JP2006173343A - Plasma CVD apparatus and electrode for CVD apparatus - Google Patents

Abstract

A thin film adhering to an upper electrode is prevented from peeling off from the upper electrode, and generation of particles in a processing chamber is suppressed as much as possible.
A processing chamber, a source gas supply unit that supplies a source gas to the inside of the processing chamber, and a first electrode and a second electrode that are disposed to face each other inside the processing chamber are provided. The processing disposed on the first substrate 2 side of the second electrode 3 by generating plasma between the first electrode 2 and the second electrode 3 and exciting the source gas supplied into the processing chamber 1. In the plasma CVD apparatus for forming a thin film on the surface of the substrate 4, the first electrode 2 has a rough surface over the entire surface on the second electrode 3 side (surface roughness Ra is 0.5 μm or more and less than 40 μm). ).
[Selection] Figure 1

Description

  The present invention relates to a plasma CVD apparatus and an electrode for a CVD apparatus.

  Silicon-based thin films such as an amorphous silicon film and a silicon nitride film constituting a thin film transistor used as a switching element in a liquid crystal display device or the like are preferably formed by a CVD (Chemical Vapor Deposition) method.

  As a film forming apparatus used for this CVD method, a plasma CVD apparatus is well known.

  For example, a parallel plate type plasma CVD apparatus has a pair of parallel plate electrodes provided inside a processing chamber, one of the parallel plate electrodes is a grounded lower electrode, and the other is connected to a high frequency power source. The upper electrode is used. A high-frequency power is applied to the upper electrode, a source gas is supplied between both electrodes, and a source gas is excited by plasma formed between the two electrodes to generate a film-forming substance, on the lower electrode. A thin film is deposited on the surface of the placed glass substrate.

  In Patent Document 1, plasma is generated on the entire surface of the electrode with uniform intensity by providing a wavy unevenness on the surface of the central portion of the cathode electrode corresponding to the upper electrode, and on the surface of a large area substrate. A high-frequency plasma CVD apparatus capable of uniformly forming a thin film with good film quality is described.

  By the way, in the plasma CVD apparatus, the thin film is formed not only on the surface of the glass substrate held inside the processing chamber but also on the surface of the upper electrode. The excess thin film formed on the surface of the upper electrode may be scattered from the surface of the electrode and then scattered inside the processing chamber. For example, if the scattered matter adheres to the glass substrate as particles (floating dust), the glass substrate may be defective.

Accordingly, it is also known that, every time a predetermined number of glass substrates are formed, self-cleaning is performed to remove the excess thin film by introducing, for example, NF ₃ gas into the processing chamber. Specifically, NF ₃ gas is decomposed using the plasma formed between the two electrodes to generate active fluorine radicals, and the fluorine radicals adhere to the surface of the upper electrode, for example, silicon-based The thin film is removed by etching.

  However, if only the periodic self-cleaning as described above is performed and the number of film forming processes after the self-cleaning is increased, the thin film formed on the upper electrode falls on the surface of the glass substrate. Inevitably becoming particles.

  On the other hand, if the self-cleaning is performed every time the film forming process is performed, the generation of particles can be surely reduced, but the manufacturing cost for the film forming becomes high, and the liquid crystal display device is manufactured. Is unrealistic.

  Therefore, Patent Document 2 discloses that a continuous or rough surface by blasting or porous plating having a large number of pores is applied to the components of the reaction chamber (processing chamber) as a surface treatment of a part or all of the components. Thus, a plasma CVD apparatus is described in which the generation of particles can be reduced even when a film is deposited.

  Further, in Patent Document 3, the surface roughness of the electrode plate for plasma CVD apparatus is maximized by blasting or spraying in order to reduce the amount of dust (particles) generated by peeling off the deposited layer by CVD. It is described that the height (Rmax) is 40 to 100 μm.

Furthermore, in Patent Document 4, in order to prevent generation of particles, contamination, and the like, the surface roughness Ra of the inner wall of the small diameter hole is 0.01% in the electrode plate having a large number of small diameter holes for reaction gas rectification. It is described as finishing in the range of ˜5 μm.
JP-A-6-5522 JP-A-7-201742 Japanese Patent Laid-Open No. 11-181570 JP-A-11-104950

  However, it is not always possible to reduce the generation of particles just by making the surface of the upper electrode rough as described above.

  Specifically, Patent Document 2 does not describe the degree of roughening (surface roughness), and unless the surface roughness of the upper electrode is defined, the adhesion between the electrode surface and the thin film deposited on the electrode surface Therefore, it is not always possible to guarantee the property and the generation of particles cannot be reduced.

