described above, when high-frequency power is supplied to the electrode 3 from a high-frequency power source (not shown) via a matching unit, an external film-forming gas supply (not shown) is supplied. The film forming gas introduced from the source into the vacuum chamber 1 is converted into plasma in the vacuum chamber 1 by capacitively coupled glow discharge using the substrate holder 2 as an anode and the electrode 3 as a cathode. In this case, since the dielectric 10 is embedded in the electrode 3, without causing abnormal discharge, the impedance in the plane is changed to make the current distribution in the plane uniform, thereby forming a uniform plasma. be able to.

  On the other hand, the large area substrate 5 is heated to a predetermined temperature in advance by a heater 4 built in the substrate holder 2. As a result, the reaction product of the film-forming gas that has been turned into plasma reaches the surface of the substrate 5 and forms a desired thin film having a good film thickness distribution on the substrate.

 By the way, in the embodiment of FIG. 4, the length of the cylindrical dielectric is changed stepwise between the central portion and the peripheral portion of the electrode surface. Instead, as shown in FIG. The length can also be shortened continuously from the edge toward the periphery.

 Further, in the illustrated embodiment, a cylindrical material is used as the dielectric, but it may be a shape having no corners in the discharge space, and a dielectric on an elliptic cylinder having an elliptical cross section may be used.

Next, the present invention will be further described with reference to FIGS.
Although the actual electrode is a plane, two-dimensional rectangular coordinates are used for the sake of simulation. Further, considering the symmetry of the shape, the vertical center line was set as the symmetry plane, and 1/2 (1800 mm) of the whole was set as the analysis region. The coordinate axes are taken as shown in FIGS.

  The drive electrode (shower plate) having the conventional structure shown in FIG. 7 has a thickness of 80 mm, and the distance to the ground electrode, that is, the substrate holder, is 15 mm.

  Further, in FIG. 8, as a case 1, a cylindrical electrode made of alumina (ε = 9.0) having a diameter of 10 mm and a length of 10 mm is formed on a drive electrode (shower plate) in a central region from a center line X = 0 to 1250 mm. Are arranged concentrically with an interval w = 5 mm, regions with X = 1250 to 1650 mm are arranged with concentric circles with an interval w = 10 mm, and regions with X = 1650-1800 mm are arranged concentrically with an interval w = 15 mm An example is shown.

  Further, in FIG. 9, as a case 2, a cylindrical region made of alumina (ε = 9.0) having a diameter of 10 mm and a length h = 10 mm is provided in the central region from the center line X = 0 to 1250 mm of the drive electrode (shower plate). Are arranged concentrically with an interval w = 10 mm, and a columnar dielectric made of alumina (ε = 9.0) having a diameter of 10 mm and a length h = 7 mm is provided in a region from X = 1250 to 1650 mm. A cylindrical dielectric made of alumina (ε = 9.0) having a diameter of 10 mm and a length of h = 4 mm is arranged in an area from X = 1650 to 1800 mm in a concentric manner with an interval w = 10 mm, and the interval w = 10 mm. Shows an example of concentric arrangement.

The calculation conditions in the simulation are as follows.
Gas species: Nitrogen gas (N ₂ )
Charged particle type: electron (e), nitrogen ion (N ₂ (+))
Reaction considered: e + N ₂ → e + N ₂ elastic collision
e + N ₂ → 2e + N ₂ (+) ionization
e + N ₂ → e + 2N dissociation
e + N ₂ → e + N ₂ (*) Excitation
N ₂ (+) + N ₂ → N ₂ (+) + N ₂ charge exchange gas pressure: 150 Pa
Supply voltage: V (t) = V0 * sin (2πft) + Vdc (t is time (sec))
V0 = 200 (V), f = 27.12 (MHz), Vdc = 0 (V)
Boundary condition: V (t) is supplied to the drive electrode
Earth electrode (y = 0mm) V = 0 (V)
Virtual boundary (x = 1800 mm), V = 0 (V) at a distance (x = 3000 mm)
Axis of symmetry (x = 0)
Secondary electron emission coefficient: 0.0
In addition, since it is a 1/2 model, the length of the diagonal of the electrode size of 2.4 m × 2.6 m is considered to be half.

