JPH11144892A - Plasma device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce unevenness in large size film formation, ion damage, increase of fixed charge in an insutating film, and the like by impressing high- frequency voltage different in polarity each other with a discharge electrode comprising plural electrodes facing holizontally to a substrate stage so as to generate discharge laterally. SOLUTION: A glass substrate 6 is mounted on a substrate heating stage 7 to be fitted via a substrate fixing plate 8. A discharge elecbode with plural electrodes 1, 2 fixed to an insulating plate 3 is arranged facing in parallel to the stage 7. The electrodes 1, 2 are preferably composed of Mg, Al, or their alloy, and have a cross-sectional shape of triangle, trapezoid, semicircle, T-shape, or the like. In this plasma generator, reaction gas fed from an injection port 4 drilled to the insulating plate 3 in the intermediate position between the electrodes 1, 2 through a homogeneously diffusing plate 5 is introduced into a chamber. Two- or three-phase high-frequency voltage is impressed thereafter, and lateral-directional discharge is generated between the odd group electrode 1 and the even group electrode 2 as mutually different electrodes to form the reaction gas into plasma.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a plasma CVD apparatus, a dry etching apparatus, and a plasma ashing apparatus used for manufacturing an active matrix liquid crystal panel, and is particularly applicable to a very large substrate. In addition, the present invention can be similarly applied to an LSI process using a Si wafer.

[0002]

2. Description of the Related Art A stage on which a glass substrate is mounted, and a discharge electrode are arranged opposite to the stage. The discharge electrode is integrated, and a number of holes are made in the surface of the electrode to discharge the reaction gas through the holes. The space between the glass substrate and the discharge electrode is usually 20 mm or more.

[0003]

When the discharge gas pressure is increased in a conventional parallel plate type integrated discharge electrode plasma generating apparatus, the space between the discharge electrode and the stage must be reduced according to the Patzen's law. The starting voltage and the sustaining voltage become very high. When the discharge starting voltage becomes high, when the discharge starts, the glass substrate is likely to be damaged by discharge on the stage, and the characteristics of the thin film amorphous transistor element are remarkably deteriorated. Furthermore, in the conventional plasma generator having a parallel plate integrated discharge electrode structure, it is difficult to deposit an amorphous Si thin film uniformly on the glass substrate as the size of the discharge electrode increases with the size of the glass substrate.
Uniform deposition is achieved in the direction of lowering the discharge gas pressure. As the discharge gas pressure decreases, the deposition rate decreases and the throughput decreases. When the discharge gas pressure is reduced, the distance of the mean free path of the ions in the plasma increases, the kinetic energy of the ions increases, and the glass substrate is damaged, so that the film quality tends to deteriorate. To increase the deposition rate, a method of increasing the frequency of the high frequency of the discharge is also possible, but when used for a large substrate, the cost of the power supply increases and the design of the apparatus becomes difficult. Further, when the discharge power is further increased, an arcing phenomenon occurs at the gas discharge port in the conventional case, and the discharge electrode is often broken.

[0004] The plasma generating apparatus of the present invention solves the above-mentioned problems, and aims at non-uniformity of film formation, which is a problem when a glass substrate is enlarged, and ions at the interface of a thin film transistor. It is an object of the present invention to improve the characteristics of a thin film transistor by reducing damage, an increase in fixed charges in an insulating film due to high-speed film formation, and to realize a super-large liquid crystal display device using a super-large glass substrate.

[0005]

Means for Solving the Problems The following means are taken in order to solve the conventional problems and achieve the object. [Means 1] In a plasma generating apparatus comprising a stage on which a glass substrate is mounted and a discharge electrode horizontally opposed to the stage, the discharge electrodes are composed of a plurality of electrodes, each of which has a polarity opposite to each other. Are applied to generate a horizontal electric field horizontal to the stage, thereby causing a horizontal discharge.

[Means 2] In the means 1, holes or slits are formed between the discharge electrodes separated from each other, and the reaction gas is introduced into the reaction chamber from this portion.