  Further, in Patent Document 3, since the surface roughness is defined by the maximum height value (Rmax), the adhesion between the electrode surface and a thin film of about 1 μm, for example, deposited on the electrode surface is ensured. It is not always possible to reduce the generation of particles.

  Furthermore, as in Patent Document 1, it is difficult to peel off an excessive thin film adhering to the entire surface of the upper electrode only by forming an uneven shape having a relatively large pitch and depth on the surface of the central portion of the upper electrode. It is difficult.

  The present invention has been made in view of such a point, and the object of the present invention is to make it difficult for the thin film attached to the upper electrode to peel off from the upper electrode, and to generate particles inside the processing chamber as much as possible. It is to deter.

  In the present invention, the surface of the first electrode (upper electrode) on the second electrode (lower electrode) side is formed to be a rough surface over the entire surface.

  Specifically, a plasma CVD apparatus according to the present invention includes a processing chamber, a source gas supply unit that supplies a source gas to the inside of the processing chamber, a first electrode and a second electrode that are opposed to each other inside the processing chamber. And generating plasma between the first electrode and the second electrode to excite the source gas supplied to the inside of the processing chamber, thereby bringing the second electrode toward the first substrate. In the plasma CVD apparatus for forming a thin film on the surface of the substrate disposed, the first electrode has a rough surface over the entire surface on the second electrode side.

  According to the above configuration, even if the thin film is formed not only on the surface of the substrate but also on the surface on the second electrode side of the first electrode, the surface on the second electrode side of the first electrode covers the entire surface. Therefore, the contact area between the formed thin film and the surface of the first electrode is increased, and the adhesion of the thin film is increased.

  For this reason, the thin film attached to the surface of the first electrode on the second electrode side is hardly peeled off, and the thin film is prevented from falling on the surface of the substrate and becoming particles.

  Accordingly, since the surface of the first electrode on the second electrode side is formed to be rough, the thin film attached to the upper electrode is hardly peeled off from the upper electrode, and the generation of particles inside the processing chamber is suppressed as much as possible. Is done.

  The surface roughness Ra of the surface on the second electrode side of the first electrode may be 0.5 μm or more and less than 40 μm.

  According to said structure, since the surface roughness Ra of a 1st electrode is 0.5 micrometer or more, the contact area of the formed thin film and the surface of a 1st electrode increases, and the adhesiveness of the thin film improves. become.

  For this reason, the thin film attached to the surface of the first electrode on the second electrode side is hardly peeled off, and the thin film is prevented from falling on the surface of the substrate and becoming particles.

  Since the surface roughness Ra of the first electrode is less than 40 μm, plasma is generated almost uniformly on the substrate during film formation, and the film thickness of the thin film formed on the surface of the substrate. Becomes almost uniform.

  The rough surface of the first electrode may be formed by blasting or lapping.

  According to said structure, the surface by the side of the 2nd electrode of a 1st electrode is easily formed in a rough surface by performing blasting processes, such as sandblasting, or a lapping process on the surface of a 1st electrode, for example. .

  The inner surface of the processing chamber may be formed into a rough surface.

  According to the above configuration, even if the thin film is formed not only on the surface of the substrate but also on the surface on the second electrode side of the first electrode and on the inner surface of the processing chamber, the second electrode side of the first electrode. Since the surface of the substrate and the inner surface of the processing chamber are formed to be rough over the entire surface, the contact area between the formed thin film and the surface of the first electrode and the inner surface of the processing chamber increases, Adhesion will increase.

  Therefore, the thin film attached to the surface of the first electrode on the second electrode side and the inner surface of the processing chamber is hardly peeled off, and the thin film is prevented from falling onto the surface of the substrate and becoming particles.

  The rough surface of the processing chamber may be formed by blasting or lapping.

  According to said structure, the internal surface of a process chamber is easily formed in a rough surface by performing blasting processes, such as sandblasting, or a lapping process to the internal surface of a process chamber.

  The electrode for a CVD apparatus according to the present invention includes a processing chamber and a source gas supply unit that supplies a source gas to the inside of the processing chamber, and generates plasma in the processing chamber, so that the processing chamber An electrode for a CVD apparatus for generating the plasma used in a plasma CVD apparatus for forming a thin film on the surface of a substrate disposed inside the processing chamber by exciting a source gas supplied to the inside of the processing chamber The substrate is disposed so as to face the substrate, and the surface on the substrate side is formed to be a rough surface over the entire surface.

