JPH08250470A - Method and device for plasma treatment - Google Patents

Abstract

PURPOSE: To provide an improved method and device for plasma treatment which can prevent the influence of the internal side faces of a vacuum chamber and can reduce the influence of materials adhering to the internal side faces without cleaning the internal side faces with heat or plasma. CONSTITUTION: In a plasma treatment device, a vacuum treatment chamber 7 is constituted so that the distance (d) from the internal side face 3 of the chamber 7 to the outer periphery of a sample stage 11 and the height (h) of the ceiling of the chamber 7 facing the stage 11 from the stage 11 can meet a relation d/h>=1/2. Therefore, the influence of materials 9 adhering to the internal side face 3 and other internal surfaces of the chamber 7 can be reduced and, at the time of performing dry etching, the etching rate and etch selectivity can be improved and the number of particles generated in the device and the secular change of characteristics of the device can be reduced. At the time of forming films, in addition, the occurrence of foreign matters can be reduced and high-quality thin films can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing method and a processing apparatus for performing dry etching or thin film formation (abbreviated as film formation) on electronic parts such as semiconductor substrates and glass substrates, and more particularly to plasma processing by plasma processing. Prevents deposits attached to the side wall surface of the chamber from scattering on the substrate and damaging the plasma processing surface, that is, preventing the side wall of the plasma processing chamber from affecting the plasma processing with high stability. The present invention relates to a plasma processing method and a processing apparatus suitable for performing the processing.

[0002]

2. Description of the Related Art Conventionally, in plasma processing, particles generated according to the gas composition during plasma processing, the material of the substrate, etc. adhere to the wall surface of the plasma processing chamber in which the sample substrate is placed. It is known that redeposition on the surface to be processed of the substrate during the plasma processing causes the quality of the plasma processing to deteriorate, and various measures have been taken.

A typical example of dry etching as plasma processing will be described below. FIG. 2 is a cross-sectional view of an essential part showing an outline of a conventional dry etching apparatus, showing an example of a microwave plasma etching apparatus. The microwave of 2.45 GHz is generated by the magnetron 1, and the microwave is propagated through the introduction window 5 to the vacuum processing chamber 7 by the waveguide 2 to generate plasma discharge in the vacuum processing chamber.

A magnetic field coil 6 is arranged on the outer peripheral portion of the vacuum processing chamber 7 and causes electron cyclotron resonance by the microwave and the magnetic field to generate plasma 7a. A sample 8 to be subjected to plasma processing is set on a sample setting table 11, placed in a vacuum processing chamber 7 and exposed to plasma. Sample table 1
The size of 1 is usually made slightly larger than the diameter of the sample 8. For example, when the wafer of 8 inches is used as the sample 8, the diameter of the sample mounting table 11 is made 9 to 10 inches. In this case, the vacuum processing chamber 7 usually has a diameter of 14 to 16 inches and a height h of about 20 to 30 cm. In the figure, 10 indicates an exhaust port connected to an exhaust pump (not shown), and 14 indicates a vacuum buffer chamber.

In the above conventional apparatus, the distance d from the side wall surface 3 of the processing chamber 7 to the peripheral portion of the sample installation table 11 is 2 to 2.
It was 3.5 inches (about 5 to 8.7 cm). In this case, a substance (such as etched fine particles) generated from the wafer surface during the plasma etching process is easily attached to the side wall surface 3, and the substance 9 attached to the side wall surface 3 is redeposited on the sample surface, so that the etching process is performed. It was inhibiting the stability of.

Since such deposits 9 easily adhere to the side wall surface 3 of the vacuum processing chamber 7, the closer the side wall surface 3 is to the sample 8, the greater the influence. In order to reduce the influence of such a wall surface as much as possible, conventionally, the side wall surface 3 is formed by a heater or the like.
A method has been used in which the deposit 9 is exhausted to the outside of the processing chamber and reduced by heating to about 00 ° C. However, there are cases where the side wall surface 3 of the vacuum processing chamber 7 is covered with a substance that is difficult to heat, such as quartz, and the deposition of the adhered substances is only possible by heating the metal container (usually made of stainless steel) of the vacuum processing chamber 7. In some cases, the removal was insufficient.

Further, instead of heating the side wall surface 3, a method has also been used in which the substance 9 once attached is removed by cleaning using plasma 7a or the like. Even in this case, it is difficult to completely clean the inner wall surface 3 of the vacuum processing chamber 7 only by plasma cleaning, and there is a problem that the processing time becomes long because cleaning takes a long time.