  As a calculation method, a plasma hybrid module method (PHM) is used, a drift / diffusion model is used for calculating electron and ion flux, a continuous equation is used for calculating electron and ion density, and an electron temperature ( The Monte Carlo method was used to calculate energy), transport parameters (mobility / diffusion coefficient), and source rate.

  As a simulation result, FIG. 10 shows the horizontal electron density distribution in the vicinity of the ground electrode. Graph (A) is for the planar electrode shown in FIG. 7, and graph (B) is for Case 1 shown in FIG. Yes, graph (c) is for case 2 shown in FIG. FIG. 11 shows the horizontal electron density distribution in the center of the plasma. The graph (A) is for the planar electrode shown in FIG. 7, and the graph (B) is for Case 1 shown in FIG. C) is the case 2 shown in FIG. As can be seen from FIGS. 10 and 11, the case 1 and case 2 constructed in accordance with the present invention are more uniform in-plane plasma treatment than in the case of planar electrodes, and the in-plane uniform film formation rate in plasma CVD. Can be realized.

Further, as a simulation result, FIG. 12 shows N ₂ + ion flux incident on the ground electrode, graph (A) shows the case of the planar electrode shown in FIG. 7, and graph (B) shows case 1 shown in FIG. The graph (c) is for the case 2 shown in FIG. In FIG. 12, it can be seen that the N2 + ion flux is more uniform in the case 1 and case 2 configured according to the present invention than in the case of the planar electrode, and thus the film quality is uniform.

  The above-described simulation regarding the zoning shown in FIG. 3 is an example in which 27.12 MHz is used as the frequency, and the plasma density and the ion flux density are calculated. Each region is divided into zones A, B, and C. As described above, the first zone A has a diameter around the center of the electrode of 1 when the wavelength of the frequency of the high-frequency power supplied to the electrode is λ. The second zone B is set to have a diameter of 1/4 to 1 / 3λ outside the first zone A and centered at the center of the electrode. C is set so that the diameter around the center of the electrode outside the second zone B is 1/3 to 1 / 2λ. For this zone A, a belly and a node in one wavelength are included one by one. The diameter is ¼ of λ, which is a length of 2.77 m or less, and the length of ８ is a length of 1.38 m or more. It is important that it is a circle with a diameter of about 2.5 m. For zone B, it is important that the diameter is 3.69 m or less, which is 1/3 of the wavelength λ, and the diameter is 2.77 m or more, which is 1/4 of λ. A circle of about 3m is desirable. In the case of an electrode larger than the electrode handled in this simulation, for example, 3.6 mm × 3.8 m, it is necessary to define the fourth zone by setting the outer diameter of the third zone C, and 1 / 2λ = It can be set to 5.54 m, more preferably 5.0 m.

Hereinafter, simulation results calculated using the analysis model case 1 shown in FIG. 8 will be described.
FIG. 13 shows a simulation result of the relationship between the diameter of one dielectric and the flux, where “flux” on the vertical axis represents the flux of ion incidence on each of the metal part and the dielectric part. The distance was 20 mm. Graph 1 shows a metal, and graph 2 shows a dielectric. As shown in the simulation results of FIG. 13, when the dielectric has a large size exceeding 30 mm, it is particularly placed on a substrate placed under standard film forming conditions in the plasma CVD method for forming a thin film transistor on glass. When grown, there is a significant difference between the deposition area facing the dielectric exposed portion and the deposition area facing the metal exposed portion. The reason why the diameter of the dielectric is set to 5 mm or more in the present invention is that there are problems in processing the dielectric, and if it is set to 5 mm or less, the number embedded in the metal electrode becomes very large and handling is practically difficult. is there.