  According to the above configuration, the substrate side surface of the CVD apparatus electrode is formed to be a rough surface over the entire surface. Therefore, if the CVD apparatus electrode is attached to the inside of the plasma CVD apparatus, the thin film becomes the surface of the substrate. In addition, even if the film is formed on the surface of the CVD apparatus electrode, the entire surface is formed to be a rough surface. The contact area increases and the adhesion of the thin film increases.

  For this reason, the thin film attached to the surface of the electrode for the CVD apparatus is hardly peeled off, and the thin film is prevented from falling onto the surface of the substrate and becoming particles. As a result, generation of particles inside the processing chamber is suppressed as much as possible.

  In the plasma CVD apparatus of the present invention, since the surface on the second electrode side of the first electrode is formed to be a rough surface over the entire surface, the thin film formed on the surface of the first electrode and the surface of the first electrode And the contact area of the thin film on the surface of the first electrode is increased. Therefore, it is difficult for the thin film attached to the surface of the first electrode to peel off, and the thin film can be prevented from falling onto the surface of the substrate and becoming particles.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiment, and may have other configurations.

  FIG. 1 is a schematic cross-sectional view of a plasma CVD apparatus 20 according to an embodiment of the present invention.

  The plasma CVD apparatus 20 includes a processing chamber 1, a gas supply unit (for example, a gas supply unit 7), an exhaust unit (for example, an exhaust pipe 9), and a high-frequency power source (RF power source) 8. Yes.

  The processing chamber 1 includes therein a first electrode (upper electrode) 2 that is an electrode for a CVD apparatus, and a second electrode (lower electrode) 3 disposed so as to face the first electrode 2.

  The first electrode 2 has a hollow portion 10 therein, and a plurality of gas jets 6 connected to the hollow portion 10 are formed on the second electrode 3 side, and the plurality of gas jets are formed. 6, the raw material gas and the cleaning gas from the gas supply unit are respectively ejected.

  Further, the first electrode 2 is made of a metal material such as an aluminum alloy, and for the reason described later, the surface roughness Ra on the second electrode 3 side is 0.5 μm or more and 40 μm on the entire surface. A rough surface is formed.

  Further, the first electrode 2 is connected to a high frequency power supply 8 and is configured to receive high frequency power from the high frequency power supply 8.

  The surface of the first electrode 2 may be subjected to a surface treatment such as anodization.

  The rough surface of the first electrode 2 is formed by subjecting the surface of the first electrode 2 to a blasting process such as sand blasting, a lapping process, a chemical process such as etching, and other surface treatments. In addition, it may be performed before or after forming a plurality of holes to be the gas ejection ports 6 in the electrode plate to be the first electrode 2.

  The second electrode 3 is configured to place a processing substrate 4 such as a glass substrate on the first electrode 2 side, and is electrically grounded.

  The second electrode 3 is made of a metal material such as an aluminum alloy, and a heater 5 is built in the second electrode 3 so that the temperature of the surface can be controlled.

  The gas supply unit is connected to a source gas cylinder (not shown) that is a source gas supply unit that supplies source gas, a cleaning gas cylinder (not shown) that supplies a cleaning gas, and a flow rate of each gas. A gas control unit (not shown) composed of a mass flow controller for individually controlling the gas, and connecting the gas control unit and the processing chamber 1 to supply the source gas or the cleaning gas into the processing chamber 1 It is comprised with the piping 7. FIG.

  The exhaust unit is provided in an exhaust device (not shown) including a vacuum pump, an exhaust pipe 9 connecting the exhaust device and the processing chamber 1, and an intermediate portion of the exhaust pipe 9, and adjusting an opening degree. And an opening variable valve 11 for controlling the internal pressure of the processing chamber 1.

  In addition, the inner surface of the processing chamber 1 is formed in a rough surface like the surface of the first electrode 2 on the second electrode 3 side.

  Next, for example, a film forming process for forming an amorphous silicon thin film and a cleaning process using the plasma CVD apparatus 20 having the above configuration will be described.

<Film formation process>
First, the processing substrate 4 is carried into the processing chamber 1 using a transfer robot or the like, and the processing substrate 4 is placed on the second electrode 3 inside the processing chamber 1, and then the gas supply pipe 7 and the first The opening of the variable opening valve 11 is adjusted while supplying a raw material gas such as SiH ₄ into the processing chamber 1 through the hollow portion 10 and the gas outlet 6 in the electrode 2, thereby processing the chamber 1. The internal pressure is set to 100 to 200 Pa.

Next, high frequency power from the high frequency power supply 8 is applied to the first electrode 2 while maintaining the internal pressure of the processing chamber 1 at 100 to 200 Pa. At this time, the source gas (SiH ₄ ) is excited by the plasma formed between the first electrode 2 and the second electrode 3 to generate a film-forming substance, which is placed on the second electrode 3. An amorphous silicon thin film is formed (deposited) on the surface of the processed substrate 4.

