JPH0785995A - Plasma generation method and apparatus - Google Patents

Abstract

(57) [Summary] [Object] The object of the present invention is to control the generation region of high density plasma of 10 ¹¹ / cm ³ or more and prevent etching of the plasma chamber and the wall surface. [Structure] A microwave is introduced into a chamber 20 through a waveguide 12 and an introduction window (quartz plate) 14 in a magnetic field generated by a solenoid coil 13, and the magnetic field distribution and electric field distribution at that time are controlled to generate microwaves. Strong absorption can be set in the center of the chamber even in high density plasma of 10 ¹¹ particles / cm ³ or more. As a result, high-speed etching at low pressure can be realized, and shape controllability and selectivity can be controlled with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma generation method and apparatus, and more particularly to a microwave plasma generation method and apparatus suitable for fine processing of a sample such as a semiconductor element substrate by reducing the influence of chamber constituent members. is there.

[0002]

2. Description of the Related Art A conventional plasma generation technique is disclosed in, for example, FIG. 7 (Hitachi Review Vol. 73, No. 9, p848, 19).
As shown in 91-9, a quartz discharge tube 4 is provided in a waveguide 2 for propagating a microwave, and plasma is generated in the discharge tube by the action of an external magnetic field 3'and a microwave electric field 2 '. It is designed to let you. Then, the semiconductor wafer 5 is processed using the plasma. Reference numeral 1 is a magnetron for outputting a microwave, 3 is a solenoid coil for supplying a magnetic field, and the sample table 6 has an RF for etching.
A high frequency power supply 7 for applying a bias voltage is provided. Reference numeral 8 is an inlet for the etching gas, and 9 is an outlet.

[0003]

FIG. 8 shows an example of the plasma density distribution in the above conventional technique. The vertical axis represents the height z on the central axis from the substrate (wafer) 5, and the horizontal axis represents the electron density Ne of plasma. When the microwave power is small, the microwave is almost ECR plane (ECR: Electron Cyc) as in the case of 0.7 W / cm ^2.
In the case of rotron Resonance, 2.45 GHz, the magnetic flux is absorbed at 875 Gauss),
A strong plasma is formed on the ECR surface. However, when the microwave power becomes 1.0 W / cm ² or more, 875 Gauss
It shows strong absorption even in the above magnetic field, and high-density plasma approaches the quartz bell jar, which is the μ-wave introduction surface. Along with this, etching of the μ-wave introduction window (in this case, the quartz bell jar 4) occurs more than before, and the purity of the plasma component due to the etching gas decreases, and the process accuracy of etching and the like changes. .

It is a first object of the present invention to provide a plasma generation method and apparatus capable of controlling the generation region of high density plasma and preventing the etching of the plasma chamber wall surface.

A second object of the present invention is to provide a plasma generation method and apparatus for controlling the shape and selectivity of a sample in etching or the film quality in film formation with high precision.

[0006]

In order to achieve the above object, a strong microwave absorption region can be set in the central portion of the plasma generation chamber even in high density plasma (electron density of 10 ¹¹ pieces / cm ³ or more). That is what I did.

Specific means will be described below. As a first means, a means for changing the influence of the magnetic field by sharply increasing the magnetic field gradient near the microwave introduction window is provided.
The second means is that a resonator is provided so that the microwave electric field in the microwave introduction window becomes small and the microwave is introduced. The third means is to set the microwave input power density, ECR plane, and plasma height to control the plasma region. The fourth means is that an antenna is used for introducing microwaves, and the antenna is provided in the central peripheral portion of the plasma generation chamber and magnetic lines of force are arranged so as to protect the plasma chamber wall with a magnetic field.

[0008]

[Function] The absorption of microwaves in plasma is being energetically studied and clarified. E
In a magnetic field close to the CR condition, Doppler shift occurs and strong absorption is obtained. Therefore, as in the first means, a gentle magnetic field gradient with a magnetic flux density closer to the ECR in the central portion,
By abruptly increasing the magnetic field gradient near the microwave introduction window, it is possible to absorb the microwaves more centrally.

Further, as the plasma density increases, EC
The ratio of electron collisional damping to R absorption increases. Therefore, by reducing the microwave electric field in the microwave introduction window as in the case of the second means, it is possible to weaken the collision attenuation directly contributed by the electric field near the introduction window.
The plasma density in the vicinity of the introduction window can be reduced.

