JPH0448928A - Microwave plasma surface treatment method and apparatus - Google Patents

Abstract

PURPOSE:To magnify a plasma forming region while forming electromagnetic field distribution of a higher mode in the vicinity of a reactor by using a plurality of antennae in order to introduce a microwave into the vicinity of the reactor. CONSTITUTION:A circular reactor 10 is arranged in a circular waveguide. Four antennae 30a - 30d are arranged within the reactor 10 at a position capable of generating plasma P. These antennae 30a - 30d are made of brass and has a columnar rod shape and are arranged at the positions corresponding to the corner parts of a square shown by (a) - (d) in Fig 2. A treatment condition is set and, by supplying a microwave to four antennae 30a - 30d from a microwave supply system, the plasma P can be generated in the reactor 10 and predetermined surface treatment can be applied to the substrate placed on the substrate holder 12 in the reactor 10.

Description

[Detailed description of the invention] [Industrial application field]

The present invention is suitable for diamond film synthesis, semiconductor device manufacturing, etc., which supplies microwaves through an antenna and generates large-sized plasma in a reaction vessel, making it possible to process large-area objects. The present invention relates to a microwave plasma surface treatment method and apparatus.

[Prior Art 1] As a conventional microwave plasma CVD apparatus, the main part of which is shown in FIG. 9 is often used. In this apparatus, a substrate (workpiece) S is placed on a substrate holder 12 installed in a reaction vessel 10, raw material gas is introduced in the direction of the arrow, and a rectangular waveguide 14 is inserted into the reaction vessel 10. A microwave is supplied from the substrate S to generate a substantially spherical plasma P.
Surface treatment such as diamond film deposition is performed on the surface. However, in a device that directly supplies microwaves to the reaction vessel 10 as shown in FIG. 9 above, the normal frequency is 2.
As long as a microwave of 45 GH2 is used, the diameter of the generated plasma P is limited to half the tube wavelength, that is, about 6011 mm. Furthermore, as a microwave plasma CVD apparatus, an antenna type microwave plasma CVD apparatus having the configuration shown in FIGS. 10 and 11 is known. In the apparatus shown in FIG. 10, a reaction vessel 10 containing a substrate holder 12 is installed in a circular waveguide f16 having a rectangular waveguide 14 at the upper end with a 1':f cross section, and the rectangular waveguide 14
An antenna 18 is attached above the reaction vessel 10. Further, the reaction vessel 10 is provided with an inlet 20 for raw material gas and an outlet 22 for excess gas, a plunger 24 is provided at the right end of the rectangular waveguide 14, and a plunger 24 is provided at the right end of the rectangular waveguide 14, and a length of the antenna 18 is provided above the plunger 24. An antenna length variable section 18A is provided for adjusting the antenna length. The device shown in Section 11 also includes a microwave oscillator (magnetron) 26 connected to one end of the rectangular waveguide 14.
The basic configuration is substantially the same as that shown in FIG. 10 above, except for the fact that . In both of the microwave plasma CVD apparatuses shown in FIGS. 10 and 11, the inside of the rectangular waveguide 14 is T E +
Microwaves transmitted in the o mode are guided to the circular waveguide 16 by one antenna 18, converted to the TMo+ mode, and discharge plasma P is generated in the reaction vessel IO. These conventional antenna-type microwave plasma CVD apparatuses can expand the generated plasma P to some extent by using the T Mo + mode propagation mode. Note that the TMo+ mode has an electromagnetic field distribution shown in FIG. 12(A). The upper row shows the cross section, and the lower row shows the cross section taken along line 12-1, where the solid line shows the electric field and the broken line shows the magnetic field. [Problem to be solved by the invention U] However, in the above antenna type device, for example,
Surface treatment of the entire surface at once (Vi, M synthesis, etching, etc.) of disk-shaped substrates such as inch (approx. 150 In)
Therefore, there was a problem in that large substrates could not be processed and productivity could not be improved. The present invention has been made in order to solve the above-mentioned problem of the conventional method, and is a microwave plasma surface treatment method and apparatus capable of generating large-sized plasma and efficiently performing uniform surface treatment over a large area. The challenge is to provide the following.

[Means to achieve section mastery]

The present invention provides a microwave plasma surface treatment method in which plasma is formed by propagating microwaves into a reaction vessel via an antenna, in which a plurality of independent antennas are installed,
The above requirements are achieved by supplying microwaves to each of the antennas. The present invention also provides a microwave plasma surface treatment apparatus for forming plasma by propagating microwaves into a reaction container via an antenna, in which a plurality of independent antenna and 1
The microwave oscillation means described above, and a phase control means for controlling the phase of the microwaves supplied from the microwave oscillation means to the plurality of antennas, the microwave oscillated from at least one microwave oscillation means as described above. The above-mentioned problem is similarly achieved by making it possible to independently control and supply the phase to the antennas on each side using the phase control means.

