Method for controlling temperature uniformity in MPCVD single crystal diamond growth process

Abstract

The invention relates to a method for controlling the temperature uniformity in the MPCVD monocrystal diamond growth process, which is mainly characterized in that a quartz plate is additionally arranged between a molybdenum support and a heat dissipation table of MPCVD equipment to serve as a cushion layer, so that cooling is uniformly dispersed, and the situation that the temperature of a substrate is further nonuniform due to nonuniform temperature distribution of the molybdenum support caused by concentrated cooling is avoided; due to the fact that the overall heat conduction efficiency is low due to isolation of the quartz plate, the water flow of water circulation of the lower heat dissipation table is synchronously increased to make up for adverse effects caused by the quartz plate, and therefore temperature uniformity control, diamond growth uniformity controllability and growth quality controllability in the single crystal diamond growth process can be achieved, the yield can be increased, and the production cost can be reduced. The production cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of single crystal diamond CVD growth, and in particular to a method for controlling temperature uniformity during MPCVD single crystal diamond growth. Background Art

[0002] Major national strategies such as energy conservation and emission reduction, intelligent manufacturing, high-frequency communications, and deep space exploration have put forward urgent demands for ultra-high thermal conductivity materials such as diamond. With the gradual implementation of leading national projects such as "new infrastructure" and "carbon neutrality", the number of applications in strategic emerging industries such as high-frequency electronic equipment, 5G communications, the Internet of Things, supercomputing and data centers has increased sharply, and the overall power consumption has increased exponentially. Device heat dissipation has become the biggest bottleneck restricting critical applications. In response to the above major strategic needs, single crystal diamond, as an important node in the scientific development direction of wide bandgap semiconductor materials, has also put forward urgent needs for large size, high performance, and especially ultra-high thermal conductivity.

[0003] As an ultra-wide bandgap semiconductor material, diamond has the advantages of large bandgap width, high carrier mobility, large carrier saturation drift velocity, strong critical breakdown field, and high thermal conductivity. It is very suitable for the preparation of high-frequency, high-power, high-temperature resistant, and radiation-resistant electronic devices and optoelectronic devices in the deep ultraviolet band. It has broad application prospects in the fields of new energy, 6G communications, and space science. Therefore, diamond, which combines multiple excellent properties, is recognized as an ideal next-generation power device material and has great application prospects in the fields of electric vehicles, photovoltaics, and military industry. In order to achieve industrial promotion, semiconductor materials need to meet the requirements of high purity, low defect density, high carrier concentration and mobility, and inch-level wafer area. The preparation technology of high-quality large-area single crystal substrates is still a challenge facing the commercial application of diamond materials and devices.

[0004] Current problems: On the one hand, during the growth process, the temperature of the diamonds around the molybdenum holder is higher than that in the middle area due to the local enhancement effect of plasma, which causes the growth of diamonds around the molybdenum holder to be faster than that in the middle of the molybdenum holder, and the growth is uneven. When multiple pieces are grown at the same time, the growth conditions of diamond pieces in different areas are different, and the consistency of the product cannot be guaranteed; see Figure 3 The red diamonds around the molybdenum holder are the high temperature area, and the black-gray diamonds in the middle are the low temperature area. The production effect in the high temperature area is higher than that in the low temperature area. On the other hand, the uneven heat dissipation of the molybdenum tray (the contact problem between water cooling and the molybdenum tray) causes uneven heat and temperature distribution, which leads to uncontrollable growth uniformity and uncontrollable growth quality. The growth of large-sized, inch-level wafer-area single-crystal diamond substrates is highly random and not highly controllable. The yield of large-size products is not high and the production cost is high. Figure 4 and Figure 3 By comparison, Figure 3 The diamonds grown by the existing technology are all small in size, and it is difficult to achieve large-size growth. Summary of the invention

[0005] The purpose of the present invention is to solve the above problems and provide a method for controlling temperature uniformity during MPCVD single crystal diamond growth.