  FIG. 14 shows a simulation result of the relationship between the dielectric embedding depth, that is, the height of the dielectric and the in-plane plasma density distribution, and the dielectric embedding depth is preferably 5 mm to 20 mm. It was confirmed from the simulation results. This was confirmed under the condition that the filling depth was changed at a metal / dielectric area ratio of 7: 3. The reason why the thickness is 20 mm or less is that it is difficult to handle due to problems in processing of the dielectric material, and if it is 20 mm or more, the uniformity effect of the voltage distribution is not improved and the problem is caused when the metal electrode is embedded. It is.

FIG. 15 shows a simulation result of the relationship between the area ratio occupied by the dielectric according to the embedded depth of the dielectric and the in-plane plasma density distribution. Graph 1 shows that the embedded depth of the dielectric is 5 m.
The graph 2 shows the correlation between the area ratio occupied by the dielectric and the plasma density distribution in the entire electrode surface. As shown in the simulation results, when the depth is 5 mm, it is about ± 8% when the surface area is about 50%, and it can be seen that the effect is increased if the area ratio is further increased. On the other hand, in the case of 10 mm, when the surface area is about 30%, it becomes about ± 10%, which shows that the surface area is improved.

  FIG. 16 shows a simulation result of the relationship between the area ratio of the dielectric in the first zone A, the second zone B and the third zone C shown in FIG. 3 and the flux, and the dielectric is divided into three zones. It shows how the “flux” in each zone has a correlation with the area occupied by the dielectric in the zone when the pattern is used. From these graphs, it is assumed that zone A: 30-50%, zone B: 20-30: 30%, zone C: 0-20%, so that the flux is uniformly uniform from zone A to zone C. can do. In other words, the plasma density is uniform in each zone because the area ratio of metal to dielectric is 7: 3 to 5: 5 in zone A, and the area ratio of metal to dielectric is 8 in zone B. 2 to 7: 3, and in zone C, the area ratio of metal to dielectric can be seen to be approximately 8: 2.

  In the above simulation, alumina is used as the dielectric material, but equivalent results can be obtained by using AlN instead of alumina.

Based on Case 1 (FIG. 8) in the above simulation, an electrode was produced, and the dielectrics were arranged concentrically as shown in FIG. Alumina (Al ₂ O ₃ ) was used as the dielectric material, and it was a cylindrical shape having a diameter of 10 mm and a height of 10 mm, and the embedding interval of the dielectric was changed for each zone. Film formation conditions were such that the gas pressure in the vacuum chamber was 200 Pa, the power density was 0.5 W / cm ^2, and SiH ₄ / N ₂ / NH ₃ was used as the gas.

  The film formation results are shown in Table 1 in comparison with the conventional planar electrode.

  In Table 1, it can be seen that the dielectric-embedded electrode has the same film formation speed value as the conventional planar electrode, and the film thickness distribution and film quality (etching rate) distribution are greatly improved.

 The present invention is particularly advantageously used for forming a thin film transistor, but can be similarly applied to a plasma processing apparatus for plasma processing other large substrates.