[Operations and Effects 1] In the present invention, since multiple antennas are used to introduce microwaves into the vicinity of the reaction vessel, it is possible to form a higher-order mode electromagnetic field distribution in the vicinity of the reaction vessel, thereby forming a plasma. It becomes possible to expand the ftJ¥ range. As a result, it is possible to perform surface treatment even on objects with large surface areas, and it is possible to improve productivity.
As a result, cost reduction becomes possible. [Examples] Examples of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram showing the main parts of a microwave plasma CVD apparatus which is an embodiment of the present invention. The apparatus of this embodiment has a circular waveguide (not shown) similar to the apparatus shown in FIG. 10, and a circular reaction vessel 10 is installed within the circular waveguide. The apparatus also includes four antennas 308 to 308 at positions where plasma P can be generated within the reaction vessel 10.
30d is arranged. This antenna 308~30d
are made of yellow 8 and have a cylindrical rod shape, and are arranged at positions corresponding to the corners of the square shown by a to d in FIG. Microwaves are supplied to the antenna 30 via transmission lines 34 from four coaxial converters 32 included in the microwave supply system shown in FIG. 3, respectively. The microwave supply system includes a microwave oscillation means 42 each consisting of one microwave oscillator 38 and a distributor 40 connected via a rectangular waveguide 36; It is composed of one variable phase shifter (phase control means) 44 and four coaxial converters 32 connected to each of the variable phase shifters 44. Further, for example, a matching element is inserted into the transmission line 34 for matching with the circular waveguide, thereby making it compatible with the dimensions of the antenna. Next, the operation of this embodiment will be explained. In the above apparatus, plasma P can be generated in the reaction vessel 10 by adjusting processing conditions and supplying microwaves from the microwave supply system to each of the four antennas 30a to 30d. A predetermined surface treatment can be performed on a substrate (not shown) placed on the substrate holder 12 in the reaction vessel 10. The device of this embodiment has the above four antennas 308 to 30d.
It is possible to independently supply microwaves of any phase to each of the two, and therefore it is possible to form electromagnetic field distributions of various modes. For example, by supplying microwaves with the same output and the same phase to each of the above antennas, the electromagnetic field distribution of the 12th [T M 21 mode shown in J(C)] is created in the circular waveguide and the reaction vessel. can be formed, so that T M formed in the case of said conventional device using one antenna
Compared to the o + mode, the plasma formation area can be expanded. Furthermore, plasma of uniform intensity can be generated over the entire area. This means that four plasma regions formed by one antenna are connected to one reaction vessel.
This is because the four plasma regions are evenly distributed within 0, and the four plasma regions are combined at the center, making it possible to form plasma with uniform intensity in the radial direction from the center. Next, an example of diamond synthesis carried out using the apparatus of this embodiment will be specifically explained. In the device used, the distance Mid from the center to each antenna shown in FIG. 2 is 3511, and all antennas 30a
7M2 by supplying microwaves with the same phase to ~30d
A one-mode electric field distribution was formed. A 5-inch silicon wafer was used as the substrate, and a diamond thin film was formed on its diamond-polished (100) surface. Methane CH4 was used as the raw material gas, and a mixed gas with a volume ratio of 1:100 with hydrogen gas H2 was mixed at a flow rate of 6005 cc.
l into the reaction vessel lO from the inlet, and the total pressure was raised to 20
It was set to torr. Also, the substrate temperature is 850℃, the microwave frequency is 2.45GH6, and the microwave power is 1.5
Kw. Under these conditions, diamond thin film synthesis was carried out for about 10 hours, and the film formation rate was 1.2μi/hr.
A diamond polycrystalline film having a film thickness distribution as shown in FIG. 4 was obtained. On the other hand, for comparison, a device basically the same as this embodiment (corresponding to the device shown in FIG. 10) was used, except that one antenna 18 as shown in FIG. 5 was anchored. FIG. 6 shows the film thickness distribution when a diamond thin film was synthesized under the same conditions. Comparing the above-mentioned 4I21 with FIG. 6, the difference Δt between the film thickness at a position 50 inches from the center of the substrate and the film thickness to at the thickest part is larger in this embodiment than in the conventional example (FIG. 6). In the example, Δt/1i=10%, which is reduced to 17'3 compared to 30% in the conventional example, and it can be seen that the uniformity is increased. Further, the region in which a film thickness of Δt/llm=30% or less can be obtained is wider in this example, indicating that large-area film formation is possible. Next, using the device of this embodiment, four antennas 308 to
For 30d, diamond synthesis was performed in the same way by shifting the phase of the microwaves supplied to 30a and 30b and the microwaves supplied to 30c and 30d by 180 degrees. As a result, compared to the case of the above-mentioned synthesis example in which microwaves of the same phase were supplied to the antennas 30a to 30d, it became possible to form a stronger electromagnetic field, and although the uniformity decreased somewhat, the plasma intensity increased. , the deposition rate is 1.2@
