Microwave plasma chemical vapor deposition device

Abstract

The invention belongs to the technical field of microwave plasma chemical vapor deposition, and discloses a microwave plasma chemical vapor deposition device which comprises a microwave resonant cavity, a bearing assembly, a quartz window, a microwave power source, a rectangular waveguide and an annular waveguide, the microwave resonant cavity is in a flat-end ellipsoid shape, the lengths of three half axes of the microwave resonant cavity are recorded as a, b and c respectively, and (a = b) lt; the half shaft with the length of c is arranged along the z direction, the two ends of the microwave resonant cavity along the z direction are respectively a top end plane and a bottom end plane, the top end plane is provided with an air inlet, and the bottom end plane is provided with an air outlet; the bearing assembly is used for placing a substrate and located on the bottom end plane. The quartz window is annularly arranged at the middle position of the microwave resonant cavity along the z direction; the microwave power source, the rectangular waveguide and the annular waveguide are sequentially connected, the annular waveguide surrounds the quartz window, a slit opening is formed in the inner side of the annular waveguide, electromagnetic waves generated by the microwave power source sequentially pass through the rectangular waveguide, the slit opening and the quartz window to be fed into the microwave resonant cavity, and deposition uniformity is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave plasma chemical vapor deposition, and particularly to a microwave plasma chemical vapor deposition device. Background Art

[0002] The electrode-free property of microwave discharge and the ability to generate a high density of excited particles make the microwave plasma chemical vapor deposition method (MPCVD) widely used in the preparation of diamond films. In related technologies, the microwave plasma chemical vapor deposition device generally has the problem of plasma etching of the quartz window, and due to the assembly error or processing error of parts, the microwave plasma chemical vapor deposition device is prone to the problem of non-central symmetry of the plasma, resulting in non-uniform deposition of the diamond film. Summary of the Invention

[0003] The purpose of the present invention is to provide a microwave plasma chemical vapor deposition device, which solves the problem of plasma etching of the quartz window and improves the uniformity of diamond film deposition.

[0004] To achieve this purpose, the present invention adopts the following technical solutions:

[0005] A microwave plasma chemical vapor deposition device includes:

[0006] A microwave resonator cavity, which is in the shape of a flat-ended ellipsoid, and the lengths of its three semi-axes are respectively denoted as a, b, and c, (a = b) < c, and the semi-axis with length c is arranged along the z direction. The two ends of the microwave resonator cavity arranged along the z direction are respectively a top plane and a bottom plane. The top plane is provided with an air inlet, and the bottom plane is provided with an exhaust port;

[0007] A carrier assembly for placing a substrate, and the carrier assembly is located on the bottom plane;

[0008] A quartz window, which is arranged around the middle position of the microwave resonator cavity along the z direction;

[0009] A microwave power supply, a rectangular waveguide, and a circular waveguide, which are connected in sequence. The circular waveguide surrounds the quartz window, and a slit opening is provided inside the circular waveguide. The electromagnetic wave generated by the microwave power supply is fed into the microwave resonator cavity through the rectangular waveguide, the slit opening, and the quartz window in sequence, and the electromagnetic wave electric field in the microwave resonator cavity is evenly distributed along the circumferential direction of the microwave resonator cavity.

[0010] In some embodiments, the height of the annular waveguide is greater than the height of the rectangular waveguide; the inner diameter of the annular waveguide is greater than the wavelength of the electromagnetic wave generated by the microwave power supply, and 1.05 ≤ c / a ≤ 1.15.

[0011] In some embodiments, the height of the annular waveguide in the z - direction is H, and the height of the rectangular waveguide in the z - direction is h, then 1.05h ≤ H ≤ 1.15h;

[0012] The outer diameter of the annular waveguide is R, the inner diameter of the annular waveguide is r, and the wavelength of the electromagnetic wave generated by the microwave power supply is λ, 2λ < R < 3λ, 1.8λ < r < 2.0λ, and 1.2 ≤ R / r ≤ 1.5.

[0013] In some embodiments, the annular waveguide is provided with a plurality of the slit openings along the circumferential direction. The slit openings are arc - shaped, the length of the slit openings is 0.5λ, and a plurality of wave nodes are arranged in the annular waveguide. The slit openings and the wave nodes are arranged in one - to - one correspondence.

[0014] In some embodiments, a frustum - shaped groove is recessed inward from the top plane. The diameter of the notch of the frustum - shaped groove is greater than the diameter of the bottom of the frustum - shaped groove. The air inlet is opened at the bottom of the groove, and the radius of the bottom of the groove is less than the wavelength of the electromagnetic wave generated by the microwave power supply;

[0015] The microwave resonator is used to converge electromagnetic waves. The microwave resonator has an upper focus and a lower focus. The upper focus corresponds to the position of the frustum - shaped groove, and the lower focus corresponds to the surface position of the substrate.

