JPH03159099A - Plasma device and plasma generation method - Google Patents

Abstract

PURPOSE:To enable the easy generation of plasma at a pertinent time, stabilize a plasma shape and prevent the disappearance thereof by supplying free electrons for stabilizing plasma generation or the plasma after generation. CONSTITUTION:A material 7 (metal, semiconductor or insulator is acceptable) set to a discharge part 1 is irradiated with light having a wave-length suitable for the material 7 to generate a photoelectric effect (such as wavelength zone of soft X-rays from ultraviolet). Electrons 8 are thereby emitted from the material 7. Once the electrons 8 are emitted in applying electric field to space, plasma is generated with the electrons 8. Also, the intensity of irradiated light is changed for controlling the amount of the emitted electrons 8. According to the aforesaid construction, a time until plasma generation is shortened and the generated plasma can be stabilized.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method and apparatus for stabilizing plasma generation during plasma generation, stabilizing the shape of plasma after plasma generation, or preventing plasma extinction in a plasma device. .

[Conventional technology]

In conventional plasma equipment, Japanese Patent Application Laid-Open No. 56-1555
There is a method of generating plasma using microwaves or high frequency waves, as described in No. 35 or JP-A-61-13634.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, no particular consideration was given to the point of supplying electrons during plasma generation, and it was not easy to generate the initial plasma. There was also the problem that the shape of the plasma generated at 1 o'clock was not stable depending on the conditions.

An object of the present invention is to easily generate plasma in a timely manner, to stabilize the shape of the plasma, and to prevent the plasma from disappearing.

[Means to solve the problem]

In order to achieve the above [1], a photoelectric material as a free electron source provided in the discharge section is irradiated with light (including from external rays to the X-ray region) using an ultraviolet irradiation lamp or an ultraviolet laser, or in some cases, X-rays. As a result, free electrons are emitted from the free electron source due to the photoelectric effect, which acts as a trigger to generate plasma.

Furthermore, in order to supply free electrons, an electron gun is installed so that the electrons fired from the electron gun act as a trigger to generate plasma.

In addition, a hot cathode ray tube was installed to supply free electrons.
The emitted electrons act as a trigger to generate plasma.

[Effect]

Irradiates the material installed in the discharge area (this can be a metal, semiconductor, or insulator) with light of an appropriate wavelength (wavelength range from ultraviolet to soft X-rays) to cause the material to produce a photoelectric effect. As a result, electrons are released from the substance. When an electric field is applied in space, once electrons are emitted, the electrons generate plasma. Furthermore, the number of emitted electrons can be controlled by changing the intensity of the irradiated light, and as a result, the plasma once generated can maintain a stable plasma state by controlling the excess or deficiency of electrons.

Furthermore, by providing a hot cathode ray tube in the discharge section or by injecting electrons with an electron gun, the collision between electrons and gas molecules will trigger plasma generation based on the same principle as described above. Furthermore, by similarly controlling the electron flow rate, the plasma can be kept in a stable state.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

Figure 1 shows an E equipped with an ultraviolet ray/irradiation device according to one embodiment of the present invention.
The six main parts of the CR plasma CVDM system are: plasma generation chamber 1. Vacuum device 3° UV lamp 4. Mirror 5. Anode 6. Photoelectric 7, IECR magnetic field coil 10. Microwave introduction window 11. It consists of a gas supply pipe 12.

Plasma generation chamber 1 is SU with a diameter of 2501n and a length of 500m.
It is made by S. The inside of the plasma generation chamber 1 is heated by a vacuum system @3.
It is exhausted to 0-4 Torr.

The microwave 2 has an intensity variable from 0 to 800 W and a frequency of 2.45 GHz, and is introduced into the plasma generation chamber 1 through the microwave introduction window 11.

The ultraviolet lamp 4 efficiently irradiates the photocathode 7 with ultraviolet light having a wavelength of 180 nm and a power of 1 mW through the concave surface #15.

The photocathode 7 is made of tungsten and is machined into a semi-cylindrical shape with a radius of 45 + m and a length of 80 + w on the inner wall of the cylindrical plasma generation chamber 1 . Since the energy of the irradiating ultraviolet lamp is greater than the work function of tungsten of the photocathode 7, photoelectrons 8 are emitted from the photocathode 7. Microwave frequency (2,45GH
z) and the magnetic field are electron cyclo1-ron resonances (hereinafter abbreviated as E).
Creates a magnetic field (referred to as CR).

In this, molecules introduced from the gas supply pipe 12 collide with electrons, and from there, plasma spreads into the plasma generation chamber 1 in an avalanche shape.

(Example 1) Using the above-mentioned apparatus, the plasma depending on the microwave intensity was
The degree of occurrence within seconds was measured. In FIG. 2, black circles and white circles represent the case of irradiation with ultraviolet rays and the case of the conventional method without irradiating ultraviolet rays, respectively. At a microwave intensity of 300 W, the probability of plasma generation within 5 seconds was 92% and 27%, respectively, with and without ultraviolet irradiation, a difference of more than three times.

Further, FIG. 3 shows the dependence of the microwave intensity on the ultraviolet light intensity when the plasma disappears when the microwave intensity is lowered from a state in which plasma exists.

The ultraviolet irradiation intensity OW is comparable to the conventional method. Increasing the intensity of ultraviolet irradiation stabilized the plasma, and the microwave intensity when the plasma disappeared was significantly reduced, making it possible to stabilize the plasma even with weak microwaves.

(Example 2) FIG. 4 shows the vicinity of the electron gun of microwave plasma CVD 1 [using an electron gun instead of the ultraviolet irradiation device used as a free electron source shown in Example 1. The structure of the plasma generation chamber 1 is the same as that shown in FIG. 1, so it is omitted.

