JP2901331B2 - Microwave plasma processing equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus used for manufacturing semiconductor devices, liquid crystal display elements, line sensors, thin-film magnetic heads, and other electronic components to which thin films are applied. More particularly, the present invention relates to a plasma processing apparatus suitable for plasma processing such as thin film formation and etching.

[Conventional technology]

As a conventional microwave plasma processing apparatus of this type, for example, one disclosed in Japanese Patent Application Laid-Open No. 62-122217 is known. In this case, a discharge tube is provided in the vacuum chamber, a coil is attached to the discharge tube, a magnetic field is applied, and a microwave having the same frequency as the electron cyclotron frequency is introduced through the waveguide to cause a discharge. As a result, the reaction gas introduced into the vacuum chamber is decomposed, whereby chemical vapor deposition is performed on a substrate, which is a sample placed in the vacuum chamber, or a thin film on the substrate is etched.

However, to process a large-area substrate requires a large discharge tube, and it is necessary to apply large power to the microwave, but a large force of the atmospheric pressure is applied to the large discharge tube, and There is a high possibility of damage due to heating by the internal plasma or the high-power microwave passing through. In such a discharge tube system, the distribution of the plasma density tends to be higher at the center and lower at the periphery, reflecting the shape of the discharge tube.

Further, a plasma processing apparatus in which a microwave radiation window provided at an end portion of the microwave waveguide is configured as a part of a partition wall of a vacuum vessel, and the electron cyclotron resonance condition is set immediately below this window. Proposed. In this apparatus, the size of the window determines the area in which plasma processing can be performed. Therefore, in the case of an apparatus for processing a substrate having a large area, a large-diameter window is required. Therefore, as the size of the window increases, it is necessary to increase the thickness to provide strength. However, since the thickness of the window generally increases microwave absorption and causes power loss, it cannot be unnecessarily increased. After all, the practical size and thickness of the window are determined from the relationship between the power loss due to the thickness of the window and the strength of the window material,
This is the reason why plasma processing of a large-area substrate has not been possible in this type of apparatus.

On the other hand, as a different method, there is a method using a rigidano coil described in JP-A-62-254419. But,
In this method, when a high-power microwave required to generate high-density plasma in a large area is introduced, a spark is easily generated in an introduction portion, and it has been difficult to commercialize the microwave.

[Problems to be solved by the invention]

As described above, the conventional technology does not consider uniform processing of a large-area substrate, and for example, it is difficult to process a liquid crystal display panel or the like using a large substrate, and it is not possible to process a large-diameter wafer. was there.

Therefore, an object of the present invention is to solve the above-mentioned conventional problems, and to provide a microwave plasma processing apparatus capable of stably performing uniform microwave plasma processing over a large area. As a result, plasma CVD using low-pressure, high-density plasma of microwave plasma
To enable the application of film deposition and plasma etching to the processing of large-area substrates, and to enable continuous processing of the equipment, realizing an equipment that can respond to mass production.
For example, it contributes to the performance of thin film production and thin film etching processing in a large liquid crystal display element, a facsimile line sensor, a thermal head, and the like, an improvement in yield, and a reduction in cost.

[Means for solving the problem]