[Means 3] In the means 2, a plurality of discharge electrodes separated from each other are alternately connected to each other, divided into two groups, and two-phase high-frequency voltages having different phases are applied to each group to apply a voltage to the stage. The battery was discharged horizontally.

[Means 4] In the means 2, a plurality of discharge electrodes separated from each other are alternately connected, divided into three groups, and three-phase high-frequency voltages having different phases are applied to each group, and the stage is applied to the stage. The battery was discharged horizontally.

[Means 5] In the means 2, a plurality of discharge electrodes separated from each other are all electrically connected to apply a high-frequency voltage having the same phase to generate a vertical discharge in a vertical direction with respect to the stage. It is possible to switch the discharge mode to the stage by electrically separating it into two or more electrode groups and generating horizontal discharge to the stage.

[Means 6] In the means 2, a plurality of discharge electrodes are embedded in an insulator fixing the electrodes, and the reactant gas is reacted through a hole or a slit between the electrodes. It was designed to be inserted into the chamber.

[Means 7] In a plasma generating apparatus comprising a stage on which a glass substrate is mounted and a discharge electrode horizontally opposed to the stage, the discharge electrode has a honeycomb shape. A high-frequency voltage was applied to generate an electric field in a direction perpendicular to the stage, so that a vertical discharge was generated.

[Means 8] In the means 7, the reaction gas discharge port is provided in the hole of the honeycomb electrode, and the reaction gas is introduced into the reaction chamber from the reaction gas discharge port.

[Means 9] In the means 7, the depth of the hole of the honeycomb electrode is larger than the diameter of the opening of the honeycomb electrode. (The surface area of the electrode was increased.)

[Means 10] In the means 2, a plus or minus DC voltage or a high frequency voltage with a DC bias voltage can be applied to a stage on which a glass substrate is placed.

[Means 11] The surface of the stage on which the glass substrate is mounted has a honeycomb shape, and the pins of the lifter for lifting the glass substrate come out from the holes of the honeycomb so that the glass substrate can be supported.

[Means 12] Magnesium, an alloy mainly composed of magnesium, aluminum, or an alloy mainly composed of aluminum is used as a discharge electrode material used in the means 1 and the means 7.

[Means 13] In the means 7, a honeycomb shield electrode having the same shape as that of the honeycomb discharge electrode is bonded together by using an insulating spacer.

[0018]

The discharge electrode is divided into a plurality of parts, and a high-frequency voltage having a different phase is applied to each of the plurality of parts to generate a horizontal discharge on the stage. In the case of this lateral discharge, ions and electrons do not flow into the glass substrate on the stage, so discharge damage is drastically reduced. When forming the interface between the gate insulating film and the semiconductor layer, which most governs the characteristics of the thin film transistor, it is important to prevent discharge damage at the interface. An inverted staggered thin film transistor in which a gate electrode is provided below and a semiconductor layer (non-doped a-Si layer) is deposited after depositing a gate insulating film is mainly used because discharge damage at the time of forming the interface can be reduced. It is. The discharge power density at the time of depositing the semiconductor layer is one more than the discharge power density at the time of depositing the gate insulating film.
It is about １０ to 1/10 smaller. By reducing the discharge power density, the interface is not damaged.
In a conventional parallel plate type plasma CVD apparatus, an electric field is applied between a discharge electrode and a glass substrate in a direction perpendicular to the glass substrate to generate a discharge in a vertical direction. In this type of plasma CVD apparatus, even if the discharge power density is reduced,
In principle, it is impossible to eliminate discharge damage. Therefore, in order to reduce discharge damage, it is necessary to reduce the mean free path of ions, and it is preferable that the discharge gas pressure be as high as possible. However, if the discharge gas pressure is high, the discharge starting voltage becomes high, and the interface may be damaged at the moment when the discharge starts. Further, when the discharge gas pressure is high, discharge is generated at the edge of the discharge electrode, and it becomes impossible to obtain a uniform film thickness and film quality.

