JPS63186874A - Vapor synthesis device for carbon film - Google Patents

Abstract

PURPOSE:To maintain the temp. of a substrate at a prescribed and uniform temp., by using a material which absorbs microwaves and can be heated up to a specific temp. when energized to constitute an imposing plate to be imposed with the substrate. CONSTITUTION:The substrate 4 is imposed on the imposing table 5 in a reaction vessel 3 and a gaseous mixture composed of hydrocarbon and hydrogen is supplied into the vessel from a supply pipe 6 and is discharged from a discharge pipe 7 to maintain the specified pressure in the vessel 3. The microwaves generated in a microwave oscillator 1 is then fed through a waveguide 2 to the inside of the vessel 3 to convert the gaseous mixture to plasma. The substrate 4 and the sample plate 5 are then heated by microwaves and the plate 5 is further supplied with the electric power from a power source 9 to cause the self-heat generation. The sample plate 5 is formed of a material (SiC, etc.) which has the property as the electric material to absorb the microwaves and has the property as an electric resistor to permit heating up to 500-1,000 deg.C when energized. The easy temp. control of the plate 5 is thereby permitted.

Description

[Detailed description of the invention] a. Industrial application field The present invention relates to an apparatus for vapor phase synthesis of carbon films.

b. Prior Art As a vapor phase synthesis apparatus for carbon film, an apparatus that performs plasma treatment using microwaves is known. The advantages of using microwaves are that plasma density can be increased more efficiently than other methods, that the pressure range that can be turned into plasma is wide, that it is possible to heat the sample as necessary, and that there is no need for electrodes to generate electric discharge. Since there are no substances in the reaction vessel, contamination of the sample surface can be reduced.

FIG. 4 is a conceptual diagram of a conventional carbon film vapor phase synthesis apparatus.

The output power of the microwave oscillator 1a is guided to a quartz reaction vessel 3a via a waveguide 2a. A mixed gas of hydrocarbon and hydrogen is introduced into the reaction vessel 3a from the gas supply section 6a, and is exhausted at a constant flow rate from the exhaust section 7a. Thereby, the inside of the reaction vessel 3a is maintained at a constant pressure.

The introduced gas is turned into plasma by microwave power, and a carbon film is formed on the substrate 4 placed on the sample stage 5. At this time, the substrate 4a and the sample 5a are heated to a required temperature by microwaves. Note that the phase of the microwave is adjusted by the plunger 8a.

Problems to be Solved by the C0 Invention This can be said about crystal preparation in general, but especially in the synthesis of carbon films by the vapor phase method, temperature control of the base coffin plays an extremely important role. That is, the temperature of the substrate must be maintained at a predetermined temperature and at a uniform temperature.

According to the prior art, when the area of the substrate is small, heating is carried out exclusively by microwave irradiation.

Since microwaves are used for two purposes: substrate heating and plasma generation, it is difficult to simultaneously achieve optimal conditions for both.

When the area of the substrate is large, the end portion of the waveguide is expanded into a tapered shape in order to uniformize the microwave energy, thereby generating plasma uniformly. However, in this case, it is difficult to raise the temperature of the substrate to the required temperature. For this reason, it is possible to use high-frequency induction heating or provide a separate heater and use it in combination with microwave heating, but this would complicate the structure and cause problems such as a source of gas contamination and a significant increase in power consumption.

According to the prior art, the temperature of the sample is mostly measured by optical means from outside the Pelger. However, since the measurement is performed through plasma, it is not always possible to obtain sufficient accuracy. Furthermore, in order to automatically control the temperature to a set value, a very complicated method must be used.

An object of the present invention is to provide a carbon film vapor phase synthesis apparatus that can uniformly heat a substrate to a predetermined temperature and achieve optimal conditions for plasma generation.

Means for Solving the d0 Problem The problem of uniformly heating a substrate is a microwave oscillation circuit, a waveguide for propagating microwaves, a reaction vessel housed at the end of the waveguide, It is equipped with a gas supply pipe that sends a mixed gas of hydrocarbon and hydrogen to the reaction container, a gas exhaust pipe that exhausts gas from the reaction container, and a sample stage that places the substrate in the reaction container. In a carbon film vapor phase synthesis apparatus that excites gas by irradiating waves to generate plasma, and uses the plasma to form a carbon film on a substrate, the sample stage serves as a dielectric material that absorbs microwaves. 500 ~ by applying electricity at the same time as having properties
The problem was solved by a carbon film vapor phase synthesis device characterized by being made of a material that can be heated up to 1000°C and has properties as an electrical resistor.

