JPH02139900A - plasma equipment - Google Patents

Abstract

(57) [Summary] 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 (Electron Cyclotron Re5o) in a plasma generation chamber.
nance.

This invention relates to plasma devices such as CVD devices and dry etching devices that utilize ECR plasma generated by ECR) excitation.

[Conventional technology]

The device that generates the plug "7" by ECR excitation has the following features: it can generate highly active plasma 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 advantages: It has many advantages, such as CVD equipment for forming thin films of desired substances on semiconductor substrates, dry etching equipment for forming fine circuit patterns on semiconductor substrates, etc. Progress is being made in applying it to manufacturing.

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 microwave oscillator 33 is connected to the microwave inlet 31c, and the plasma generation chamber 31 and one end of the waveguide 32 connected thereto are energized so as to surround them. Coils 35 are arranged concentrically.

Inside the reaction chamber 34, a sample stage 36 on which a sample S such as a wafer is mounted is disposed facing the plasma extraction window 31d, and on the rear wall of the sample chamber 34 located on the rear side, there is a hole shown in the figure. An exhaust port 37 connected to an exhaust device that is not connected 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 microwave oscillator 33 is passed through the microwave waveguide 32 and the microwave introduction window 31.
c into the plasma generation chamber 31. 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 excited (introduced into the sample chamber 34 by a divergent magnetic field formed by the d coil 35) and projected onto the sample S, forming a thin film of a desired substance 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, a circularly polarized wave generator is installed in a microwave waveguide in order to eliminate non-uniformity in electric field strength on the cross section of the microwave waveguide that introduces microwaves into a plasma generation chamber. An apparatus for uniformly generating plasma by connecting two devices 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 a plasma generation chamber, there are problems as described below. In other words, it is known that according to Maxwell's equations, radio waves propagating in a circular waveguide filled with magnetic material exist only in circularly polarized mode (S
Uhl, Wa! ker: Bl:LLSyst, T
ech, J., 33. (1954) P579), the tensor of the permittivity of magnetic plasma is isomorphic to the tensor of magnetic permeability of radio waves, so similarly, using Maxwell's equation, the conventional εCl? Even when the circular waveguide of the plasma device is filled with magnetic plasma, it can be said that the microwave propagating through the plug 7 exists only in the circularly polarized mode. Microwaves in circularly polarized mode propagating through plasma are clockwise circularly polarized (R
wave) and left-handed circularly polarized wave (L wave).

In Fig. 3, the horizontal axis is ωC/ω (ω) of R waves and L waves.

: cyclotron frequency, ω: microwave frequency), the refractive index n of the microwave is taken on the vertical axis, and R wave and L wave
It is a graph showing the magnetic field dependence of the refractive index of waves. ωp/
ω (ωp: plasma frequency) = 0.5. Koro-3
, 0 (Ko: wave number in vacuum, ro: radius of cylindrical magnetic plasma), when R waves and L waves were introduced into the plasma generation chamber, ω.

When /ω is around 1.0, the refractive index n of the R wave increases rapidly as ωC/ω decreases, which confirms that the ECR effect appears. On the other hand, the refractive index n of the L wave is ωC/
It does not depend on the value of ω. In other words, it does not show the effect of ECR.

As can be seen from this, R is useful for absorbing energy and generating plasma through EC[l excitation.
L waves are not absorbed sufficiently, but are reflected and are only lost in terms of energy. Therefore, when microwaves are introduced into the plasma generation chamber using a circular four-wave tube, both R waves and L waves exist in the microwaves as described above, but the microwaves due to ECR excitation in the plasma generation chamber are Since L waves are not involved in absorption, there is a problem in that efficient plasma generation cannot be achieved.

The present invention has been made in consideration of such circumstances, and uses circularly polarized wave modes, namely TE, TM, which propagate in a circular waveguide filled with a magnetic material. (m, n: integer, n≠0) mode microwave is converted into R waves, only R waves are introduced into the plasma generation chamber, energy loss due to L waves is prevented, and E
An object of the present invention is to provide a device that improves microwave absorption efficiency in a CR plasma device.

[Means to solve the problem]

A plasma device according to the present invention introduces microwaves into a plasma generation chamber, applies a magnetic field, and generates plasma by electron cyclotron resonance excitation. TEmn+T in the waveguide introduced into
Mmn (m, n: integer.

The present invention is characterized in that it includes a circularly polarized wave generator that converts microwaves in the n≠0) mode into right-handed circularly polarized waves.

[Effect]

A circularly polarized wave generator installed in a waveguide that introduces microwaves oscillated from a microwave oscillator into the plasma generation chamber is
Es+n+ TMmn (m, n: integer, n≠O
) mode of microwaves is converted to right-handed circularly polarized waves. This right-handed circularly polarized wave is transmitted to the plasma generation chamber and efficiently absorbed by ECR excitation.