When the lateral discharge of the present invention is used, the space between the discharge electrodes can be reduced to 10 mm or less. Therefore, even if the gas pressure is increased, the discharge starting pressure does not become high and non-uniform discharge occurs. Absent. Even if the gas pressure is reduced, discharge damage cannot be obtained on the glass substrate in principle because of the lateral discharge. Since the range of discharge conditions is very wide, it is possible to find high-speed deposition conditions that do not generate dust without deteriorating the characteristics of the thin film transistor.

[0020] The weight of the discharge electrode when the glass substrate is about the size of a meter also becomes a problem. The plate thickness of the conventional PCVD discharge electrode is more than 20mm, and replacement of the electrode is very difficult. The honeycomb electrode of the present invention can reduce the weight to 1/3 to 1/4 of the conventional one. The cost can be reduced to about 1/3 of the conventional cost. Since the hole can be deeper than the conventional parallel plate electrode, the discharge surface area can be increased. As a result, the potential drop near the discharge electrode can be reduced, so that the plasma reaction can be prevented from being concentrated on the discharge electrode side. Therefore, generation of dust and particles can be reduced as compared with the conventional electrode. Abnormal discharge disappears.

A method has been proposed in which the frequency of the high-frequency voltage is increased twice or three times the conventional frequency in order to improve the throughput and the productivity, but as the size of the glass substrate increases, the capacity of the electrode increases and the electrode capacity increases. The device design becomes very difficult because the surface resistance increases. In the case of the present invention, plasma damage can be reduced in the lateral discharge, and conversely, in the case of a large size, it is possible to study in the direction of decreasing the discharge frequency. When the discharge frequency is reduced, the design of the high-frequency power supply is simplified, and the stability of the discharge of the PCVD apparatus is also improved.

In the conventional parallel plate type plasma apparatus, since the vertical discharge occurs between the discharge electrode and the stage even when the potential of the stage on which the glass substrate is mounted is changed, the surface potential of the glass substrate is controlled. However, in the plasma generator of the present invention, since the discharge occurs between the discharge electrodes separated into a plurality of discharge electrodes, the potential of the stage on which the glass substrate is placed is changed by changing the potential of the stage on which the glass substrate is placed. The potential can be controlled.
This makes it possible to control the polarity of fixed charges and the number of fixed charges incorporated in the insulating film when the insulating film is deposited, so that the quality of the insulating film can be significantly improved. The yield can be improved because the stress of the film can be easily controlled.

[0023]

[Embodiment 1] FIGS. 1, 3, 4, 5, 7, 8, 9, 10, 22, and 23 show a horizontal direction with respect to a glass substrate of the present invention. 3A and 3B are a cross-sectional view and a plan view of a discharge electrode for causing a horizontal discharge to occur. The cross sections of the discharge electrodes divided into two groups may have various shapes such as a triangle, a trapezoid, a semicircle, and a T-shape. The surface of the material is anodized using aluminum or an aluminum alloy. These discharge electrodes are fixed to an insulating plate having a hole in the reaction gas discharge port. As shown in FIG. 2, a high frequency voltage is applied to two groups of electrodes to generate a lateral discharge.

The discharge electrodes are separated into three groups as shown in FIG. 17, and a three-phase high-frequency voltage having a phase shift of 120 degrees can be applied to each group. The applied voltage waveform may be not only a sine waveform but also a rectangular waveform as shown in FIG. As shown in FIG. 19, a modulated sine waveform or a rectangular waveform may be used.

7 and 8, a shield plate (20) and a porous gas diffusion shield electrode (21) are provided on the back side of the insulating plate to which the discharge electrode is fixed so that the discharge does not flow around. . In Fig. 10, a part of the discharge electrode near the gas outlet is cut in a circular shape so that a strong electric field is not applied to the gas outlet. Fig. 23 shows a structure in which the reactant gas outlet is located away from the discharge electrode.

FIG. 6 shows a structure in which a discharge electrode is embedded in an insulating plate. With this structure, the inner surface of the reaction chamber can be entirely covered with ceramic, so that the deposited film is less likely to peel.