[0016] In some embodiments, the radius of the bottom of the groove is r1, and r1 = 0.25λ.

[0017] In some embodiments, there are a plurality of air inlets, and all the air inlets are axially symmetrically distributed along the semi - axis with a length of c; there are a plurality of air outlets, and all the air outlets are axially symmetrically distributed along the semi - axis with a length of c;

[0018] The microwave resonator includes a first cavity and a second cavity arranged along the z - direction. A sealing groove is formed between the first cavity and the second cavity. The quartz window is embedded in the sealing groove, and the quartz window is hermetically connected to the first cavity and the second cavity through sealing members respectively.

[0019] In some embodiments, the carrier assembly includes a bracket and a lift - adjustable tuning structure. The bracket is arranged on the lift - adjustable tuning structure. The lift - adjustable tuning structure is located at the center of the bottom plane. The lift - adjustable tuning structure and the microwave resonator are insulated and isolated by high - thermal - conductivity silicon carbide ceramics; the bracket and the microwave resonator are connected by a DC power supply and form a current loop.

[0020] In some embodiments, the microwave plasma chemical vapor deposition apparatus further includes a bias electrode and a pulsed bias power supply. The bias electrode is disposed on the support, and the pulsed bias power supply is disposed outside the microwave resonant cavity. One end of the pulsed bias power supply is connected to the bias electrode, and the other end of the pulsed bias power supply is connected to the microwave resonant cavity.

[0021] In some embodiments, an observation window is provided on the side of the microwave resonant cavity, which is used to observe the state of the plasma inside the microwave resonant cavity and measure the substrate temperature.

[0022] The beneficial effects of this invention are:

[0023] In the microwave plasma chemical vapor deposition apparatus provided by this invention, a microwave power supply generates electromagnetic waves. These waves sequentially pass through a rectangular waveguide, a ring waveguide, and a quartz window before entering the microwave resonant cavity. By altering the shape of the waveguides, the propagation symmetry of the electromagnetic waves is broken, causing a redistribution of the electromagnetic field components and achieving a conversion from TE mode to TM mode. Within the microwave resonant cavity, the electromagnetic waves continuously reflect and superimpose to form a stable standing wave. This wave concentrates electric field energy in the region above the supporting components, creating a strong electric field region that meets the requirements for gas ionization. The reactive gas introduced into the microwave resonant cavity through the inlet is endowed with sufficient kinetic energy by the strong electric field. When these high-speed electrons collide with the gas molecules, they cause ionization and dissociation of the gas, leading to the formation of a high-density plasma for the deposition of heteroepitaxial diamond. The ring waveguide coupling method enables axially symmetrical distribution of the electromagnetic waves, thereby improving the uniformity of the electromagnetic field and the plasma. By combining the focusing effect of the ellipsoidal microwave resonant cavity, the electromagnetic electric field within the cavity is uniformly distributed along its circumference. This achieves plasma homogeneity while simultaneously increasing the electromagnetic electric field intensity and plasma number density at the substrate, thereby improving the uniformity of diamond film deposition. Furthermore, the annular quartz window is located on the side of the microwave resonant cavity, away from the plasma, preventing plasma etching of the quartz window. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the microwave plasma chemical vapor deposition apparatus provided by the present invention;

[0025] Figure 2 This is a schematic diagram of the assembly of the ring waveguide, quartz window and microwave resonant cavity provided by the present invention;

[0026] Figure 3 This is a front view of the numerical simulation electric field intensity distribution results of the microwave plasma chemical vapor deposition apparatus provided by the present invention;

[0027] Figure 4This is a left view of the numerical simulation results of the electric field intensity distribution of the microwave plasma chemical vapor deposition apparatus provided by the present invention;

[0028] Figure 5 This is a top view of the numerical simulation results of the electric field intensity distribution of the microwave plasma chemical vapor deposition apparatus provided by the present invention;

[0029] Figure 6 This is a schematic diagram of the three-dimensional distribution of the electric field intensity in the numerical simulation of the microwave plasma chemical vapor deposition apparatus provided by the present invention;

[0030] Figure 7 This is a comparison diagram showing the radial distribution of microwave electric field intensity on a substrate surface with a radius of 40 mm between the microwave plasma chemical vapor deposition apparatus provided by this invention and a typical TM02 mode MPCVD apparatus.

