JPH06188237A - Apparatus for forming plasma - Google Patents

Abstract

PURPOSE:To realize the formation of a uniform plasma in a wide area, by feeding to a discharge tube an electromagnetic wave leaked from the microstrip line which comprises a grounded conductor board and a conductor line capacitor-coupled thereto. CONSTITUTION:By the multiplier action between the electromagnetic wave in a microwave region which is fed from an electromagnetic-wave feeding part 3 and the magnetic field fed from electromagnets 1, the raw material gas introduced into a discharge tube 2 is put in a plasma condition. In this case, one end part of the electromagnetic- wave feeding part 3 made of copper which is cylindrical is opened to the outside, and the other end part thereof is closed with a grounded conductor board 5, and further, in the inner part thereof a spiral conductor line 6 is provided oppositely to the grounded conductor board 5 with a fixed space between. The central part of the spiral conductor line 6 is terminated by the grounded conductor board 5 via a resistor load 7, and to the starting point of the spiral conductor line 6 the power of the electromagnetic wave in a microwave region is fed. When the permittivity of the medium between the grounded conductor board 5 and the spiral conductor line 6 is the same one as air, the electromagnetic wave propagated in the spiral conductor line 6 is radiated from the part parallel with the line 6 to the outside space at a fixed ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma forming apparatus, and more particularly to a plasma forming apparatus suitable for etching a large diameter semiconductor substrate or depositing a thin film.

[0002]

2. Description of the Related Art Conventionally, in order to form a high-density plasma in a low vacuum, an apparatus for forming a plasma by a synergistic effect of a magnetic field and an electromagnetic wave in a microwave region has been used. This is called magnetic field microwave plasma. But,
Irradiation of electromagnetic waves to the discharge tube portion that forms plasma tends to be nonuniform in this conventional device, and especially when trying to form plasma in a region having a diameter larger than the wavelength of the electromagnetic wave used, uniform plasma is generated in that region. Are very difficult to form.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to realize uniform plasma formation over a wide area, which has been difficult with a conventional apparatus, while utilizing the advantages of the magnetic field microwave plasma.

[0004]

To achieve the above object, the present invention uses a microstrip line composed of a ground conductor substrate and a conductor line capacitively coupled to the ground conductor substrate. A leaked electromagnetic wave is supplied to the discharge tube to form plasma.

[0005]

By uniformly extending the microstrip line in the plasma formation region, the electromagnetic wave leaked from the microstrip line is uniformly irradiated to the plasma formation region, and uniform plasma can be formed in a wide area.

[0006]

EXAMPLE An example of the present invention will be described with reference to FIG. Figure 1
FIG. 3 is an explanatory diagram of a basic configuration of the present invention. The main components are the electromagnet 1, the discharge tube 2 installed in the center of the electromagnet 1, and the discharge tube 2.
The electromagnetic wave supply unit 3 supplies electromagnetic waves to the. The source gas introduced into the discharge tube 2 can be made into a plasma state by the synergistic action of the electromagnetic wave in the microwave region from the electromagnetic wave supply unit 3 and the magnetic field of the electromagnet 1.

FIG. 2 is a detailed explanatory view of the electromagnetic wave supply section 3. The electromagnetic wave supply unit 3 is formed of copper in a cylindrical shape, and has a structure in which one end is open and the other is closed by a flat plate of copper (hereinafter referred to as a ground conductor substrate 5). Spiral conductor lines 6 are installed inside the ground conductor substrate 5 at regular intervals. The central portion of the spiral conductor line 6 is terminated to the ground conductor substrate 5 via the resistance load 7. Further, an electromagnetic wave in the microwave region is fed from the outside to the starting point of the spiral conductor line 6.

Here, as a method of bringing the spiral conductor line 6 close to the ground conductor substrate 5 at a constant interval, for example, a minute insulator spacer is used to form the spiral conductor line 6 and the ground conductor substrate 5.
There is a means such as installing between.