[Embodiment 2] FIGS. 12, 14, 16, 24, 26, and 27 are a cross-sectional view of a plasma generator using the honeycomb discharge electrode of the present invention and a plan view of the honeycomb discharge electrode. is there. As shown in FIG. 11, a conventional plasma generator uses an anodized aluminum alloy having a thickness of 25 mm or more. When a meter-sized discharge electrode is manufactured with a conventional structure, the weight becomes extremely heavy, which has been a problem during maintenance. Further, in the conventional case, since the drilling process is performed one by one using a drill, the manufacturing cost is very high. By using the honeycomb electrode of the present invention, the weight can be reduced to 1/3 to 1/4 of the conventional one, and the cost can be greatly reduced. By disposing the ground electrode near the honeycomb discharge electrode as shown in FIGS. 15, 16, and 26, a stable discharge can be uniformly maintained over the entire discharge electrode even when the reaction gas pressure is increased. In the case of FIG. 16, the discharge concentrates on the gas discharge port of the insulating spacer (17) and the discharge is narrowed. (17) does not melt because it is a heat-resistant ceramic. Since the surface area of the honeycomb electrode is larger than that of the conventional discharge electrode, the cathode drop voltage is reduced and the heat generation of the electrode is also reduced. The electron density in the holes of the honeycomb electrode can be increased by making the opening diameter (a) of the honeycomb smaller than the mean free path of electrons and making the depth (b) larger than (a). The electron density can be further improved by using a honeycomb electrode made of magnesium or a magnesium alloy oxide. This makes it possible to significantly increase the ionization and radical formation of the reaction gas. In the case of deposition, the deposition rate can be increased, and in the case of dry etching, the etching rate can be increased. In the case of ashing, the speed of ashing can be increased.

The honeycomb electrode of the present invention can be injection-molded by using a thixomolding method when a magnesium alloy is used. In this case, the cost can be significantly reduced. The thixomolding method can also be used for manufacturing the honeycomb stage. This method is suitable for manufacturing a large-area honeycomb plate because it is light, can be thin, and can improve accuracy.

[Embodiment 3] FIGS. 20 and 21 are a plan view and a sectional view of a stage having a honeycomb structure according to the present invention. Since the contact area with the glass substrate is small, the generation of static electricity when lifting the glass substrate is very small. Even if the glass substrate becomes large, there is no need to lift the glass substrate by the edge. Since the lifter pins can be installed at the point where the deflection of the glass substrate becomes the least, the glass substrate will not be destroyed. Since no stress is applied to the glass substrate, disconnection of the wiring formed on the glass substrate does not occur. By utilizing the hole of the lifter pin by flowing N ₂ gas will be possible to break the vacuum suction of the glass substrate.
Honeycomb-shaped stages, for which various effects can be expected as the glass substrate becomes larger, can be used not only for stages in vacuum equipment but also for stages in heating and drying devices such as hot plates used in the atmosphere. .

[0030]

According to the present invention, a thin film transistor having excellent characteristics with little interface damage can be formed by using the plasma CVD apparatus of the lateral discharge electrode system of the present invention.
When used for a liquid crystal panel by improving the electron mobility, the W / L of the thin film transistor can be designed to be small, so that the aperture ratio can be improved and a bright liquid crystal panel can be manufactured. Further, since the effect of the gate electrode on the pixel electrode potential can be reduced by reducing the W / L, the problem of the afterimage can be reduced.

Further, when an insulating film is deposited using a lateral discharge type plasma CVD apparatus, the amount of fixed charges in the insulating film can be reduced because the plasma potential of the glass substrate can be freely controlled. Thereby, the reliability of the characteristics of the thin film transistor can be significantly improved.

The lateral discharge device of the present invention is a plasma CVD device.
The present invention can be applied not only to a device but also to a plasma dry etching device, a plasma ashing device, and the like, and can be used not only for a glass substrate but also for a Si single crystal substrate.