The case of dry etching as the plasma treatment has been described above as an example. However, the same problem as in dry etching is involved in the principle of film formation because the raw material gas handled is different.

[0009] As related to the prior art of the present invention, for example, the Journal of the American Vacuum Society, Journal Vacuum Society Technology B8 (6), No. 1192
P. To p. 1198, November / December, 1990 [J.
Vac. Sci. Technol. B8 (6), pp1
192-1198, Nov / Dec, (1990)].

[0010]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to eliminate such a conventional problem, and does not rely on heating of the side wall surface of the vacuum processing chamber or cleaning of the side wall surface by plasma, but the side wall surface. It is an object of the present invention to provide an improved plasma processing method and processing apparatus capable of preventing the effects of the above and reducing the effects of substances adhering to the side wall surface of the vacuum processing chamber.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted various experiments to achieve the above-mentioned object. As a result, the relationship between the sample stage and the vacuum processing chamber inner wall surrounding the sample stage is set under specific conditions. This prevents the side wall surface of the vacuum processing chamber from being affected by heating the side wall surface of the vacuum processing chamber and the wall surface cleaning with plasma, which are conventionally required, and prevents the substances adhering to the side wall surface of the vacuum processing chamber. It was possible to reduce the influence, and as a result, it was possible to obtain effective knowledge that a good plasma treatment can be realized regardless of whether it is a film forming treatment or an etching treatment.

The present invention has been made on the basis of such knowledge, and the side wall surface 3 of the vacuum processing chamber 7 is fixed to the sample table 11.
A certain distance from the outermost peripheral portion of the sample, and the shortest distance is d, and the height (spacing) from the sample table 11 to the upper ceiling wall (in the case of FIG. 2, the surface of the introduction window 5 is micro in the case of FIG. 2) is h. Then, the relationship between them is configured as d / h ≧ 1/2.

It has been found that when the value of d / h is less than 1/2, the effect is drastically reduced, approaching the case of the conventional device, which is not preferable. According to experiments conducted by the present inventors, d / h ≧ 1 is more preferable, and d / h ≧ 3 / is more preferable.
It is 2. It should be noted that the upper limit of d / h is preferably 3 ≧ d / h for practical purposes due to restrictions on the device configuration.

Further, the structure is such that the conductance of the exhaust port of the vacuum processing chamber 7 is increased, the interval h between the processing chamber ceiling facing the sample installation table 11 is reduced, and the processing chamber side wall surface 3 is expected to be seen from the sample surface. It is desirable to have small corners.

The plasma generating means is constituted by a means for discharging by applying high frequency energy. For example, microwave discharge, especially electron cyclotron resonance (ECR) is desirable to obtain high plasma density, but other high frequency discharge (RF discharge). Known sources can be used.

Specifically, when an energy supply source for generating plasma is provided on the sample table or the ceiling portion facing the sample table and plasma is generated in the gap between the sample table and the ceiling portion, the plasma density of 10 ⁹ The configuration is such that the portion of cm ^-3 or more does not contact the side wall of the vacuum processing chamber.
That is, since the plasma density on the sample substrate to be the plasma processing region is usually about 10 ¹⁰ to 10 ¹¹ cm ⁻³ , or higher in some cases, the density of the side wall of the vacuum processing chamber is set to 10 ⁹ cm ^−3. The following can prevent the influence of the side wall surface of the vacuum processing chamber and reduce the influence of the substance attached to the side surface.

A method of performing plasma etching or plasma film formation processing using the plasma processing apparatus having the above-described structure will be described. First, a predetermined substrate to be processed is placed on the sample table, and a source gas is supplied into the vacuum processing chamber from a source supply gas source provided outside the vacuum processing chamber at a predetermined flow rate. When the raw material gas is a film forming material, the raw material gas is decomposed in the plasma formed by the plasma generating means, and a thin film is formed on the substrate to be processed.

On the other hand, if the source gas is an etching gas, the surface of the substrate to be processed is etched and a predetermined pattern is formed on the substrate. In any of these plasma processes, the plasma density on the side wall of the vacuum processing chamber is 10 ⁹ cm ^-3.
Since it is controlled below, the influence of the side wall surface is prevented,
Since the influence of substances adhering to the wall surface can be reduced, high quality plasma processing is realized.