The problem of maintaining the substrate at a predetermined temperature is to include a microwave oscillation circuit, a waveguide for propagating microwaves, a reaction vessel housed at the end of the waveguide, and a reaction vessel containing hydrocarbons and hydrogen. Equipped with a gas supply pipe for sending a mixed gas, a gas exhaust pipe for discharging gas from the reaction container, and a sample stage for placing a substrate in the reaction container, the gas in the reaction container is irradiated with microwaves to excite the gas. In a carbon film vapor phase synthesis apparatus that generates plasma and uses the plasma to form a carbon film on a substrate, the sample stage has properties as a dielectric material that absorbs microwaves, and at the same time its electrical resistance. This problem was solved by a carbon film vapor phase synthesis device that is characterized by being made of a material that changes with temperature.

e. Function The function will be explained by taking as an example a case where carbon silicon SiC is used as a sample stage in the vapor phase synthesis apparatus for carbon film according to the present invention.

SiC is known as a heating element, and generates heat when energized. Therefore, by selecting an appropriate current value depending on its shape, dimensions, etc., it can easily be heated to several 100 to 1000 degrees Celsius. The sample stage made of SiC also generates heat by absorbing microwave energy, so
Energy equivalent to the difference between the energy required to maintain a predetermined temperature and the absorbed energy from the microwave is supplied from a DC or AC power source.

FIG. 3 is a graph showing the relationship between electrical resistance and temperature of silicon carbide SiC. Note that the resistance values are shown using arbitrary coordinates that indicate only relative values.

By accurately calibrating the relationship between electrical resistance and temperature in advance, the sample stage can be heated to a predetermined temperature.

Furthermore, by applying negative feedback to the energy source so as to keep the resistance value constant, the temperature of the sample stage can be maintained at a predetermined temperature.

f. Embodiment FIG. 1 is a conceptual sectional view of a preferred embodiment of the carbon film vapor phase synthesis apparatus according to the present invention.

Microwaves generated by a microwave oscillator 1 are sent to a quartz reaction vessel 3 through a waveguide 2 whose end is expanded into a tapered shape. A substrate 4 is placed on a sample stage 5 inside the quartz reaction vessel 3 . On the other hand, a mixed gas of hydrocarbon CH4 and hydrogen H2 (mixing ratio of about 1:100) is sent into the reaction vessel 3 from the gas supply pipe 6, and the pressure inside the reaction vessel 3 is kept constant (for example, 1 Qtorr). The gas is exhausted from the exhaust pipe 7 (flow rate approximately 300 cc/+++in).

The microwave turns the supplied gas into plasma, and at the same time, the substrate 4. The sample stage 5 is heated by microwave.

The sample stage 5 is made of silicon carbide StC, and power is sent to the sample stage 5 itself from a power source 9. In other words, the sample stage 5
is heated by microwave heating and self-heating due to electric power from the power source 9. Temperature control is performed by adjusting the power supplied from the power source 9.

Since the electrical resistance of silicon carbide SiC has temperature dependence,
The voltage and current applied to the SiC sample stage 5 are detected in advance by the voltage detection means 10. The current is measured using the current detection means 11, and the relationship between these values and temperature is calibrated. Using this, the temperature can be determined from the voltage and current values during carbon film synthesis.

Specifically, when the microwave power is IKW, a voltage of about 50V is applied to a SiC sample stage with a diameter of 140φ and a thickness of 51m.
.

By supplying power with a current of about 21 A, the temperature of the silicon wafer, which is the substrate 4, could be brought to about 800°C.

Based on the temperature dependence of SiC's electrical resistance, it is also possible to use SiC only as a temperature detector without energizing the SiC sample stage, or to use the SiC sample stage only as a heating means and use other detection means to detect the temperature. It is also possible to measure using

FIG. 2 is a conceptual sectional view of another preferred embodiment of the carbon film vapor phase synthesis apparatus according to the present invention.

