JPH02119100A - Plasma apparatus - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention uses electron cyclotron resonance (E 1 ectron Cyclotron Res) in a plasma generation chamber.
This invention relates to plasma devices such as CVO devices and dry etching devices that utilize ECR plasma generated by excitation (onance+ECR).

[Conventional technology]

The device that generates plasma by ECR excitation has the following characteristics: it can generate plasma with high activity at low gas pressure, it can select the ion energy and the size of the ion flow over a wide range, and it has the following characteristics: It has many advantages, such as CVO equipment for forming a thin film of a desired substance on a semiconductor substrate, and dry etching equipment for forming a fine circuit pattern on a semiconductor substrate. Application to manufacturing is underway.

FIG. 4 is a schematic vertical cross-sectional view of a conventional CVD apparatus using ECR plasma, and numeral 31 indicates a plasma generation chamber. The plasma generation chamber 31 has a double structure around the surrounding wall, and is equipped with a cooling water passage 31a, and a quartz glass plate 3 in the center of the side wall.
1b, and a plasma extraction window 31d is provided at the center of the other side wall facing the microwave introduction port 31c.
A sample chamber 34 is arranged facing 1d. One end of a microwave waveguide 32 whose other end is connected to a high frequency oscillator 33 is connected to the microwave inlet 31c, and the plasma generation chamber 3
An excitation coil 35 is concentrically arranged over one end of the waveguide 1 and the waveguide 32 connected thereto so as to surround them.

A sample stage 36 on which a sample S such as a wafer is mounted is disposed in the reaction chamber 34 facing the plasma extraction window 31d, and an exhaust gas (not shown) is provided on the rear wall of the sample chamber 34 located on the rear side. An exhaust port 37 connected to the device is opened.

In such a CVD apparatus, ECR plasma is generated in the following process. After setting the plasma generation chamber 31 and the sample chamber 34 to the required degree of vacuum, the plasma generation chamber 31
A source gas is supplied to the excitation coil 35 to form a magnetic field, and the microwave oscillated from the high frequency oscillator 33 is transmitted to the microwave waveguide 32. The microwave is introduced into the plasma generation chamber 31 through the microwave introduction window 31c. Then, electrons in the magnetic field absorb the microwave energy transmitted into the plasma generation chamber 31 by cyclotron resonance, collide with the gas molecules, ionize them, and generate plasma in the plasma generation chamber 31. Ru. The generated plasma is introduced into the sample chamber 34 by a divergent magnetic field formed by the excitation coil 35 and projected onto the sample S, so that a thin film of a desired substance is formed on the surface of the sample S.

As mentioned above, when plasma is generated using microwaves in an ECR plasma device and a sample is subjected to processing such as film formation or etching, in order to increase the plasma generation efficiency and improve the processing capacity of film formation or etching, etc. Improvements have been made to plasma devices focusing on microwaves and microwave waveguides.

For example, in Japanese Patent Publication No. 62-53920, circularly polarized waves were introduced into the microwave waveguide in order to eliminate the non-uniformity of the electric field strength in the cross section of the microwave waveguide that introduces microwaves into the plasma generation chamber. A device for uniformly generating plasma by connecting a generator is disclosed.

[Problem to be solved by the invention]

By the way, when a circular waveguide is used as a waveguide for introducing microwaves into the plasma generation chamber, the fundamental mode of the microwave is the TL+ mode, which causes problems as described below. In other words, it is known that radio waves propagating in a circular waveguide filled with magnetic material exist only in circularly polarized mode according to Maxwell's equations (Suhl,
Walker: Phys, Rev.

86 (1952N22.), since the tensor of permittivity of magnetic plasma is isomorphic to the tensor of l-factor of radio waves, similarly according to Maxwell's equation, when the circular waveguide of a conventional ECR plasma device is filled with magnetic plasma, too,
It can be said that microwaves propagating in plasma exist only in circularly polarized mode. Microwaves in circularly polarized mode propagating through plasma are divided into right-handed circularly polarized waves (R waves) and left-handed circularly polarized waves (I waves).
- wave), and of these, only the R wave is useful for absorbing energy by ECR and generating plasma, while the L wave is not absorbed sufficiently and is reflected, resulting in the generation of plasma. It is known that efficiency decreases. In other words, when microwaves are transmitted only through a circular waveguide, the absorption of microwaves by ECR is not divided by 1, and there is a problem that plasma generation efficiency deteriorates.

In order to solve the above-mentioned problems, the present inventor conducted experiments and research on microwave modes and microwave waveguides with good absorption efficiency by ECR, and found that TMo, (n
:Natural number) mode microwaves are introduced into the plasma generation chamber, the absorption efficiency of the microwaves is good, and in order to obtain TM and immode microwaves, it is necessary to use a rectangular waveguide and a circular waveguide. We discovered that it is possible to perform microwave mode conversion by bonding them together.

The present invention has been made based on this knowledge, and by providing a mode conversion means in a part of the waveguide of a conventional ECR plasma device to introduce microwaves in the TM mode into the plasma generation chamber, an ECR plasma device can be produced. The purpose of the present invention is to provide a device that increases microwave absorption efficiency in a plasma device and improves plasma generation efficiency.