[0031] In the picture:

[0032] 1. Microwave power supply; 2. Rectangular waveguide; 3. Short-circuit piston; 4. Three-pin tuner; 5. Ring waveguide; 51. Slit opening; 6. Seal; 7. Quartz window; 8. Microwave resonant cavity; 81. Frustum-shaped slot; 82. Top plane; 83. Air inlet; 84. Exhaust port; 85. Observation window; 86. First cavity; 87. Second cavity; 88. Bottom plane; 9. Support; 10. Adjustable tuning structure; 20. Pulse bias power supply; 30. Plasma. Detailed Implementation

[0033] To make the technical problems solved by the present invention, the technical solutions adopted, and the technical effects achieved clearer, the technical solutions of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0035] In the present invention, unless otherwise clearly specified or limited, the first feature being "above" or "below" the second feature may include direct contact between the first and second features, or may include the first and second features not being in direct contact but in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or simply indicating that the first feature has a higher horizontal height than the second feature. The first feature being "below", "beneath" and "underneath" the second feature includes the first feature being directly below and obliquely below the second feature, or simply indicating that the first feature has a lower horizontal height than the second feature.

[0036] Since the emergence of the MPCVD diamond film deposition technology, a series of microwave plasma chemical vapor deposition devices have emerged, including quartz tube type, quartz bell jar type, cylindrical resonator type and ellipsoidal resonator type. However, these devices generally have the following problems:

[0037] First, the plasma will etch the quartz dielectric window.

[0038] Second, for a 2.45 GHz microwave power supply, the diameter of the diamond film that can be prepared by traditional microwave plasma chemical vapor deposition devices is usually 2 inches, which is difficult to meet the application requirements of diamond materials in large-size infrared windows, microwave windows and heat sinks. In addition, in order to give full play to the application advantages of diamond in key fields such as ultraviolet detectors, radiation detectors and field effect transistors, inch-level large-size single-crystal diamond is required.

[0039] Third, due to part assembly errors or machining errors, traditional microwave plasma chemical vapor deposition devices are prone to non-central symmetry of the plasma, resulting in non-uniform deposition of large-size diamond films.

[0040] As <( Figure 1 and Figure 2 shown, the present invention provides a microwave plasma chemical vapor deposition device, which includes a microwave resonator 8, a carrier assembly, a quartz window 7, a microwave power supply 1, a rectangular waveguide 2 and an annular waveguide 5, and the microwave power supply 1, the rectangular waveguide 2 and the annular waveguide 5 are connected in sequence.

[0041] The microwave resonator 8 is in the shape of a flat-end ellipsoid, and the lengths of its three semi-axes are respectively denoted as a, b and c, a = b, and b < c, and the semi-axis with a length of c is arranged along the z direction. The two ends of the microwave resonator 8 arranged along the z direction are respectively a top plane 82 and a bottom plane 88; the top plane 82 is provided with an air inlet 83 for introducing reaction gases, such as: a mixed gas of hydrogen and methane; the bottom plane 88 is provided with an exhaust port 84.

[0042] The support assembly is used to place the substrate and is located at the bottom plane 88. Specifically, the substrate can be a heterogeneous substrate, that is, the substrate material is not diamond.

[0043] The quartz window 7 is located at the middle position along the z-direction of the microwave resonant cavity 8.

[0044] Microwave power supply 1 is used to generate electromagnetic waves, the frequency of which can be 2.4GHz~2.5GHz, such as 2.4GHz, 2.45GHz or 2.5GHz.

[0045] A ring waveguide 5 is arranged around a quartz window 7. A slit opening 51 is provided inside the ring waveguide 5. The electromagnetic waves generated by the microwave power supply 1 are fed into the microwave resonant cavity 8 through the rectangular waveguide 2, the slit opening 51 and the quartz window 7 in sequence. The electromagnetic wave electric field in the microwave resonant cavity 8 is uniformly distributed along the circumference of the microwave resonant cavity 8.

[0046] The electromagnetic waves generated by microwave power supply 1 pass sequentially through the slit opening 51 of rectangular waveguide 2 and ring waveguide 5, and then through the quartz window 7 into the ellipsoidal microwave resonant cavity 8. The rectangular waveguide 2 and ring waveguide 5 alter the waveguide shape, breaking the propagation symmetry of the electromagnetic waves and causing a redistribution of the electromagnetic field components, thus converting the electromagnetic waves from TE mode to TM mode. Within the microwave resonant cavity 8, the electromagnetic waves continuously reflect and superimpose to form a stable standing wave, converging electric field energy in the region above the supporting components to form a strong electric field region that meets the requirements for gas ionization. The reactive gas introduced into the microwave resonant cavity 8 through the gas inlet 83 is endowed with sufficient kinetic energy by the electrons outside the nuclei of the gas molecules by the strong electric field. When the high-speed electrons collide with the gas molecules, they cause the gas to ionize and dissociate, thereby breaking down the gas to form a high-density plasma 30, achieving the deposition of a diamond thin film on the substrate.

