JP4650919B2 - CVD equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to chemical vapor deposition (referred to herein as “CVD”), and more particularly to a CVD apparatus suitable for film formation on a large flat panel substrate.
[0002]
[Prior art]
As a method for manufacturing a large-sized liquid crystal display, conventionally, a method using a high-temperature polysilicon TFT (thin film transistor) and a method using a low-temperature polysilicon TFT are known. In a manufacturing method using a high-temperature polysilicon TFT, a quartz substrate that can withstand a high temperature of 1000 ° C. or higher is used in order to obtain a high-quality oxide film. On the other hand, in the production of a low temperature polysilicon type TFT, since a normal TFT glass substrate is used, it is necessary to form a film in a low temperature environment (eg, 400 ° C.). The method of manufacturing a liquid crystal display using low-temperature polysilicon type TFTs has the advantage that it does not require the use of a special substrate and the setting of film forming conditions is simple, and has been put into practical use in recent years. Is expanding.
[0003]
In the production of a liquid crystal display using a low-temperature polysilicon type TFT, when a suitable silicon oxide film is formed as a gate insulating film at a low temperature, plasma CVD is used.
[0004]
When forming a silicon oxide film by this plasma CVD, silane, tetraethoxysilane (TEOS) or the like is used as a typical material gas.
[0005]
When a silicon oxide film is formed by plasma CVD using silane or the like as a material gas, a conventional plasma CVD apparatus introduces a material gas and oxygen into the front space of the substrate, and mixes the material gas and oxygen. By generating plasma with gas and exposing the substrate to the plasma, a silicon oxide film is formed on the surface of the substrate. As described above, in the conventional plasma CVD apparatus, the material gas is configured to be directly supplied into the plasma generated in the plasma CVD apparatus. Therefore, according to the configuration of the conventional plasma CVD apparatus, high energy ions are incident on the film formation surface of the substrate from the plasma existing in the front space of the substrate, damages the silicon oxide film, and the film characteristics are There was a problem of getting worse. In addition, since the material gas is directly introduced into the plasma, the material gas and the plasma react violently to generate particles, thereby causing a problem that the yield decreases.
[0006]
Therefore, in order to solve the above problem, Japanese Patent Application Laid-Open No. 2000-345349, an earlier application, attempted to improve a conventional remote plasma CVD apparatus and proposed a new CVD apparatus.
[0007]
The CVD apparatus proposed in Japanese Patent Application Laid-Open No. 2000-345349 is an apparatus that generates plasma in a vacuum vessel to generate active species (radicals), and performs film formation on the substrate with the active species and material gas. . The vacuum vessel is provided with a conductive partition that separates the inside of the vacuum vessel into two chambers. Of these two chambers, the inside of one chamber is formed as a plasma generation space in which high-frequency electrodes are arranged, and the inside of the other chamber is formed as a film forming processing space in which a substrate holding mechanism for mounting a substrate is arranged. The The conductive partition wall has a plurality of through holes that let the plasma generation space and the film formation processing space pass through, is isolated from the plasma generation space, and communicates with the film formation processing space and the plurality of diffusion holes. Has an internal space. A material gas supplied from the outside to the internal space of the conductive partition wall is introduced into the film forming space through a plurality of diffusion holes. On the other hand, the active species generated in the plasma generation space are introduced into the film formation processing space through a plurality of through holes formed in the conductive partition wall. Here, the size (length, diameter, etc.) and structure of the through hole and the diffusion hole are such that the material gas introduced into the film formation processing space does not reversely diffuse into the plasma generation space. (Length, diameter, etc.) / Structure, size (length, diameter, etc.) so that the active species introduced into the film formation processing space do not reversely diffuse into the internal space of the conductive partition wall. Has been.
[0008]
With the CVD apparatus proposed in Japanese Patent Laid-Open No. 2000-345349, the deterioration of the film characteristics of the silicon oxide film formed on the glass substrate can be prevented and the product yield can be improved.