[Means to solve the problem]

The plasma device according to the present invention introduces source gas and microwaves into a plasma generation chamber, applies a magnetic field, and generates plasma by electron cyclotron resonance excitation. It is characterized in that a part of the waveguide introduced into the plasma generation chamber is provided with means for converting microwaves into TMOfi (n: natural number) mode.

[Effect]

When the microwaves oscillated from the microwave oscillator are transmitted to a mode converter installed in a part of the waveguide that introduces them into the plasma generation chamber, the microwaves are converted into TMOo (n: natural number) mode and sent to the plasma generation chamber. will be introduced in As a result, only a mode having an ECR effect exists in the plasma, and efficient plasma generation is achieved.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, an embodiment in which the present invention is configured as a CVD apparatus will be described in detail based on the drawings. FIG. 1 is a schematic vertical cross-sectional view of a plasma device according to the present invention. Similar to the conventional device shown in FIG. Also, in the center of the side wall is a microwave inlet 3 sealed with a quartz glass plate 31b.
1c is further provided with a plasma extraction window 31d at the center of the other side wall facing the microwave introduction port 31c, and a sample chamber 34 is arranged facing the plasma extraction window 31d. The other end of the microwave inlet 31c is connected to the high frequency oscillator 3.
One end of microwave waveguides 32a, 32b connected to plasma generation chamber 31 and one end of waveguides 32a, 32b connected to this are connected, and an excitation coil 35 is concentrically arranged so as to surround these. be done.

A sample stage 36 on which a sample S such as a wafer is mounted is disposed in the reaction chamber 34 facing the plasma extraction window 31d, and an exhaust gas (not shown) is provided on the rear wall of the sample chamber 34 located on the rear side. An exhaust port 37 connected to the device is opened.

32a in FIG. 1 is a rectangular waveguide, one end of which is connected to the high frequency oscillator 33, and the other end connected to the circular waveguide 3.
Connected to 2b. One end of 32b on the side not connected to 32a is connected to microwave inlet 31c.

When the microwave in TE, 0 mode is transmitted to the circular waveguide 32b by the rectangular waveguide 32a, the microwave mode is converted to T M o + mode, and the plasma generation chamber 3
1.

When a circular waveguide is joined to a rectangular waveguide in this way, the circular waveguide plays the role of a mode converter, and the microwave mode is converted into the T Mo + mode that is easily absorbed by ECR. FIG. 2 is a schematic vertical cross-sectional view of a mode converter in which a circular waveguide is joined to a rectangular waveguide. The end portion of the wave tube 32b is removed by the size of the opening, and at that portion, the above-mentioned 321] is connected in a direction perpendicular to the above-mentioned 32a. FIG. 3 is a schematic top view showing a mode converter similar to that in FIG. 2 with the end of the circular waveguide 32b that is not connected to the rectangular waveguide 32a as the top surface.

In the plasma apparatus of the present invention provided with the mode converter as described above, the microwave frequency is set to 2.45 Gllz,
The inner diameter of the circular waveguide 32b of the mode converter is 100 m.

The inner diameter of the rectangular waveguide 32a is 54.66 u+ horizontally and 11 vertically
9.22mm.

The inner diameter of the plasma generation chamber 31 is 100 mm, and the length is 100 mm.
**, N2 gas is supplied into the plasma generation chamber 31 from a gas supply system (not shown), and the excitation coil 35 generates 875
Plasma was generated by ECR excitation by forming a Gaussian magnetic field.

The absorption rate of the microwave at that time was calculated by installing a power meter at an appropriate part of the rectangular waveguide 32a and measuring the strength of the reflected wave. Also, almost no reflected waves were detected, and the microwave introduced into the plasma generation chamber 31 was ECI? It was efficiently absorbed by excitation.

〔Effect of the invention〕

As described in detail above, in the plasma apparatus of the present invention, a moat converter is provided in the waveguide that introduces the microwave oscillated from the microwave oscillator into the plasma generation chamber, thereby generating a TM in the plasma generation chamber.

Introducing microwaves in the (n: natural number) mode prevents reflected waves without using a matching device for antireflection, and improves microwave absorption efficiency by ECR.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical cross-sectional view of a plasma device according to the present invention, FIG. 2 is a schematic vertical cross-sectional view of a mode converter used in the plasma device according to the present invention, and FIG. 3 is a schematic top view of the mode converter. Figure 4 shows a conventional plasma device! It is a schematic diagram of ItJi surface. 31... Plasma generation chamber 32a... Rectangular waveguide 3
2b...Circular waveguide 33...High frequency oscillator 35.
... Exciting coil patent Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Noboru Kono 2a Funeral diagram 2a

Claims (1)

[Claims] 1. In a plasma device that introduces raw material gas and microwaves into a plasma generation chamber, applies a magnetic field, and generates plasma by electron cyclotron resonance excitation, the microwaves oscillated from a microwave oscillator are Microwaves are introduced into a part of the waveguide that is introduced into the plasma generation chamber using TM_
A plasma device characterized by comprising means for converting into an o_n (n: natural number) mode.