[0047] Furthermore, plasma 30 contains key particles such as electrons, active carbon atoms, and hydrogen radicals. Hydrogen radicals can help suppress the formation of graphitic carbon, providing a pure environment for diamond deposition. Active carbon atoms will grow in an orderly arrangement along specific crystal orientations of the substrate, ultimately completing the deposition of heteroepitaxial diamond.

[0048] The coupling method of the ring waveguide 5 enables the axial symmetrical distribution of electromagnetic waves, thereby improving the uniformity of the electromagnetic wave electric field and plasma 30. Combined with the focusing effect of the ellipsoidal microwave resonant cavity 8 on microwaves, the electromagnetic wave electric field in the microwave resonant cavity 8 is uniformly distributed along the circumference of the microwave resonant cavity 8. This not only achieves the uniformity of plasma 30, but also improves the electromagnetic wave electric field intensity and plasma number density at the substrate, thereby enhancing the uniformity of diamond film deposition.

[0049] In addition, since the annular quartz window 7 is located on the side of the microwave resonant cavity 8 and far away from the plasma 30, the plasma 30 is avoided from etching the quartz window 7.

[0050] In some embodiments, the height of the ring waveguide 5 is greater than the height of the rectangular waveguide 2; the inner diameter of the ring waveguide 5 is greater than the wavelength of the electromagnetic wave generated by the microwave power supply 1.

[0051] Through the above settings, on the one hand, the internal transmission space of the ring waveguide 5 can be expanded, the power capacity can be increased, and the effective transmission cross-sectional area of ​​the ring waveguide 5 can be increased, avoiding the breakdown phenomenon caused by electromagnetic waves transmitted from the rectangular waveguide 2 after being transmitted to the ring waveguide 5; on the other hand, the distribution pattern of the electromagnetic field inside the ring waveguide 5 can be changed, reducing the coupling effect between electromagnetic waves and the wall of the ring waveguide 5, thereby reducing the energy attenuation caused by wall loss and ensuring the stability of signal transmission.

[0052] In some embodiments, 1.05 ≤ c / a ≤ 1.15, for example, c / a is 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, 1.11, 1.12, 1.13, 1.14, or 1.15. The height of the microwave resonant cavity 8 is close to the length of the other two axes, so that the internal three-dimensional space is used evenly, avoiding excessive concentration of electromagnetic field due to insufficient height, and avoiding excessive dispersion of electromagnetic field due to excessive height.

[0053] In some implementations, the height of the ring waveguide 5 along the z-direction is H, and the height of the rectangular waveguide 2 along the z-direction is h. Then, 1.05h ≤ H ≤ 1.15h, for example, H / h can be 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, 1.11, 1.12, 1.13, 1.14, or 1.15. For instance, if the rectangular waveguide 2 is a WR430 rectangular waveguide, then h = 54.61 mm, and the height of the ring waveguide 5 is (1.05 × 54.61) mm ≤ H ≤ (1.15 × 54.61) mm. The height of the ring waveguide 5 should be slightly greater than the height of the rectangular waveguide 2 to avoid excessive height, which would cause structural redundancy and increase the volume and weight of the ring waveguide 5.

[0054] In some embodiments, the outer diameter of the annular waveguide 5 is R, the inner diameter is r, the wavelength of the electromagnetic wave generated by the microwave power supply 1 is λ, 2λ < R < 3λ, 1.8λ < r < 2.0λ, and 1.2 ≤ R / r ≤ 1.5; for example: R / λ is 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, or 2.9, r / λ is 1.81, 1.83, 1.86, 1.89, 1.92, 1.94, 1.96, 1.97, 1.98, or 1.99, and R / r is 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, or 1.5. Exemplarily, the microwave power supply 1 generates an electromagnetic wave of 2.45 GHz with a wavelength of 122.4 mm, then (2×122.4) mm < R < 3×122.4 mm, (1.8×122.4) mm < r < (2.0×122.4) mm.

[0055] The ratio of the outer diameter to the inner diameter determines the transmission characteristics of the annular waveguide 5, and the dimensional values of both determine the power capacity of the annular cavity of the annular waveguide 5. When R / r is within a reasonable range, the effective space of the annular cavity is fully utilized, the electric field distribution is uniform and the peak intensity is low, which can not only increase the power capacity (avoid breakdown) but also avoid structural redundancy due to too large an outer diameter. When R / r is too large and the inner diameter is too small, the effective transmission space will be compressed, and the electric field concentration will cause a breakdown risk; if R / r is too small and the inner and outer diameters are close, it will affect the power capacity. The larger the inner diameter, the more the electromagnetic field distribution will be away from the inner wall, which can reduce the coupling with the wall surface, reduce the conductor loss, and improve the energy transmission efficiency. Therefore, setting the inner diameter between 1.8λ and 2.0λ can not only improve the energy transmission efficiency and reduce the breakdown risk but also ensure the power capacity. Increasing the outer diameter can make the propagation path of the electromagnetic wave in the annular waveguide 5 longer and reduce the resonance frequency, but too large an outer diameter will damage the transmission stability and increase the volume and weight of the annular waveguide 5; by setting the outer diameter of the annular waveguide 5 between 2λ and 3λ, stable transmission of the electromagnetic wave in the annular waveguide 5 can be achieved, and the effect is the best.

