JPH01201099A - Removal of useless material - Google Patents

Abstract

PURPOSE:To prevent the damage of the inner wall of a reaction furnace or a substrate holder and to improve the mass-production efficiency, by forming a material composed mainly of carbon on a substrate under specific condition using a plasma CVD apparatus, taking the formed material out of the apparatus, introducing O2 or O2+H2 gas into the apparatus and etching useless material by the application of high-frequency wave or microwave. CONSTITUTION:A substrate 10 is supported on a substrate holder 10' in a plasma generation space 1 maintained in evacuated state in a plasma CVD apparatus. The substrate 10 is made to be heatable with an infrared heater 20, a parabolic reflector 21, etc. A microwave electric field and an external magnetic field can be applied to the substrate by a microwave generator 4 and electromagnets 5, 5'. A gas produced by mixing H2 6 with CH4 7, etc., is introduced into a high-density plasma generation region 2 and imposed with microwave electric field and external magnetic field to generate a high-density carbon plasma in the plasma generation space 1. The pressure in the space 1 is increased to increase the hydrogen radical concentration per unit volume and form a material composed mainly of carbon on the substrate 10. The substrate having deposited carbon material is taken out of the space, O2 gas or a mixture of O2 and H2 gas is introduced into the space 1 and microwave electric field and magnetic field are applied to effect the etching of the useless material.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention applies a microwave electric field and an external magnetic field, and uses their interaction to form a plasma that forms carbon or an object mainly composed of carbon. The present invention relates to a method of increasing the efficiency of mass production of a reaction apparatus by cleaning the inner wall by etching unnecessary substances attached to the inner wall of the apparatus with oxygen, hydrogen, or an oxygen compound during the production of such objects.

[Prior Art] Conventionally, ECR (Electron Cyclotron Resonance) is used as a thin film etching means under low pressure conditions of 10"3 to 10-5 Torr, which is low enough for electrons to make at least one revolution for cyclotron resonance. Activated species are created by pressure, and the divergent magnetic field is used to place a substrate "at a distance" from this resonant space, where a halogen element such as fluoride gas or chloride gas is used to form a coating, especially an amorphous structure. Methods are known for etching coatings that contain.

[Conventional Problems] However, in such an etching method using a reactive gas of a halogen element, a fluoride or a chloride is used as the etching gas. As a result, the equipment deteriorates and
In particular, the exhaust oil deteriorated.

Therefore, after forming a film on a substrate of carbon or carbon-based material without using such fluoride gas or chloride gas, this substrate is removed and the film is then deposited on the inner wall of this plasma CVD apparatus. There has been a need for a method for removing unnecessary materials without damaging the inner walls of such devices due to corrosion or the like.

(Means to Solve the Problem) The present invention satisfies such needs, and in particular,
D. Remove deposits mainly composed of carbon that are inadvertently attached to the inner walls of the device and onto the substrate holder with a gas that does not deteriorate the device at all, that is, oxygen or oxide gas (NO, N, etc.).
O2, N20. Etching is performed using O20, etc.). For this purpose, the ECI? By changing the strength of this magnetic field, the position where the active state of oxygen persists at or near 875 Gauss (in the case of a microwave frequency of 2.45 GII2) is determined, and this strong plasma is generated. The surface is moved across the entire inner wall to remove unnecessary carbon (anything containing carbon as a main component will hereinafter be simply referred to as carbon) on the inner wall of the device and the substrate holder.

That is, first, the process of producing carbon using this plasma CVD apparatus will be described.

A substrate having a surface to be formed is inserted into the apparatus.

This substrate is held under vacuum and heated to 600-1000°C, for example 850°C. Furthermore, hydrogen is introduced here and the pressure in the space is gradually increased to 1 x 10" to 3 x 10"tor.
Further, a hydrocarbon gas such as methane, ethylene, or acetylene is mixed with hydrogen at a concentration of 0.1 to 5x, for example, methane/hydrogen = 1.5x. Then add microwaves and a magnetic field. Then, the concentration of active hydrogen in this space can be increased to about 102 to 10' compared to the conventional ECRCVD method. Then, only at such high pressure can the concentration of active hydrogen become extremely high, so that the amorphous structure can be etched away and carbon mainly having a diamond structure can be produced. Thereafter, the microwave introduction is stopped, the magnetic field is removed, and the inside of the reactor is brought to atmospheric pressure by the atmosphere. After cooling, the substrate on which i-carbon (a mixture of diamond grains and amorphous) or carbon whose main component is diamond grains is formed is removed, and the substrate holder is placed in the reactor again. Furthermore, the whole is evacuated and oxygen (0□) is introduced. The pressure inside this reactor is set to 0.1 to 10 torr, and microwaves and a magnetic field are applied to produce active oxygen. When carbon is formed on the substrate on the inner wall of the plasma warping furnace, at the same time, unnecessary carbon that has been formed unintentionally is removed by etching.