In order to achieve the above object, the present inventors have obtained the following findings as a result of various experiments. That is, the structure of the radiator at the end of the microwave waveguide is, for example, an electromagnetic horn type, the microwave is expanded to the processing area of the substrate, and a large area plasma is generated. At this time, in order to homogenize the plasma, the microwave introduction window for introducing the microwave into the plasma region forms a part of a partition of the vacuum vessel as a large area flat plate made of, for example, quartz and is parallel to the substrate holder. In addition, in order to make the decomposition of the reaction gas in the plasma uniform, a perforated plate is installed in close proximity to the microwave window, and the reaction gas is passed between the perforated plate and the microwave window to pass through the holes in the perforated plate. The reaction gas was ejected toward the substrate. Of course, a point satisfying the electron cyclotron resonance conditions exists between the porous plate and the perforated plate immediately below the microwave introduction window in order to generate microwave discharge. Also, when atmospheric pressure is applied to the large-area microwave window from the waveguide side during plasma generation, the microwave window is liable to be broken due to the pressure difference due to the vacuum inside the vacuum vessel. A pressure reducing means is provided on the electromagnetic horn side (waveguide side) to reduce the pressure difference. However, it is important to set the decompression condition so that discharge does not occur on the electromagnetic horn side, that is, on the waveguide side, so that the electromagnetic horn side satisfies the electron cyclotron resonance condition. Even if it can be performed, no discharge occurs, and no microwave power is lost due to unnecessary discharge. It was found that the pressure on the electromagnetic horn side (waveguide side) that does not cause this discharge should be 5 to 50 kPa or 10 ⁻⁴ Pa or less. Even if the electromagnetic horn side (waveguide side) is decompressed, the conditions are set so that no discharge occurs. Further, it is not necessary to apply a magnetic field for this purpose in the electromagnetic horn, and the coil can be downsized. . When 5 to 50 kPa is selected as the pressure on the electromagnetic horn side (waveguide side), the cooling effect by the heat conduction of the gas occurs to the microwave window heated by the microwave or plasma, and the apparatus is continuously operated. It was found that the window was not damaged even when used, and the reaction gas was not thermally decomposed. In this device description,
The structure of the radiator at the end of the microwave waveguide is described as an example using an electromagnetic horn. However, the present invention is not limited to this, and the microwave introduction window forms a part of the partition wall of the vacuum vessel. Can be generally applied to a microwave plasma processing apparatus configured such that a point satisfying the electron cyclotron resonance condition exists directly below the apparatus.

The present invention has been made based on the above findings, and specific means for achieving the object of the present invention will be described below.

The object of the present invention is as follows: (1). A gas supply unit, a vacuum container provided with a vacuum exhaust unit, a waveguide for guiding microwaves into the vacuum container, a radiator connected to one end of the waveguide, and an opening of the radiator. A microwave window which forms a part of a partition wall of the vacuum container, and a magnetic field generating means for causing electron cyclotron resonance at a frequency of the microwave immediately below the microwave window in the vacuum container. A microwave plasma processing apparatus comprising: means for reducing the pressure of at least the inside of the radiator provided with the microwave window under conditions that do not cause discharge; and the microwave window for introducing a microwave into the vacuum vessel. A pressure reducing portion of the waveguide to which the radiator is connected, and a pipe connecting the vacuum vessel,
This is achieved by a microwave plasma processing apparatus configured to connect a safety valve that opens when the pressure difference between the two is equal to or higher than the pressure resistance of the microwave window in the middle of the pipe and to prevent damage to the microwave window. You. And more preferably, (2). The pressure in the radiator connected to the waveguide is 1 ×
The microwave plasma processing apparatus according to the above (1), which serves as a means for reducing the pressure to 10 ⁻⁴ Pa or less or 5 to 50 kPa; The pressure in the radiator connected to the waveguide is 5 to
(2) The microwave window according to the above (2), wherein the microwave window is cooled by 50 kPa and cooling means is added to at least the radiator connected to the waveguide, and convection of gas in the radiator is performed. This is achieved by a microwave plasma processing apparatus.

As the cooling means, preferably, a cooling pipe is provided on the outer periphery of the radiator, and for example, water or air is circulated as a refrigerant in the radiator, and water or air is cooled to exchange heat with gas in the radiator. It is to be. More preferably, (4). The microwave according to any one of the above (1) to (3), further comprising means for sealing the material in the middle of the waveguide with a material through which microwaves pass, and providing a means for evacuating and decompressing the space from this portion to the microwave window. (5). This is achieved by the microwave plasma processing apparatus according to (5), wherein a cooling means is added to a portion of the waveguide that is sealed with a material through which microwaves pass, and cooling means is provided to cool the sealed portion. Is done. As the cooling means, the periphery of a portion sealed with a material such as a quartz plate through which microwaves pass through the middle of the waveguide is water-cooled, and the sealed material is kept from the waveguide side held at atmospheric pressure. It is desirable to blow compressed air directly into the air to cool the air.

