A microwave plasma diamond film deposition device

Abstract

The application discloses a microwave plasma diamond film deposition device, and belongs to the technical field of diamond film preparation. The structure comprises an air inlet hole (1), a cavity (2), an observation window (3), an air outlet hole (4), a microwave coaxial transmission port (5), a rounded table bottom column (6), an annular quartz glass (7), a copper table (8), a sample deposition table (9), a plasma hemisphere (10) and a temperature measurement window (11). The device has simple structure and is easy to process, direct water cooling can be adopted, and the situation that the cavity wall is overheated when the equipment works under high power condition is avoided.

Description

Technical Field

[0001] This invention belongs to the field of diamond thin film preparation technology, specifically relating to a microwave plasma diamond film deposition apparatus. Background Technology

[0002] Diamond is well-known as the hardest naturally occurring material. In addition, it possesses excellent properties such as a very low coefficient of friction and adhesion, a low coefficient of thermal expansion, a wide bandgap, and excellent optical transparency. These properties make diamond widely applicable in the field of semiconductor devices. However, the demanding conditions and scarcity of natural diamond formation limit its practical applications. Advances in diamond synthesis processes have made these applications possible.

[0003] Compared with other chemical vapor deposition methods, microwave plasma chemical vapor deposition (MPCVD) has the advantage of being able to synthesize large-area, high-quality diamond films. It generally uses metal as the cavity and does not introduce catalysts or impurities during the synthesis of single-crystal diamond, thus improving the quality of the diamond.

[0004] With the development of MPCVD technology, in order to increase microwave input power, people began to study and design deposition devices with different structures. From the initial quartz tube type, quartz bell type, and cylindrical resonant cavity, to the later non-cylindrical multimode and ellipsoidal resonant cavity, the power has increased from hundreds of watts to thousands of watts or even tens of kilowatts.

[0005] Patent CN 103668127 A uses a thin metal plate reflector to regulate the field strength within the cavity. However, because the metal reflector is thin, it is difficult to achieve direct cooling with water, so the thin plate is prone to overheating and thus depositing polycrystalline carbon. The quartz window of this device is close to the discharge area and is easily etched.

[0006] Both patents CN103305816 A and CN101864560 B employ tuning mechanisms to adjust the electric field distribution within the resonant cavity. However, during high-power, long-term deposition, graphite and other carbides are easily generated in the tuning mechanism or areas close to the discharge region. While the tuning mechanism allows for the control of the electric field distribution within the cavity, its protruding nature can affect water cooling, leading to an increase in the temperature of the cavity's inner wall and making it easier to deposit impurities such as non-diamond carbon.

[0007] To address these technical shortcomings, how to suppress the formation of non-diamond carbon and maintain high-quality, long-term growth has become an urgent issue. Summary of the Invention

[0008] To overcome the above difficulties, the present invention provides a novel cylindrical microwave plasma diamond film deposition device, which has advantages such as simple structure, quartz glass far from the discharge area, direct water cooling, and the ability to deposit diamond under high power conditions.

[0009] A microwave plasma diamond film deposition apparatus comprises an inlet 1, a cavity 2, an observation window 3, an outlet 4, a microwave coaxial transmission port 5, a frustum-shaped base 6, a ring-shaped quartz glass 7, a copper stage 8, a sample deposition stage 9, a plasma hemisphere 10, and a temperature measuring window 11. The upper half of the cavity 2 has an elliptical wall, and the lower half has a cylindrical wall. The elliptical wall is obtained by rotating a 1 / 4 elliptical characteristic curve around an axis located outside the ellipse and parallel to its major axis. The inlet 1 is located at the center of the top of the cavity 2, and the observation window 3 and... The vent 4 is located on the cylindrical side wall of the cavity 2. The microwave coaxial transmission port 5 is located at the bottom of the cavity 2. The inverted frustum base column 6, the annular quartz glass 7, the copper stage 8, the sample deposition stage 9, and the plasma hemisphere 10 are located inside the cavity 2. The inverted frustum base column 6 and the annular quartz glass 7 are of equal height and their bottoms are fixed to the bottom inside the cavity 2. The copper stage 8 is located on top of the inverted frustum base column 6 and the annular quartz glass 7. The sample deposition stage 9 is located on top of the copper stage 8. The plasma hemisphere 10 is located on top of the sample deposition stage 9 with its spherical surface facing upwards. The temperature measuring window 11 is located on the elliptical wall of the cavity 2.

[0010] As an optimized technical solution, the 1 / 4 elliptical feature curve is Where a is 40-50mm, b is 40-50mm, and θ∈[π, 3π / 2].

[0011] As an optimized technical solution, the distance from the center point of the sample deposition stage 9 to all walls of the cavity 2 is not less than 4λ / 5, where λ is the wavelength of the introduced microwave.

[0012] As an optimized technical solution, the thickness of the annular quartz glass 7 is 10mm.

[0013] Beneficial effects:

[0014] 1. This device has a simple structure and is easy to manufacture. It is mainly based on a cylinder and cut using a 1 / 4 elliptical characteristic curve. Figure 1 As shown, direct water cooling can be used to avoid overheating of the cavity wall when the equipment is working under high power conditions.

[0015] 2. The annular quartz glass is hidden below the sample deposition stage, away from the plasma discharge area, effectively avoiding overheating, breakage, and etching of the quartz glass.

[0016] 3. The distance from the cavity wall to the center of the substrate is not less than 4λ / 5, which reduces the thermal radiation to the inner wall of the resonant cavity and prevents the deposition of non-diamond carbon.