That is, the present invention adds the force of a magnetic field to the conventionally known plasma CVD method using microwaves, and the interaction between the electric field of the microwave and the magnetic field, preferably ECI? (electron cyclotron resonance) conditions or Whistler resonance conditions to form carbon. Furthermore, the present invention etches and removes unnecessary materials in the reactor using microwaves and magnetic fields used in the formation of carbon.

In addition, in the configuration of the present invention, after high-density plasma is generated by the interaction between microwaves and a magnetic field, high-energy light (for example, ultraviolet light) is irradiated on the way to the substrate surface to impart energy to the active species. If we continue to apply the
Etching hydrogen excited to a high energy state exists even at a distance of ~50 cm, making it possible to etch amorphous or diamond-structured particles or carbon in a film over a larger area.

Examples will be shown below to further explain the present invention.

〔Example〕

FIG. 1 shows a microwave plasma device capable of applying a magnetic field used in the present invention.

In the figure, this device includes a plasma generation space (1) that can be maintained in a reduced pressure state, a heating space (3), an auxiliary space (2),
Electromagnet (5), (5") that generates a magnetic field and its power source (25), microwave oscillator (4), turbo molecular pump (8) that constitutes the exhaust system, rotary pump (14)
, pressure adjustment pulp (11), infrared heater (20)
, and its power source (23), infrared reflective surface (21), substrate holder (10'), substrate (10), microwave introduction window (15), gas introduction system (6L (7), water cooling system (18)
), (18”).

First, the substrate (10) is placed on the holder (10'). This holder has high thermal conductivity and was made of ceramic aluminum nitride to minimize disturbance of microwave and magnetic fields. Place this substrate holder on an infrared heater (2
0), the parabolic reflecting surface (21) and lens system (22) are used to condense and heat the light. (e.g. 800°C) then hydrogen (6)
100 SCCM and 1.5 SCCM of methane are mixed in and passed through the gas system (7) to the high-density plasma generation area (2).
A microwave with a frequency of 2.45 GIlz is applied at an intensity of 500 W from the outside. Furthermore, a magnetic field of about 2 Gauss is applied from the magnets (5) and (5') to generate high-density carbon plasma in the plasma generation space (1).

And the pressure in the space maintains the plasma state while I
10-' to 3 X 10"torr, preferably 3 to
The pressure can be changed to 300 tOrr, for example, 10 torr.

By increasing the pressure in this space, the concentration of hydrogen radicals per unit space can be increased (and the growth rate of carbon, especially crystallized carbon, that is, diamond) can be increased.

Next, the cooling of the substrate and the introduction of microwaves and magnetic fields are stopped, and the substrate on which carbon has been formed is taken out. Furthermore, the substrate holder was introduced into this reactor again, and the whole was
Oxygen is introduced while heating to ~1000°C. 0 more
．． After setting the pressure to 1 to 10 torr, microwaves and a magnetic field are applied in the same manner as during film formation.

As a result, it was possible to remove the carbon that was inadvertently formed on the inner wall of the reactor during carbon formation.

In Figure 1, the magnetic field is connected to two ring-shaped magnets (5).
, (5') was adopted. Furthermore, FIG. 2 shows the results of examining the strength of the electric and magnetic fields for the space (30) divided into four parts.

In FIG. 2 (A), the horizontal axis (X-axis) is the horizontal direction of the space (20) (reactive gas release direction), and the vertical axis (R-axis)
indicates the diameter direction of the magnet. The curves in the drawings indicate equipotential surfaces of the magnetic field. The number shown on the line indicates the strength of the magnetic field obtained when the magnet (5) is approximately 2000 Gauss. By adjusting the strength of the magnet (5), the strength of the magnetic field is made approximately uniform over a large area of the formation surface of the substrate in the space (100) (875 ± 185 Gauss) where the electrode-magnetic field interacts. be able to. The drawing shows an isomagnetic scene, in particular the isomagnetic scene that gives rise to the resonance condition where the line (26) is 875 Gauss.

