A new MPCVD device base based on third-order Bezier curve

Abstract

The present invention discloses a novel MPCVD device base based on a third-order Bezier curve, which mainly solves the problem that the right-angle transition edge of the traditional base causes distortion of the surrounding electric field, affects the chemical vapor deposition process, and leads to unsatisfactory crystallization effect. The solution includes: the base is in the shape of a flat cylinder, the edge shape of which is formed by a third-order Bezier curve, the bottom of the flat cylinder longitudinal section is two right angles, and the top is two arc angles formed by the third-order Bezier curve; the curve is generated by four control points, with the center of the bottom of the MPCVD device as the origin, the axis parallel to the bottom surface of the base as the horizontal axis, and the vertical direction as the vertical axis, to construct a two-dimensional cylindrical coordinate system; the shape of the curve is defined by adjusting the position coordinates of the four control points in the coordinate system. The present invention can eliminate the electric field distortion phenomenon, thereby enhancing the electric field strength above the base, increasing the plasma density, and effectively improving the deposition rate of diamond materials to be prepared.

Description

Technical Field

[0001] The present invention belongs to the field of electrical technology and further relates to a microwave plasma chemical vapor deposition device base, specifically a novel microwave plasma chemical vapor deposition MPCVD (Microwave Plasma Chemical Vapor Deposition) device base based on a third-order Bezier curve, which can be used to eliminate electric field distortion and increase plasma density. Background Art

[0002] Diamond has a range of advantages, including high hardness, high thermal conductivity, high electron mobility, low thermal expansion coefficient, and high light transmittance. Therefore, it is widely used in aerospace, integrated circuits, and mechanical processing. Natural diamond is expensive, so the artificial synthesis of diamond using microwave plasma chemical vapor deposition devices is a current research hotspot. The working principle of this device is to use a microwave excitation source to generate high-power microwaves, which are transmitted to a resonant cavity through waveguides and antennas. A strong electric field is generated above the bottom base. The reaction gases such as methane and hydrogen in the resonant cavity are ionized into a plasma state by the strong electric field. The methane molecules are decomposed, releasing carbon atoms, which are deposited and crystallized on the base at the bottom of the resonant cavity, forming a diamond film.

[0003] When a microwave plasma chemical vapor deposition (MCPD) system is operating, the distribution of areas with high plasma density is similar to that of strong electric fields, primarily concentrated in the upper region near the base. The base's shape significantly influences the distribution of these areas. The base of a conventional microwave plasma CVD system is a standard oblate cylinder with a rectangular longitudinal section. Its right-angled transition edges distort the surrounding electric field, causing reduced electric field strength and plasma density above the base. This impacts the CVD process on the base and results in suboptimal crystallization. Summary of the Invention

[0004] The purpose of the present invention is to address the deficiencies of the above-mentioned existing technologies and propose a new MPCVD device base based on a third-order Bezier curve. The third-order Bezier curve is used to construct a smooth transition area at the edge of the base, eliminate the electric field distortion phenomenon, thereby enhancing the electric field strength above the base and increasing the plasma density.

[0005] In order to achieve the above-mentioned purpose, the present invention proposes the following specific solutions:

[0006] A novel microwave plasma chemical vapor deposition (MPCVD) device base based on a third-order Bezier curve, which is placed at the bottom of the MPCVD device resonant cavity and is detachable;

[0007] The base is in the shape of a flat cylinder, and its edge shape is formed by a third-order Bezier curve;

[0008] The third-order Bezier curve is generated by four control points, with the center of the bottom of the MPCVD device as the origin, the axis parallel to the bottom surface of the base as the horizontal axis, and the vertical direction as the vertical axis, to construct a two-dimensional cylindrical coordinate system; the shape of the curve is defined by adjusting the position coordinates of the four control points in the coordinate system;

[0009] The bottom of the longitudinal section of the flat cylinder is two right angles, and the upper part is two arc angles formed by a third-order Bezier curve.

[0010] Furthermore, the bottom radius of the flat cylinder is 25.4 cm and the highest point height is 4.2 cm.

[0011] Furthermore, the above four control points are respectively recorded as P0, P1, P2 and P3, and the third-order Bezier curve is expressed as follows:

[0012] B(t)=(1-t) 3 [P0(r),P0(z)]+3(1-t) 2 t[P1(r),P1(z)]+3(1-t)t 2 [P2(r),P2(z)]+t 3 [P3(r),P3(z)],

[0013] Among them, t∈[0,1], B(t) is the coordinate of the point on the curve, [P i (r),P i (z)] represents the coordinate of the i-th control point in the cylindrical coordinate system, i = 0, 1, 2, 3; the shape of the base edge curve is changed by adjusting the coordinates of the four control points.

[0014] Furthermore, the coordinates of the above control points in the cylindrical coordinate system are set according to the following data: P0(r)=19.15mm, P0(z)=424.4mm, P1(r)=22mm, P1(z)=424.2mm, P2(r)=25mm, P2(z)=423.4mm, P3(r)=25.4mm, P3(z)=422.6mm.