[0009]
However, when a silicon oxide film is formed on a glass substrate having a large area of 370 mm × 470 mm by the CVD apparatus proposed in Japanese Patent Laid-Open No. 2000-345349, both the film thickness and film quality of the silicon oxide film are uniform. In some cases, this was insufficient. This is because, in the conductive partition wall portion 14 of the CVD apparatus proposed in Japanese Patent Laid-Open No. 2000-345349 shown enlarged in FIG. 5, the plasma generation space 15 side divided by the conductive partition wall portion 14 and the film formation processing space. In the internal space 32 of the opening on the plasma generation space 15 side of the through-hole 25 that passes through the 16th side, a localized abnormal discharge (hollow cathode discharge) is induced, which may cause the plasma to become unstable. It is thought that there was.
[0010]
In addition, the through hole of the conductive partition wall which influences the film quality and film thickness uniformity of the silicon oxide film formed on the large area substrate as described above is the internal space of the conductive partition wall filled with the material gas. In order to provide important functions to prevent gas leakage from the air, to prevent abnormal discharge at the through-holes, and to transport good neutral excited species, etc., the most sophisticated in production is required. Part.
[0011]
Therefore, the CVD apparatus proposed in Japanese Patent Application Laid-Open No. 2000-345349 has a sufficient through-hole structure and sufficient manufacturing means as well as performance such as improvement in film thickness uniformity on the substrate. There was room for further study.
[0012]
[Problems to be solved by the invention]
An object of the present invention is to produce a large-sized liquid crystal display using a low-temperature polysilicon type TFT, and on the basis of CVD using plasma, a silicon oxide film or the like is formed on a large area substrate using a material gas such as silane. In this case, a high product yield can be maintained by improving the stability of the plasma compared to the above-mentioned CVD apparatus newly proposed in Japanese Patent Laid-Open No. 2000-345349, which prevents back diffusion of the material gas into the plasma generation region. Another object of the present invention is to provide a CVD apparatus capable of forming a film with a uniform film thickness and film quality over a large area by being able to operate stably and stably.
[0013]
In addition, gas leakage from the conductive partition filled with the material gas is prevented, abnormal discharge is prevented in the through-hole portion that leads from the plasma generation space side to the film formation processing space side, It is an object of the present invention to provide a CVD apparatus capable of stably maintaining many functions to be performed by a conductive partition wall centering on a through hole, such as transport of a sex excited species.
[0014]
[Means for Solving the Problems]
The CVD apparatus according to the present invention has the following structure in order to achieve the above object.
[0015]
That is, the CVD apparatus according to the present invention is a CVD apparatus that generates plasma in a vacuum vessel to generate active species and forms a film on a substrate with the active species and the material gas. The vacuum vessel is provided with a conductive partition wall in the vacuum vessel that isolates the interior of the vacuum chamber into two chambers, and one of the two separated chambers has a plasma generation space in which a high-frequency electrode is disposed. As described above, the inside of the other chamber is formed as a film formation processing space in which a substrate holding mechanism for mounting the substrate is arranged. The conductive partition wall has a plurality of through-holes passing through the plasma generation space and the film formation processing space, is isolated from the plasma generation space, and passes through the film formation processing space and the plurality of diffusion holes. It has an internal space that communicates with it. A material gas supplied from the outside to the internal space of the conductive partition wall is introduced into the film formation space through the plurality of diffusion holes, and a high frequency power is applied to the high frequency electrode to generate a plasma discharge in the plasma generation space. Is a CVD apparatus in which the active species generated in the plasma generation space are introduced into the film formation processing space through a plurality of through holes of the conductive partition wall.
[0016]
In this CVD apparatus, plasma is generated using oxygen gas, and a thin film is deposited on the surface of a substrate using a material gas such as silane. The structure is separated into a plasma generation space for generating plasma and a film formation processing space, and the processing surface of the substrate disposed in the film formation processing space is not exposed to the plasma. Moreover, since it is isolated by the conductive partition wall portion, the movement of the material gas introduced into the film formation processing space toward the plasma generation space is sufficiently limited. That is, a plurality of through holes are formed in the conductive partition wall, and the plasma generation space and the film formation processing space on both sides of the conductive partition wall are connected only through the through holes. A size and structure are employed to prevent the material gas introduced into the space from back-diffusing into the plasma generation space.
