A TM022 mode microwave plasma diamond film deposition device

Abstract

The present invention discloses a TM022 mode microwave plasma diamond film deposition device, which belongs to the field of microwave plasma chemical vapor deposition technology. The device comprises an air inlet (1), a cavity (2), an observation window (3), a temperature measurement window (4), a plasma hemisphere (5), a sample stage (6), a copper stage (7), an annular quartz glass (8), an inverted rounded stage bottom column (9), an air outlet (10), a microwave coaxial transmission port (11), and a top tuning module (12). The device adopts the TM022 resonance mode and can deposit large-area high-quality diamond film growth under high-power conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave plasma chemical vapor deposition, and in particular relates to a novel TM022 mode microwave plasma diamond film deposition device. Background Art

[0002] Diamond's excellent physical and chemical properties make it widely used in many fields. Diamond is an indirect bandgap semiconductor material with a band gap of about 5.2eV, a thermal conductivity of up to 22W / (cm•K), and a room temperature electron and hole mobility of up to 4500cm 2 / (V•s) and 3380cm 2 / (V•s), far exceeding that of third-generation semiconductor materials GaN and SiC. Therefore, diamond has broad application prospects in high-temperature, high-power power electronics and high-frequency, high-power microwave devices. Furthermore, due to its high exciton binding energy (80 MeV), diamond can achieve high-intensity free exciton emission (emission wavelength of approximately 235 nm) at room temperature. This holds great potential for the fabrication of high-power deep-ultraviolet light-emitting diodes (DUV-LEDs). It also plays a key role in the development of extreme ultraviolet, deep ultraviolet, and high-energy particle detectors.

[0003] Although the growth of semiconductor diamond materials and the development of devices currently face numerous challenges, the application of semiconductor diamond materials and devices is highly likely to bring about significant technological changes in the near future. Chemical vapor deposition (CVD), a method for depositing solid materials on a substrate through a chemical reaction of reactant gases, is a promising approach for producing uniform thin films. Hot-wire, DC arc-jet, and microwave plasma methods have been successfully applied to the production of diamond films. Compared to other CVD methods, microwave plasma CVD (MPCVD) offers the advantage of being able to synthesize large, high-quality diamond films. It typically uses a metal cavity, and the absence of catalysts and impurities during the synthesis of single-crystal diamond improves the quality of the diamond.

[0004] With the development of MPCVD technology, researchers have begun researching and designing deposition devices with different structures to increase microwave input power. Initially, these devices used quartz tubes, quartz bell jars, and cylindrical resonators, and later developed non-cylindrical multimode and ellipsoidal resonators. Power has increased from hundreds of watts to several kilowatts and even tens of kilowatts. The microwave plasma chemical vapor deposition device fundamentally determines the extent of diamond growth, making its design crucial. Classic cylindrical MPCVD devices often suffer from problems such as etching of the quartz glass, introducing silicon impurities, carbon-containing impurities in the tuning mechanism, and an inability to operate at high power for extended periods.

[0005] In summary, how to design a method to grow high-quality, large-area diamond films for a long time under high-power conditions has become an urgent problem to be solved. Summary of the Invention

[0006] The present invention aims to solve the problem that existing MPCVD devices cannot deposit high-quality, large-area diamond films for a long time under high-power conditions.

[0007] The technical solutions of the present invention are as follows:

