JP2006086470A - Plasma generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma generator which uniformly treats even a large size substrate to be treated. <P>SOLUTION: The plasma generator 10 comprises a plasma generating electrode 11, a substrate setting table 12, provided below the electrode 11, on which a substrate 20 to be treated is set so that the top surface thereof faces the plasma generating electrode 11, and a plate-like mesh electrode 13 provided between them with a space from both of them. Parallel keeping means 16 which regulate bending of the center part of the mesh electrode 13 to keep a positional relationship between the lower surface of the mesh electrode 13 and the upper surface of the substrate 20 to be treated set on the substrate setting table 12 parallel on the whole. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a plasma generating apparatus such as a plasma CVD apparatus.

  The plasma CVD (chemical vapor deposition) method realizes lowering of the CVD process and is widely applied to semiconductor processes and the like.

  In Patent Document 1, a mesh electrode in which a large number of reaction gas passage holes are formed between an RF electrode to which a high frequency is applied and an electrically insulated substrate in a reaction chamber is set to ground potential. There has been disclosed a plasma CVD apparatus provided with a reaction gas inflow pipe that is disposed outside a sheath region of plasma generated from an electrode and supplies a reaction gas to the RF electrode. According to this, it is described that the reaction gas having the potential lowered by passing through the sheath region on the ground electrode side by the mesh electrode is reacted with the substrate, so that ion collision does not occur.

In Patent Document 2, in a capacitively coupled plasma CVD apparatus provided with a parallel plate type cathode and an anode, a glass substrate as a film formation is placed on the anode, and a metal mesh or the like is placed directly on the glass substrate. It is disclosed that three electrodes are arranged and the distance between the third electrode and the glass substrate is 10 mm or less. And, according to this, it can be applied to the production of microcrystalline silicon solar cells, etc., it is possible to deposit a microcrystalline film having high crystallinity at high speed, and there is little generation of powder and excellent productivity. ing.
Japanese Patent Laid-Open No. 6-49648 JP 2002-289530 A

  A plasma CVD apparatus having a structure having a flat mesh electrode as disclosed in Patent Documents 1 and 2 is used for forming a silicon thin film on a processing substrate in a TFT substrate manufacturing process of a liquid crystal display device. When used, it is expected that a TFT exhibiting high characteristics can be obtained.

  However, in recent years, the size of the processing substrate has increased with the increase in the size of the liquid crystal display device, and the plasma CVD apparatus for processing it has also increased in size. Therefore, the size of the mesh electrode is bent, and the distance to the processing substrate on the substrate setting table is shortened at that portion. As a result, the thickness of the coating formed on the processing substrate corresponding to the central portion of the mesh electrode is thicker than that formed corresponding to the peripheral portion, and the thickness and physical properties of the coating formed as a whole are increased. There is a problem that non-uniformity occurs.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a plasma generating apparatus in which processing on a large processing substrate is uniform.

The plasma generator of the present invention that achieves the above-described object provides:
An electrode for plasma generation; and a substrate set base on which the processing substrate is set so that the upper surface of the substrate faces the electrode for plasma generation, provided below the electrode for plasma generation;
Between the plasma generating electrode and the substrate set stand, a plate-like mesh electrode provided with an interval from any of them,
With
There is provided parallel holding means for restricting the deflection of the central portion of the mesh electrode and holding the positional relationship between the lower surface of the mesh electrode and the upper surface of the processing substrate set on the substrate setting table in parallel. .

  According to the above configuration, the parallel holding means regulates the deflection of the central portion of the mesh electrode, and the positional relationship between it and the upper surface of the processing substrate set on the substrate setting table is held in parallel as a whole. The distance between them is the same in any part, and as a result, for example, in a plasma CVD application, a film having a uniform thickness can be formed on a processing substrate.

  Further, since the deflection of the mesh electrode is regulated, the distance between the mesh substrate and the processing substrate can be set close, and thereby the film formation rate can be significantly increased.

  As a specific configuration, in the plasma generator of the present invention, the parallel holding means is a connecting member made of an insulating material provided to connect the plasma generating electrode and the mesh electrode. Can do.

  In this case, it is preferable that a plurality of connecting members as the parallel holding means are provided at intervals in the lateral direction in order to achieve the above-described effects. In addition, since plasma is generated in a space where the plasma generating electrode, the connecting member, and the mesh electrode form a boundary, the plasma does not depend on the electrode size even if the mesh electrode area is enlarged if the interval between the connecting members is constant. Can be generated.

  In the plasma generator of the present invention, the connecting member may be fixed to the plasma generating electrode, and the mesh electrode may be detachably attached to the connecting member.

  According to the above configuration, since the mesh electrode is detachably attached to the connecting member fixed to the plasma generating electrode, maintenance of the plasma forming space between the plasma generating electrode and the mesh electrode is facilitated. It can be carried out.