The high-density plasma region shown in FIG. 2 is originally based on the plasma generated by ECR absorption, and the position of the ECR plane also affects the high-density region. Therefore, it is effective to lower the ECR surface as much as possible from the center to bring the high density plasma to the center. However, EC
If the R surface is brought close to the substrate position, the microwave absorption surface becomes the plasma extinction position, which poses a problem in stabilizing the plasma. Therefore, it is effective to set it as low as possible while stabilizing the plasma by separating it from the substrate to some extent.

With respect to the fourth means, since the diffusion of plasma can be limited only to the central portion, it is possible to keep the portion having high plasma density away from the wall.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a microwave plasma processing apparatus (etching apparatus) according to the present invention will be described with reference to FIG. 11 is a magnetron, 12 is a waveguide, 13 is a solenoid coil, 14 is a quartz plate, 15 is a wafer, 16 is a sample stage, 17 is a high frequency power source, 18 is an etching gas introduction system,
Reference numeral 19 is an exhaust system.

The quartz plate 14 serves as a μ-wave introduction window, on which the step-expanded waveguide 12 is installed, and a part of the solenoid coil is also installed above the expanded waveguide. .

An example of the plasma density distribution according to this embodiment is shown in FIG. The μ-wave power is 1.6 W / cm ² . As in the description of the conventional example, the height z from the substrate is taken on the vertical axis, the electron density Ne is shown on the horizontal axis, and the magnetic field distribution B is also shown. The position where B = 875 Gauss is ECR
Surface, and in this embodiment, L ₁ = 1/4 L was set (L ₁ / L ₂ = 1/3).

According to this embodiment, a gentle magnetic field gradient is provided as it goes upward from the ECR plane, and the magnetic field gradient is sharply increased as it approaches the μ wave introduction window. In addition, the waveguide is designed so that the plasma side of the introduction window serves as a reflecting surface of the microwave standing wave and acts as a resonator. Therefore, by increasing the ECR absorption due to the Doppler shift in the central portion and reducing the electric field in the vicinity of the μ-wave introducing surface, a high density plasma having a central height in the vertical direction can be obtained.

[0016] Indeed, compared with the ion current Iw for etching the ion current I _Q reaching the quartz plate 14 is μ-wave introduction window reaches the wafer 15 shown in FIGS. 3 and 4.

In FIG. 3, the height L / D of the plasma region
Ion current I incident on the wafer when w becomes 1.0 or more
Ion current I entering the quartz plate without significantly reducing w
_Q can be greatly reduced. When the plasma region is too large, the height of the entire apparatus becomes large and the room in the clean room is lost. Therefore, L / Dw should be as close to 1.0 as possible.

[0018] In FIG. 4, mu the wave power density is too upstream, 10 ¹¹ / cm ³ or more electron density high power density since the ion current I _Q increases sharply as 1.0 W / cm ² or more achieve density plasma, it is appropriate to suppress the maximum value of the ion current I _Q as 1.6 W / cm ² or less.

FIG. 5 shows the plasma density distribution in the radial direction together with the distribution of the microwave electric field E. In order to prevent the etching of the side wall of the plasma chamber, it is also important to control the plasma distribution in the radial direction. In this embodiment, a combination mode of TE ₁₁ and TE ₀₁ is supplied, and in the range of the substrate diameter Dw, it is slightly high. However, the electron density distribution is within ± 5%, and plasma can be suppressed to a low plasma density in the peripheral portion due to the disappearance of plasma on the walls.

As described above, according to the present invention, a high-density plasma having an electron density of 10 ¹¹ pieces / cm ³ or more can be controlled and generated in the central portion of the plasma generation region. Etching can be prevented. Further, this makes it possible to control the shape controllability and selectivity in etching with high accuracy.

Although the etching apparatus has been described in the embodiment of the present invention, the film quality and the like can be controlled with high accuracy when used for film formation in a CVD apparatus or the like.

Another embodiment of the present invention is shown in FIG. Reference numeral 21 is a μ-wave introducing antenna, and several antennas are provided in the circumferential direction.
A magnetic field as shown in the drawing is formed around the chamber 24 by the permanent magnet 22. Reference numeral 25 is a wafer, 26 is a sample stage, 29 is an exhaust system, and 28 is an etching gas supply system, which is supplied in a shower shape from the upper part of the chamber 24. In the present embodiment, the position of the magnetic field satisfying the ECR condition is near the wall, but the magnetic flux density sharply decreases from there to the center, so that the plasma diffuses toward the central part and the central part Since high-density plasma can be generated, the same effect as that of the above-described embodiment can be obtained.