[0018]
The CVD apparatus according to the present invention is characterized in that, in the above-described CVD apparatus, the through hole is formed such that the hole diameter on the film formation processing space side is larger than the hole diameter on the plasma generation space side.
[0019]
Here, the shape of the through-hole formed so that the hole diameter on the film formation space side is larger than the hole diameter on the plasma generation space side is a cylindrical shape from the plasma generation space side to the film formation space side. Alternatively, it is possible to adopt a shape composed of a cylindrical portion that extends from the plasma generation space side to the film forming processing space side and a conical portion that continuously expands in diameter to the cylindrical portion.
[0020]
By making the through hole have the characteristic shape as described above, it is possible to eliminate a portion that satisfies the conditions of hollow cathode discharge. Therefore, the stability of the plasma is improved, and abnormal discharge on the plasma generation space side of the through-hole portion that leads from the plasma generation space side to the film formation processing space side can be prevented. The excited species can be transported. In addition, a CVD apparatus that enables film formation with a uniform film thickness and film quality over a large area can be provided by being able to stably operate continuously while maintaining a high product yield.
[0021]
In the CVD apparatus of the present invention, the through hole can be formed by a structure independent of the conductive partition wall.
[0022]
As a result, in addition to the above-described action, the through hole is isolated from the internal space of the conductive partition wall as an independent structure, and therefore gas leaks from the internal space of the conductive partition filled with the material gas to the through hole. A CVD apparatus in which prevention is achieved can be provided.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.
[0024]
An embodiment of a CVD apparatus according to the present invention will be described with reference to FIGS. 1 and 2, in this CVD apparatus, silane is preferably used as a material gas, and a silicon oxide film is formed as a gate insulating film on the upper surface of a normal TFT glass substrate 11. The container 12 of the CVD apparatus is a vacuum container whose interior is maintained in a desired vacuum state by the exhaust mechanism 13 when performing a film forming process. The exhaust mechanism 13 is connected to an exhaust port 12b-1 formed in the vacuum vessel 12.
[0025]
A partition wall 14 made of a conductive member in a horizontal state is provided inside the vacuum vessel 12, and the partition wall 14 having a rectangular planar shape, for example, has a peripheral edge on the lower surface of the conductive material fixing portion 22. Are arranged so as to form a sealed state.
[0026]
Thus, the interior of the vacuum vessel 12 is separated into two upper and lower chambers by the partition wall portion 14, the upper chamber forms the plasma generation space 15, and the lower chamber forms the film formation processing space 16. The partition wall portion 14 has a desired specific thickness, has a flat plate shape as a whole, and has a planar shape similar to the horizontal sectional shape of the vacuum vessel 12. An internal space 24 is formed in the partition wall 14.
[0027]
The glass substrate 11 is disposed on a substrate holding mechanism 17 provided in the film formation processing space 16. The glass substrate 11 is substantially parallel to the partition wall portion 14 and is disposed so that the film formation surface (upper surface) faces the lower surface of the partition wall portion 14.
[0028]
The potential of the substrate holding mechanism 17 is held at a ground potential 41 that is the same potential as the vacuum vessel 12. Further, a heater 18 is provided inside the substrate holding mechanism 17. The temperature of the glass substrate 11 is maintained at a predetermined temperature by the heater 18.
[0029]
The structure of the vacuum vessel 12 will be described. The vacuum vessel 12 includes an upper vessel 12a that forms a plasma generation space 15 and a lower vessel 12b that forms a film formation processing space 16 from the viewpoint of improving its assemblability. When the vacuum container 12 is made by combining the upper container 12a and the lower container 12b, the partition wall 14 is provided at a position between them. The isolation part 14 is attached so that the peripheral part thereof is in contact with the conductive material fixing part 22 having the same potential as the vacuum vessel 12. As a result, an isolated plasma generation space 15 and film formation processing space 16 are formed above and below the partition wall portion 14. A plasma generation space 15 is formed by the partition wall 14 and the upper container 12a.
