JPH0775152B2 - Plasma equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a plasma device, and more particularly to a plasma device suitable for producing and processing a thin film using plasma.

[Conventional technology]

A conventional apparatus for performing microfabrication is, for example, as described in FIG. 3 on page 45 and description on page 46 of the April 1986 issue of Monthly Semiconductor World, plasma with a strong magnetic field of 800 gauss or more. , It is difficult to generate a uniform magnetic field. Due to the effects of non-uniformity of plasma due to the difficulty of generating a uniform magnetic field and the rotational motion of ions due to a strong magnetic field, more precise microfabrication and uniforming of large area wafers are possible. No consideration was given to the treatment.

Also, Journal of Applied Physics 57
(5), (March 1985), pages 1638 to 1647 (J.Ap
pl.Phys.57 (5), March (1985), pp1638-1647) generates a DC discharge plasma due to the filament, so the instability of the discharge due to the insulator made by the plasma and the heavy metal impurities in the filament The impact on the sample,
It was not considered.

[Problems to be Solved by the Invention]

Therefore, the above-mentioned conventional technique has a problem in that a large-area sample cannot be formed into a film by uniform and stable plasma for a long time, or fine processing cannot be performed.

An object of the present invention is to provide a plasma device capable of uniformly and stably performing plasma processing on a large-area sample for a long time.

[Means for Solving the Problems]

The above-mentioned object is to configure the plasma device into two chambers, a plasma generation chamber for generating plasma and a plasma expansion chamber for expanding and utilizing the generated plasma, and the plasma generation chamber is optimal for generating plasma. With the above configuration, the plasma expansion chamber is configured to have an optimal configuration for processing a sample with plasma, so that the functions are separated and the high frequency power supply for bias application is connected to the sample stage.

[Action]

Since the plasma generation chamber heats and maintains plasma by alternating current such as high frequency and microwave, an insulator is generated as a product by plasma of etching gas and film forming gas,
Even when attached to the surrounding wall, the discharge can be stably maintained for a long time.

The plasma expansion chamber expands the high-density plasma generated in the plasma generation chamber by the adiabatic expansion principle.
In particular, it has the effect of lowering the temperature of ions, and can improve the dimensional accuracy of fine processing.

Also, in the plasma expansion chamber, the plasma is confined by the line cusp magnetic field where the magnetic field strength becomes almost zero when it is separated from the wall surface by several cm, and the plasma loss at the plasma expansion chamber wall is reduced. High-frequency electromagnetic field caused by plasma generation, or non-uniformity of plasma due to DC magnetic field, and non-uniformity of directionality due to rotational motion on ions, have the effect of erasing, and it is possible to confine a uniform plasma with a large diameter. Becomes for that reason,
It is possible to perform uniform plasma treatment within a large-diameter sample surface.

Film formation by accelerating positive ions by generating a bias voltage for accelerating positive ions in the sample stage by passing a high-frequency current through the sample stage that holds the sample for processing or film formation in the plasma expansion chamber. The film quality at the time of etching and the etching rate at the time of fine processing are improved.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a vertical sectional view of a plasma device. In the figure, the plasma generating chamber 1 is a quartz glass cylindrical chamber having an inner diameter of 100 mm and a length of 150 mm, and the upper end of the cylinder is used for etching.
This is a structure in which SF ₆ gas, SiH ₄ gas for film formation, etc. are introduced. The high frequency coil 4 of 4 turns is wound around the outer periphery,
Plasma is generated and maintained in the plasma generation chamber 1 by the high frequency power of 13.56 MHz and the axial magnetic field of 50 Gauss or more formed by the DC magnetic field generation coil 7. The axial DC magnetic field generation coil 7 has a confinement effect of reducing plasma loss on the side wall of the plasma generation chamber 1, an effect of facilitating coupling or absorption of high frequency power to the plasma, and improving plasma generation efficiency. It has an effect of transporting the plasma generated in the generation chamber 1 toward the plasma expansion chamber 2 by the divergent magnetic field gradient. The lower end of the plasma generation chamber 1 is
It is connected to the central portion of the upper end of the plasma expansion chamber 2.
The plasma expansion chamber 2 is a stainless steel cylindrical container 17 having an inner diameter of 300 mm and a length of 300 mm, and has a length of 300 mm, a width of 8 mm, and a height on the outer circumference.
As shown in FIG. 2, 24 pieces of 25 mm cobalt samarium permanent magnets 5 are provided so that the N poles and the S poles alternate. The magnets 5 having the same width and height are also installed in the upper and lower parts of the plasma expansion chamber 2, and the distance between them is 40 mm or less, and the magnetic poles are cylindrical containers 17
Facing the outer wall of the and the polarity is alternately changed. Further, the wall thickness of the installation portion of the permanent magnet 5 of the cylindrical container 17 is set to 4 mm or less, so that the magnetic field strength of the magnetic pole portion on the inner surface is set to 1000 Gauss or more. The sample stage 3 is connected to a high-frequency power source 6 of 400 KHz via a blocking capacitor to generate a bias voltage for accelerating positive ions in the sample direction, and a temperature controller (not shown) for performing necessary cooling and heating. Connected). The sample table 3 has a diameter of 150 mm
In order to be able to hold even the wafer sample of 160 mm, it is made of a rotary stage with a diameter of 160 mm, improving the uniformity of processing in the circumferential direction. The magnetic field in the portion of the sample table 3 is 5 gausses or less, and the change in the uniformity of the plasma density is ± 5% or less.