  In the plasma generator of the present invention, the plasma generating electrode may be provided with a reactive gas inlet.

  According to the above configuration, since the reactive gas inlet is provided in the plasma generating electrode, it is possible to efficiently generate plasma in the immediate vicinity of the plasma generating electrode.

  As the size of the mesh electrode is larger, bending due to its own weight is more likely to occur. Therefore, the plasma generator of the present invention is particularly effective when the size of the mesh electrode is 150 mm square or more.

  According to the present invention, the parallel holding means makes the distance between the lower surface of the mesh substrate and the upper surface of the processing substrate set on the substrate setting table the same in any part, and as a result, the processing on the processing substrate is uniform. Can be made.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic configuration of a plasma CVD apparatus (plasma generator) 10 according to an embodiment of the present invention.

  The plasma CVD apparatus 10 is of a parallel plate type, and an amorphous silicon film or an insulating film (silicon nitride film, silicon oxide film) is applied to the processing substrate 20 when a TFT substrate of a large liquid crystal display device is manufactured. It is used to form.

  The plasma CVD apparatus 10 includes a chamber (not shown), plasma generating electrodes 11 and a substrate set base 12 provided above and below the chamber, and a mesh provided between them at intervals. And an electrode 13. In addition, a reaction gas supply system, a vacuum exhaust system, and an exhaust gas treatment system (not shown) are connected to the chamber.

  The plasma generating electrode 11 is formed, for example, in a flat plate shape using an anodized aluminum alloy and has a larger area than the processing substrate 20, and a reactive gas introduction hole drilled in the thickness direction thereof. A plurality of 14 are provided at intervals. The reactive gas introduction hole 14 communicates with the reactive gas supply control system. The plasma generating electrode 11 is connected to a high frequency power supply 15.

  The substrate set base 12 is formed in a flat plate shape with, for example, an anodized aluminum alloy, and includes a substrate heating heater (not shown). In addition, the substrate set base 12 is grounded. A processing substrate 20 such as glass, plastic, or silicon is set on the substrate setting table 12 so that the upper surface of the substrate faces the plasma generating electrode 11 side.

  The mesh electrode 13 is formed of, for example, an aluminum alloy in a flat plate shape, and has a mesh structure in which a large number of pores are formed. As a specific configuration, in addition to a structure like a net knitted with a wire, a structure in which a hole is formed in an iron plate may be used. In addition, the range of the pore size varies depending on the working pressure and the desired film quality, and the influence of the hollow effect, ion trap effect, etc. has a correlation with the pressure, so the absolute size is uniquely limited. Although it is difficult to do this, it is generally preferable that the thickness is 100 μm or more from the viewpoint of workability and 10 mm or less from the viewpoint of the width of the sheath region at the portion where the electric field is generated. Furthermore, the shape of the pore is not particularly limited. The mesh electrode 13 has a size of 150 mm square or more. The mesh electrode 13 is grounded in the same manner as the substrate setting table 12 so that no discharge occurs between the mesh electrode 13 and the substrate setting table 12.

  The plasma generating electrode 11 and the mesh electrode 13 are connected and fixed via a plurality of connecting members (parallel holding means) 16. Each connecting member 16 is formed in the shape of a flat bar with an insulating material such as alumina or an alumina mixed material (for example, the width is 10 to 20 mm, the thickness is 5 to 10 mm, and the length in the depth direction in FIG. The size of the plasma generation electrode 11 is fixed so as to form a partition wall and hangs downward. The plurality of connecting members 16 are provided so as to extend in parallel to each other at regular intervals in the lateral direction. The lower surface (top surface) of each connecting member 16 is on the same plane, and the mesh electrode 13 is detachably attached and fixed to the lower surface of each connecting member 16 with a set screw 17, whereby the mesh electrode 13 is regulated so that the positional relationship between the lower surface of the mesh electrode 13 and the upper surface of the substrate set base 12, that is, the upper surface of the processing substrate 20 set therein is maintained in parallel. It has become.

When forming a film on the processing substrate 20, first, the processing substrate 20 is set on the substrate set stand 12 so that the upper surface of the substrate faces the plasma generating electrode 11 side, and then the chamber is sealed and evacuated by a vacuum exhaust system. The inside of the chamber is depressurized. Next, a high frequency is applied from the high frequency power supply 15 to the plasma generating electrode 11 and a reaction gas (SiH ₄ , H ₂ , NH _3, etc.) is introduced into the chamber from the reaction gas supply system through the reaction gas introduction hole 14. Is done. As a result, discharge occurs in the space between the plasma generating electrode 11 and the mesh electrode 13, and plasma in which the reaction gas is excited or ionized is formed there. The formed highly reactive neutral radicals reach the processing substrate 20 through the pores of the mesh electrode 13, but most of the ions forming the plasma are trapped by the mesh electrode 13. A film with less damage is formed.