[0030]
In the first embodiment of the CVD apparatus according to the present invention shown in FIG. 1, the region where the plasma 19 is generated in the plasma generation space 15 is disposed at the partition wall 14, the upper container 12 a, and the substantially central position thereof. And a plate-like electrode (high-frequency electrode) 20. The electrode 20 has a plurality of electrode holes 20a. The electrode 20 is supported and fixed by two insulating members 21a and 21b provided along the inner side surface of the upper container 12a. A power introducing rod 29 connected to the electrode 20 is provided on the ceiling of the upper container 12a. The electrode 20 is fed with high-frequency power for discharge by the power introduction rod 29. The electrode 20 functions as a high frequency electrode. The power introduction rod 29 is covered with an insulator 31 so as to be insulated from other metal parts.
[0031]
The partition wall portion 14 is at a ground potential 41 through the conductive material fixing portion 22.
[0032]
The insulating member 21 a is provided with an oxygen gas introduction pipe 23 a that introduces oxygen gas into the plasma generation space 15 from the outside, and a cleaning gas introduction pipe 23 b that introduces a cleaning gas such as a fluorinated gas.
[0033]
The inside of the vacuum vessel 12 is separated into the plasma generation space 15 and the film formation processing space 16 by the partition wall portion 14, and the material gas introduced into the film formation processing space 16 is moved to the plasma generation space 15 side in the partition wall portion 14. A plurality of through-holes 25 having a size (length, diameter, etc.) and structure for preventing reverse diffusion are uniformly formed so as to penetrate the internal space 24, and plasma is transmitted only through these through-holes 25. The generation space 15 and the film formation processing space 16 are connected.
[0034]
FIG. 3 is a schematic enlarged view of the internal structure viewed from the cross-sectional direction of the partition wall portion 14, and FIG. 4 is a schematic enlarged view of the internal structure viewed from the cross-sectional direction of another embodiment of the partition wall portion 14.
[0035]
The through hole 25 is formed by one independent structure 30. Therefore, the through hole 25 can be finely processed in a separate process from the partition wall part 14 when the partition wall part 14 is manufactured, and the independent structure 30 having the through hole 25 thus finely processed is formed in the partition wall part 14 in the final process. It is assembled into the main body and fixed by caulking as shown in FIGS.
[0036]
The structure 30 is mainly made of aluminum and has a rectangular parallelepiped shape or a cylindrical shape, but is not limited thereto. In the structure 30, considering that the entire partition wall 14 receives heat from the substrate and the temperature rises, a gap is generated between the partition wall 14 and the structure 30 even in such a case. As long as the material has a thermal expansion coefficient equivalent to that of the member constituting the partition wall 14 and has no problem in the transportability and workability of the excited species through the through hole 25, various materials can be used. Can be used.
[0037]
The internal space 24 formed in the partition wall portion 14 is a space for diffusing a material gas introduced from the outside into the partition wall portion 14 and supplying it uniformly to the film formation processing space 16. Further, a plurality of diffusion holes 26 for supplying a material gas to the film formation processing space 16 are formed in the lower plate 27 c of the partition wall portion 14.
[0038]
A material gas introduction pipe 28 for introducing material gas from the outside is connected to the internal space 24 (FIGS. 1 and 2). The material gas introduction pipe 28 is arranged so as to be connected from the side.
[0039]
In the internal space 24, a uniform plate 27 b that is perforated so as to have a plurality of holes is provided substantially horizontally so that the material gas is uniformly supplied from the diffusion holes 26. The internal space 24 of the partition wall 14 is divided into two upper and lower space portions by a uniform plate 27b.
[0040]
Accordingly, the material gas introduced into the internal space 24 of the partition wall 14 by the material gas introduction pipe 28 is introduced into the upper space, reaches the lower space through the holes of the uniform plate 27b, and further passes through the diffusion holes 26. The film is diffused through the film forming process space 16.
[0041]
Based on the above structure, the material gas can be uniformly supplied over the entire film formation processing space 16. However, the internal structure of the partition wall 14 supplies the material gas uniformly over the entire film formation processing space 16. The structure is not limited to the above-described structure as long as it can be performed.
[0042]
The shape of the through-hole 25 is a cylindrical shape from the plasma generation space 15 side to the film formation processing space 16 side, or a cylindrical part from the plasma generation space 15 side to the film formation processing space 16 side and the cylindrical shape. For example, a shape including a conical portion that continuously expands in diameter can be employed.