[0056] In some embodiments, the annular waveguide 5 is provided with a plurality of slit openings 51 along the circumferential direction. The slit openings 51 are arc-shaped, the length of the slit openings 51 is 0.5λ, and a plurality of wave nodes are arranged in the annular waveguide 5. The slit openings 51 and the wave nodes are arranged in one-to-one correspondence. For example, the microwave power supply 1 generates an electromagnetic wave of 2.45 GHz with a wavelength of 122.4 mm, then the length of the slit openings 51 is 61.2 mm. By setting the slit openings 51 with a circumferentially uniform distribution and a length of 0.5λ, axisymmetric radiation can be achieved and the electric field uniformity can be improved.

[0057] In some embodiments, a frustum-shaped groove 81 is recessed inward from the top plane 82. The diameter of the groove opening of the frustum-shaped groove 81 is larger than the diameter of the groove bottom. The air inlet 83 is located at the bottom of the groove, and the radius of the groove bottom is smaller than the wavelength of the electromagnetic wave generated by the microwave power supply 1. For example, the radius of the groove bottom is r1, where r1 = 0.25λ.

[0058] The microwave resonant cavity 8 has a focusing effect on electromagnetic waves. The microwave resonant cavity 8 has an upper focus and a lower focus. The upper focus corresponds to the position of the frustum-shaped groove 81, which avoids the generation of parasitic plasma 30 at this location. The lower focus corresponds to the surface position of the substrate, which is beneficial to enhancing the electric field strength and uniformity at the substrate surface.

[0059] Furthermore, multiple air inlets 83 are provided, and all air inlets 83 are symmetrically distributed along a semi-axis of length c; multiple exhaust outlets 84 are provided, and all exhaust outlets 84 are symmetrically distributed along a semi-axis of length c, to ensure the uniformity of the gas flow field in the microwave resonant cavity 8.

[0060] Understandably, the number of air inlets 83 and the number of exhaust outlets 84 may be the same or different. In one embodiment, an air inlet 83 is provided every 90° along the axial direction, for a total of 4 air inlets 83, and an exhaust outlet 84 is provided every 60° along the axial direction, for a total of 6 exhaust outlets 84; or an air inlet 83 is provided every 60° along the axial direction, for a total of 6 air inlets 83, and an exhaust outlet 84 is provided every 60° along the axial direction, for a total of 6 exhaust outlets 84; or an air inlet 83 is provided every 60° along the axial direction, for a total of 6 air inlets 83, and an exhaust outlet 84 is provided every 90° along the axial direction, for a total of 4 exhaust outlets 84.

[0061] In some embodiments, the microwave resonant cavity 8 includes a first cavity 86 and a second cavity 87 arranged along the z-direction, a sealing groove is formed between the first cavity 86 and the second cavity 87, a quartz window 7 is embedded in the sealing groove, and the quartz window 7 is sealed to the first cavity 86 and the second cavity 87 respectively through a sealing member 6, so that the quartz window 7 and the microwave resonant cavity 8 form a vacuum cavity.

[0062] For example, the relative permittivity of the quartz window 7 is 4.2, the microwave resonant cavity 8 is made of stainless steel, and the sealing element 6 is an O-ring.

[0063] In some embodiments, the support component includes a support 9 and a height-adjustable tuning structure 10. The support 9 is disposed on the height-adjustable tuning structure 10, which is located at the center of the bottom plane 88. The height-adjustable tuning structure 10 and the microwave resonant cavity 8 are insulated and isolated by a high thermal conductivity silicon carbide ceramic. The support 9 and the microwave resonant cavity 8 are connected by a DC power supply to form a current loop, which is used to constrain the spatial distribution of the plasma 30, so that the plasma 30 is located in the area above the support 9, avoiding the plasma 30 from bombarding the cavity wall of the microwave resonant cavity 8 and causing losses, and accelerating the charged particles in the plasma 30, thereby improving the interaction efficiency between the plasma 30 and the workpiece.