[0023]

As described above, according to the present invention, a high density plasma having an electron density of 10 ¹¹ pieces / cm ³ or more can be controlled and generated in the central portion of the plasma generation region. Etching can be prevented, and the purity of plasma etching gas can be increased. Therefore, it is possible to realize high-speed etching at low pressure in the etching gas, and to control shape controllability and selectivity with high accuracy. Further, when applied to a film forming apparatus such as a CVD apparatus, it is possible to obtain a remarkable effect that the film quality and the like can be controlled with high accuracy.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a distribution diagram showing a plasma density distribution in FIG.

FIG. 3 is a characteristic diagram showing characteristics of an ion current incident on the quartz plate in FIG.

FIG. 4 is a characteristic diagram showing the μ-wave power dependence of the ion current in FIG.

5 is a distribution diagram showing a plasma density distribution in a radial direction in FIG.

FIG. 6 is a block diagram showing another embodiment.

FIG. 7 is a configuration diagram showing a conventional μ-wave etching apparatus.

FIG. 8 is a distribution diagram showing a conventional plasma density distribution.

[Explanation of symbols]

11 ... Magnetron, 12 ... Waveguide, 13 ... Solenoid coil, 20, 24 ... Plasma chamber (plasma generation chamber), 14 ... Microwave introduction window (quartz plate), 15, 25 ... Wafer (substrate), 21 ... Micro Wave antenna, 22 ... Permanent magnet.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kento Usui 502 Jinritsu-cho, Tsuchiura-shi, Ibaraki Machinery Research Institute, Hiritsu Manufacturing Co., Ltd. (72) Inventor Katsuya Watanabe 794, Higashi-Toyoi, Kazamatsu City, Yamaguchi Prefecture Stock Company Hitachi Ltd., Kasado Factory

Claims (16)

[Claims] 1. A plasma chamber having a central portion of 10 ¹¹ cells / cm.
A plasma generation device characterized by generating plasma with a high electron density of ³ or more. 2. The plasma generation apparatus according to claim 1, wherein plasma is generated by the action of a microwave to introduce a microwave. 3. The ECR surface is separated from the microwave introduction part from the center of the chamber, and the power density is 1.0 to 1.6 W / cm ^2.
The plasma generating apparatus according to claim 2, wherein the high density portion is set at the center of the chamber. 4. The plasma generation apparatus according to claim 1, wherein a processing substrate is installed in the plasma generation chamber for processing. 5. The plasma generator according to claim 2, wherein the magnetic field gradient is rapidly changed in the vicinity of the microwave introduction window to reduce the plasma density in the vicinity of the introduction window. 6. The plasma generator according to claim 2, wherein the microwave electric field mode is a mode in which the electric field at the outermost circumference is small, such as TE ₀₁ , and the plasma density around the chamber member is reduced. . 7. The plasma generator according to claim 2, wherein the height of the plasma generation chamber is equal to or larger than the size of the processing substrate. 8. The plasma generating apparatus according to claim 2, wherein the inner diameter of the plasma generating chamber is at least twice as large as that of the processing substrate. 9. Etching or CV of a semiconductor device
The plasma generating apparatus according to claim 1, wherein the plasma generating apparatus performs a D process. 10. The plasma generating apparatus according to claim 2, wherein the microwave is introduced only into the central portion of the plasma chamber, and the chamber is covered with magnetic lines of force. 11. The central portion of the plasma chamber is 10 ¹¹ pieces / cm.
A plasma generation method characterized in that plasma having a high electron density of ³ or more is generated. 12. The plasma generation method according to claim 1, wherein the plasma is generated by the action of a microwave by introducing a microwave. 13. The power density is 1.0 to 1.6 W / cm, with the ECR surface away from the center of the chamber from the microwave introduction part.
^3. The plasma generation method according to claim ² , wherein the high density portion is set in the center of the chamber as 2. 14. The plasma generation method according to claim 1, wherein a processing substrate is placed in the plasma generation chamber for processing. 15. Semiconductor device etching or C
A VD process is performed, The said 10-14 characterized by the above-mentioned.
The plasma generation method described in 1. 16. The plasma generating method according to claim 11, wherein the microwave is introduced only into the central portion of the plasma chamber, and the chamber is covered with magnetic lines of force.