[0043]
FIG. 3 illustrates a case where the through hole 25 has a cylindrical shape from the plasma generation space 15 side to the film formation processing space 16 side. In this case, the diameter of the opening portion of the through hole 25 facing the plasma generation space 15 is such a size that the opening portion of the through hole 25 does not have a spread causing a holocathode discharge induction .
[0044]
FIG. 4 shows a case where the through hole 25 has a shape composed of a cylindrical portion that extends from the plasma generation space 15 side toward the film forming treatment space 16 side and a conical portion that continuously expands in diameter to the cylindrical portion. Is. In the case of FIG. 4 as well, for the same reason as described above, the diameter of the opening of the through hole 25 facing the plasma generation space 15 and the size and shape of the through hole 25 are the same as in the case of FIG. Must satisfy.
[0045]
However, the diameter of the conical portion in this case is not particularly limited because it does not cause a holocathode discharge because it is open to the film forming treatment space 16.
[0046]
In short, the through-hole 25 does not induce localized abnormal discharge at the opening facing the plasma generation space 15, and the diameter of the through-hole 25 at the opening facing the film formation processing space 16 is larger than that of the plasma generation space 15. It is a feature of the present invention that it is formed to be larger than the generation space 15 side.
[0047]
FIG. 2 shows a second embodiment of the CVD apparatus according to the present invention. The characteristic configuration of the embodiment shown in FIG. 2 is that an insulating member 21a is provided on the inner side of the ceiling portion of the upper container 12a, and the electrode 20 is disposed below the insulating member 21a. The electrode 20 does not have the electrode hole 20a as in the case of the first embodiment shown in FIG. 1, but has a single plate shape. A plasma generation space 15 having a parallel plate electrode structure is formed by the electrode 20 and the partition wall 14. Other configurations are substantially the same as those of the first embodiment. Therefore, in FIG. 2, elements that are substantially the same as the elements described in FIG. 1 are denoted by the same reference numerals, and the detailed description is not repeated here. Furthermore, the operations and effects of the CVD apparatus according to the second embodiment are the same as those in the first embodiment.
[0048]
A film forming method using the CVD apparatus configured as described above will be described. The glass substrate 11 is carried into the vacuum container 12 by a transfer robot (not shown) and placed on the substrate holding mechanism 17. The inside of the vacuum vessel 12 is evacuated by the exhaust mechanism 13, decompressed, and maintained in a predetermined vacuum state. Next, oxygen gas is introduced into the plasma generation space 15 of the vacuum vessel 12 through the oxygen gas introduction pipe 23a.
[0049]
On the other hand, for example, silane which is a material gas is introduced into the internal space 24 of the partition wall portion 14 through the material gas introduction pipe 28. Silane is first introduced into the upper part of the internal space 24, is homogenized through the uniform plate 27 b and moves to the lower part, and then passes directly through the diffusion holes 26 into the film forming treatment space 16, that is, It is introduced without contacting the plasma. The substrate holding mechanism 17 provided in the film forming processing space 16 is held in advance at a predetermined temperature because the heater 18 is energized.
[0050]
In the above state, high frequency power is supplied to the electrode 20 through the power introduction rod 29. Electric discharge is generated by the high frequency power, and oxygen plasma 19 is generated around the electrode 20 in the plasma generation space 15. By generating the oxygen plasma 19, radicals (excited active species) that are neutral excited species are generated, which pass through the through-holes 25 and are introduced into the film forming treatment space 16, while the material gas is separated from the partition walls. The film is introduced into the film forming treatment space 16 through the internal space 24 and the diffusion hole 26 of the portion 14. As a result, the radicals and the material gas come into contact with each other for the first time in the film formation processing space 16 to cause a chemical reaction, and silicon oxide is deposited on the surface of the glass substrate 11 to form a thin film.
[0052]
The CVD apparatus according to the present invention described above can be applied to a nitride film, a fluoride film, and a carbonized film by changing a material gas or the like.
[0053]
Further, in the above-described embodiment, the through-hole having a shape formed so that the diameter of the opening facing the film formation processing space 16 is larger than the diameter of the plasma generation space 15 side than the diameter of the plasma generation space 15 side. 3 and 4 as an example, the shape of the through hole 25 is not limited to the form shown in FIGS.