The radiator connected to one end of the waveguide preferably has a structure extending toward the vacuum vessel, and is preferably an electromagnetic horn radiator.

Furthermore, as a microwave window that constitutes a part of the partition wall of the vacuum vessel by sealing the opening of the radiator connected to one end of the waveguide, the microwave is well transmitted, and has heat resistance, Any material that has excellent mechanical strength and is chemically stable may be used, and a quartz plate or the like is practical and preferable.

[Action]

The electromagnetic horn constituting the microwave radiator enlarges the microwave to the opening diameter of the horn. The microwave intensity is not uniform, but if the input power of the microwave is sufficiently large, the plasma density is saturated and the plasma density becomes uniform. By passing the reaction gas between the perforated plate and the microwave window arranged parallel to the substrate surface and blowing it out from the hole of the perforated plate toward the substrate, the degree of decomposition by the plasma of the reaction gas becomes constant, Acts uniformly on the substrate surface. Microwave windows are exposed to high power microwaves and plasma and are susceptible to heating and surface damage. Here, when the electromagnetic horn side (waveguide side) is set to the atmospheric pressure as in the related art, a great force is applied to the microwave window, and the window is easily damaged. Therefore, in the present invention, the pressure on the electromagnetic horn side (waveguide side) is reduced to a state in which no discharge occurs by the pressure reducing means, the pressure difference with the vacuum vessel is reduced, the force applied to the microwave window is reduced, and the microwave window is reduced. Avoid damage. In this case, when the pressure on the electromagnetic horn side (waveguide side) is 10 ⁻³ Pa to 1 kPa, microwave discharge occurs in the electromagnetic horn and microwave power loss is large, so this region must be avoided. It is also possible to select a lower pressure of 10 ^-4 Pa or less, which is more certain to prevent discharge, but requires a high-vacuum evacuation system. In order to exhaust gas, it is necessary to increase the conductance. However, this requires a large number of holes to be formed in the microwave waveguide system, resulting in a decrease in microwave transmission efficiency. on the other hand,
If the higher pressure of 5 to 50 kPa is selected, the exhaust system may be of the order of an oil rotary pump, and the exhaust hole may be small. In addition, at pressures of 1 kPa and above, heat conduction by gas convection is almost the same as at atmospheric pressure, and therefore heat conduction by gas convection cools the microwave window heated by microwaves or plasma. It is very practical and preferable because it works. In the case of performing plasma CVD or the like, a gas having a relatively low thermal decomposition temperature, such as monosilane or disilane, is often used as the reaction gas. This causes loss of gas and deterioration of characteristics of a film formed on the substrate. However, if the microwave window is cooled as in the present invention, such a problem due to overheating of the microwave window does not occur.

〔Example〕

Embodiment 1 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic longitudinal sectional view of an essential part of a microwave plasma processing apparatus according to the present invention.

From a microwave source 1 through a microwave waveguide system 2,
The configuration was such that microwaves of 2.45 GHz were guided to the electromagnetic horn 4 constituting the radiator.

A vacuum seal is provided in the middle of the waveguide 2a of the microwave waveguide system 2 with the quartz plate 3 interposed therebetween, and the inside of the electromagnetic horn is evacuated by the exhaust pump 16 while adjusting the pressure to 10 kPa using the valve 15. did.

5 m thick microwave window at the opening of the electromagnetic horn 4
A quartz partition plate 8 of m m is placed to seal the space between the reaction chamber 6 and the electromagnetic horn 4 constituting the vacuum vessel. A magnetic field is generated by passing an electric current through the electromagnetic coil 5, and the electron cyclotron resonance point exists in a space region between the quartz porous plate 9 directly below the partition plate 8 and the substrate 10 placed on the substrate holder 11. Set to.