Furthermore, the space (100) that produces this resonance condition is shown in Figure 2 (
As shown in B), the area is set to have the maximum electric field. The horizontal axis in Figure 2 (B) indicates the flow direction of the reactive gas as in Figure 2 (A), and the vertical axis indicates the electric field (field strength).
Shows the strength of

Then, in addition to the electric field region (100), the region (100'') also corresponds to the region where the maximum occurs.However, the magnetic field corresponding to this region (FIG. 2 (A)) has many isomagnetic fields. That is, in the region (100'), there is a large variation in film thickness in the diametrical direction (vertical axis direction in FIG. 2 (8)) of the surface on which the substrate is formed, and the ECR that satisfies the resonance condition of (26'')
Only certain coatings can be etched quickly under certain conditions.

When the microwave output was 500H, the etching rate was 0.3 μ/min. However, when this output was set to 1.2 KW, the etching speed could be increased approximately three times. Also, the etching pressure is Q, 30 from l torr.
If the pressure is higher than 30 torr, the etching rate can be increased.However, it has been experimentally shown that if the pressure is increased to 30 torr or higher, it is difficult to maintain a plasma state continuously, making it difficult to use in practice.

Furthermore, there is a region on the opposite side of the region (100) symmetrical to the origin, where the electric field is maximum and the magnetic field is constant over a wide region. Etching in such a space is effective when there is no need to heat the substrate. However, it is difficult to find a way to perform heating without disturbing the microwave electric field.

As a result, in order to perform uniform etching, the second [ff
It is estimated that the region 1(A) (100) is the position with the highest industrial productivity among the three regions.

FIG. 3 is a diagram of equal magnetic fields and equal electric fields of the magnetic field (A) and electric field (B) in a circular space at the position of the substrate (10) in FIG. 2. FIG. As is clear from FIG. 3(B), it can be seen that the electric field can reach a maximum of 25 KV/m.

(Effects) In the present invention, etching uses an oxide gas instead of a halide gas such as fluoride or chloride, so that the inner wall of the reactor, the substrate holder, etc. are not damaged at all. The carbon that has been created in areas other than the formation surface is reacted with oxygen to become carbon dioxide,
It is gasified and removed. As a result, it is possible to eliminate the need for wet etching of the hard carbon inner wall of the reactor every time a film is formed.

[Brief explanation of the drawing]

FIG. 1 schematically shows a microwave CVD apparatus using magnetic field/electric field interaction used in the present invention. FIG. 2 shows the magnetic field and electric field characteristics by computer simulation. Figure 3 shows the characteristics of the magnetic field and electric field at a position where the electric field and magnetic field interact. 1... Plasma generation space 10, 10'... Substrate and substrate holder 4... Microwave oscillator 5.5''... External magnetic field generator 20... Substrate heating heater 100... Maximum Space that becomes an electric field

Claims (1)

[Claims] 1. Using a carbon production device that uses high frequency or microwaves, a product gas consisting of a carbon material gas containing hydrogen is introduced under reduced pressure to deposit an object mainly composed of carbon on a substrate. a step of generating diamond or i-carbon on the surface to be formed by a plasma vapor phase method, a step of taking out the substrate having the surface on which the diamond or i-carbon is formed, and then adding oxygen or oxygen and hydrogen into the carbon production apparatus. An unnecessary carbon substance in a carbon manufacturing apparatus, characterized in that diamond or i-carbon deposited on unnecessary parts in the apparatus is etched and removed by introducing a mixture gas and applying high frequency or microwaves. How to remove. 2. In claim 1, the carbon waste in a carbon manufacturing apparatus is characterized in that the mixture gas is made of oxygen and argon, is turned into plasma, reacts with carbon, and is removed by etching as carbon oxide. How to remove. 3. In claim 1, 0.1 to 300t
1. A method for removing unnecessary carbon materials in a carbon production device, the method comprising performing etching under a pressure of 0.05 to 10.0 m.