[0019]

By moving the side wall surface of the vacuum processing chamber away from the sample surface, substances generated from the sample surface during processing are less likely to adhere to the side wall surface of the processing chamber, and plasma is generated at a position distant from the side wall surface of the processing chamber. Therefore, even if the substance adheres to the wall surface, it is possible to prevent the substance from re-separating from the side wall surface and adhering to the sample surface due to the influence of the plasma. Since the side wall surface is located far from the sample surface and close to the exhaust port, the re-extracted material can be effectively exhausted to the outside of the vacuum processing chamber. By reducing the distance between the sample table and its ceiling wall, the projected angle of the side wall surface of the processing chamber viewed from the sample surface becomes small, and it becomes difficult for the re-desorbed substance from the side wall surface to return to the sample surface.

The plasma density generally sharply decreases by diffusing from the plasma processing region on the substrate toward the side wall. The present invention effectively applies this phenomenon, and the above condition of d / h ≧ 1/2 is also a condition for controlling the plasma density on the side wall of the vacuum processing chamber to 10 ⁹ cm ⁻³ or less.

[0021]

An embodiment of the present invention will be described below with reference to the drawings. <Embodiment 1> (1) Configuration example of plasma processing apparatus FIG. 1 is a sectional view of a main part of a plasma processing apparatus according to an embodiment of the present invention. As a plasma generating means, a microwave of 2.45 GHz is generated by the magnetron 1, and the microwave is propagated to the vacuum processing chamber 7 through the introduction window 5 by the waveguide 2 to generate plasma discharge in the vacuum processing chamber. A magnetic field coil 6 is arranged on the outer peripheral portion of the vacuum processing chamber 7, and electron cyclotron resonance is caused by the action of the microwave and the magnetic field to generate plasma 7a. A sample 8 to be subjected to plasma processing is set on a sample table 11, placed in a vacuum processing chamber 7 and exposed to plasma 7a. A raw material gas supply pipe 12 is connected to the vacuum processing chamber 7, and a gas required for plasma processing is supplied into the processing chamber 7 from a gas supply source (not shown) via a flow meter.

The sample table 11 is large enough to mount an 8-inch wafer as a sample 8 thereon.
The inner wall of the vacuum processing chamber 7 on the upper facing side of the sample table 11 is the microwave introduction window 5, and the distance h between the sample table 11 and the microwave introduction window 5 is set to about 20 cm.

The side wall surface 3 of the processing chamber is a wall surface h ₀ (30 cm) whose width is widened laterally as shown in FIG. 1 from the structure of the conventional apparatus shown in FIG. The distance d from the outer peripheral portion of the sample table 11 to the side wall surface 3 is about 1
It was 5 cm. The relationship between the distance d and the height h is d / h
= 3/4 (= 0.75).

A practically preferable range of h ₀ / h is h ₀ /h≧1.5, and there is no reason to limit the upper limit, but in order to prevent the device from becoming unnecessarily large, 3 ≧.
It is desirable that h ₀ /h≧1.5.

(2) Example of plasma processing method (dry etching) Gas supply pipe 12 of the microwave plasma processing apparatus of FIG.
Then, this apparatus is used as a plasma etching processing apparatus by introducing an etching gas as a source gas. Dry etching of polysilicon was performed by the procedure shown below.

First, a sample substrate 8 is prepared by forming a SiO ₂ film on a silicon wafer in advance, a polysilicon film thereon in sequence, and forming a resist pattern (mask) on the polysilicon film. As the etching gas, Cl ₂ gas was supplied from the gas supply pipe 12 into the processing chamber 7 to etch the polysilicon.

At this time, the microwave power was 1 kW, the bias power was 50 W, the gas pressure was 5 mTorr, and the gas flow rate was 100 sccm. As a result of etching,
The polysilicon etching rate was 400 nm / min, and the polysilicon / SiO ₂ selection ratio was 50. The conventional device of FIG. 2 (d / h = 7 cm / 2) used as a comparative example.
5 cm = 0.28), polysilicon /
Since the SiO ₂ selection ratio was 25, this example had the effect of doubling the selection ratio of the conventional device.

In FIG. 3, the polysilicon / SiO ₂ selectivity and the number of particles in the apparatus (piece / wafer) are d /
It is a characteristic curve figure which showed the result of having measured what kind of effect h has. As described above, d is the distance from the outer periphery of the sample table 11 to the side wall surface 3 of the vacuum processing chamber, and h is the sample table 11
To the ceiling wall above. It is measured by fixing h of the apparatus of FIG. 1 to 20 cm and changing the value of d.

As is apparent from this figure, the polysilicon / SiO ₂ selection ratio increases as the d / h value increases, that is, the distance d increases. For example, the distance d
Where 7 cm is a comparative example (conventional device d / h = 0.2
8), and the selection ratio at this time is 25, but d / h = 0.75 when d is further away and 15 cm.
With the selection ratio twice that of the conventional one, and at 25 cm,
At d / h = 1.25, the selection ratio is 2.5 times or more that of the conventional one.

