WO2021196341A1

WO2021196341A1 - Substrate table for growing single crystal diamonds by using microwave plasma technology and growing method

Info

Publication number: WO2021196341A1
Application number: PCT/CN2020/089024
Authority: WO
Inventors: 满卫东
Original assignee: 上海征世科技有限公司
Priority date: 2020-03-31
Filing date: 2020-05-07
Publication date: 2021-10-07
Also published as: CN111519248A

Abstract

Provided in the present invention is a substrate table for growing single crystal diamonds by using a microwave plasma technology. The substrate table comprises a circular microwave plasma substrate table. Above the substrate table, and sticking closely to a surface of the substrate table is spherical plasma excited that is by microwaves. A pit is formed in an axial symmetry center of the surface of the substrate table, and a crystal support used for diamond growth may be placed in the pit. An annular metal thin pipe is provided at the bottom of the pit around the crystal support, and small holes are formed in the thin pipe. The thin pipe is connected to a gas supply system, and the gas flow in the thin pipe is controlled by means of a gas flow meter. An annular metal thin pipe is provided at the top of the pit around the crystal support, and small holes are formed in the thin pipe. The thin pipe is connected to an air exhaust system, and the gas flow in the thin pipe is controlled by means of a gas flow meter. According to the solution, normal growth of diamonds on the upper surface of the seed crystal may be prevented from being affected by non-diamond carbon accumulated on the side face of the seed crystal, and at the same time, the surface growth speed of the seed crystal may be increased.

Description

Substrate table and growth method for growing single crystal diamond by microwave plasma technology

Technical field

The invention belongs to the technical field of vacuum microelectronics, and in particular relates to a device for preparing single crystal diamonds and a method for improving growth quality when the device is used to grow single crystal diamonds.

Background technique

Diamond is a high-quality single crystal diamond. Because of its superior performance, it has a wide range of applications in many fields. Natural diamonds are scarce in quantity and expensive; artificial diamonds prepared by the high temperature and high pressure method (HTHP method), because they contain metal catalysts, also affect the properties of the diamond; using microwave plasma chemical vapor deposition (MPCVD) technology, in a specific seed High-quality single crystal diamonds can be grown on the surface, which is an ideal technology for man-made diamond growth.

The microwave plasma chemical vapor deposition device generally includes a microwave system, a vacuum system, a gas supply system and a plasma reaction chamber. A crystal support is placed in the center of the pit, and the diamond seed crystal required for diamond growth is placed on the crystal support. The microwave generated by the microwave system enters the plasma reaction chamber, and the gas provided by the gas supply system is excited above the substrate stage to generate a plasma ball. The plasma ball is tightly attached to the surface of the seed crystal for growing diamonds. The process parameters of the plasma can continuously deposit carbon on the surface of the diamond seed crystal, making the diamond seed crystal grow from small to large.

Usually, the traditional way to pass the reaction gas is to pass the gas from the cavity wall of the vacuum chamber, so that the gas flows in the whole cavity, basically in a relatively uniform flow state.

However, in the process of growing diamond on the surface of the diamond seed crystal, due to the difference in the atomic arrangement of the upper surface of the seed crystal and the side surface, it often leads to the continuous deposition of new diamond components on the upper surface of the seed crystal, and a large number of polycrystalline diamonds on the side surface of the seed crystal. And non-diamond carbon is produced, and the continuous accumulation of these polycrystalline diamond and non-diamond carbon will affect the growth of normal diamond composition on the upper surface of the seed crystal. If during the growth process, without affecting the growth of the upper surface of the seed crystal, the production of polycrystalline diamond and non-diamond carbon on the side of the seed crystal can be suppressed or the polycrystalline diamond component and non-diamond carbon produced can be etched away at all times, So it is very beneficial to improve the normal deposition of the diamond composition on the upper surface of the seed crystal. However, due to the uniqueness of microwave, it is not possible to set up an air inlet pipe inside the vacuum chamber at will. Because the pipe is generally made of metal, it is easy to cause discharge in the microwave electric field, and metal will affect the distribution of the microwave electric field. Therefore, in order not to affect the distribution of the electromagnetic field, the air inlet of the traditional vacuum chamber is often arranged on the wall of the metal cavity.

