CN110913556A

CN110913556A - Microwave plasma reaction device

Info

Publication number: CN110913556A
Application number: CN201811084569.5A
Authority: CN
Inventors: 刘艳青; 丁明辉; 王闯; 常秀英; 苏静杰; 段路明
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2018-09-18
Filing date: 2018-09-18
Publication date: 2020-03-24

Abstract

The invention relates to a microwave plasma reaction device, comprising: a reaction chamber, the bottom of which is provided with an opening for transmitting microwave; the coaxial waveguide is connected with the bottom opening of the reaction cavity and used for conveying microwaves into the reaction cavity; the circumferential antenna is used for conveying microwaves into the reaction cavity, a concave part is arranged on the upper surface of the circumferential antenna to better focus the microwaves, and the bottom surface of the concave part is simultaneously used as a base station; the base material is positioned above the base station; the antenna part is combined with the reaction cavity to clamp the dielectric window, and the dielectric window is completely isolated from the plasma, so that the dielectric window is protected from being etched by the plasma; the upper part of the reaction chamber is provided with a microwave reflecting plate with adjustable height for optimizing the distribution of plasma inside the reaction chamber; the device has simple structure and convenient adjustment, and is suitable for deposition of high-quality diamond material.

Description

Microwave plasma reaction device

Technical Field

The invention relates to a microwave plasma reaction device which can be used for synthesizing carbon materials such as diamond films, diamond-like films and graphene, and is particularly suitable for synthesizing high-quality diamond materials.

Background

The microwave plasma is a plasma formed by ionizing a precursor gas by using microwave energy, has no electrode discharge pollution, and has continuously controllable plasma density. And are therefore widely used, especially for Chemical Vapour Deposition (CVD) of diamond material and the like.

During deposition of diamond material, high power and pressure can produce high plasma density, and increasing plasma density is considered to be an effective means to increase deposition rate and deposition quality. However, under such conditions, the high density plasma may affect the microwave plasma reactor, and thus the quality of the synthesized material.

Over the past several decades, numerous microwave plasma devices have been invented. Earlier, US patent US 4866346a was seen. In this apparatus, a probe antenna is used to deliver microwaves, the reaction chamber is cylindrical in shape, and a quartz bell jar is used to maintain a vacuum. In this case, the plasma is directly confined by the quartz bell jar, inevitably etching the quartz material, whereby the released silicon element causes degradation of the diamond material.

In US 5954882a, the probe antenna is likewise used for microwave transmission, but the cavity is arranged in an ellipsoid shape. The device utilizes the characteristics of two focuses of an ellipsoid to design the probe antenna at the upper focus, and the vacuum chamber is arranged at the lower focus. The design is beneficial to microwave focusing, and simultaneously, the input power can be improved to some extent due to the fact that a larger quartz bell jar is used for restraining vacuum. However, since the plasma is still directly restricted by the quartz bell jar, the improvement of the input power is limited, and the etching of the quartz material is inevitable after the quartz bell jar runs for a long time with high power. Therefore, when the probe antenna is used for coupling, the plasma is directly restricted by the quartz window, and the high-power and long-time operation is difficult.

In order to solve the problem of etching the quartz material by plasma, a circumferential antenna coupling is adopted in the U.S. Pat. No. 8, 5501740a, in which a quartz ring is used as a dielectric window and hidden under the circumferential antenna, thereby avoiding the etching of plasma. However, in the device, the vacuum chamber has an irregular shape and a relatively fixed chamber height, so that the plasma and the like are difficult to regulate in real time in the deposition process, and the problem of overhigh microwave reflection power can occur in high-power operation.

Chinese patent CN 101864560a also proposes a device related to a circumferential antenna, which mainly consists of a cylinder, has a simple structure, and has an adjustable microwave reflector. However, in this device, the microwave reflector is too far into the cavity, carbon-containing compounds are deposited on the surface of the reflector under high power, and the carbon-containing compounds fall onto the surface of the substrate when the deposition time is too long, so that the synthesis of the diamond material is interrupted.

Aiming at various problems of the device, a device with more perfect structure and performance needs to be designed to meet the preparation of high-quality diamond materials.

Disclosure of Invention

The invention aims to solve the problem existing in the existing Microwave Plasma Chemical Vapor Deposition (MPCVD) device, namely, when the plasma density is increased, the plasma can not etch a medium window; the adjustable microwave reflecting plate is arranged, and carbon impurities such as graphite and the like cannot be deposited on the reflecting plate; the invention aims to provide a microwave plasma reaction device capable of depositing diamond material with high power for a long time, which can be used for synthesizing high-quality diamond material so as to solve the problems in the background technology.

In order to solve the problems, the invention uses the annular dielectric window, and completely isolates the window from the plasma, thereby avoiding the window from being etched by the high-density plasma; the appearance of the cavity is changed, the position of the microwave reflector in the reaction cavity is improved, and carbon impurities such as graphite and the like deposited on the end face of the reflecting plate can be avoided.

The invention is realized by the following technical scheme:

the invention relates to a microwave plasma reaction device, comprising:

a reaction chamber having an opening at the bottom for transmitting microwaves;

a coaxial waveguide for transmitting the microwave to the opening of the reaction chamber;

the circumferential antenna is used for conveying microwaves into the reaction cavity, and simultaneously used as a base station for supporting the base material in the reaction cavity;

the dielectric window is used for isolating the reaction cavity from the outside and guiding the microwaves into the reaction cavity, and the dielectric window is clamped between the inner surface of the reaction cavity and the circumferential antenna and is shielded by the circumferential antenna;

the microwave reflecting plate is used for optimizing the distribution of the plasma in the reaction cavity;

the end surface of the circumferential antenna facing the reaction chamber forms a concave part.