On the other hand, the number of particles generated in the apparatus was about 76 on the 8-inch wafer in the conventional apparatus, but about 43 when d / h = 0.75 and d / h.
When h = 1.25 or more, it is about 30 or less, which is half or less of that of the conventional apparatus, and the effect of preventing the influence of the side wall of the vacuum processing chamber was sufficiently recognized.

The count of the number of particles generated is
The number of particles adhering to the wafer was measured by a wafer foreign matter measuring device, and most of these particles were scattered from the side wall of the vacuum processing chamber. Further, the change with time of the etching rate of polysilicon and SiO ₂ is reduced to less than about half that of the conventional device.

<Embodiment 2> In this embodiment, the plasma generating means is constituted by a high frequency discharge instead of the microwave discharge of the first embodiment. Fig. 4 shows Transformer couple plasma.
FIG. 3A is a cross-sectional view of a main part of an apparatus in which the present invention is applied to an inductively coupled dry etching apparatus called etching.

Further, FIG. 5 is a sectional view showing the main part of a conventional structure of this device for comparison. In the conventional apparatus, the distance d from the outer peripheral portion of the sample table 11 to the side wall surface 3 of the vacuum processing chamber,
The relationship between the height h of the ceiling wall opposite to the sample table 11 is d
/ H <1/2.

On the other hand, in the apparatus according to the present invention shown in FIG. 4, the distance d from the outer peripheral portion of the sample table 11 to the side wall surface 3 is further increased by setting d / h ≧ 1/2 as in the case of the first embodiment. With the structure, the width h ₀ of the side wall surface 3 adjacent to the exhaust port 10 is expanded vertically. As an example, the height h of the ceiling wall facing the sample table 11 is set to 30 cm, and the sample table 11 is
The distance d from the outer peripheral part to the side wall surface 3 of the vacuum processing chamber is 20c
As m, d / h = 0.67. The vertical width h ₀ of the side wall surface 3 was set to 60 cm.

Cl ₂ gas as an etching gas is supplied from the gas supply pipe 12 into the processing chamber 7 by this apparatus, and a glass substrate for a liquid crystal panel having an aluminum alloy film formed on its surface in advance as a sample 8 is prepared. A resist mask having a predetermined pattern was formed on the aluminum alloy film by known photolithography, and a wiring pattern was formed by dry etching. As a result, aluminum alloy / S
The etch rate selectivity of io ₂ increased by 30% compared to the conventional equipment,
The number of particles in the device was reduced to 1/2 or less.

<Embodiment 3> In this embodiment, an example in which a SiO ₂ film is formed on a silicon substrate by CVD using the plasma processing apparatus shown in FIG. 1 will be described. The plasma processing apparatus of FIG. 1 becomes a film forming apparatus by plasma CVD simply by switching the source gas from the etching gas to the CVD gas.

First, monosilane Si is used as a source gas.
Gas supply pipe 12 for supplying H ₄ , disilane Si ₂ H ₆ and oxygen gas
The film is fed from the above and the film is formed at a film forming speed of 500 nm / min for 2 minutes.
A 1.0 μm SiO ₂ film was formed. The film quality was good, and the generation of foreign matter due to the scattering of the deposit 9 from the side wall surface 3 of the vacuum processing chamber 7 was drastically reduced as compared with the conventional apparatus.

[0038]

As described above in detail, according to the present invention, the intended purpose can be achieved. That is, by reducing the influence of the wall of the plasma processing apparatus, for example, in dry etching, there are effects such as an improvement in etching selection ratio, an increase in etching rate, a reduction in particles in the apparatus, and a reduction in characteristics over time. The generation of foreign matter is reduced and high quality thin film can be formed.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a plasma processing apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a main part of a conventional device as a comparative example.

FIG. 3 shows a relationship of d / h which is a parameter of a device configuration,
The characteristic curve figure which becomes an Example of this invention which showed the influence which it has on etching characteristic.

FIG. 4 is a sectional view of a main part of a plasma processing apparatus according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view of essential parts of another conventional device serving as a comparative example.