The reaction gas is fed into the reaction gas buffer 7 from the gas inlet 7a, and is jetted into the reaction chamber 6 through a hole in the perforated plate 9 through a 0.3 mm gap between the partition plate 8 and the perforated plate 9.

Since the quartz plate 3 sandwiched in the middle of the waveguide 2a is heated because high-density microwaves pass through it, a cooling water pipe 19 is provided as a cooling means at a flange portion thereof, and is cooled.
Compressed air is blown out toward the quartz plate 3 from a nozzle 18 provided on the waveguide side maintained at atmospheric pressure to perform air cooling.

In addition, the partition plate 8 and the perforated plate 9 are connected to the microwave and the reaction chamber 6.
Since it is heated by the plasma inside, the following configuration is employed as a cooling means for the plasma. That is, a pipe 20 through which cooling water flows as a heat exchanger is provided on the outer periphery of the electromagnetic horn 4, whereby the electromagnetic horn 4 is indirectly cooled by heat conduction by convection of air having a pressure of 10 kPa.

The opening diameter of the electromagnetic horn 4 is 400 mm, and the partition plate (microwave window) 8 and the perforated plate 9 are both 420 mm in diameter.
When nitrogen plasma is continuously generated at approx. 200 ° C
The balance is constant.

When the quartz plate 3 is damaged or the reaction chamber 6 leaks, a pressure difference is generated between the circular electromagnetic horn 4 side and the reaction chamber 6 side, and the partition plate 8 is connected through the communication pipe 21 to prevent the damage. A safety valve 17 is provided. The safety valve 17 is configured so as to be opened by a pressure difference of 20 kPa so that no more pressure is applied to the partition plate 8.

In the figure, 12 is a conductance adjusting valve, 13 is a turbo molecular pump, 14 is an exhaust pump, and 22 is a tuner provided on the waveguide.

Although the partition plate 8 of this embodiment is made of quartz having a diameter of 420 mm and a thickness of 5 mm, the pressure applied to the partition plate 8 is reduced because the inside of the electromagnetic horn 4 connected to the waveguide is in a reduced pressure state.
Even with such a thickness, the plasma processing can be performed sufficiently stably. However, when the inside of the electromagnetic horn 4 is maintained at the atmospheric pressure as in the conventional apparatus, the thickness of the microwave window 8 capable of performing the plasma processing without worry is about six times that of the present embodiment.
30mm is the minimum requirement, and if you look at the safety factor three times more, 45mm
Is required. When the thickness of the window is increased in this manner, the power loss due to the absorption of microwaves is significantly increased, and a practical device is no longer possible.

It is important in the present invention that the inside of the radiator (electromagnetic horn) 4 connected to the waveguide is not simply reduced in pressure but is reduced in pressure so that microwave discharge does not occur even if the pressure is reduced. .

The apparatus configuration has been described above. Next, three representative examples of actual plasma processing using this apparatus will be introduced.

Embodiment 2 First, a first example will be described in which a silicon nitride film is formed by this apparatus.

A glass disk having a diameter of 300 mm was used as the substrate 10, and was placed on the substrate holder 11.

The reaction gas was monosilane at 40 cm ³ per minute, and nitrogen gas at 4 cm per minute.
About 100 cm ^{3 of the} gas flowed through the hole of the perforated plate 9 through the reaction gas buffer 7 and was evacuated by the turbo molecular pump 13. Reaction chamber 6
Was adjusted to 0.4 Pa by the conductance adjusting valve 12. A microwave of 4 kW was applied for 5 minutes to generate plasma, and the center was 0.60 μm at the center of the substrate and 0.55 μm at the end.
Was formed.

Embodiment 3 In a second example, a case where a silicon nitride film is etched by this apparatus will be described.

A silicon nitride film formed in the above-mentioned Example 2 having a diameter of 300 mm
A 0.5 μm thick aluminum film patterned into a 3 μm line and space pattern on a glass substrate 10 was used as a mask.

