JPS5943991B2 - Microwave plasma processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a microwave plasma processing apparatus that performs etching and other processing using plasma generated by microwaves, ions, and activated gas generated in the plasma.

Compared to high-frequency discharge, microwave discharge can produce stable plasma at a wide range of gas pressures from low to high pressures, and the microwave generation source, the magnetron, is inexpensive and has high conversion efficiency, so it is used as a means of generating positive energy. It's advantageous.

Conventionally, a plasma generation tube is inserted in the E direction of a low impedance rectangular waveguide that transmits microwaves generated by a magnetron. A microwave plasma processing apparatus has been proposed for gas chemical etching of a sample in a processing chamber located far downstream of the production tube.

Although good matching can be obtained with this method, since the plasma generation section is small, it has the disadvantage that the processing capacity is inferior when plasma is used.

Additionally, a microwave plasma processing device has been proposed in which a plasma tube is placed inside a cylindrical waveguide that transmits microwaves generated by a magnetron, and the plasma generated in the tube is utilized. The drawback is that a good matching between the plasma and laser loads cannot be obtained. Furthermore, a glass pipe is connected to the tip of the center conductor of the coaxial waveguide that transmits the microwaves generated by the magnetron, and a discharge plasma is generated by flowing the required 5 ion species gas into the pipe. Microwave ion sources that form and extract ions from them have been proposed, but have the drawback that the efficiency of microwave to plasma conversion is not very high.

9 A microwave excitation light source is used in which the plasma in the capillary forming the internal conductor of a coaxial waveguide is excited by magnetic coupling with the internal conductor of another coaxial waveguide through which a microwave current flows. It was proposed by one of the inventors.

The present invention is based on this microwave plasma source proposed by one of the inventors, eliminates the drawbacks of conventional microwave plasma processing equipment, and allows most of the input ζ-microwave energy to be transferred to the plasma. The purpose of the present invention is to provide a microwave plasma processing apparatus having a means for not only converting but also generating high-density plasma over a wide area. A system comprising a transmission line for transmitting microwave power, a plasma generation section coupled to the transmission line and connected to a gas source, and a vacuum chamber connected to the plasma generation section and utilizing plasma generated in the plasma generation section. A means for coupling an internal conductor of a coaxial line in the transmission line and plasma generated in the plasma generation section by a magnetic flux generated by a mithal wave current flowing through the internal conductor, the plasma generation section and The present invention is characterized in that it has a waveguide section made of a N outer conductor surrounding the waveguide section and an outer conductor connected to the outer conductor, and means for expanding the plasma in the plasma generation section.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment in which a sample is subjected to a treatment such as etching by bringing an activated gas into contact with the sample. In the figure, 1
For example, is a magnetron that oscillates a 2.45 GHz microwave, 2 is a rectangular waveguide, 2a is a plunger matching device,
3 is a coaxial line, 3a is a doorknob antenna, 3b is an internal conductor, 3c is a coupling loop at one end of the internal conductor 3b, 3d
3e is an external conductor, 3e is a coaxial plunger matching device, and 4-1 is a plasma generation tube, one end of which is connected to the gas chamber 5, and the other end connected to the vacuum chamber 6-1 via the conical tube portion 4a-1. connected to.

T-1 is an external conductor surrounding the plasma generation tube 4-1,
It is connected to the outer conductor 3d of the coaxial line 3 and also connected to one end of the coupling loop 3c at one end of the inner conductor 3b. 7a-1 is a conical external conductor connected to one end of the external conductor 7-1 and surrounding the conical tube portion 4a-1.

The vacuum chamber 6-1 had a base 6b-1 on which the sample 6a-1 was placed, and was connected to a diffusion pump 8 that evacuated the vacuum chamber 6-1.

The microwave power output from the magnetron 1 is first transmitted to a rectangular waveguide 2 with a suitably adjusted plunger 2a, and then to a suitably designed doorknob antenna 3.
a, the signal is transmitted to the coaxial line 3 without any power loss due to reflection.