Summary of the invention

The technical problem to be solved by the present invention is to solve the above-mentioned shortcomings in the prior art. Under the premise of not changing the overall fluidity of the gas in the vacuum chamber, in addition to the traditional reaction gas (first path) In addition to the air intake), the second air intake is input into the vacuum chamber through the substrate stage. At the bottom of the pit of the substrate table, a second air inlet pipe is set. The gas type of the second inlet can be the same or different from the traditional gas type. Because the second inlet input point is very close to the diamond growth, when selecting a gas that is different from the traditional growth gas, a plasma active body concentration distribution different from the overall growth environment can be formed in the local area around the diamond seed growth. area. In order to better control the flow range of the second inlet gas, a second gas extraction pipeline is set near the top of the pit of the substrate stage. The second air extraction rate can be adjusted separately relative to the second air intake rate, which increases the flexibility of controlling the process of growing single crystal diamonds: when the second air intake rate is greater than the second air extraction rate, some The gas released from the second inlet gas path can diffuse to the crystal surface growth area; when the second inlet gas rate is less than the second pumping rate, the reaction gas that can enter the first inlet pipe is controlled Sexually guided through the vicinity of the grain growth area.

The present invention includes providing a substrate table for growing single crystal diamonds by microwave plasma technology, including a microwave plasma substrate table in a circular shape, the upper part of the substrate table is close to the surface of the substrate table and there is microwave excitation In a spherical plasma, the substrate table has a pit close to the center of the plasma ball, and a crystal holder for diamond growth can be placed in the pit.

Optionally, a cylindrical shape with a diameter or a truncated cone shape with a thick top and a thin bottom; the depth of the pit is between 6.0-15.0 mm and the diameter is between 10.0-30.0 mm.

Optionally, there is one pit in the entire substrate stage, which is located at the center of the upper surface of the substrate stage; or a plurality of pits are symmetrically distributed on the upper surface of the substrate stage with the center of the substrate stage.

Optionally, an annular metal thin tube A arranged around the crystal holder is arranged close to the bottom of the pit. The metal thin tube A has 2 or more small holes symmetrically distributed with the crystal holder as the center. The outer diameter is between 1.5-2.5 mm and forms the second air intake pipe of the system.

Optionally, the thin metal tube A is connected to the air intake system of the system, and the diameter of the small hole is between 0.2-0.5 mm.

Optionally, the part of the thin metal tube A in the pit is composed of high melting point metal, preferably metallic molybdenum; the part of the thin metal tube A outside the pit is composed of metal, preferably copper; The material in the substrate and the material outside the pit of the substrate table are connected by welding.

Optionally, the small hole on the thin metal tube A is used to release a specified single gas or a mixture of multiple gases.

Optionally, an annular metal thin tube B arranged around the crystal holder is arranged in the pit close to the inner wall of the top of the pit, and the metal thin tube B has 2 or more small holes symmetrically distributed with the crystal holder as the center. The outer diameter of the thin tube B is between 1.5-2.5 mm. The small hole on the thin metal tube B is connected to the vacuuming system of the vacuum chamber to form the second pumping line of the system; the pumping speed depends on the flow controller. control.

Optionally, the part of the thin metal tube B in the pit is composed of high melting point metal, preferably metal molybdenum; the part of the thin metal tube B outside the pit is composed of metal, preferably copper; The material in the substrate and the material outside the pit of the substrate table are connected by welding.

The present invention also provides a growth method using microwave plasma technology, which includes the substrate stage described in any one of the above, and a plasma excited by microwave is placed on the substrate stage, and further includes a microwave system, a vacuum system, and a power supply. A gas system and a plasma reaction chamber, wherein the diamond seed crystal used for diamond growth is placed on a crystal holder, the crystal holder is placed in a pit, and the inner wall of the pit is provided with a metal thin tube A for outgassing near the bottom. There are several vent holes symmetrically distributed around the crystal holder on the surface, which can selectively release a gas or a mixture of gases during operation; the top of the pit surrounds the crystal holder with a metal thin tube B for air extraction. , The surface of the thin tube has a number of air extraction holes symmetrically distributed with the crystal holder as the center, and the air extraction holes are connected with the vacuum system of the vacuum chamber, and the flow rate is controlled by the controller.

The invention provides a microwave plasma CVD method to grow a single crystal diamond component on the surface of a seed crystal. By setting up ring-shaped metal thin tubes at the top and bottom of the pit where the seed crystals are placed, the thin tubes are equipped with suction and air inlets respectively, and the flow of gas is controlled by a flow meter to inject specific gas into the seed crystal during the diamond growth process. The side area is excited into a plasma state under the action of microwave energy, which can selectively suppress or etch away the non-diamond carbon generated on the side of the seed crystal, so as to ensure that the diamond component grown on the upper surface of the seed crystal can ensure high quality. Further, by selectively inputting the composition and flow rate of the second reaction gas, the non-diamond carbon generated on the side of the seed crystal can be etched away more effectively and at the same time, the growth of polycrystalline diamond carbon can be inhibited. The type of reaction gas can be flexibly adjusted, usually O ₂ or a gas that can decompose O atoms in a plasma environment, such as H ₂ O, CO and other gases, can generate a large amount of O radicals in a plasma environment. It has a very strong etching effect on non-diamond carbon and polycrystalline carbon; and the single crystal diamond carbon deposited on the upper surface of the diamond seed crystal is more resistant to O etching than polycrystalline diamond carbon and non-diamond carbon; The O-containing gas starts from the bottom of the crystal support and moves above the seed crystal, and continuously reacts with the polycrystalline carbon and non-diamond carbon on the side of the seed crystal to gradually reduce its ability to etch carbon. The type and amount of the second reaction gas introduced can be adjusted by a gas mass flow meter. The entire process is simple to operate and has significant effects. In order to prevent the introduced second gas from diffusing to the surface of the seed crystal, thereby affecting the normal growth of the surface of the seed crystal, a second gas extraction pipeline is set near the top of the pit. When the gas flow rate of the second air extraction pipeline is greater than that of the second air inlet pipeline, it can not only extract most of the etching gas that enters from the second air inlet pipeline, but also the vacuum chamber The reaction gas that enters from the first gas inlet pipe flows through the surface of the substrate table, thereby improving the flow of reaction gas on the growth surface of the seed crystal and increasing the growth rate of the upper surface of the seed crystal.