By using the honeycomb discharge electrode of the present invention, the maintenance work of the plasma apparatus for an ultra-large glass substrate becomes easy, and the cost of the discharge electrode can be reduced. By installing an earth electrode near the honeycomb discharge electrode, the discharge spreads over the entire electrode even if the discharge gas pressure is increased, so that high-speed deposition can be realized and interface damage can be reduced. This improves productivity.

By using the honeycomb stage of the present invention, the generation of static electricity at the time of lifting up a very large glass substrate can be greatly reduced, and the damage to the glass substrate can be reduced. Since the lifter pins can be installed at the parts where the distortion of the glass substrate is minimized, the disconnection of the wiring pattern on the glass substrate is drastically reduced. The material of the honeycomb stage may be an aluminum alloy or a magnesium alloy. Stainless steel alloys may be used. A ceramic insulator may be used. Although the present invention features a honeycomb shape, the same effect can be obtained with a stripe shape. Although it is easy to provide the function of vacuum suction in the honeycomb shape, it is difficult to provide the function of vacuum suction in the stripe shape. When the stripe shape is formed by using the thixomolding method, the stripe shape is easy to manufacture, and the cost can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a sectional structural view of a plasma generator employing a lateral discharge electrode of the present invention. (triangle)

FIG. 2 is a diagram showing application of a high-frequency voltage to a lateral discharge electrode according to the present invention.

FIG. 3 is a cross-sectional view of a lateral discharge electrode of the present invention. (Trapezoid)

FIG. 4 is a cross-sectional view of a lateral discharge electrode of the present invention. (Semicircular)

FIG. 5 is a cross-sectional view of a lateral discharge electrode of the present invention. (T-shaped)

FIG. 6 is a cross-sectional view of the embossed lateral discharge electrode of the present invention.

FIG. 7 is a cross-sectional view of a lateral discharge electrode of the present invention. (triangle)

FIG. 8 is a cross-sectional view of a lateral discharge electrode of the present invention. (triangle)

FIG. 9 is a plan view of a lateral discharge electrode of the present invention.

FIG. 10 is a plan view of a lateral discharge electrode of the present invention.

FIG. 11 is a cross-sectional structural view of a conventional plasma generator using a vertical discharge electrode.

FIG. 12 is a cross-sectional structural view of a plasma generator employing the honeycomb discharge electrode of the present invention.

FIG. 13 is a plan view of a vertical discharge electrode of the present invention.

FIG. 14 is a plan view of a honeycomb discharge electrode of the present invention.

FIG. 15 is a cross-sectional structural view of a plasma generator using a vertical discharge electrode of the present invention.

FIG. 16 is a sectional structural view of a vertical plasma generator using the honeycomb discharge electrode of the present invention.

FIG. 17 is a diagram illustrating application of a high-frequency voltage to a lateral discharge electrode according to the present invention.

FIG. 18 is a pulse voltage waveform applied to a lateral discharge electrode of the present invention.

FIG. 19 is a modulated high-frequency voltage waveform applied to a lateral discharge electrode of the present invention.

FIG. 20 is a plan view of a honeycomb stage of the present invention.

FIG. 21 is a sectional view of a honeycomb stage of the present invention.

FIG. 22 is a plan view of a lateral discharge electrode of the present invention.

FIG. 23 is a sectional structural view of a plasma generator employing the lateral discharge electrode of the present invention.

FIG. 24 is a sectional structural view of a vertical plasma generator using the honeycomb discharge electrode of the present invention.

FIG. 25 is a plan view of a honeycomb discharge electrode of the present invention.

FIG. 26 is a sectional structural view of a vertical plasma generator using the honeycomb discharge electrode of the present invention.