The electromagnetic wave supply unit 3 shown in FIG. 2 according to FIG.
The operation of will be described. FIG. 3 shows a part of the spiral conductor line 6 on the ground conductor substrate 5, and shows a state of the electromagnetic wave when the electromagnetic wave propagates between the spiral conductor line 6 and the ground conductor substrate 5. Let ε _{1 be} the permittivity between the ground conductor substrate 5 and the spiral conductor line 6, and let ε _{0 be} the permittivity in air. At this time, if ε ₁ >> ε ₀ , the electric field of the electromagnetic wave fed to the spiral conductor line 5 is concentrated between the ground conductor substrate 5 and the spiral conductor line 6, and becomes as shown in FIG. In such a state, the electromagnetic wave is not so much released into the air and propagates along the spiral conductor line 6 between the ground conductor substrates 5.
Next, the state of the electromagnetic wave when ε ₁ = ε ₀ is shown in FIG. As can be seen from this figure, when ε ₁ = ε ₀ , the electric field of the electromagnetic wave cannot be concentrated between the ground conductor substrate 5 and the spiral conductor line 6, and a considerable proportion of the electromagnetic wave is emitted into the space. In other words, it creates a very inefficient state as an electromagnetic wave transmission path. If the ground conductor substrate 5 and the spiral conductor line 6 in the state as shown in FIG. 3B are realized,
The electromagnetic waves propagating in the spiral conductor line 6 are emitted into the space along the spiral conductor line 6 at a constant rate. Therefore, it is possible to radiate a relatively uniform electromagnetic wave in the plane direction of the ground conductor substrate 5 having the spiral conductor line 6 stretched around.

By using the above principle, it is possible to irradiate a relatively uniform electromagnetic wave on a surface considerably wider than the wavelength of the electromagnetic wave to be used by enlarging the area over which the spiral conductor line 6 extends. However, since the electromagnetic wave introduced from the feeding point of the spiral conductor line 6 is considerably attenuated at the terminal end of the spiral conductor line, when the electromagnetic wave is supplied from the spiral outer shell, the amount of electromagnetic waves radiated in the central portion is increased. It may decrease. Therefore, in such a case, it is necessary to increase the density of the number of turns in the spiral center portion.

As shown in FIG. 2, the terminal end, which is the other end of the electromagnetic wave feeding point, is terminated by the resistive load 7. The size of the resistance load 7 is set in consideration of the impedance of the spiral conductor line 6 so that the radiation efficiency or radiation uniformity of electromagnetic waves is optimized. At that time, when the power consumption of the resistive load 7 becomes large, a mechanism for cooling the resistive load by water cooling or air cooling is added. Further, instead of adding a resistance load, the same effect can be obtained by terminating the end portion and opening the end portion to the ground conductor substrate by capacitive coupling.

In this way, it is possible to form a uniform plasma over a wide area. By applying the present invention to the etching and the film volume apparatus that apply plasma, which is a semiconductor manufacturing process, it is possible to uniformly process a large-diameter sample, which has been difficult in the past.

FIGS. 4 and 5 are explanatory views when the conductor line shown in FIG. 2 is arranged in a structure different from the spiral shape. First, in the case of FIG. 4, it is an explanatory view in the case where the conductor lines 9 are arranged in a rectangular wave shape on the ground conductor substrate 5. Even in the configuration of FIG. 4, over a wide area like the spiral arrangement,
Radiation of uniform electromagnetic waves is possible. Further, FIG. 5 is an explanatory diagram in the case where the conductor lines 12 are arranged in a single loop shape. In the case of FIG. 5, there is a possibility that the intensity of the electromagnetic wave can be increased or decreased in the central portion of the loop and the portion where the loop is arranged, but there is an advantage in that a relatively uniform electromagnetic wave can be supplied to a large area with a simple configuration.

FIG. 6 shows an embodiment in which the present invention is applied to a device other than a semiconductor manufacturing apparatus. This is a device configuration in which the electromagnetic wave supply source according to the present invention is used in a flat quartz tube 15 in which a gas is enclosed and the inside of the quartz tube is put into a plasma state.
With the configuration shown in FIG. 6, uniform plasma is formed inside the quartz tube over a wide area. Thereby, the light emitted from the quartz tube can be used as a flat light source.