[0008] A TM022 mode microwave plasma diamond film deposition device, comprising an air inlet 1, a cavity 2, an observation window 3, a temperature measurement window 4, a plasma hemisphere 5, a sample stage 6, a copper stage 7, an annular quartz glass 8, an inverted frustum bottom column 9, an air outlet 10, a microwave coaxial transmission port 11, and a top tuning module 12; the upper half of the cavity 2 is an elliptical wall, and the lower half is a cylindrical wall. The elliptical wall is a surface obtained by rotating a 1 / 4 elliptical characteristic curve around an axis located outside the ellipse and parallel to the major axis of the ellipse. The equation of the elliptical characteristic curve is: , where a is 59mm, b is 100mm, ; The air inlet 1 is located at the top edge of the cavity 2, the top tuning module 12 is located in the middle of the top of the cavity 2, the air outlet 10 is located on the cylindrical wall of the cavity 2, the observation window 3 and the temperature measurement window 4 are located on the elliptical wall of the cavity 2, and the microwave coaxial transmission port 11 is located at the bottom of the cavity 2, which is used to transmit microwave energy to the cavity. There is an annular groove 13 around the bottom of the cavity 2, so that the bottom of the cavity 2 presents a sunken structure. The annular quartz glass 8 and the inverted frustum bottom column 9 are located inside the cavity 2, and the bottom surface is fixed to the bottom of the cavity 2, and the top is flush, which is used to support the copper table 7. The top of the copper table 7 supports the sample table 6, and the plasma hemisphere 5 is placed on the sample table 6 with the spherical surface facing up.

[0009] Preferably, the material used for the sample stage 6 is metal molybdenum.

[0010] Preferably, the relative dielectric constant of the annular quartz glass 8 is 3.78.

[0011] Preferably, the top tuning module 12 is composed of a circular side and a 1 / 2 ellipsoidal surface, wherein the 1 / 2 ellipsoidal surface is obtained by rotating the elliptical characteristic curve for one circle, and the equation of the elliptical characteristic curve is: , where a is 57mm, b is 20mm, The bottom of the tuner is ellipsoidal in shape, which makes it difficult to deposit carbon on the bottom of the tuner.

[0012] The rounded bottom column 9 is conducive to the convergence of microwave energy.

[0013] The annular quartz glass 8 is arranged below the copper platform 7 in order to keep it away from the plasma discharge area.

[0014] The cavity 2 is provided with a top tuning module 12 for tuning the secondary electric field at the top to prevent the generation of an excessively strong secondary electric field.

[0015] The annular groove 13 around the bottom of the cavity 2 can better concentrate microwave energy.

[0016] Furthermore, in order to avoid the problem of heat accumulation during long-term operation, the cavity 2, the copper platform 7, and the inverted round platform bottom column 9 are all directly water-cooled.

[0017] The advantages of this device are as follows:

[0018] 1. The TM022 resonance mode is used to generate a uniformly distributed microwave high field strength area on the sample stage. At the same time, the plasma discharge area is relatively far away from the reactor wall, avoiding the risk of overheating of the reactor wall and deposition of amorphous carbon.

[0019] 2. By introducing the top tuning module 12, the top high field strength area disappears.

[0020] 3. The sunken structure at the bottom of the cavity 2 can affect the convergence effect of microwave energy, so that it can be better concentrated above the sample stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of a TM022 mode microwave plasma diamond film deposition device of the present invention.

[0022] Figure 2 This is an electric field simulation diagram of a TM022 mode microwave plasma diamond film deposition device of the present invention.

[0023] In the figure: air inlet 1, cavity 2, observation window 3, temperature measurement window 4, plasma hemisphere 5, sample stage 6, copper stage 7, annular quartz glass 8, inverted frustum bottom column 9, air outlet 10, microwave coaxial transmission port 11, top tuning module 12, annular groove 13. DETAILED DESCRIPTION