The acceleration voltage of the electron gun 13 is IKV, and the electrons g8 are thrown into the plasma generation device 1, collide with molecules, and cause a reaction.

An experiment similar to Example 1 was conducted. As a result, the microwave intensity was 300W as in Fig. 2.

The probability of generating plasma within 5 seconds was more than three times higher than when no electrons were injected. Also,
As in Figure 3, when the microwave intensity is lowered from the state where plasma exists, the microwave intensity when the plasma disappears is 90 W when no electrons are implanted, and 7 W when f11 electrons are implanted. By injecting electrons, the stability of the plasma was significantly improved.

(Example 3) FIG. 5 shows the vicinity of a hot cathode ray tube of a microwave plasma CVD apparatus using a hot cathode ray tube instead of the ultraviolet irradiation device used as a free electron source shown in Example 1. The structure of the plasma generation chamber 1 is the same as that shown in FIG. 1, so it is omitted. When the cathode 15 is heated to 800°C by the heater 16, the bias voltage between the cathode 15 and the anode 14 (100V)
Thermionic electrons are accelerated and fly as electron beams.

As a result of the same experiment as in Example 1, when the microwave intensity was 300 W as shown in Figure 2, the probability of plasma generation within 5 seconds was more than three times that of the case without using a hot cathode ray tube. It was seen.

Also, as shown in Figure 3, when the microwave intensity is lowered from the state where plasma exists, the microwave intensity when the plasma disappears is 90 W when no electrons are emitted, and 5 W when electrons are emitted. By installing a cathode ray tube,
Plasma has become much more stable.

(Example 4) In FIG. 6, an ultraviolet irradiation device was used as a free electron source.

S deposited by ECR microwave plasma CVD equipment
i Ox film deposition rate (solid line) and deposited SiO2
The variation in film thickness (dotted line) is shown. 9# The deposition rate was 210% when external radiation was irradiated and when it was not irradiated.
The number of people/win increased from 0 to 2,600 people/win, and the variation in film thickness decreased from 8.2% to 2.1%.

Here, the flow rate of 02 and 5iHa is 200 mQ/vnin
, l OOmQ/r&in and the field strength of 6J& is 500 Gauss near the substrate.

(Example 5) FIG. 7 shows a high frequency plasma CVD apparatus equipped with an ultraviolet irradiation apparatus according to an embodiment of the present invention as a free electron source. A high frequency power of 0 to 500 W and a frequency of 13.6 MHz is applied by the high frequency application electrode 17. The ultraviolet lamp 4 emits photoelectrons irradiated near the substrate 9, collides with molecules sent from the gas supply pipe, and triggers plasma generation.

FIG. 8 shows the same experimental results as in FIG. 2 using this apparatus. As expected, when the high-frequency power was 200 W, the plasma generation probability was more than three times greater than when no ultraviolet rays were irradiated, and the ultraviolet irradiation had the effect of generating plasma with lower high-frequency power.

〔Effect of the invention〕

According to the present invention, by supplying free electrons by ultraviolet irradiation, an electron gun, or a hot cathode ray tube, there is an effect of shortening the time until plasma generation and stabilizing the generated plasma.

Further, the present invention has the effect of improving film quality and reducing individual differences in film quality by applying it to thin film formation by plasma or high frequency CVD.

[Brief explanation of the drawing]

Fig. 1 shows an ECR microwave plasma CVD apparatus equipped with an ultraviolet irradiation apparatus according to an embodiment of the present invention as a free electron source. A diagram showing the degree to which this occurs within 5 seconds,
Figure 3 is a diagram showing the dependence of the microwave intensity on the ultraviolet light intensity when the plasma disappears when the microwave intensity is lowered from a plasma existing state using the apparatus shown in Figure 1. Fig. 1 shows a microwave plasma device using an electron gun instead of the ultraviolet irradiation device used as a free electron source, and Fig. 5 shows a microwave plasma device using an electron gun instead of the ultraviolet irradiation device used as the free electron source in Fig. 1. , a diagram showing a microwave plasma device using hot cathode rays. FIG. 6 shows a device equipped with an ultraviolet irradiation device according to an embodiment of the present invention as a free electron source. FIG. 7 is a diagram showing the variation in deposition rate and film thickness of a 5iOz film deposited by ECR microwave plasma CVD, and shows a high-frequency plasma CVD device using an ultraviolet irradiation device according to an embodiment of the present invention as a free electron source. 8 are diagrams showing the degree to which plasma is generated within 5 seconds due to high frequency power using the apparatus shown in FIG. 7. 1... Plasma generation chamber, 2... Microwave, 3...
・Vacuum device, 4...Ultraviolet lamp, 5...Mirror, 6.
... Anode, 7... Photocathode, 8... Photoelectron, 9...
Substrate, 10...E CR magnetic field coil, 11...Microwave introduction window, 12...Gas supply pipe, 13...Electron gun, 14...Anode, 15...Cathode, 16... - Heater, 17... High frequency application electrode, 18... High frequency power supply.

Claims (1)

[Scope of Claims] 1. A plasma generation method characterized by supplying free electrons to generate plasma or to stabilize plasma after generation. 2. A plasma device characterized by irradiating ultraviolet rays as a free electron source for generating plasma or stabilizing plasma after generation. 3. By providing a free electron source using ultraviolet irradiation,
A plasma generation method characterized by stabilizing the generation or shape of plasma. 4. A plasma device according to claim 1, characterized in that an electron gun is provided as means for supplying free electrons. 5. A plasma device according to claim 1, characterized in that a hot cathode ray tube is provided in the discharge section as means for supplying free electrons. 6. A film forming method characterized in that claims 2, 5, and 6 are utilized in microwave plasma CVD or Rf plasma CVD.