[0017] 4. The inverted frustum base column is conducive to reflecting microwaves and converging them.

[0018] 5. This equipment can deposit large-area diamond films under microwave input power of 6kW. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a microwave plasma diamond film deposition device disclosed in this invention.

[0020] In the figure: 1. Inlet; 2. Cavity; 3. Observation window; 4. Outlet; 5. Microwave coaxial transmission port; 6. Frustum base; 7. Ring-shaped quartz glass; 8. Copper stage; 9. Sample deposition stage; 10. Plasma hemisphere; 11. Temperature measurement window.

[0021] Figure 2 This describes the electric field distribution of a microwave plasma diamond film deposition device. Detailed Implementation

[0022] Example 1: Overall Structure of the Invention

[0023] A schematic diagram of the structure of a microwave plasma diamond film deposition device of the present invention is shown below. Figure 1 As shown, the structure comprises an air inlet 1, a cavity 2, an observation window 3, an air outlet 4, a microwave coaxial transmission port 5, a frustum-shaped base 6, a ring-shaped quartz glass 7, a copper stage 8, a sample deposition stage 9, a plasma hemisphere 10, and a temperature measuring window 11. The upper half of the cavity 2 has an elliptical wall, and the lower half has a cylindrical wall. The elliptical wall is obtained by rotating a quarter-elliptical characteristic curve around an axis located outside the ellipse and parallel to its major axis. The quarter-elliptical characteristic curve is... In this embodiment, a is 40mm, b is 50mm, and θ∈[π, 3π / 2]. The air inlet 1 is located at the top center of the cavity 2, the observation window 3 and the air outlet 4 are located on the cylindrical sidewall of the cavity 2, the microwave coaxial transmission port 5 is located at the bottom of the cavity 2, the inverted frustum base column 6, the annular quartz glass 7, the copper stage 8, the sample deposition stage 9 and the plasma hemisphere 10 are located inside the cavity 2. The inverted frustum base column 6 and the annular quartz glass 7 are of equal height and their bottoms are fixed to the bottom inside the cavity 2. The thickness of the annular quartz glass 7 is 10mm. The copper stage 8 is located on top of the inverted frustum base column 6 and the annular quartz glass 7, the sample deposition stage 9 is located on top of the copper stage 8, the plasma hemisphere 10 is located on top of the sample deposition stage 9 with the spherical surface facing upwards, and the temperature measuring window 11 is located on the elliptical wall 2 of the cavity 2. The distance from the center point of the sample deposition stage 9 to all walls of the cavity 2 is not less than 4λ / 5, where λ is the wavelength of the introduced microwave. Because the cavity wall is far from the plasma discharge area, overheating of the cavity wall and the formation of non-diamond carbon are avoided.

[0024] Example 2: Working process of the present invention

[0025] 1. Turn on the water cooling circulation system and place the diamond substrate onto the sample deposition stage 9 of the cavity.

[0026] 2. Use a molecular pump to evacuate the microwave plasma cavity to 1 Pa, and at the same time, introduce hydrogen gas to repeatedly clean the cavity. Start the microwave source and input 2.45 GHz microwaves into the cavity. After being excited by the electric field, plasma is generated above the sample deposition stage 9.

[0027] 3. After the temperature rise is complete, introduce 5% methane, 0.005% nitrogen and 0.5% oxygen.

[0028] 4. Gradually increase the pressure and power until the conditions for diamond deposition are met.

[0029] 5. The thickness of the grown diamond depends on the deposition time, and the state of the plasma and diamond can be determined by observing window 3.

[0030] 6. When the deposition process is finished, gradually reduce the pressure and power.

[0031] like Figure 2 As shown, the device exhibits a concentrated electric field distribution within the cavity at an input power of 6kW, with a unique high field strength region located above the substrate of the sample deposition stage.

Claims

1. A microwave plasma diamond film deposition device, which comprises an air inlet hole (1), a cavity (2), an observation window (3), an air outlet hole (4), a microwave coaxial transmission port (5), a rounded platform column (6), an annular quartz glass (7), a copper platform (8), a sample deposition platform (9), a plasma hemisphere (10), and a temperature measurement window (11); the upper half of the wall 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 for one revolution; the surface is concave towards the cavity; the 1 / 4 elliptical characteristic curve is: wherein a is 40-50 mm, b is 40-50 mm, ; the air inlet hole (1) is located at the center of the top of the cavity (2), the observation window (3) and the air outlet hole (4) are located at the cylindrical side wall of the cavity (2), the microwave coaxial transmission port (5) is located at the bottom of the cavity (2), the rounded platform column (6), the annular quartz glass (7), the copper platform (8), the sample deposition platform (9), and the plasma hemisphere (10) are located inside the cavity (2); the rounded platform column (6) and the annular quartz glass (7) are at the same height and are fixed at the bottom of the cavity (2); the copper platform (8) is located at the top of the rounded platform column (6) and the annular quartz glass (7); the sample deposition platform (9) is located at the top of the copper platform (8); the plasma hemisphere (10) is located at the top of the sample deposition platform (9) with the spherical surface facing upwards; and the temperature measurement window (11) is located on the elliptical wall of the cavity (2).​​​​ 2. A microwave plasma diamond film deposition apparatus according to claim 1, wherein The distance from the center point of the sample deposition stage (9) to all wall surfaces of the cavity (2) is not less than 4λ / 5, λ being the wavelength of the introduced microwave.

3. The microwave plasma diamond film deposition apparatus of claim 1, wherein The thickness of the annular quartz glass (7) is 10 mm.

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