1 is a schematic cross-sectional view showing a plasma CVD apparatus according to one embodiment of the present invention. The elements on larger scale which show the example of arrangement | positioning with the dielectric material embedded in the electrode of the apparatus of FIG. 1, and a gas discharge hole. The figure which shows the setting of the zone which divides the arrangement | sequence or magnitude | size (height) of the dielectric material embedded in the electrode of the apparatus of FIG. The schematic sectional drawing which shows the plasma CVD apparatus by another embodiment of this invention. FIG. 5 is a schematic cross-sectional view showing an enlarged arrangement example of dielectrics embedded in electrodes in the apparatus of FIG. 4. FIG. 5 is an enlarged schematic cross-sectional view showing another example of arrangement of dielectrics embedded in electrodes in the apparatus of FIG. 4. The schematic sectional drawing which shows the analysis model of a normal plane electrode. The schematic sectional drawing which shows the analytical model of the electrode used in the apparatus shown in FIG. FIG. 5 is a schematic cross-sectional view showing an electrode analysis model used in the apparatus shown in FIG. 4. The graph which shows the horizontal direction electron density distribution in the earth electrode vicinity by the simulation using the analysis model shown in FIGS. The graph which shows the horizontal direction electron density distribution in the plasma center by the simulation using the analysis model shown in FIGS. Graph showing N _{2 +} ion flux incident on the earth electrode by simulation using the analytical model shown in FIGS. 7-9. The graph which shows the simulation result of the relationship between the diameter of one dielectric material, and a flux. The graph which shows the simulation result of the relationship between the embedding depth of a dielectric material, ie, the height of a dielectric material, and the plasma density distribution in a surface. The graph which shows the simulation result of the relationship between the area ratio which a dielectric occupies by the embedding depth of a dielectric, and the plasma density distribution in a surface. The graph which shows the simulation result of the relationship between the area ratio which the dielectric material occupies in the 1st zone A shown in FIG. 3, the 2nd zone B, and the 3rd zone C, and a flux. The schematic sectional drawing which shows an example of the conventional plasma CVD apparatus.

Explanation of symbols

1: Vacuum chamber 2: Substrate holder 3: Electrode 4: Heater 5: Large area substrate 6: Insulating member 7: Electrode substrate 8: Shower head 9: Shower plate 10: Dielectric 11: Gas discharge hole 12: Supply of film forming gas mouth

Claims (8)

A substrate placed on the substrate holder, placed in the vacuum chamber, with a substrate holder and an electrode facing each other, introducing a gas into the vacuum chamber and supplying high-frequency power to the electrode. In a plasma processing apparatus using capacitively coupled glow discharge for performing plasma processing on
The electrode is composed of a metal electrode body and a plurality of dielectrics embedded in the surface of the metal electrode body facing the substrate holder,
The surface of the electrode facing the substrate holder is flat;
End surfaces of a plurality of dielectrics embedded in the surface are located in the same plane as the surface of the electrode;
When the wavelength of the frequency of the high-frequency power supplied to the electrode is λ, in the first circular region in which the diameter centered on the center of the electrode is set in the range of λ / 8 to λ / 4, the surface of the electrode The plasma processing apparatus is characterized in that the ratio of the surface area of the metal to the surface area of the dielectric is 7: 3 to 5: 5 . When the surface of the electrode facing the substrate holder is flat and the wavelength of the frequency of the high frequency power supplied to the electrode is λ, the diameter around the center of the electrode outside the first circular region is λ In the second circular region set in a range of / 4 to λ / 3, the ratio of the surface area of the metal to the surface area of the dielectric is 8: 2 to 7: 3. The plasma processing apparatus according to claim 1. When the surface of the electrode facing the substrate holder is flat and the wavelength of the frequency of the high-frequency power supplied to the electrode is λ, the diameter around the center of the electrode outside the second circular region is λ The ratio of the surface area of the metal to the surface area of the dielectric is approximately 8: 2 in the third circular region set in a range of / 3 to λ / 2λ. The plasma processing apparatus according to 1. The plasma processing according to claim 1, wherein a plurality of dielectrics embedded in the surface of the electrode facing the substrate holder are arranged concentrically on the surface of the electrode. apparatus. The plasma processing apparatus according to claim 4 , wherein a plurality of dielectrics embedded in the surface of the electrode facing the substrate holder are arranged at equal intervals on the surface of the electrode . The plasma processing according to any one of claims 1 to 5, wherein each dielectric is made of a material selected from a group including ceramics such as alumina, A1N, and macerite and a combination thereof. apparatus. The plasma according to any one of claims 1 to 6, wherein the electrode is made of aluminum and an alloy thereof and is subjected to any surface treatment of alumite, alumina spraying, or Y2O3 spraying. Processing equipment. The plasma processing apparatus according to claim 1, wherein the electrode includes a shower plate configured integrally with a shower head and a metal electrode main body .

Images