FIG. 27 is a plan view of a honeycomb discharge electrode according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Odd group discharge electrode 2 Even group discharge electrode 3 Discharge electrode fixed insulating plate 4 Reactive gas injection port 5 Reactive gas uniform diffusion plate 6 Glass substrate (or Si wafer) 7 Glass substrate heating stage 8 Glass substrate fixed plate 9 Reactive gas exhaust port DESCRIPTION OF SYMBOLS 10 High frequency AC power supply 11 Discharge electrode with a trapezoidal cross section 12 Discharge electrode with a semicircular cross section 13 Discharge electrode with a T-shaped cross section 14 Discharge electrode embedded in a fixed insulating plate 15 Integrated discharge electrode with a hole 16 Honeycomb type Discharge electrode 17 Insulating spacer 18 Perforated integral earth electrode 19 Perforated integral discharge electrode 20 Shield electrode 21 Porous gas diffusion shield electrode 22 High-frequency three-phase AC power supply a Honeycomb electrode opening diameter b Honeycomb electrode hole 23 Odd group discharge electrode voltage waveform 24 Even group discharge electrode voltage waveform 25 Honeycomb stage 6 lifter pins c electrode plate and the electrode plate distance d electrode plate depth h electrode plate tip distance 27 shield the honeycomb electrode 28 the discharge electrode holders 29 honeycomb grounding electrode to the glass substrate from the

Claims (13)

[Claims] 1. A plasma generating apparatus comprising a stage on which a glass substrate is mounted and a discharge electrode horizontally opposed to said stage, wherein said discharge electrode comprises a plurality of electrodes, Is a plasma generator characterized in that high-frequency voltages having different polarities are applied to each other to form a horizontal electric field horizontal to a stage, thereby generating a horizontal discharge. 2. A plasma generating apparatus according to claim 1, wherein a hole or a slit is formed between the discharge electrodes separated from each other and a reaction gas is introduced into the reaction chamber from the hole or slit. apparatus. 3. The method according to claim 2, wherein a plurality of discharge electrodes separated from each other are alternately connected, divided into two groups, and a two-phase high-frequency voltage is applied to cause a lateral discharge. Plasma generator 4. The method according to claim 2, wherein a plurality of discharge electrodes separated from each other are alternately connected, divided into three groups, and a three-phase high-frequency voltage is applied to perform lateral discharge. A plasma generator. 5. The method according to claim 2, wherein a plurality of separate electrodes are electrically connected to each other to cause a vertical discharge to the glass substrate or to separate two or more electrode groups to generate a horizontal discharge. A plasma generator capable of switching the discharge mode for the stage. 6. A method according to claim 2, wherein a plurality of discharge electrodes are embedded in an insulator fixing the electrodes, and a reaction gas is introduced into the reaction chamber through a hole between the electrodes. A plasma generator characterized by a recessed structure. 7. A plasma generating apparatus comprising a stage on which a glass substrate is mounted and a discharge electrode horizontally opposed to said stage, wherein said discharge electrode has a honeycomb shape, and a high-frequency voltage is applied to said honeycomb electrode. A plasma generator in which an electric field is generated in a direction perpendicular to the stage by applying an electric field, thereby generating a discharge in a vertical direction. 8. A plasma generating apparatus according to claim 7, wherein a reaction gas discharge port is provided in the hole of the honeycomb electrode, and the reaction gas is introduced into the reaction chamber from the reaction gas discharge port. apparatus. 9. A plasma generator according to claim 7, wherein the depth of the hole of the honeycomb electrode is larger than the diameter of the opening of the honeycomb electrode. 10. The method according to claim 2, wherein a positive or negative DC voltage can be applied to the stage on which the glass substrate is mounted, or a high-frequency voltage with a DC bias voltage can be applied. A plasma generator. 11. A stage characterized in that the surface of a stage on which a glass substrate is mounted has a honeycomb shape, and a pin of a lifter for lifting the glass substrate comes out of a hole in the honeycomb to hold the glass substrate. 12. The discharge electrode material according to claim 1, wherein the discharge electrode material is magnesium, an alloy mainly composed of magnesium, aluminum, or an alloy mainly composed of aluminum. Plasma generator. 13. A plasma generator according to claim 7, wherein a honeycomb shield electrode having the same shape as the honeycomb discharge electrode is bonded by an insulating spacer.