[0015] Furthermore, the base is made of molybdenum metal or a metal with the same properties.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] First, the present invention uses a third-order Bezier curve to optimize the edge shape of the base of the existing microwave plasma chemical vapor deposition device, making the edge transition of the base smoother, thereby eliminating the distorted electric field around the base, effectively enhancing the electric field strength above the base, and increasing the plasma density;

[0018] Second, since the edge shape of the base of the microwave plasma chemical vapor deposition device proposed in the present invention has been optimized, the plasma density above it is relatively high, thereby increasing the deposition rate of the diamond film material to be prepared and improving economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the MPCVD device;

[0020] Figure 2 This is a longitudinal cross-section of the base of a traditional MPCVD device;

[0021] Figure 3 A longitudinal cross-sectional view of the base of the novel MPCVD device of the present invention;

[0022] Figure 4 Schematic diagram of the electric field distribution inside the resonant cavity when using a conventional MPCVD device base and the novel MPCVD base of the present invention; (a) shows the electric field distribution inside the resonant cavity when using a conventional MPCVD device base, and (b) shows the electric field distribution inside the resonant cavity when using the novel MPCVD base of the present invention;

[0023] Figure 5 Schematic diagram of the plasma density distribution inside the resonant cavity when using a conventional MPCVD device base and the novel MPCVD base of the present invention; (a) is the plasma density distribution inside the resonant cavity when using a conventional MPCVD device base, Figure 5 (b) shows the plasma density distribution inside the resonant cavity when the novel MPCVD base of the present invention is used. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below with reference to the accompanying drawings.

[0025] Example 1: Reference Figure 1 and Figure 3 The present invention proposes a novel microwave plasma chemical vapor deposition MPCVD device base based on a third-order Bezier curve, which is placed at the bottom of the MPCVD device resonant cavity and is detachable. Figure 1 As shown;

[0026] The base is made of molybdenum metal or metal with the same properties, and is in the shape of a flat cylinder, and its edge shape is formed by a third-order Bezier curve, such as Figure 3 As shown;

[0027] The bottom of the longitudinal section of the flat cylinder is two right angles, and the upper part is two arc angles formed by a third-order Bezier curve; the bottom radius of the flat cylinder is 25.4 cm, and the highest point height is 4.2 cm.

[0028] The third-order Bezier curve is generated by four control points. A two-dimensional cylindrical coordinate system is constructed with the center of the bottom of the MPCVD device as the origin, the axis parallel to the bottom surface of the base as the horizontal axis, and the vertical direction as the vertical axis. The shape of the curve is defined by adjusting the position coordinates of the four control points in the coordinate system. The four control points are respectively recorded as P0, P1, P2 and P3. The third-order Bezier curve is expressed as follows:

[0029] B(t)=(1-t) 3 [P0(r),P0(z)]+3(1-t) 2 t[P1(r),P1(z)]+3(1-t)t 2 [P2(r),P2(z)]+t 3 [P3(r),P3(z)],

[0030] Among them, t∈[0,1], B(t) is the coordinate of the point on the curve, [P i (r),P i (z)] represents the coordinate of the i-th control point in the cylindrical coordinate system, i = 0, 1, 2, 3; the shape of the base edge curve is changed by adjusting the coordinates of the four control points.

[0031] The coordinates of the control points in the cylindrical coordinate system are set according to the following data: P0(r)=19.15mm, P0(z)=424.4mm, P1(r)=22mm, P1(z)=424.2mm, P2(r)=25mm, P2(z)=423.4mm, P3(r)=25.4mm, P3(z)=422.6mm.

[0032] Example 2: The overall structure of the base of the new plasma chemical vapor deposition MPCVD device proposed in this example is the same as that of Example 1. Figure 1-3 , giving specific parameters to further describe the novel base station in the present invention in detail:

[0033] Reference Figure 1-3 , microwave plasma chemical vapor deposition equipment such as Figure 1 As shown, a detachable molybdenum base is placed at the bottom of the resonant cavity, that is, the original base of the microwave plasma chemical vapor deposition device. The longitudinal section of the original base is shown in FIG. Figure 2 As shown; The present invention proposes a novel microwave plasma chemical vapor deposition MPCVD device base based on a third-order Bezier curve, specifically a flat cylinder, the longitudinal section of the flat cylinder is as shown Figure 3 shown; wherein:

[0034] The base radius of the flat cylinder is 25.4 cm and the highest point height is 4.2 cm;

[0035] The edge shape of the flat cylinder is described by a third-order Bezier curve, which is generated by four control points, namely P0, P1, P2 and P3. These four points define the shape of the third-order Bezier curve. The mathematical expression of the third-order Bezier curve is:

[0036] B(t)=(1-t) 3 [P0(r),P0(z)]+3(1-t) 2 t[P1(r),P1(z)]+3(1-t)t 2 [P2(r),P2(z)]+t 3 [P3(r),P3(z)],

[0037] Among them, t∈[0,1], B(t) is the coordinate of the point on the curve, [P i (r),P i (z)] represents the coordinate of the i-th control point in the cylindrical coordinate system, i = 0, 1, 2, 3; the shape of the abutment edge curve is changed by adjusting the coordinates of the four control points;

[0038] Reference Figure 1 The cylindrical coordinate system is a two-dimensional coordinate system consisting of an r-axis and a z-axis, wherein the r-axis is parallel to the bottom surface of the base, the z-axis is perpendicular to the r-axis, and the origin is located at the bottom center of the MPCVD device.