[Explanation of symbols]

1 ... Magnetron, 2 ... Waveguide, 3 ... Side wall of processing chamber,
4 ... ceiling wall of processing chamber, 5 ... microwave introduction window,
6 ... Magnetic field coil, 7 ... Vacuum processing chamber,
7a ... Plasma, 8 ... Sample (substrate, wafer), 9 ... Adhesion matter, 10 ...
Exhaust port, 11 ... Sample stage, 12 ... Gas supply pipe, 1
4 ... Vacuum buffer chamber, 15 ... Plasma excitation coil, d ...
Distance from the outer peripheral portion of the sample stage to the side wall surface, h ... sample stage facing the ceiling wall buttocks height, h ₀ ... vertical width of the processing chamber side wall.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsumi Mizutani 1-280, Higashi Koigokubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (10)

[Claims] 1. A sample processing chamber is evacuated to a vacuum, a processing gas is introduced into the chamber, and high frequency energy is applied to generate plasma in the processing chamber. A substrate placed on a sample table in the plasma space. In a plasma processing method having a step of performing plasma processing by exposing the surface, the shortest distance from the outer peripheral portion of the sample table to the side wall surface of the vacuum processing chamber is d, and the height of the ceiling wall facing the sample table is h. Then, the plasma processing method comprising the step of performing plasma processing under the condition that the relationship between the two is d / h ≧ 1/2. 2. A sample processing chamber is evacuated to a vacuum, a processing gas is introduced into the chamber, and high-frequency energy is applied to generate plasma in the processing chamber. A substrate placed on a sample table in the plasma space. In a plasma processing method having a step of performing plasma processing by exposing a surface, when plasma is generated in a space area sandwiched between a sample table and a ceiling wall of a processing chamber, a plasma density on a sample substrate to be a plasma processing area ^Is at least 10 ¹⁰ cm ⁻³ and the plasma density in contact with the side wall of the vacuum processing chamber is 10 ⁹
A plasma treatment method consisting of cm ⁻³ or less. 3. An etching gas is introduced as a processing gas,
3. The plasma processing method according to claim 1, wherein the step of performing plasma processing on the substrate surface is a dry etching step. 4. The plasma processing method according to claim 1, wherein the step of introducing a CVD gas as a processing gas and performing the plasma processing on the substrate surface is a film forming step by CVD. 5. The method according to claim 1, further comprising the step of forming the sample substrate with an electronic component substrate made of a semiconductor or glass, and subjecting the surface of the electronic component substrate to a desired plasma treatment.
4. The plasma processing method according to any one of 4 to 4. 6. A vacuum processing chamber, means for supplying a processing gas into the vacuum processing chamber, means for generating plasma in the processing chamber by applying high circumferential energy, means for exhausting the vacuum processing chamber, and vacuum. In a plasma processing apparatus having means for exposing a plasma-processed surface of a sample substrate to plasma generated in a processing chamber, the distance from the outer peripheral portion of the sample table to the side wall surface of the vacuum processing chamber is defined as d When the height of the ceiling wall opposite to is defined as h, the relationship between the two is d /
A plasma processing apparatus comprising a vacuum processing chamber set under the condition of h ≧ 1/2. 7. A vacuum processing chamber, means for supplying a processing gas into the vacuum processing chamber, means for generating plasma in the processing chamber by applying high circumferential energy, means for exhausting the vacuum processing chamber, and vacuum. In a plasma processing apparatus having a means for exposing a plasma-processed surface of a sample substrate to plasma generated in a processing chamber, a plasma processing region among plasmas generated in a space region between a sample stage and a ceiling wall surface of the processing chamber. Plasma density on the sample substrate of at least 10
¹⁰ cm ^-3 or more, a plasma processing apparatus comprising comprises a vacuum processing chamber which is controlled plasma density in contact with the vacuum processing chamber side wall surface 10 ⁹ cm ^-3 or less. 8. The plasma according to claim 6, wherein the lower end of the side wall of the vacuum processing chamber is located at a position lower than the sample stage, and an exhaust port is provided at the bottom of the vacuum processing chamber adjacent to the lower end. Processing equipment. 9. The height of the upper end of the side wall of the vacuum processing chamber is higher than the height h of the ceiling wall of the processing chamber facing the sample stage, and the lower end of the side wall of the vacuum processing chamber is lower than that of the sample stage. Exists,
The plasma processing apparatus according to claim 6 or 7, wherein an exhaust port is provided at the bottom of the vacuum processing chamber adjacent to the lower end. 10. When the vertical width from the upper end to the lower end of the side wall of the vacuum processing chamber is h ₀ and the height of the ceiling wall of the processing chamber facing the sample stage is h, the relationship between the two is h ₀ / h. ≧ 1.
10. The plasma processing apparatus according to claim 6, further comprising a vacuum processing chamber set under the condition of 5.