[0064] The height-adjustable tuning structure 10 moves up and down, changing the equivalent size of the microwave resonant cavity 8 and tuning the microwave electric field and plasma 30. This achieves precise tuning of the resonant frequency, mode stabilization, and impedance matching optimization, enabling real-time tuning of the microwave electric field and plasma 30, while adapting to load changes and process requirements. When the height-adjustable tuning structure 10 moves upward, the resonant frequency increases, the field strength shifts upward, the peak value becomes more concentrated, and the standing wave ratio decreases. When the height-adjustable tuning structure 10 moves downward, the resonant frequency decreases, the field strength shifts downward, and the distribution becomes more uniform. The specific movement is determined according to requirements. The specific structures of the height-adjustable tuning structure 10 and the support 9 are based on existing technologies and will not be elaborated further.

[0065] In some embodiments, the microwave plasma chemical vapor deposition apparatus further includes a bias electrode and a pulsed bias power supply 20. The bias electrode is disposed on the support 9, and the pulsed bias power supply is disposed outside the microwave resonant cavity 8. One end of the pulsed bias power supply is connected to the bias electrode, and the other end of the pulsed bias power supply is connected to the microwave resonant cavity 8.

[0066] For example, the pulsed bias power supply 20 provides a potential of −100V to −300V, providing a bias electric field to the substrate during heteroepitaxial growth of single-crystal diamond. In heteroepitaxial growth, there is a lattice mismatch between the substrate and diamond. The bias electric field can accelerate the migration of particles such as active carbon atoms in the plasma 30 to the substrate surface, while simultaneously enhancing the adsorption capacity of particles on the substrate surface, significantly increasing the nucleation density and reducing nucleation defects. This enhances diamond nucleation on the substrate and promotes the uniformity of diamond nucleation and growth on the heteroepitaxial substrate, making it suitable for the fabrication of large-size heteroepitaxial single-crystal diamond. Compared to the 2-inch effective deposition area of ​​typical TM01 or TM02 mode MPCVD devices, this solution can achieve a larger plasma 30 discharge, enabling the fabrication of inch-scale large-size heteroepitaxial single crystals. The effective deposition area can be expanded to 3 inches, thus meeting the application requirements of diamond materials in large-size infrared windows, microwave windows, heat sinks, and ultra-wide bandgap semiconductor materials, such as ultraviolet detectors, radiation detectors, and field-effect transistors.

[0067] In some embodiments, an observation window 85 is provided on the side of the microwave resonant cavity 8. The observation window 85 is used to observe the state of the plasma 30 inside the microwave resonant cavity 8 and to measure the substrate temperature.

[0068] Furthermore, a non-contact infrared thermometer can be used for temperature measurement. The infrared thermometer is positioned outside the observation window 85, and it measures the temperature of the substrate through the observation window 85.

[0069] With the above settings, there is no need to separate two windows, simplifying the structure. Observation window 85 is used for real-time temperature measurement during the diamond growth process, which can achieve precise control, improve reliability, and avoid risks.

[0070] In some embodiments, the rectangular waveguide 2 is provided with a three-pin tuner 4 and a short-circuit piston 3. By adjusting the three-pin tuner 4 and the short-circuit piston 3, the microwave reflection coefficient can be adjusted to minimize the microwave reflection coefficient.

[0071] In some embodiments, the microwave resonant cavity 8 is provided with a cooling structure, such as a cooling water channel on the outer wall of the microwave resonant cavity 8, which is cooled by circulating water to avoid local overheating and ensure long-term operation of the equipment.

[0072] By simulating the aforementioned microwave plasma chemical vapor deposition apparatus, the following results were obtained: Figures 3 to 6 The results show that by using this microwave plasma chemical vapor deposition apparatus, a circumferentially uniform microwave electric field distribution can be formed, improving plasma uniformity and thus enhancing the uniformity of thin film deposition.

[0073] In one implementation, such as Figure 7 As shown, Figure 7 This is a comparison of the radial distribution of microwave electric field intensity on a substrate surface with a radius of 40 mm using the microwave plasma chemical vapor deposition apparatus provided by this invention and a typical TM02 mode MPCVD apparatus, with an input microwave power of 1000 W. Figure 7 It can be seen that the microwave electric field strength and radial uniformity of the microwave plasma chemical vapor deposition device proposed in this invention are superior to those of the TM02 mode MPCVD device.

[0074] Example 1

[0075] This embodiment provides a method for growing diamond thin films using the above-described microwave plasma chemical vapor deposition apparatus, specifically including:

[0076] S1: Place a 60mm diameter single-crystal silicon substrate in the support 9 on the height-adjustable tuning structure 10.

[0077] S2: Evacuate the microwave resonant cavity 8 to 1.0 × 10⁸ ozonated. −2Pa, then H2 is introduced into the microwave resonant cavity 8, and then H2 and CH4 are introduced into the microwave resonant cavity 8 to make the gas pressure in the microwave resonant cavity 8 1500Pa.