  Next, the output of the high frequency power from the high frequency power supply 8 is stopped, the pressure control inside the processing chamber 1 and the supply of the raw material gas to the processing chamber 1 are stopped, and then the processing substrate 4 is processed using a transfer robot or the like. Remove from chamber 1.

  As described above, one film formation process is completed.

  And after repeating the said film-forming process 5 times, the following cleaning processes will be performed as regular self-cleaning.

<Cleaning process>
With the processing substrate 4 having been subjected to the film forming process being carried out of the processing chamber 1, the opening degree variable valve 11 is fully opened, the hollow portion 10 in the gas supply pipe 7 and the first electrode 2, and the gas injection While supplying a cleaning gas such as NF _{3 to} the inside of the processing chamber 1 through the outlet 6, a high-frequency power from a high-frequency power source 8 is applied to the first electrode 2 to generate fluorine radicals, or Fluorine radicals generated in advance are introduced into the processing chamber 1 and the amorphous silicon thin film adhering to the surface of the first electrode 2 and the inner surface of the processing chamber 1 is etched. Then, using a vacuum pump or the like, the gas generated by the etching is discharged to the outside of the processing chamber 1 through the exhaust pipe 9.

  The cleaning process is completed as described above.

  As described above, the plasma CVD apparatus 20 according to the present invention has the same structure even when the amorphous silicon thin film is formed not only on the surface of the processing substrate 4 but also on the surface of the first electrode 2 on the second electrode 3 side. Since the surface of the first electrode 2 on the second electrode 3 side is a rough surface over the entire surface, specifically, the surface roughness Ra is 0.5 μm or more and less than 40 μm. When the surface roughness Ra of the electrode 2 is 0.5 μm or more, the contact area between the formed amorphous silicon thin film and the surface of the first electrode 2 increases, and the adhesion of the amorphous silicon thin film increases. become.

  Therefore, the amorphous silicon thin film attached to the surface of the first electrode 2 on the second electrode 3 side is hardly peeled off, and the amorphous silicon thin film can be prevented from falling onto the surface of the processing substrate 4 and becoming particles.

  Accordingly, since the surface of the first electrode 2 on the second electrode 3 side is formed to be rough, the amorphous silicon thin film attached to the upper electrode 2 is difficult to peel off from the upper electrode 2, and particles inside the processing chamber 1 Occurrence can be suppressed as much as possible.

  Further, since the surface roughness Ra of the first electrode 2 is less than 40 μm, plasma is generated almost uniformly with respect to the processing substrate 4 during film formation, and the film is formed on the surface of the processing substrate 4. The film thickness of the amorphous silicon thin film can be made substantially uniform.

  Furthermore, since the inner surface of the processing chamber 1 is also formed into a rough surface, the amorphous silicon thin film is not only the surface of the processing substrate 4 but also the surface of the first electrode 2 on the second electrode 3 side and the inside of the processing chamber 1. Even if the film is formed on the surface, the surface of the first electrode 2 on the second electrode 3 side and the inner surface of the processing chamber 1 are formed to be rough over the entire surface. The contact area between the silicon thin film and the surface of the first electrode 2 and the inner surface of the processing chamber 1 increases, and the adhesion of the amorphous silicon thin film increases.

  Therefore, the amorphous silicon thin film attached to the surface of the first electrode 2 on the second electrode 3 side and the inner surface of the processing chamber 1 is difficult to peel off, and the amorphous silicon thin film falls on the surface of the processing substrate 4 and becomes particles. Can be suppressed.

  Next, a specific experiment will be described.

  As examples and comparative examples of the present invention, electrodes having surface roughness Ra of 0.1 μm, 0.3 μm, 0.5 μm, 1.0 μm, and 1.5 μm prepared by lapping are prepared. Is attached as the first electrode of the same plasma CVD apparatus as in the above-described embodiment, and thereafter, the amorphous silicon thin film is formed on the glass substrate five times on the glass substrate in the same manner as in the above-described embodiment. The number of particles on the glass substrate on which the amorphous silicon thin film was formed was measured.

  FIG. 2A is data obtained by measuring the surface roughness of the surface of the electrode having a surface roughness Ra of 0.3 μm prepared as a comparative example, and FIG. 2B is prepared as an example. It is the data which measured the surface roughness of the surface of the electrode formed with surface roughness Ra of 1.0 micrometer.

  The results are shown below.

  3 and 4 are graphs showing changes in the number of particles for each prepared electrode. Here, the horizontal axis in the figure indicates the number of deposited films after cleaning, and the vertical axis in the figure indicates the number of particles per glass substrate.