[0006] The technical solution of the present invention is: a method for controlling temperature uniformity during MPCVD single crystal diamond growth, comprising the following steps; a. Preparation of molybdenum support Prepare a specific molybdenum tray that matches the shape of the single crystal diamond substrate as needed, clean the surface impurities after processing with acetone, alcohol, and deionized water in turn, and blow dry with a nitrogen gun for later use; a clean molybdenum tray is conducive to good contact with the diamond substrate and good thermal conductivity; b. Preparation of single crystal diamond substrate The substrate is made of single crystal diamond prepared under high temperature and high pressure; c. Substrate cleaning d. Substrate etching The dried diamond substrate needs to be etched in the MPCVD device before growth to remove impurities, defects and stress on the surface of the diamond substrate. e. Preparation of quartz pad A quartz plate with a shape matching that of the bottom surface of the molybdenum support and a larger area than that of the bottom surface of the molybdenum support is prepared. The quartz plate is used to control the uniformity of the temperature distribution on the molybdenum table to avoid uneven heat and temperature distribution on the molybdenum table and the substrate during the growth process affecting the growth quality.

[0007] f. Growth preparation First, place the quartz plate on the water-cooled heat sink in the MPCVD equipment, then place the molybdenum tray on the quartz plate, and at the same time place the substrate on the corresponding position on the molybdenum tray; g. Start the MPCVD equipment, start growth, adjust the flow rate of cooling water inside the water-cooled heat sink, and control the internal growth temperature until the growth is completed. In the present invention, the quartz plate is added as a cushion layer to evenly disperse the cooling, solving the problem of unevenness. At the same time, the overall thermal conductivity is low due to the isolation of the quartz plate, so it is necessary to increase the water flow rate of the water circulation of the heat sink below to compensate for the deficiency caused by the quartz plate and ensure the efficiency of heat dissipation.

[0008] Preferably, the single crystal diamond substrate in step b is sized as a square of 7 mm x 7 mm.

[0009] Preferably, the etching conditions in step d are: the gases introduced are hydrogen and oxygen, the hydrogen flow rate is 190 sccm, the oxygen flow rate is 10 sccm, the etching temperature is 650° C., and the etching time is 30 minutes.

[0010] Preferably, the bottom surface of the molybdenum support is polished, and the surface of the quartz plate is polished, so as to achieve good contact and facilitate heat conduction.

[0011] Preferably, the thickness of the quartz plate is 0.5 mm; Preferably, the substrate is first soaked in aqua regia for 24 hours to remove metal impurities, and then the substrate is taken out of the aqua regia with a polytetrafluoroethylene tool, and the aqua regia attached to the surface is rinsed with deionized water until it is clean; then, ultrasonic cleaning is performed in acetone for 15 minutes each, ultrasonic cleaning is performed in alcohol for 15 minutes each, and ultrasonic cleaning is performed in deionized water for 15 minutes, and finally, it is blown dry with nitrogen for standby use; Preferably, the starting equipment of step g comprises evacuating the MPCVD equipment to below 10-5 Torr, then starting in a hydrogen atmosphere, then increasing the power and pressure to raise the substrate temperature to about 850°C, and then introducing methane for growth.

[0012] Preferably, the substrate temperature is monitored during the growth process, and the temperature is controlled to be around 850° C. by adjusting the pressure and power.