[0078] S3: Turn on the microwave power supply 1 with a frequency of 2.45GHz, adjust the output power of the microwave power supply 1 to 1000W, and the electromagnetic waves generated by the microwave power supply 1 form a standing wave on the surface of the support 9, which excites the formation of plasma 30.

[0079] S4: Adjust the three-pin tuner 4 and the short-circuit piston 3 to minimize the microwave reflection coefficient.

[0080] S5: Gradually increase the output power of microwave power supply 1 to 7000W at a rate of 100W / min, and gradually increase the pressure of microwave resonant cavity 8 to 16000Pa at a rate of 200~300Pa / min.

[0081] S6: Turn on the pulse bias power supply 20 and adjust the pulse bias power supply 20 to make the substrate bias potential −200V.

[0082] By achieving the ideal microwave plasma 30 discharge state for the thin film deposition process through the above steps, diamond thin film deposition can be realized.

[0083] S7: After the diamond film deposition is complete, turn off microwave power supply 1 and pulse bias power supply 20, stop the supply of H2 and CH4, evacuate to the ultimate vacuum and then shut down.

[0084] Example 2

[0085] This embodiment provides a method for growing diamond thin films using the above-described microwave plasma chemical vapor deposition apparatus, specifically including:

[0086] S1: Place a 3-inch diameter single-crystal silicon substrate in a support 9 on a height-adjustable tuning structure 10.

[0087] S2: Evacuate the microwave resonant cavity 8 to 1.0 × 10⁸ ozonated. −2 Pa, then H2 is introduced into the resonant cavity, and then H2 and CH4 are introduced into the microwave resonant cavity 8 to make the gas pressure in the microwave resonant cavity 8 1200Pa.

[0088] S3: Turn on the microwave power supply 1 with a frequency of 2.45GHz, adjust the output power of the microwave power supply 1 to 1000W, and the electromagnetic waves generated by the microwave power supply 1 form a standing wave on the surface of the support 9, which excites the formation of plasma 30.

[0089] S4: Adjust the three-pin tuner 4 and the short-circuit piston 3 to minimize the microwave reflection coefficient.

[0090] S5: Gradually increase the output power of microwave power supply 1 to 8000W at a rate of 100W / min, and gradually increase the pressure of microwave resonant cavity 8 to 15000Pa at a rate of 200~300Pa / min.

[0091] S6: Turn on the pulse bias power supply 20 and adjust the pulse bias power supply 20 to make the substrate bias potential −250V.

[0092] By achieving the ideal microwave plasma 30 discharge state for the thin film deposition process through the above steps, diamond thin film deposition can be realized.

[0093] S7: After the diamond film deposition is complete, turn off microwave power supply 1 and pulse bias power supply 20, stop the supply of H2 and CH4, evacuate to the ultimate vacuum and then shut down.

[0094] Example 3

[0095] This embodiment provides a method for growing thin films using the above-described microwave plasma chemical vapor deposition apparatus, specifically including:

[0096] S1: Place a MgO substrate with an Ir film coating and a diameter of 3 inches in the support 9 on the adjustable tuning structure 10.

[0097] S2: Evacuate the microwave resonant cavity 8 to 1.0 × 10⁸ ozonated. −2 Pa, then H2 is introduced into the resonant cavity, and then H2 and CH4 are introduced into the microwave resonant cavity 8 to make the gas pressure in the microwave resonant cavity 8 1200Pa.

[0098] S3: Turn on the microwave power supply 1 with a frequency of 2.45GHz, adjust the output power of the microwave power supply 1 to 1000W, and the electromagnetic waves generated by the microwave power supply 1 form a standing wave on the surface of the support 9, which excites the formation of plasma 30.

[0099] S4: Adjust the three-pin tuner 4 and the short-circuit piston 3 to minimize the microwave reflection coefficient.

[0100] S5: Gradually increase the output power of microwave power supply 1 to 8000W at a rate of 100W / min; gradually increase the pressure of microwave resonant cavity 8 to 15000Pa at a rate of 200~300Pa / min.

[0101] S6: Turn on the pulse bias power supply 20 and adjust the pulse bias power supply 20 to make the substrate bias potential −300V.

[0102] By achieving the ideal microwave plasma 30 discharge state for the thin film deposition process through the above steps, diamond thin film deposition can be realized.

[0103] S7: After the diamond film deposition is complete, turn off microwave power supply 1 and pulse bias power supply 20, stop the supply of H2 and CH4, evacuate to the ultimate vacuum and then shut down.

[0104] Example 4

[0105] This embodiment provides a method for growing diamond thin films using the above-described microwave plasma chemical vapor deposition apparatus, specifically including:

[0106] S1: Arrange 36 10mm×10mm HTHP diamond seed crystal substrates in a 6×6 arrangement in the support 9 on the height-adjustable tuning structure 10.