Became. As described above, the device of this embodiment has the advantage of being able to control and supply microwaves with different phases to the antenna 30#, forming electromagnetic fields in various modes, and generating plasma. There is also. Next, another example of a microwave supply system applicable to the apparatus of this embodiment will be shown. In addition to the system shown in FIG. 3, examples of the case where the oscillator is a leather include the system shown in the perspective view of FIG. The system shown in the block diagram can be mentioned. In addition, in the figure, two points I! The part surrounded by is the microwave oscillation means 42 of the present invention. In the former (FIG. 7(A)), a coaxial converter mH4b is connected to one oscillator 38 via a rectangular waveguide 36, and four variable phase FIs 44 each connect a coaxial cable 48 to the converter 46. They are connected via In this system, microwaves from an oscillator 38 are transmitted through a rectangular waveguide 36.
The microwave is propagated in a 1M22 mode, divided into four parts by a coaxial converter 46, and supplied to a variable phase shifter 44, and then transmitted from each phase shifter 44 to the antennas 30a to 30d via a coaxial cable 48. Microwaves can be supplied to each of them independently. The latter (FIG. 7(B)) has basically the same configuration as the former except that a distributor 5o is interposed between the coaxial converter 46 and the variable phase shifter 44. Further, as an example equipped with four fli generators, the one shown in FIG. 8 can be mentioned. In the system shown in FIG. 8(A), a variable phase shifter 44 is connected to each oscillator 38, and a coaxial converter 32 is connected to each of the phase shifters 4. 32 supplies microwaves to each antenna 30. The system shown in FIG. 8(B) consists of the configuration shown in FIG. When microwaves are supplied to each antenna 30, there are advantages such as being able to supply stable and large output to each antenna 30 and easily controlling the phase of the microwave supplied to each antenna 3o. Although the present invention has been specifically described, the present invention is not limited to that shown in the above embodiment.For example, in the above embodiment, the antenna is made of brass and has a cylindrical shape, but the present invention is not limited to this. The material may be a good conductor, and it is even better if the material does not cause a decrease in conductivity due to surface oxidation or corrosion.The material may also have a variety of shapes, such as an elliptical cross-sectional shape, a sector shape, a vibrator shape, etc. In addition, when surface treating a substrate, it can be performed while rotating the substrate.Also, magnets may be placed around the circular waveguide so as to satisfy the conditions for electron cyclotron resonance. The number of antennas is not limited to four, but can be any number as long as there are a few.For example, using two antennas, the TM++ mode shown in FIG. It is also possible to form an electromagnetic field distribution.Furthermore, as a method of propagating microwaves to multiple antennas, it is also possible to propagate microwaves using a rectangular waveguide rather than a single oscillator. It may also be performed via a rectangular waveguide or a coaxial cable.Furthermore, although only CVD has been described in the embodiment, the present invention can also be applied to plasma etching and the like.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing the main parts of a microwave plasma CVD apparatus according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the arrangement of an antenna installed in the apparatus, and FIG. , a block diagram showing the microwave supply system of the above device, FIG. 4 is a diagram showing the film thickness distribution of diamond synthesized by the above device, and FIG. 5 shows the main parts of the conventional microwave plasma CVD device. , a diagram corresponding to FIG. 1 above, FIG. 6 is a diagram showing the diamond film thickness distribution synthesized by the above-mentioned conventional apparatus, FIGS. 7 and 8 are block diagrams showing modified examples of the microwave supply system, Figure 9 is a schematic explanatory diagram showing the main parts of a conventional microwave plasma CVD apparatus. 10 and @11 are schematic configuration diagrams showing a conventional antenna type microwave plasma CVD apparatus, and FIG. 12 is an explanatory diagram showing modes of electromagnetic field distribution. DESCRIPTION OF SYMBOLS 10... Reaction container, 12... Substrate holder, 14... Rectangular waveguide, 16... Circular waveguide, 18.30... Antenna, 26.38... Oscillator, P. ...Plasma, S...Substrate.

Claims (2)

[Claims] (1) In a microwave plasma surface treatment method in which plasma is formed by propagating microwaves into a reaction vessel via an antenna, a plurality of independent antennas are installed and microwaves are supplied to each of the antennas. Characteristic microwave plasma surface treatment method. (2) In a microwave plasma surface treatment device that forms plasma by propagating microwaves into a reaction vessel via an antenna, a plurality of independent antennas installed at positions where microwaves can be propagated within the reaction vessel; comprising one or more microwave oscillation means, and a phase control means for controlling the phase of microwaves supplied from the microwave oscillation means to the plurality of antennas, the microwave oscillated from the at least one microwave oscillation means; A microwave plasma surface treatment apparatus characterized in that the phase control means can independently control and supply a phase to each of the antennas.