According to this embodiment, since the plasma is expanded, the temperature of the plasma is lowered, and the effect of reducing the damage of the sample due to the energy of the ions is exerted. Further, in the plasma expansion chamber 2, since the nonuniformity during plasma generation in the plasma generation chamber 1 is smoothed, uniform plasma treatment can be performed within the large-diameter sample surface. Further, since the magnetic field in the vicinity of the sample table 3 can be set to several Gauss or less, there is an effect that the characteristics are not deteriorated by the magnetic field when etching or forming a thin film using a magnetic film.

FIG. 3 shows another embodiment of the microwave waveguide 20 of 2.45 GHz and the electron cyclotron resonance magnetic field 875.
A Gaussian magnetic field generating coil (magnet) 21 is used to generate microwave plasma in the cylindrical plasma generating chamber 11.

According to this example, the energy based on the acceleration of the ions
It is smaller than the high frequency of 13.56MHz, and since the plasma is further expanded, the energy of the ions is further reduced, so there is an effect that the damage to the semiconductor sample etc. is small due to the ion energy colliding with the sample, It is suitable for semiconductor microfabrication equipment and amorphous silicon film formation equipment.

As described above, according to the present invention, since the plasma is generated by the high frequency of the alternating current, there is no instability of the discharge due to the insulator generated by the plasma, so that the stable discharge can be maintained for a long time, and the part of several Gauss or less is used. Then, since the sample is etched and film-formed by the plasma, the non-uniformity of the plasma due to the non-uniformity of the magnetic field, the non-uniformity of the processing and the film formation are small, and it can be applied to a large area wafer such as a wafer with a diameter of 150 mm. Also, there is an effect that the uniformity of processing and film formation can be suppressed within a fluctuation of 5% or less.

〔The invention's effect〕

According to the plasma device of the present invention described above, the plasma generation chamber is provided with plasma generation means by high frequency, and a plurality of permanent magnets having different polarities alternately in the plasma expansion chamber,
Since the magnetic poles are provided so as to face the wall surface of the expansion chamber, and a high-frequency power source for bias application is connected to the sample table, a large-area sample can be treated uniformly and stably for a long time. effective.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a plasma device showing an embodiment of the present invention, FIG. 2 is a sectional view taken along the line II of FIG. 1, and FIG. 3 is a vertical sectional view of another embodiment of the present invention. is there. 1, 11 ... Plasma generation chamber, 2 ... Plasma expansion chamber, 3 ...
… Sample stand, 4 …… High frequency coil, 5 …… Permanent magnet, 6 ・ ・ ・
… High frequency power supply, 7… DC magnetic field generating coil, 17 …… Cylinder container, 20 …… Microwave waveguide, 21 …… Coil for magnetic field generation.

Claims (2)

[Claims] 1. A plasma generation chamber for generating plasma, a plasma expansion chamber connected to the plasma generation chamber for expanding plasma generated in the plasma generation chamber, and provided in the plasma expansion chamber for a predetermined process. And a sample table for supporting a sample to be subjected to, the plasma generating chamber is provided with a high-frequency plasma generating means, a plurality of permanent magnets of different polarities alternately in the plasma expansion chamber, the magnetic pole of the expansion chamber A plasma apparatus, which is provided so as to face a wall surface, and a high frequency power source for bias application is connected to the sample stage. 2. The high-frequency plasma generating means is arranged outside the plasma generating chamber, applies a high-frequency coil for supplying high-frequency power into the plasma generating chamber, and applies a DC magnetic field in the central axis direction of the plasma generating chamber. The plasma device according to claim 1, comprising a direct current magnetic field generating coil.