[0013] The present invention provides a method for controlling temperature uniformity during the growth of MPCVD single crystal diamond. The method mainly comprises adding a quartz plate as a cushion layer between a molybdenum tray and a heat sink of an MPCVD device to evenly disperse the cooling, thereby avoiding the concentration of cooling causing uneven temperature distribution of the molybdenum tray, which further causes uneven temperature of the substrate. The overall thermal conductivity is low due to the isolation of the quartz plate, and the water flow rate of the water circulation of the heat sink below is simultaneously increased to compensate for the adverse effects of the quartz plate. In this way, the temperature uniformity during the growth of the single crystal diamond can be controlled, the uniformity of diamond growth can be controlled, the growth quality can also be controlled, the yield rate can be improved, and the production cost can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the three-dimensional structure after the substrate, molybdenum support and quartz plate are assembled in this method; Figure 2 This is a schematic diagram of the cross-sectional structure of the substrate, molybdenum support and quartz plate after assembly in this method; Figure 3 This is a picture of a diamond growth product without a quartz plate cushion in the prior art; Figure 4 This is a picture of a diamond growth product using the patented technical solution; In the figure, 1. molybdenum support, 2. substrate, 3. quartz plate. DETAILED DESCRIPTION

[0015] Example 1: See Figure 1 , 2 4. A method for controlling temperature uniformity during MPCVD single crystal diamond growth, comprising the following steps; a. Preparation of molybdenum support Prepare a specific molybdenum tray that matches the shape of the single crystal diamond substrate as needed, clean the surface impurities after processing with acetone, alcohol, and deionized water in turn, and blow dry with a nitrogen gun for later use; b. Preparation of single crystal diamond substrate The substrate is made of single crystal diamond prepared under high temperature and high pressure; c. Clean the substrate to remove impurities and avoid affecting product quality.

[0016] The substrate was first soaked in aqua regia for 24 hours to remove metal impurities, and then the substrate was taken out of the aqua regia with a polytetrafluoroethylene tool, and the aqua regia attached to the surface was rinsed with deionized water until it was clean; then ultrasonic cleaning was performed in acetone for 15 minutes each, in alcohol for 15 minutes each, and in deionized water for 15 minutes, and finally dried with nitrogen for later use; d. Substrate etching The dried diamond substrate needs to be etched in the MPCVD device before growth to remove impurities, defects and stress on the surface of the diamond substrate. e. Preparation of quartz pad A quartz plate having a shape matching that of the bottom surface of the molybdenum support and having an area larger than that of the bottom surface of the molybdenum support is prepared, and the thickness of the quartz plate is 0.5 mm; the quartz plate is used to control the temperature distribution on the molybdenum support to be uniform, so as to avoid uneven heat and temperature distribution on the molybdenum support and the substrate during the growth process affecting the growth quality.

[0017] f. Growth preparation First, place the quartz plate on the water-cooled heat sink in the MPCVD equipment, then place the molybdenum tray on the quartz plate, and at the same time place the substrate on the corresponding position on the molybdenum tray, see Figure 1-2 As shown, in this embodiment, multiple pieces of single crystal diamond are grown simultaneously; g. Start the MPCVD equipment, start growth, and adjust the flow rate of cooling water inside the water-cooled heat sink; in the present invention, the quartz plate is added as a cushion layer to evenly disperse the cooling, thereby solving the problem of unevenness. At the same time, the overall thermal conductivity is low due to the isolation of the quartz plate, so it is necessary to simultaneously increase the water flow rate of the water circulation of the heat sink below to compensate for the deficiency caused by the quartz plate and ensure the efficiency of heat dissipation. The increase in water flow rate here is relative to the original growth process without a quartz plate.

[0018] The temperature uniformity control state during the specific growth process of this embodiment is shown in Figure 3 As shown, basically all diamond pieces have the same red color, so the single crystal diamond grown in this way grows evenly in all parts and can be larger in size. At the same time, multiple pieces grow basically synchronously, and the yield is high.

[0019] The single crystal diamond substrate in step b is 7 mm×7 mm square in size.

[0020] The etching conditions in step d are as follows: the gases introduced are hydrogen and oxygen, the hydrogen flow rate is 190 sccm, the oxygen flow rate is 10 sccm, the etching temperature is 650° C., and the etching time is 30 minutes.

[0021] The bottom surface of the molybdenum tray is polished, and the surface of the quartz plate is polished, so as to achieve good contact and facilitate heat conduction.