Preferably, the reaction chamber, the circumferential antenna, the coaxial waveguide and the microwave reflector are all made of metal, and direct water cooling can be realized.

Preferably, there is a recess in the end face of the circumferential antenna facing the vacuum chamber.

Preferably, the recess may be cylindrical or frustoconical.

Preferably, the dielectric window is isolated from the plasma, so that the window is prevented from being etched by the plasma, the purity of the interior of the plasma cavity is kept, and the synthesis of the high-quality diamond material is facilitated.

Preferably, the microwave plasma reaction device is provided with an adjusting mechanism with a large adjustable stroke, so that the device can adapt to diamond material synthesis under various process conditions, and is particularly suitable for high-power processes.

Preferably, the upper and lower chamber walls and the microwave reflector in the microwave plasma reaction device are far away from the central position of the substrate, and particularly, the distance is not less than 3/4 input microwave wavelength, so that the heat radiation of the chamber and the formation of carbon impurities such as graphite by plasma are effectively avoided.

Drawings

FIG. 1 is a schematic view of a first structure of a microwave plasma reactor according to the present invention;

FIG. 2 is a schematic diagram of a second structure of the microwave plasma reactor according to the present invention;

FIGS. 3a-3b are schematic views of a concave portion of a microwave plasma reactor according to the present invention.

The reference numbers in the figures are:

17,27 a reaction chamber; 4,5 coaxial waveguides; 6,26 circumferential antennas; 7 a base material; 8, an observation window; 9 a microwave reflector; 10 microwave reflector adjusting device; 11 an air inlet duct; 12 air outlet; 13 plasma body; 14 temperature measuring holes; 15 a dielectric window; 16, microwave; 18 circumferential antenna recess

Detailed Description

In order to make the implementation objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be described in more detail below with reference to the accompanying drawings in the embodiments of the present invention. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are only some, but not all embodiments of the invention. The embodiments and the directional terms described below with reference to the drawings are exemplary and intended to be used in the explanation of the invention, and should not be construed as limiting the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. The device of the invention will be further explained with reference to the drawings and the specific embodiments

As shown in fig. 1 and 2, the microwave plasma device of the present invention has

reaction chambers

17,27, and the

reaction chambers

17,27 are made of metal, preferably stainless steel. The

reaction chambers

17,27 are open at the bottom and connected to coaxial waveguides 4,5, from which microwaves 16 are fed into the

reaction chambers

17, 27. The

circumference antenna

6,26 is located at the lower part of the

reaction chamber

17,27, and is used for conveying the microwave 16 into the

reaction chamber

17,27, a dielectric window 15 is clamped between the

circumference antenna

6,26 and the

reaction chamber

17,27, the material of the dielectric window 15 can be a low microwave loss dielectric material such as sapphire or quartz glass, and preferably a quartz material; o-rings are arranged between the dielectric window 15 and the

circumferential antennas

6 and 26 and the inner surfaces of the

reaction cavities

17 and 27, or the O-rings are welded together by Kovar and the like so as to ensure the vacuum of the

reaction cavities

17 and 27; the end faces of the

circumferential antennas

6,26 facing the vacuum chamber form a circumferential antenna recess 18, the recess is shaped as shown in fig. 3, the substrate 7 is placed on the bottom surface of the recess, the microwave 16 enters the

reaction chambers

17,27 and then the plasma 13 is formed on the substrate.

The microwave reflectors 9 are arranged on the tops of the

reaction cavities

17 and 27, and the microwave reflectors 9 are connected with microwave reflector adjusting devices 10 and can be adjusted up and down on the upper parts of the

reaction cavities

17 and 27. Inside the microwave reflector tuning arrangement 10, gas inlet tubes 11 are nested, from which precursor gases enter the interior of the

reaction chambers

17, 27. The gas outlet 12 is located below the

reaction chambers

17, 27.

The device uses 2.45GHz or 915MHz microwaves, but is not limited to the above microwave frequencies, and is suitable for use in any frequency band capable of generating plasma.

The coaxial waveguide inner and outer conductors, the

circumferential antennas

6 and 26, the reaction cavity, the microwave reflector adjusting device and the like which are contacted with each other when microwaves are transmitted in the microwave device can realize direct water cooling.

As described above, the microwave plasma reaction apparatus according to the present invention can synthesize large-area high-quality diamond material under high power and high pressure for a long time. Since a stable plasma can be generated directly above the substrate by adjusting the microwave reflector even when deposition parameters such as pressure and microwave input power are changed.

Finally, it should be pointed out that: the above examples are only for illustrating the technical solutions of the present invention, and are not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. A microwave plasma reaction apparatus, comprising:

a reaction chamber having an opening at the bottom for transmitting microwaves and an observation window at the side;

the circumferential antenna faces the end face of the microwave plasma reaction device of the reaction cavity to form a concave part.

2. A microwave plasma reaction apparatus as claimed in claim 1, wherein the reaction chamber, the circumferential antenna, the coaxial waveguide, and the microwave reflector are made of metal, and direct water cooling is possible.

3. A microwave plasma reaction apparatus as recited in claim 1, wherein the recess is cylindrical or frustoconical.

4. A microwave plasma reactor according to claim 1, wherein the dielectric window is isolated from the plasma to prevent etching of the window by the plasma.

5. A microwave plasma reaction device according to claim 1, wherein the microwave plasma reaction device has an adjustment mechanism to enable the device to accommodate diamond material synthesis under a variety of process conditions.

6. A microwave plasma reactor apparatus as claimed in claim 1, wherein the upper and lower chamber walls and the microwave reflector in the microwave plasma reactor apparatus are located at a distance of not less than three-quarters of the wavelength of the input microwave from the center of the substrate.