Description of the drawings

1A and 1B are schematic diagrams of the pore arrangement structure in the pit of the substrate table and the placement of the crystal holder and the seed crystal.

Fig. 2 shows the Raman spectrum of the side of the seed crystal in Example 1 (a) without O ₂ growth; (b) the Raman spectrum of the side of the seed crystal after _{O 2 growth.}

Reference signs: 1. Plasma; 2. Diamond seed crystal; 3. Crystal support; 4. Air inlet; 5. Substrate table; 6. Copper air supply pipe; 7. Flow controller; 8. Air extraction port.

Detailed ways

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below in conjunction with embodiments.

Fig. 1A and Fig. 1B are an embodiment of the present invention, including a microwave plasma deposition device used for microwave plasma deposition, including a circular microwave plasma (1) substrate stage (5) that is circular, so There is a pit in the center of the upper surface of the substrate table (5), and the crystal holder (3) is placed in the pit. The height of the crystal holder must ensure that the upper surface of the diamond seed crystal is in contact with the plasma, which is conducive to the growth of diamond. Diamond seed crystal (2), the upper surface of the seed crystal is continuously deposited with diamond components, so as to realize the continuous growth of the diamond seed crystal. There is a ring-shaped molybdenum metal thin tube close to the bottom of the pit, and the thin tube is symmetrical with the crystal support as the center. The outlet holes (4) can selectively release O ₂ , and the outlet direction faces the side wall of the pit. Through the rebound effect of the side wall on the air flow, the outflow of gas is more uniform, thereby reducing the impact on the upper surface of the seed crystal. The influence of uniform plasma distribution; the gas flow out of the pores is controlled by a flow meter (7); there is a ring-shaped molybdenum metal thin tube near the top in the pit, and the thin tube has suction holes symmetrically distributed with the crystal holder as the center; suction holes The direction faces the side wall of the pit, so that the pumping gas flow is evenly distributed, and the influence on the uniform distribution of plasma on the surface of the seed crystal is reduced.

Example 1:

The diameter of the substrate table (5) is 60 mm; there is a pit in the center of the substrate table with a diameter of 20 mm and a depth of 8.0 mm; close to the bottom of the pit is a thin metal molybdenum tube (4) with an outer diameter of 2.0 mm and an inner diameter of 1.0 Mm, 4 vent holes are symmetrically arranged with the crystal support as the center, the vent hole diameter is 0.5 mm, and the vent direction faces the side wall of the pit. Close to the top of the pit is a thin metal molybdenum tube (8) with an outer diameter of 2.0 mm and an inner diameter of 1.0 mm. 4 vent holes are symmetrically arranged with the crystal holder as the center. The vent holes have a diameter of 0.5 mm, and the suction direction faces the side wall of the pit. The crystal support (3) is a high-purity metal tungsten with a diameter of 12 mm and a thickness of 7.5 mm. Diamond seed crystal (2) a square diamond single wafer with a geometric size of 5.0*5.0*0.2 mm.

The deposition process parameters of diamond film are: microwave power 4000W, deposition pressure 21.0kPa, _{flow ratio of H 2} , CH ₄ and N ₂ 200:6.0:6.0 (sccm), deposition temperature 1060℃, metal thin tube (4) is released The gas is O ₂ , the flow rate is 0.8 (sccm); the suction rate of the metal thin tube (8) is 0.5 (sccm), and the deposition time is 8.0 h. (Note: sccm: standard cubic centimeters per minute).

The result is: the growth rate of the seed crystal is 11.6 micrometers per hour; Raman spectroscopy is used to detect the composition of the upper surface and side surface of the seed crystal after growth. The test results are shown in Figure 2(a).