[0015]

According to the present invention, it becomes possible to uniformly supply an electromagnetic wave to a wide area. As a result, it becomes possible to form a uniform plasma over a large area in an apparatus that forms plasma by the synergistic effect of electromagnetic waves and magnetic fields. By applying this plasma forming device to the processing of semiconductor devices,
A silicon wafer having a large diameter (for example, a diameter of 8 inches or more) can be uniformly processed over the entire surface.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a basic configuration of the present invention.

FIG. 2 is a detailed explanatory diagram of a main part of the present invention.

FIG. 3 is an explanatory diagram of an operation principle of a main part of the present invention.

FIG. 4 is an explanatory diagram of another application example of the main part of the present invention.

FIG. 5 is an explanatory diagram of another application example of the main part of the present invention.

FIG. 6 is an explanatory diagram of another embodiment to which the main part of the present invention is applied.

[Explanation of symbols]

5 ... Ground conductor board, 9 ... Conductor line, 10 ... Electromagnetic wave feeding point, 11 ... Termination part.

Claims (18)

[Claims] 1. A plasma forming apparatus for bringing a gas into a plasma state by an electromagnetic wave in a microwave region, comprising a discharge tube constituting a plasma forming region, and irradiating the discharge tube with the electromagnetic wave in the microwave region, A plasma forming apparatus, characterized in that a microstrip line composed of a ground conductor substrate and a conductor line capacitively coupled to the ground conductor substrate is used to supply the electromagnetic wave leaking from the conductor line to the discharge tube. 2. The plasma forming apparatus according to claim 1, further comprising means for applying a magnetic field to the plasma forming region. 3. The plasma forming apparatus according to claim 1, wherein the conductor line is stretched around the ground conductor substrate so as to uniformly cover the plane thereof. 4. The plasma forming apparatus according to claim 1 or 3, wherein the conductor line is spirally wound so as to uniformly cover the ground conductor substrate plane. 5. The plasma forming apparatus according to claim 1, wherein the conductor line is stretched in a square wave shape so as to uniformly cover the ground conductor substrate plane. 6. The plasma forming apparatus according to claim 1, wherein there is a vacuum between the ground conductor substrate and the conductor line. 7. The plasma forming apparatus according to claim 1, wherein air is present between the ground conductor substrate and the conductor line. 8. The plasma forming apparatus according to claim 1, wherein the electromagnetic wave in the microwave region is supplied from one end of the conductor line and the other end is terminated by a resistance load. 9. The plasma forming apparatus according to claim 1, wherein electromagnetic waves in the microwave region are supplied from one end of the conductor line, and the other end is opened and terminated. 10. The plasma forming apparatus according to claim 1, wherein the ground conductor substrate and the conductor line are made of copper. 11. The plasma forming apparatus according to claim 1, further comprising means for keeping a distance between the ground conductor substrate and the conductor line constant between all lines of the conductor line. 12. The means according to claim 11, wherein the ground conductor substrate and the conductor line are kept at a constant distance between all the conductor lines, and the ground conductor substrate and the conductor line are spaced at regular intervals. A plasma forming apparatus in which spacers made of minute insulators are arranged. 13. The ground conductor substrate according to claim 1, wherein the ground conductor substrate has a cylindrical shape with one end closed, the conductor line is arranged on the closed plane, and the cylindrical ground conductor substrate is opened. Forming apparatus arranged so as to enclose the entire discharge tube from a part. 14. The plasma forming apparatus according to claim 1, wherein a material having a relative permittivity close to 1 is provided between the ground conductor substrate and the conductor line. 15. The plasma forming apparatus according to claim 4, wherein, when the conductor line is formed in a spiral shape, the winding number density at the terminal end of the conductor line is made higher than the winding number density on the power feeding side. 16. The plasma forming apparatus according to claim 8, further comprising means for cooling the resistive load. 17. The conductor line according to claim 1, wherein the conductor line has a single loop shape, and an electromagnetic wave is supplied from one of the conductor lines.
A plasma forming apparatus having a structure in which the other end is terminated by a resistive load. 18. A plasma forming apparatus according to claim 3, wherein the quartz tube filled with gas is irradiated with electromagnetic waves by means for irradiating electromagnetic waves in the microwave region to bring the inside of the quartz tube into a plasma state.