[0039] In this embodiment, P0(r)=19.15mm, P0(z)=424.4mm, P1(r)=22mm, P1(z)=424.2mm, P2(r)=25mm, P2(z)=423.4mm, P3(r)=25.4mm, P3(z)=422.6mm.

[0040] The present invention can replace the base of the existing microwave plasma chemical vapor deposition device. Since the present invention uses a third-order Bezier curve to optimize the edge shape of the base, compared with Figure 2 and Figure 3 It can be seen that the edge transition of the base in the present invention is smoother; using the base proposed by the present invention can increase the plasma density above the base, and effectively improve the deposition rate of diamond materials to be prepared.

[0041] The effects of the present invention will be further described below in conjunction with simulation experiments.

[0042] 1. Simulation conditions:

[0043] The conventional microwave plasma chemical vapor deposition device base and the microwave plasma chemical vapor deposition device base of the present invention are respectively installed on Figure 1In the MPCVD device shown, electromagnetic-plasma multi-physics field simulation was performed on the MPCVD device using two bases in COMSOL software, with a simulation frequency of 2.45 GHz and an input power of 1900 W.

[0044] 2. Simulation content:

[0045] The electric field distribution and plasma density distribution inside the resonant cavity are simulated when using two bases respectively.

[0046] 3. Simulation results:

[0047] The simulation results are as follows Figure 4 and Figure 5 As shown; Figure 4 (a) is the electric field distribution inside the resonant cavity when using the traditional MPCVD device base, and (b) is the electric field distribution inside the resonant cavity when using the new MPCVD in the present invention. By comparison, it can be seen that the distorted electric field around the new MPCVD base of the present invention is successfully eliminated. Figure 5 (a) is the plasma density distribution inside the resonant cavity when using the traditional MPCVD device base, and (b) is the plasma density distribution inside the resonant cavity when using the new MPCVD base in the present invention. By comparison, it can be seen that the plasma density is significantly improved by using the new MPCVD base in the present invention.

[0048] The above simulation analysis proves the correctness and effectiveness of the method proposed in the present invention.

[0049] Parts of the present invention that are not described in detail belong to common knowledge among those skilled in the art.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Obviously, for professionals in this field, after understanding the content and principles of the present invention, they may make various modifications and changes in form and details without departing from the principles and structure of the present invention. However, these modifications and changes based on the ideas of the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. A novel microwave plasma chemical vapor deposition (MPCVD) device base based on a third-order Bezier curve, which is placed at the bottom of the MPCVD device resonant cavity and is detachable; characterized by: The base is in the shape of a flat cylinder, and its edge shape is formed by a third-order Bezier curve; The third-order Bezier curve is generated by four control points. A two-dimensional cylindrical coordinate system is constructed with the center of the bottom of the MPCVD device as the origin, the axis parallel to the bottom surface of the base as the horizontal axis, and the vertical direction as the vertical axis. The shape of the curve is defined by adjusting the position coordinates of the four control points in the coordinate system. The four control points are respectively denoted as P0, P1, P2 and P3. The third-order Bezier curve is expressed as follows: B(t)=(1-t) 3 [P0(r),P0(z)]+3(1-t) 2 t[P1(r),P1(z)]+3(1-t)t 2 [P2(r),P2(z)]+t 3 [P3(r),P3(z)], Among them, t∈[0,1], B(t) is the coordinate of the point on the curve, [P i (r),P i (z)] represents the coordinate of the i-th control point in the cylindrical coordinate system, i = 0, 1, 2, 3; the shape of the abutment edge curve is changed by adjusting the coordinates of the four control points; The coordinates of the control points in the cylindrical coordinate system are set according to the following data: P0(r)=19.15mm, P0(z)=424.4mm, P1(r)=22mm, P1(z)=424.2mm, P2(r)=25mm, P2(z)=423.4mm, P3(r)=25.4mm, P3(z)=422.6mm; The bottom of the longitudinal section of the flat cylinder is two right angles, and the upper part is two arc angles formed by a third-order Bezier curve; the bottom radius of the flat cylinder is 25.4 cm, and the highest point height is 4.2 cm.

2. The base according to claim 1, characterized in that: Made of molybdenum metal or metal with similar properties.

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