  According to the plasma CVD apparatus 10 configured as described above, the bending of the central portion of the mesh electrode 13 is regulated by the plurality of connecting members 16 that are spaced apart from each other in the lateral direction. Since the positional relationship with the upper surface of the set processing substrate 20 is held in parallel as a whole, the distance between them is the same in any part, and as a result, a coating with a uniform thickness on the processing substrate 20 is obtained. Can be formed.

  Further, since plasma is generated in a space where the plasma generating electrode 11, the connecting member 16 and the mesh electrode 13 form a boundary, the electrode can be used even if the area of the mesh electrode 13 is increased if the distance between the connecting members 16 is constant. It is possible to generate a plasma independent of size.

  Further, since the mesh electrode 13 is detachably attached to the connecting member 16 fixed to the plasma generating electrode 11, maintenance of the plasma forming space between the plasma generating electrode 11 and the mesh electrode 13 is facilitated. It can be carried out.

  Further, since the reactive gas inlet is provided in the plasma generating electrode 11, it is possible to efficiently generate plasma in the immediate vicinity of the plasma generating electrode 11.

  Further, since the deflection of the mesh electrode 13 is restricted, the distance between the mesh substrate and the processing substrate 20 can be set close, and thereby the film formation rate can be significantly increased.

  In the above embodiment, the plasma CVD apparatus 10 is used. However, the present invention is not particularly limited to this, and a plasma etching apparatus may be used. In this case, an etching gas is used as the reaction gas, and an effect is obtained that the etching process on the processing substrate 20 is performed uniformly.

  In the above embodiment, the connecting member 16 is formed in the shape of a flat bar. However, the connecting member 16 is not particularly limited to this, and may be a columnar shape standing on the lower surface of the plasma generating electrode 11. .

  A silicon thin film was formed by vapor phase growth on a processing substrate using a plasma CVD apparatus having the same configuration as that of the above embodiment (invention example). The high frequency was 13 MHz, the supplied power was 100 W, and the substrate temperature was 300 ° C. Silane diluted to 20% with hydrogen as a reaction gas was allowed to flow at 50 sccm. A 180 × 150 cm glass substrate was used as the treatment substrate. The distance between the lower surface of the mesh electrode and the upper surface of the processing substrate was set to 3 cm.

  As shown in FIG. 2, a silicon thin film was formed by vapor phase growth on a processing substrate in the same manner as described above except that a CVD apparatus in which a connecting member was not provided and a mesh electrode was arranged at the same position was used ( Comparative example).

  FIG. 3 shows the distribution of the thickness of the coating along the direction from the substrate edge to the center of the substrate as a standard value based on a predetermined value for each of the inventive example and the comparative example.

  According to FIG. 3, it can be seen that in the inventive example, the film thickness uniformity is excellent enough to be within ± 3%.

  On the other hand, in the comparative example, it can be seen that the thickness of the central portion is 20% or more thicker than that of the end portion. This is presumably because the center portion of the mesh electrode is bent by its own weight, and the distance from the substrate set base to the processing substrate is shortened at that portion.

  The present invention is useful for a plasma generation apparatus such as a plasma CVD apparatus.

It is a figure which shows the structure of the plasma CVD apparatus which concerns on embodiment of this invention. It is a figure which shows the structure of the plasma CVD apparatus in which the connection member is not provided. It is a graph which shows the relationship between the distance from a substrate edge, and the normalized film thickness.

Explanation of symbols

10 Plasma CVD equipment (plasma generator)
11 Plasma generating electrode 12 Substrate set base 13 Mesh electrode 14 Reactive gas introduction hole 15 High frequency power supply 16 Connecting member (parallel holding means)
17 Set screw 20 Processed substrate

Claims (6)

An electrode for plasma generation; and a substrate set base on which the processing substrate is set so that the upper surface of the substrate faces the electrode for plasma generation; provided below the electrode for plasma generation;
Between the plasma generating electrode and the substrate set stand, a plate-like mesh electrode provided with an interval from any of them,
With
There is provided parallel holding means for restricting the deflection of the central portion of the mesh electrode and holding the positional relationship between the lower surface of the mesh electrode and the upper surface of the processing substrate set on the substrate setting table in parallel. , Plasma generator. In the plasma generator according to claim 1,
The plasma generation apparatus, wherein the parallel holding means is a connecting member made of an insulating material provided to connect the plasma generating electrode and the mesh electrode. In the plasma generator according to claim 2,
The plasma generating apparatus, wherein a plurality of connecting members as the parallel holding means are provided in the lateral direction at intervals. In the plasma generator according to claim 2,
The connecting member is fixed to the plasma generating electrode,
The plasma generating apparatus, wherein the mesh electrode is detachably attached to the connecting member. In the plasma generator according to claim 1,
The plasma generating apparatus, wherein the plasma generating electrode is provided with a reactive gas inlet. In the plasma generator according to claim 1,
The mesh generator is a plasma generator having a size of 150 mm square or more.

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