[0024] Example 1 Specific structure of the present invention

[0025] The main body of the device consists of two parts. The first part is a cylindrical resonant cavity with a radius of R = 121mm and a height of H = 90mm. The second part is a curved surface above the cylindrical resonant cavity, which is a 1 / 4 ellipsoidal curve around the axis of the cylindrical cavity. Microwave energy is input from the microwave coaxial transmission port 11 at the bottom of the device, enters the cavity through the annular quartz glass 8, and is reflected by the cavity wall and converges above the sample stage 6. At the same time, there is a secondary electric field at the top of the cavity, and the secondary electric field value is large. At this time, the top tuning module 12 at the upper end is introduced. By changing the size of the top tuning module 12, the secondary electric field disappears, so that there is a strongest electric field in the cavity and it converges above the sample stage 6. The top tuning module 12 is composed of a cylinder and a 1 / 2 ellipsoidal surface, where the 1 / 2 ellipsoidal surface is represented by the elliptical characteristic curve equation as follows: , where a is 57mm, b is 20mm, The tuning bottom is ellipsoidal in shape, which is less likely to cause carbon buildup on the tuning bottom than a typical cylindrical tuning mechanism.

[0026] Example 2 Operation process of the present invention

[0027] 1) Turn on the water cooling circulation system and place the diamond substrate on the sample deposition table in the chamber.

[0028] 2) Use a molecular pump to evacuate the microwave plasma cavity to 1 Pa, and at the same time, introduce hydrogen to repeatedly clean the cavity. Start the microwave source and input 2.45 GHz microwaves into the cavity. The microwaves are reflected by the cavity surface, forming a TM022 mode electric field distribution. The electric field excites the hydrogen to crack, and finally generates plasma above the deposition table.

[0029] 3) After the temperature is raised, introduce 5% methane, 0.005% nitrogen and 0.5% oxygen.

[0030] 4) Gradually increase the pressure and power until diamond deposition conditions are achieved.

[0031] 5) The thickness of the grown diamond depends on the deposition time, and the plasma and diamond states can be judged through the observation window.

[0032] 6) When the deposition process ends, gradually reduce the pressure and power.

Claims

1. A TM022 mode microwave plasma diamond film deposition device, comprising an air inlet (1), a cavity (2), an observation window (3), a temperature measurement window (4), a plasma hemisphere (5), a sample stage (6), a copper stage (7), an annular quartz glass (8), an inverted rounded stage bottom column (9), an air outlet (10), and a microwave coaxial transmission port (11), characterized in that the structure further comprises a top tuning module (12); the upper half wall surface of the cavity (2) is an elliptical wall surface, and the lower half wall surface is a cylindrical wall surface, the elliptical wall surface is a surface obtained by rotating a 1 / 4 elliptical characteristic curve around an axis located outside the ellipse and parallel to the major axis of the ellipse, and the equation of the elliptical characteristic curve is: , where a is 59mm, b is 100mm, The air inlet (1) is located at the top edge of the cavity (2), the top tuning module (12) is located in the middle of the top of the cavity (2), the air outlet (10) is located on the cylindrical wall of the cavity (2), the observation window (3) and the temperature measurement window (4) are located on the elliptical wall of the cavity (2), the microwave coaxial transmission port (11) is located at the bottom of the cavity (2) for transmitting microwave energy to the cavity, and an annular groove (13) is provided around the bottom of the cavity (2) so that the bottom of the cavity (2) presents a sunken structure, the annular quartz glass (8) and the inverted frustum bottom column (9) are located inside the cavity (2), and the bottom surface is fixed to the bottom of the cavity (2) and the top is flush with each other for supporting the copper table (7), the top of the copper table (7) supports the sample table (6), and the plasma hemisphere (5) is placed on the sample table (6) with the spherical surface facing upward.

2. The TMO22 mode microwave plasma diamond film deposition device according to claim 1, characterized in that: The material used for the sample stage (6) is metal molybdenum.

3. The TMO22 mode microwave plasma diamond film deposition device according to claim 1, characterized in that: The relative dielectric constant of the annular quartz glass (8) is 3.

78.

4. The TMO22 mode microwave plasma diamond film deposition device according to claim 1, characterized in that: The top tuning module (12) is composed of a circular side and a 1 / 2 ellipsoidal surface, wherein the 1 / 2 ellipsoidal surface is obtained by rotating the elliptical characteristic curve for one circle. The equation of the elliptical characteristic curve is: , where a is 57mm, b is 20mm, .

Images