[0022] The starting equipment of step g comprises evacuating the MPCVD equipment to 10 -5 Torr or less, then start in a hydrogen atmosphere, then increase the power and pressure to raise the substrate temperature to 850°C, and then introduce methane for growth.

[0023] The substrate temperature is monitored during the growth process, and the temperature is controlled at 850° C. by adjusting the pressure and power.

[0024] The method of the present invention solves the problem of uniform temperature distribution on the molybdenum table, can ensure the synchronization of growth between multiple sheets when growing multiple sheets, and ensure the improvement of the yield rate. At the same time, for each piece of grown single crystal diamond, the temperature distribution of each part of the sheet is also uniform. Compared with the prior art, it can achieve the growth of single crystal diamond of larger size. Figure 3 The above is the growth state in the prior art. Figure 4 The above is the growth state of the method of the present invention, and it can be clearly seen that Figure 4 The single crystal diamond in the Figure 3 In.

Claims

1. A method for controlling temperature uniformity during MPCVD single crystal diamond growth, comprising the following steps; a. Preparation of molybdenum support Prepare a specific molybdenum tray that matches the shape of the single crystal diamond substrate as needed, clean the surface impurities after processing with acetone, alcohol, and deionized water in turn, and blow dry with a nitrogen gun for later use; b. Preparation of single crystal diamond substrate The substrate is made of single crystal diamond prepared under high temperature and high pressure; c. Substrate cleaning d. Substrate etching The cleaned single crystal diamond substrate needs to be etched in the MPCVD equipment before growth. e. Preparation of quartz pad Prepare a quartz plate with a shape that matches the shape of the bottom surface of the molybdenum support and a larger area than the bottom surface of the molybdenum support. f. Growth preparation First, place the quartz plate on the water-cooled heat sink in the MPCVD equipment, then place the molybdenum tray on the quartz plate, and at the same time place the substrate on the corresponding position on the molybdenum tray; g. Start the MPCVD equipment, start growth, adjust the flow of cooling water inside the water-cooled heat sink, and control the internal growth temperature until the growth is completed.

2. The method for controlling temperature uniformity during MPCVD single crystal diamond growth according to claim 1, characterized in that: The single crystal diamond substrate in step b is 7 mm×7 mm square in size.

3. The method for controlling temperature uniformity during MPCVD single crystal diamond growth according to claim 1, characterized in that: The etching conditions in step d are as follows: the gases introduced are hydrogen and oxygen, the hydrogen flow rate is 190 sccm, the oxygen flow rate is 10 sccm, the etching temperature is 650° C., and the etching time is 30 minutes.

4. The method for controlling temperature uniformity during MPCVD single crystal diamond growth according to claim 1, characterized in that: The bottom surface of the molybdenum support is polished, and the surface of the quartz plate is polished.

5. The method for controlling temperature uniformity during MPCVD single crystal diamond growth according to claim 1, characterized in that: The thickness of the quartz plate is 0.5 mm.

6. The method for controlling temperature uniformity during MPCVD single crystal diamond growth according to claim 1, characterized in that: The substrate was first soaked in aqua regia for 24 hours to remove metal impurities, then the substrate was taken out of the aqua regia with a polytetrafluoroethylene tool, and the aqua regia attached to the surface was rinsed with deionized water until it was clean; then, it was ultrasonically cleaned in acetone for 15 minutes each, in alcohol for 15 minutes each, and in deionized water for 15 minutes, and finally dried with nitrogen for later use.

7. The method for controlling temperature uniformity during MPCVD single crystal diamond growth according to claim 1, characterized in that: The starting equipment of step g comprises evacuating the MPCVD equipment to 10 -5 Torr or less, then start the glow in a hydrogen atmosphere, then increase the power and pressure to raise the substrate temperature to around 850°C, and then introduce methane for growth.

8. The method for controlling temperature uniformity during MPCVD single crystal diamond growth according to claim 7, characterized in that: During the growth process, the substrate temperature is monitored and the temperature is controlled to be around 850° C. by adjusting the pressure and power.

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