  First, the results shown in FIG. 3 will be described.

  FIG. 3 is a graph showing a change in the number of particles having a size of 1 μm or more per glass substrate in a glass substrate having a size of 400 mm × 500 mm.

  In the example using the electrodes having the surface roughness Ra of 0.5 μm, 1.0 μm, and 1.5 μm, the number of particles does not increase even when the number of deposited films increases, and the number of deposited films is 5 sheets. Even in this case, the number of particles was less than 10.

  On the other hand, in the comparative example using the electrodes having the surface roughness Ra of 0.1 μm and 0.3 μm, the number of particles increases each time the number of deposited films increases, and the number of deposited films is 5 sheets. In some cases, the number of particles reached 350-400.

  Next, the results shown in FIG. 4 will be described.

  FIG. 4 is a graph showing changes in the number of particles of 5 μm or more per glass substrate in a glass substrate having a size of 1500 mm × 1800 mm.

  In the embodiment using the electrode having the surface roughness Ra of 0.5 μm or more, the number of particles does not increase even when the number of deposited films increases, and even if the number of deposited films is five, The number was less than 50.

  On the other hand, in the comparative example using an electrode formed with a surface roughness Ra of less than 0.5 μm, the number of particles increases as the number of deposited films increases, and the number of deposited films is five. The number of particles reached 800-900.

  As described above, in the example in which the surface roughness Ra using the plasma CVD apparatus of the present invention is 0.5 μm or more, the number of particles hardly increased even when the number of deposited films increased. In the comparative example in which the thickness Ra is less than 0.5 μm, as the number of deposited films increases, the number of particles increases in proportion to the number of deposited films. Therefore, it can be confirmed that the present invention suppresses the generation of particles. It was.

  In addition, when an amorphous silicon thin film is formed using an electrode having a surface roughness Ra of 40 μm or more, the variation in film thickness of the amorphous silicon thin film on the glass substrate increases, and the amorphous silicon thin film A decrease in film quality was confirmed.

  As described above, since the generation of particles in the processing chamber is suppressed, the present invention is useful for a CVD apparatus in which continuous film formation is indispensable at a high throughput such as manufacturing a liquid crystal display device.

It is a cross-sectional schematic diagram of the plasma CVD apparatus 20 which concerns on embodiment of this invention. It is the data which measured the surface roughness of the surface by the side of the 2nd board | substrate side of the 1st board | substrate in the Example and comparative example of this invention. It is a graph which shows the change of the particle number in the Example and comparative example of this invention. It is a graph which shows the change of the particle number in the other Example and comparative example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Processing chamber 2 1st electrode 3 2nd electrode 4 Processing board | substrate 5 Heater 6 Gas outlet 7 Gas supply piping 8 High frequency power supply 9 Exhaust piping 10 Hollow part 11 Opening variable valve 20 Plasma CVD apparatus

Claims (6)

A processing chamber;
A source gas supply unit for supplying source gas into the processing chamber;
A first electrode and a second electrode disposed opposite to each other inside the processing chamber;
Plasma is generated between the first electrode and the second electrode to excite the source gas supplied to the inside of the processing chamber, whereby the substrate disposed on the first substrate side of the second electrode is A plasma CVD apparatus for forming a thin film on a surface,
2. The plasma CVD apparatus according to claim 1, wherein the first electrode has a rough surface over the entire surface on the second electrode side. In the plasma CVD apparatus according to claim 1,
The plasma CVD apparatus, wherein the surface roughness Ra of the surface of the first electrode on the second electrode side is 0.5 μm or more and less than 40 μm. In the plasma CVD apparatus according to claim 1,
The plasma CVD apparatus, wherein the rough surface of the first electrode is formed by blasting or lapping. In the plasma CVD apparatus according to claim 1,
A plasma CVD apparatus, wherein an inner surface of the processing chamber is formed to be a rough surface. In the plasma CVD apparatus according to claim 4,
The plasma CVD apparatus, wherein the rough surface of the processing chamber is formed by blasting or lapping. A processing chamber and a source gas supply unit that supplies a source gas to the inside of the processing chamber are provided, and plasma is generated inside the processing chamber to excite the source gas supplied to the inside of the processing chamber. Is used in a plasma CVD apparatus for forming a thin film on the surface of a substrate disposed inside the processing chamber, and is an electrode for a CVD apparatus for generating the plasma,
A CVD apparatus electrode, wherein the electrode is disposed opposite to the substrate, and the surface on the substrate side is formed to be a rough surface over the entire surface.

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