The reaction gas is 90 cm / min carbon tetrafluoride containing 3% oxygen.
About ^three holes were made to flow through the hole of the perforated plate 9 and exhausted by the turbo molecular pump 13. The ECR point (electron cyclotron resonance point) was placed 20 mm above the substrate 10 and a microwave of 2.5 kW was applied. As a result, almost uniform plasma was generated, and etching of silicon nitride occurred using the aluminum pattern as a resist. The etching rate is 0.08-0.085 per minute
μm, and was almost uniform over the entire surface.

Example 4 A third example shows an example in which this device is used as an oxygen asher.

On a substrate 10 consisting of a glass disk having a diameter of 300 mm, a thickness of 1.5 mm
A polyimide film having a thickness of 0.2 μm is formed thereon, and a hole pattern having a diameter of 2 μm is formed on the silicon oxide film as a mask pattern.
Used as

Oxygen gas is introduced from the inlet 7a through the gas bach 7 every minute
100 cm ³ flow, pressure 1Pa in the reaction chamber 6, a microwave power 2kW
Was supplied to generate plasma.

As a result, the etching rate of polyimide is about 1 / min.
It was almost constant over the entire surface at μm.

〔The invention's effect〕

According to the present invention, processing by microwave plasma can be uniformly performed over a large area, and high-speed processing by high-density microwave plasma can be performed in manufacturing a large-area element. Also, there is no problem of microwave window breakage and overheating,
A large number of substrates can be processed continuously. As this type of device, the size of the coil can be reduced in proportion to the processing area, and the power consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional view of an essential part of a microwave plasma processing apparatus according to an embodiment of the present invention. <Explanation of reference numerals> 1... Microwave source, 2.
... quartz plate, 4 ... electromagnetic horn (radiator), 5 ... electromagnetic coil, 6 ... reaction chamber (vacuum container chamber), 7 ... reaction gas buffer, 8 ... partition plate (microwave window), 9: perforated plate, 10: substrate, 11: substrate holder, 12: conductance adjusting valve, 12: turbo molecular pump, 14, 16 ...
Exhaust pump, 15… Valve, 17… Safety valve, 19, 20 ……
Cooling water pipe, 21 ... Communication pipe.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoru Satoru 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Manufacturing Research Laboratory, Hitachi, Ltd. (72) Mitsuo Nakaya 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Stock (72) Inventor Kazuo Suzuki 2-9-1, Aise-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Engineering Services Co., Ltd. (56) References JP-A-62-31112 (JP, A) JP-A-62-264623 (JP, A) JP-A-63-60530 (JP, A) JP-A-62-216334 (JP, A) Actually open JP-A-62-197847 (JP, U) (58) Int.Cl. ⁶ , DB name) H01L 21/302

Claims (3)

(57) [Claims] A vacuum vessel provided with gas supply means, a vacuum exhaust means, a waveguide for guiding microwaves into the vacuum vessel, a radiator connected to one end of the waveguide, A microwave window which forms a part of the partition of the vacuum vessel, and a magnetic field which causes electron cyclotron resonance at the microwave frequency immediately below the microwave window in the vacuum vessel. A microwave plasma processing apparatus comprising: means for reducing pressure in at least the radiator provided with the microwave window under conditions in which no discharge occurs, and introducing microwaves into the vacuum vessel. And a pipe for connecting the vacuum vessel to a depressurized portion of the waveguide to which the radiator is connected, and a pipe in the way of the pipe. The microwave plasma processing apparatus pressure difference between the two is configured to connect the safety valve such that the opening to be the more the breakdown voltage of the microwave window, to prevent damage to the microwave window. 2. The microwave plasma processing apparatus according to claim 1, wherein the pressure in the radiator connected to the waveguide is reduced to 1 × 10 ⁻⁴ Pa or less or 5 to 50 kPa. 3. The radiator connected to the waveguide has a pressure of 5 to 50 kPa, and cooling means is added to at least the radiator connected to the waveguide, so that the radiator is connected to the radiator. 3. The microwave plasma processing apparatus according to claim 2, wherein the microwave window is cooled by convection of gas.