Almost all the microwave power flowing through the coaxial line 3 having an appropriately adjusted coaxial plunger matching device 3e connects the plasma 9-1 in the plasma generation tube 4-1 and the coupling loop 3c through which the microwave current flows. By sufficiently magnetically coupling, the o gas supplied from the gas chamber 5 is transmitted to the plasma waveguide constituted by the plasma 9-1 in the plasma generation tube 7-1 and the outer conductor 7-1. For example, carbon tetrachloride (CCl4) gas is transferred to the plasma generation tube 4-
1 becomes a plasma 9-1, and this plasma 9-1 flows into the conical tube portion 4a-1 and becomes expanded plasmas 9a-1 and 9b.
-1,9c-1 is formed.

The plasma 9-1, expanded plasma 9a-1, 9b-1,
9c-1, outer conductor 7-1, and conical outer conductor 7a-1
A microwave current flows through the secondary circuit consisting of the gaps 10-1 and 10a-1 between the two, and the expanded plasma 9a
A gradually attenuating microwave electric field 11-1 is formed between -1, 9b-1, 90-1 and the conical outer conductor 7a-1.

Due to the formation of this secondary circuit, plasma 9-1,
The microwave power from the magnetron 1 is stably and completely absorbed into the expanded plasmas 9a-1, 9b-1, and 9c-1, and the expanded plasma 9a-1 as well as the plasma 9-1
The density of 1,9b-1,9c-1 remains higher.
Since the plasma density of the expanded plasmas 9a-1, 9b-1, 9c-1 gradually decreases in the direction of expansion of the conical tube portion 4a-1, the expanded plasmas 9a-1, 9b-1, 9c-1 as conductors.
The impedance of 9c-1 gradually increases, and this gradual increase in impedance terminates the plasma waveguide formed by the outer conductor 7-1 and the plasma 9-1 in the plasma generation tube 4-1 in a stable and consistent state. do.

The activated gas generated in the expanded plasmas 9a-1, 9b-1, 9c-1 is pumped into the vacuum chamber 6-1, which is evacuated by a diffusion pump.
The soil sample 6a-1 of the base 6b-1 is uniformly etched.

FIGS. 2A and 2B show an embodiment in which drilling and other processing are performed by irradiating an ion beam.

In this embodiment, the plasma generation tube 4-2 has a circular shape and communicates with the vacuum chamber 6-2 via the coupling hole 4a-2. Coupling loop 3c at the end of the inner conductor 3b of the coaxial line 3
is arranged along the plasma generating tube 4-2 as in FIG. 1, and terminates at a flat spherical outer conductor 7-2 connected to the outer conductor 3d of the coaxial line 3. The flange 7a-2 of the external conductor 7-2 is coupled to the metal plate 6c-2 on the upper wall of the vacuum chamber 6-2. Magnetron 1, similar to the one shown in the first diagram.
Microwave power outputted from the rectangular waveguide 2 and transmitted through the coaxial line 3 is absorbed by the gas flowing from the gas chamber 5, and the gas is ionized to become plasma 9-2.

This plasma 9-2 is sufficiently magnetically coupled with the coupling group 3c of the inner conductor 3b of the coaxial line 3 and forms a secondary circuit together with the gap 10-2 and the outer conductor 7-2, so that this plasma 9-2 Microwave current flows through and microwave power is absorbed. Then, this plasma 9-2 passes through the coupling hole 4a-2 and expands into the upper part of the vacuum chamber 6-2.
a2, and this expanded plasma 9a-2 is strengthened and maintained by ionization caused by the electric field formed between the upper wall metal plates 6c-2 of the vacuum chamber 6-2. For example, argon gas ions in the expanded plasma 9a-2 generated in the vacuum chamber 6-2 are accelerated by the electrostatic lens 12 and focused on the sample 6a-2 as shown by the line 13, so that the sample 6a-2 is 6a-2 is subjected to drilling and other processing using ions. FIG. 3 shows an embodiment in which processing such as etching is performed by irradiating plasma.