This embodiment is an improvement on the embodiment shown in FIG. 1 so that the temperature of the sample stage is maintained at a set value by negatively feeding back the temperature of the sample stage to the power supply. Components common to those in FIG. 1 are given the same reference numerals and explanations will be omitted.

The voltage applied to the sample stage 5 and the current flowing through the sample stage are detected by voltage detection means 10. Detected by the current detection means 11,
The conversion circuit 12 converts the signal into a signal corresponding to the electrical resistance of the sample stage 5.

In the temperature setting section 13, a resistance value corresponding to the temperature to be set on the sample stage 5 is set, and in the comparison section 14, the output of the conversion circuit 12 and the output of the temperature setting section 13 are compared.

The output of the comparison section 14 is sent to the power control section 15, and the power sent from the power source 9 to the sample stage 5 is controlled by the output of the power control section 15.

The electrical resistance of a SiC plate changes depending on both microwave absorption and applied power, but the temperature has a constant relationship with the resistance value, so regardless of the magnitude of the microwave power, the applied power can be controlled to any desired value. By setting the resistance value to , it is possible to accurately set the temperature of the sample stage 5 even when the sample stage 5 is irradiated with microwaves. That is, the plasma energy and the temperature of the sample stage 5 can be controlled independently.

Using the carbon film vapor phase synthesis apparatus according to the present invention, silicon S
By holding the substrate 4 made of an i-wafer at about 800° C. for 3 hours, it was possible to synthesize a diamond-like carbon film with good crystallinity and a thickness of about 1 μm.

g0 Effects of the invention i) In addition to heating the sample stage by microwave absorption, it is possible to generate heat by directly supplying power to the sample stage from the power supply. At this time, since there is no need to separately provide a heater or the like which is a source of gas contamination, the structure is simple and gas contamination is reduced.

ii) Temperature can be measured directly electrically without using optical means. As a result, the accuracy of temperature measurement is improved and automatic temperature control is facilitated.

[Brief explanation of the drawing]

FIG. 1 is a conceptual sectional view of a preferred embodiment of the carbon film vapor phase synthesis apparatus according to the present invention, and FIG. 2 is a conceptual sectional view of another preferred embodiment of the carbon film vapor phase synthesis apparatus according to the present invention. FIG. 3 is a graph showing the relationship between electrical resistance and temperature of silicon carbide (SiC), and FIG. 4 is a conceptual diagram of a conventional vapor phase synthesis apparatus for a carbon film. 1... Microwave oscillator, 2... Waveguide, 3...
Reaction container, 4...Substrate, 5...Sample stand,
6... Gas supply pipe, 7... Exhaust pipe,
9...Power supply, 10...Voltage detection means, 1
1... Current detection means, 12... Conversion circuit,
13... Temperature setting section, 14... Comparison section,
15...Power control unit.

Claims (4)

[Claims] (1) A microwave oscillation circuit, a waveguide for propagating microwaves, a reaction vessel housed at the end of the waveguide, and a gas supply pipe for sending a mixed gas of hydrocarbon and hydrogen to the reaction vessel; Equipped with a gas exhaust pipe for discharging gas from the reaction vessel and a sample stage for placing a substrate in the reaction vessel, the gas in the reaction vessel is irradiated with microwaves to excite the gas and generate plasma. In a carbon film vapor phase synthesis apparatus that forms a carbon film on a substrate using A vapor phase synthesis device for a carbon film, characterized in that it is made of a material having properties as a resistor. (2) The carbon film vapor phase synthesis apparatus according to claim 1, wherein the material of the sample stage is silicon carbide (SiC). (3) a microwave oscillation circuit, a waveguide for propagating microwaves, a reaction vessel housed at the end of the waveguide, and a gas supply pipe for sending a mixed gas of hydrocarbon and hydrogen to the reaction vessel; Equipped with a gas exhaust pipe for discharging gas from the reaction vessel and a sample stage for placing a substrate in the reaction vessel, the gas in the reaction vessel is irradiated with microwaves to excite the gas and generate plasma. In a carbon film vapor phase synthesis apparatus that forms a carbon film on a substrate using A carbon film vapor phase synthesis device featuring: (4) The carbon film vapor phase synthesis apparatus according to claim 3, wherein the material of the sample stage is silicon carbide (SiC).