Example 2:

The deposition process parameters of diamond film are: microwave power 4000W, deposition pressure 21.0kPa, _{flow ratio of H 2} , CH ₄ and N ₂ 200:6.0:6.0 (sccm), deposition temperature 1060℃, metal thin tube (4) is released The gas is O ₂ , the flow rate is: 1.8 (sccm); the suction rate of the metal thin tube (8) is: 0.5 (sccm); the deposition time is 8.0h.

The results are: the seed crystal growth rate is 11.2 microns per hour; Raman spectroscopy is used to detect the upper surface and side surface of the seed crystal after growth. The test results are shown in Figure 2(b). Comparing Example 1 and Example 2, it can be seen from Figure 2(a) and Figure 2(b) that when the pumping rate in the pit is lower than the second air intake rate, the second air intake should be increased appropriately The flow rate of gas O ₂ basically has no effect on the growth of the upper surface of the seed crystal, but can significantly improve the growth quality of the side surface of the seed crystal.

Example 3:

The deposition process parameters of diamond film are: microwave power 4000W, deposition pressure 21.0kPa, _{flow ratio of H 2} , CH ₄ and N ₂ 200:6.0:6.0 (sccm), deposition temperature 1060℃, metal thin tube (4) is released The gas is O ₂ , the flow rate is 0.8 (sccm); the suction rate of the metal thin tube (8) is 3.5 (sccm), and the deposition time is 8.0 h.

The result is: the seed crystal growth rate is 14.1 micrometers per hour; comparing Example 2 and Example 3, it can be seen that when the second air extraction speed is greater than the second air intake speed, the growth rate of the seed crystal is significant promote.

The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. Inside.

Claims

A substrate table for growing single crystal diamonds using microwave plasma technology, which is characterized in that it comprises a circular microwave plasma substrate table, and the upper part of the substrate table is close to the surface of the substrate table with microwave excitation In a spherical plasma, the substrate table is provided with a pit close to the center of the plasma ball, and a crystal holder for diamond growth can be placed in the pit.
The substrate table according to claim 1, wherein the pits are cylindrical with the same upper and lower diameters or circular truncated cones with the upper and lower diameters; the depth of the pits is between 6.0-15.0 mm and the diameter Between 10.0-30.0 mm.
The substrate table according to claim 1, wherein the pit is one in the entire substrate table and is located at the center of the upper surface of the substrate table; or a plurality of pits are distributed symmetrically on the substrate table center. The upper surface of the film table.
The substrate stage according to claim 1, wherein a ring-shaped metal thin tube arranged around the crystal holder is arranged close to the bottom of the pit, and the metal thin tube has 2 symmetrically distributed with the crystal holder as the center. One or more small holes, the outer diameter of the thin metal tube is between 1.5-2.5 mm.
4. The substrate stage according to claim 4, wherein the small hole on the thin metal tube is used to release a specified single gas or a mixture of multiple gases, and the diameter of the small hole is between 0.2-0.5 mm.
The substrate table according to claim 5, wherein the part of the thin metal tube in the pit of the substrate table is made of high-temperature resistant elemental metal or alloy, and the thin metal tube is in the pit of the substrate table. The other part is metal; the material in the pit of the substrate table and the material outside the pit of the substrate table are connected by welding.
The substrate table according to claim 1, characterized in that: the pit is provided with an annular metal thin tube arranged around the inner wall of the pit close to the top, and the metal thin tube is symmetrically distributed with the crystal holder as the center. 2 or more small holes, the outer diameter of the thin metal tube is between 1.5-2.5 mm.
The substrate table according to claim 7, wherein the part of the thin metal tube in the pit of the substrate table is made of high-temperature resistant elemental metal or alloy, which is located in the part outside the pit of the substrate table. It is metal; the material in the pit of the substrate table and the material outside the pit of the substrate table are connected together by welding.
7. The substrate stage according to claim 6, wherein the small hole on the thin metal tube is connected to the suction system of the vacuum chamber, and the diameter of the small hole is between 0.2-0.5 mm.
A growth method using microwave plasma technology, characterized in that it comprises the substrate stage according to any one of claims 1-9, and a plasma excited by microwave is placed above the substrate stage, and further comprises a microwave system, A vacuum system, a gas supply system, and a plasma reaction chamber, wherein the diamond seed crystal used for diamond growth is placed on a crystal holder, the crystal holder is placed in a pit, and the bottom of the pit is provided with a gas outlet close to the inner wall of the pit. There are a number of vent holes symmetrically distributed around the crystal holder on the surface of the thin metal tube, which can selectively release a gas or a mixture of gases during operation; the top of the pit is provided with a pump around the crystal holder. The thin metal tube for gas has a number of suction holes symmetrically distributed around the crystal holder on the surface of the thin tube, which can control the speed of suction when working.