[0054]
【The invention's effect】
As is clear from the above description, a device capable of forming a silicon oxide film or the like on a large-area substrate by using a material gas such as silane by plasma CVD, for example, a vacuum partition by a conductive partition having a plurality of through holes. The inside is separated into a plasma generation space and a film formation processing space, and active species generated in the plasma generation space are introduced into the film formation processing space only through the through holes of the partition wall and supplied to the partition wall from the outside. The material gas is introduced into the film formation processing space through the diffusion space and the internal space of the partition wall, which is isolated from the plasma generation space and communicates with the film formation processing space through the plurality of diffusion holes. In a CVD apparatus that forms a film on a substrate with active species and a material gas introduced into the film processing space, the stability of plasma can be improved, a high product yield can be maintained, and a stable connection can be achieved. Allowing the operation, thereby improving the uniformity of the film thickness and film quality over a large area.
[0055]
For example, the typical film thickness distribution achieved in the conventional plasma CVD apparatus is ± 10% to 15%, but according to the CVD apparatus of the present invention, ± 5.2 on a 370 mm × 470 mm glass substrate. % Thickness distribution (silicon oxide film thickness: 200 nm).
[0056]
Furthermore, centering on the through-hole, such as prevention of gas leakage from the internal space of the partition wall filled with material gas, prevention of abnormal discharge at the through-hole part, transport of good neutral excited species through the through-hole, etc. By making the through hole an independent structure while stably maintaining many functions that the conductive partition wall that should be able to function, the part that forms the through hole is finely processed separately from the partition wall part It can be finished to fully satisfy the function of the hole.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a first embodiment of a CVD apparatus of the present invention.
FIG. 2 is a longitudinal sectional view showing a second embodiment of the CVD apparatus of the present invention.
FIG. 3 is a schematic enlarged view of the internal structure viewed from the cross-sectional direction of the partition wall of the CVD apparatus of the present invention.
FIG. 4 is a schematic enlarged view of the internal structure as viewed from the cross-sectional direction of another embodiment of the partition wall of the CVD apparatus of the present invention.
FIG. 5 is a schematic enlarged view of the internal structure viewed from the cross-sectional direction of the partition wall in a CVD apparatus according to another invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Mounting screw 11 Glass substrate 12 Vacuum container 12a Upper container 12b Lower container 12b-1 Exhaust port 13 Exhaust mechanism 14 Partition part 15 Plasma generation space 16 Deposition process space 17 Substrate holding mechanism 18 Heater 19 Plasma 20 Electrode 20a Electrode hole 21a, 21b, 21c Insulating member 22 Conductive material fixing portion 23a Oxygen gas introduction pipe 23b Cleaning gas introduction pipe 24 Internal space 25 Through hole 26 Diffusion hole 27a Upper plate 27b Uniform plate 27c Lower plate 28 Material gas introduction pipe 29 Power introduction rod 30 Structure 31 Insulator 41 Ground potential

Claims (1)

This is a CVD device that generates active species by generating plasma in a vacuum vessel and forms a film on the substrate with this active species and material gas. The conductive partition that separates the inside of the vacuum vessel into two chambers is a vacuum. One of the two chambers provided in the container is isolated as a plasma generation space in which a high-frequency electrode is disposed, and in the other chamber is disposed a substrate holding mechanism for mounting a substrate. Each of the conductive partition walls has a plurality of through-holes passing through the plasma generation space and the film formation processing space, and is isolated from the plasma generation space. An internal space communicating with the film formation space through a plurality of diffusion holes, and a material gas supplied from the outside to the internal space of the conductive partition wall through the plurality of diffusion holes, the film formation space. Introduced into The active species generated in the plasma generation space by applying high-frequency power to the high-frequency electrode to generate plasma discharge in the plasma generation space pass through the plurality of through holes of the conductive partition wall to form the film. In the CVD apparatus introduced into the processing space, the through hole is formed such that the hole diameter on the film forming processing space side is larger than the hole diameter on the plasma generation space side.

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