〔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 microwave inlet 31c includes microwave waveguides 32a, 32b whose other ends are connected to the microwave oscillator 33.
One ends of 32c and 32d are connected to the plasma generation chamber 31 and waveguides 32a, 32b, 3 connected thereto.
An excitation coil 35 is disposed concentrically over one end of 2c and 32d so as to surround them.

In the reaction chamber 34, a sample stage 36 on which a sample S such as a wafer is placed is arranged 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.

After the microwave oscillated from the microwave oscillator 33 is transmitted to the rectangular waveguide 32a, TE. It is transmitted as a mode microwave to the rectangular/circular converter 32b, where it is converted into a circular TE mode microwave.

Furthermore, this TEz mode microwave is transmitted to a circularly polarized wave generator 32.
c and is converted into R waves useful for generating plasma by ECR.

FIG. 2 is a cross-sectional view of the circularly polarized wave generator 32c, in which the fundamental mode is TE, and metal plates C1 and C2 made of aluminum or the like are placed on the wall of the circular waveguide at an angle of 45 degrees to the incident electric field. It is installed opposite the position. This causes a phase difference in the incident waves, and only the R wave enters the circular waveguide 3.
2d. Furthermore, this R wave is caused by the quartz glass temporary 31b.
, the plasma generation chamber 31 through the microwave inlet 31c.
is introduced into the atmosphere, absorbed by ECR excitation, and generates plasma.

In the plasma device of the present invention and the conventional plasma device described above, the microwave frequency is 2.45 GHz.

The rectangular waveguide 32a has a length of 109.22 mm, a width of 54.61 mm, and a length of 200 mm, and the rectangular/circular converter 32b has a length of 4 ji81 mm.
．． 13 am, width 67.82 am, length 46.66 am
, the circularly polarized wave generator 32c has an inner diameter of 84+em and a length of 165.
71 track Distance between opposing metal plates 72 long, circular waveguide 32 d
has an inner diameter of 84m++, a length of 100mm, and a plasma generation chamber of 31mm.
has an inner diameter of 84mm and a length of 100n, and a gas pressure of 3.5 x 1 is supplied into the plasma generation chamber 31 from a gas supply system (not shown).
N2 gas of 0'' Torr was supplied for 30 seconds, a magnetic field of 875 Gauss was formed by the excitation coil 35, and plasma was generated by microwave incident power of 2.0 kW.

At that time, a Langmuir probe was installed in the plasma generation chamber 31 to measure the reflected power and plasma density, and in the device of the present invention, the reflected power was 0.1 kW and the plasma density was 1.6 x 10"cm-'. .

On the other hand, when plasma is generated under the same conditions as above using a conventional plasma device without a circularly polarized wave generator in the waveguide, the reflected power is 0.7 kW and the plasma density is 8 x 1010 cm -
'Met.

As is clear from this, in the device of the present invention, compared to the conventional device, the reflected power inside the plasma generation chamber is reduced, the plasma density is increased, the absorption efficiency of microwaves by the plasma is improved, and the plasma is efficiently generated. generated.

In this example, the TE mode microwave was converted to right-handed circularly polarized waves by a circularly polarized wave generator, but the inner diameter or length of the circularly polarized wave generator, the shape of the metal plate, etc. By varying TE,..., TMffi.

Any microwave in the (m, n: integer, n≠0) mode can be converted into a right-handed circularly polarized wave, and the same effect as described above can be obtained.

Further, in the above embodiment, an example was shown in which the source gas is introduced into the plasma generation chamber, but the source gas may also be introduced into the sample chamber. Since the introduced raw material gas diffuses into the plasma generation chamber, the same effect as when introduced into the plasma generation chamber can be obtained.

〔Effect of the invention〕

As detailed above, in the device of the present invention, TE□.

TM, lIn (m, rl: integers, n≠0) mode microwaves are converted into clockwise circularly polarized waves before being introduced into the plasma generation chamber, reducing reflections within the plasma generation chamber and reducing microwaves due to ECR excitation. The wave absorption efficiency is improved and plasma is generated efficiently.

[Brief explanation of the drawing]

Fig. 1 is a schematic longitudinal cross-sectional view of a plasma device according to the present invention, Fig. 2 is a schematic cross-sectional view of a circularly polarized wave generator used in the plasma device according to the present invention, and Fig. 3 is a refraction of R and L waves. FIG. 1 is a graph showing the dependence of the rate on the magnetic field, and is a schematic vertical cross-sectional view of a conventional plasma device. 31...Plasma generation chamber 32 (,...Circularly polarized wave generator 33...Microwave oscillator 35...Excitation C) Coil patent Applicant: Sumitomo Metal Industries, Ltd. Name: Take Company Agent Patent attorney Kawa No Noboru 2a Diagram No. Z (βC, /ヮ酩V

Claims (1)

[Claims] 1. In a plasma device that introduces 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 transmitted to the plasma generation chamber. TE_m_n in the waveguide introduced into
A plasma device comprising a circularly polarized wave generator that converts a TM_m_n (m, n: integer, n≠0) mode microwave into a right-handed circularly polarized wave.