The plasma generation tube 4-3 is formed in a semicircular shape, and both ends thereof communicate with a roof top-shaped chamber 4a-3 that opens into the vacuum chamber 6-3.

A flat hemispherical outer conductor 7-3 and a roof-top-shaped external conductor 7a-3 continuous thereto are disposed around the outer periphery of the plasma generation tube 4-3 and the roof-top shaped chamber 4a-3. Vacuum chamber 6-
3, a mesh electrode 14 and a linear cathode 15 are arranged. In this way, the microwave output from the magnetron 1 is transmitted to the plasma generation tube 4-3 via the waveguide 2 and the coaxial line 3 in the same manner as described above, and the gas in the tube is ionized to generate plasma 9-3, 9a-. It becomes 3.

The coupling loop 3c at the end of the inner conductor 3b of the coaxial line 3 magnetically couples with the plasmas 9-3, 9a-3 and the outer conductors 7-3, 7a.
A microphone mouth wave current flows through the secondary circuit including -3, and microwave power is absorbed into the plasmas 9-3 and 9a-3.
The plasmas 9-3 and 9a-3 are maintained at high density over a wide range. Gas ions, such as argon ions, in this plasma 9a-3 are accelerated and parallelized by the mesh electrode 14, and electrons emitted from the linear cathode 15 are added to the gas ions, for example, argon ions, and the electrons are neutralized as a whole. This results in a flow of ions, which flows into the sample 6a-3 on the base 6b-3.
shock. This device is thus used as a plasma processing tool. As described above, according to the present invention, the internal conductor of the coaxial line and the plasma generated in the plasma generating section are coupled by the microwave magnetic flux generated by the current flowing through the internal conductor, and the plasma in the plasma generating section is and an external conductor surrounding the waveguide section, and means for expanding the plasma in the plasma generation section, which has an external conductor connected to the external conductor, so that microwave power is sufficiently absorbed into the plasma. It is possible to increase the conversion efficiency from microwave power to plasma, and also to obtain higher density plasma over a wider area, resulting in an increase in processing capacity.

[Brief explanation of the drawing]

1 to 3 each show an embodiment of the present invention, in which FIG. 1 is a cross-sectional view, FIG. 2 A1 and FIG. 3 A are respectively FIG.
1 Cross-sectional view along the chain line in Figure 3 B, Figure 2 B1 Figure 3 B
2A and 3A are partial cross-sectional views taken along the chain line in FIG. 2A and FIG. 3A. 1... Magnetron, 2... Rectangular waveguide, 3... Coaxial line, 3c... Coupling loop, 4-1, 4-2, 4 -3... Plasma generation tube, 4a-1... Conical tube part, 4a-2...
...Joining hole, 4a-3... Roof top shaped chamber, 5... Gas chamber, 6-1, 6-2, 6-3...
...Vacuum chamber, 6a-1, 6a-2, 6a-3...
...Sample, 6b-1, 6b-2, 6b-3...
・Base, 7-1, 7-2, 7-3...Outer conductor, 7a-1...Conical outer conductor, 7a-3...
...Roof top shape external conductor, 8...Diffusion pump, 9-1, 9-2, 9-3...Plasma,
9a-1... Expanded plasma, 10-1...
...Gap, 11...Electric field, 12...Electrostatic lens.

Claims (1)

[Claims] 1. A microwave oscillator, a transmission line for transmitting microwave power output from the microwave oscillator, a plasma generation section coupled to the transmission line and connected to a gas source, and a plasma generation section connected to the plasma generation section. In a type equipped with a vacuum chamber that utilizes the generated plasma, magnetic flux is generated by a microwave current flowing through the internal conductor of the coaxial line in the transmission line and the plasma generated in the plasma generation section. a waveguide section consisting of the plasma generation section and an outer conductor surrounding the plasma generation section; and means for expanding the plasma in the plasma generation section, the waveguide section having an outer conductor connected to the outer conductor. Microwave plasma processing equipment.