[0107] S2: Evacuate the microwave resonant cavity 8 to 1.0 × 10⁸ ozonated. −2 Pa, then H2 is introduced into the resonant cavity, and then H2 and CH4 are introduced into the microwave resonant cavity 8, with a gas pressure of 1200 Pa.

[0108] S3: Turn on the microwave power supply 1 with a frequency of 2.45GHz, adjust the output power of the microwave power supply 1 to 1000W, and the electromagnetic waves generated by the microwave power supply 1 form a standing wave on the surface of the support 9, which excites the formation of plasma 30.

[0109] S4: Adjust the three-pin tuner 4 and the short-circuit piston 3 to minimize the microwave reflection coefficient.

[0110] S5: Gradually increase the output power of microwave power supply 1 to 9000W at a rate of 100W / min, and gradually increase the pressure of microwave resonant cavity 8 to 15000Pa at a rate of 200~300Pa / min.

[0111] S6: Turn on the pulse bias power supply 20 and adjust the pulse bias power supply 20 to make the substrate bias potential −100V.

[0112] By achieving the ideal microwave plasma 30 discharge state for the thin film deposition process through the above steps, diamond thin film deposition can be realized.

[0113] S7: After the diamond film deposition is complete, turn off microwave power supply 1 and pulse bias power supply 20, stop the supply of H2 and CH4, evacuate to the ultimate vacuum and then shut down.

[0114] In the four embodiments described above, the microwave plasma chemical vapor deposition apparatus is used to grow diamond films. The film deposition rate is high, it can realize the preparation of large-area heteroepitaxial single crystals with good uniformity, the apparatus has a simple structure, good vacuum performance, stable operation and easy parameter control.

[0115] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A microwave plasma chemical vapor deposition apparatus, characterized in that, Comprising: A microwave resonator (8), which is in a flat-ended ellipsoidal shape, and the lengths of its three semi-axes are denoted as a, b, and c respectively, (a = b) < c, the semi-axis with a length of c is arranged along the z-direction, and the two ends of the microwave resonator (8) arranged along the z-direction are respectively a top plane (82) and a bottom plane (88). An air inlet (83) is provided on the top plane (82), and an air outlet (84) is provided on the bottom plane (88); A carrier assembly for placing a substrate, and the carrier assembly is located on the bottom plane (88); A quartz window (7) is annularly arranged at the middle position of the microwave resonator (8) along the z-direction; A microwave power supply (1), a rectangular waveguide (2) and an annular waveguide (5), the microwave power supply (1), the rectangular waveguide (2) and the annular waveguide (5) are connected in sequence, the annular waveguide (5) surrounds the quartz window (7), a slit opening (51) is provided inside the annular waveguide (5), and the electromagnetic wave generated by the microwave power supply (1) is fed into the microwave resonator (8) through the rectangular waveguide (2), the slit opening (51) and the quartz window (7) in sequence, and the electromagnetic wave electric field in the microwave resonator (8) is evenly distributed along the circumferential direction of the microwave resonator (8).

2. The microwave plasma chemical vapor deposition apparatus according to claim 1, characterized in that, The height of the annular waveguide (5) is greater than the height of the rectangular waveguide (2); the inner diameter of the annular waveguide (5) is greater than the wavelength of the electromagnetic wave generated by the microwave power supply (1); 1.05 ≤ c / a ≤ 1.

15.

3. The microwave plasma chemical vapor deposition device according to claim ₂, wherein The height of the annular waveguide (5) along the z-direction is H, and the height of the rectangular waveguide (2) along the z-direction is h, then 1.05h ≤ H ≤ 1.15h; The outer diameter of the annular waveguide (5) is R, the inner diameter of the annular waveguide (5) is r, the wavelength of the electromagnetic wave generated by the microwave power supply (1) is λ, 2λ < R < 3λ, 1.8λ < r < 2.0λ, and 1.2 ≤ R / r ≤ 1.

5.

4. The microwave plasma chemical vapor deposition apparatus according to claim 3, characterized in that, The annular waveguide (5) is provided with a plurality of the slit openings (51) along the circumferential direction, the slit openings (51) are arc-shaped, the length of the slit openings (51) is 0.5λ, and a plurality of wave nodes are arranged inside the annular waveguide (5), and the slit openings (51) are arranged corresponding to the wave nodes one by one.

5. The microwave plasma chemical vapor deposition apparatus according to claim 1, characterized in that, A frustum-shaped groove (81) is recessed inward from the top plane (82), the diameter of the groove opening of the frustum-shaped groove (81) is greater than the diameter of the groove bottom of the frustum-shaped groove (81), the air inlet (83) is opened at the groove bottom, and the radius of the groove bottom is less than the wavelength of the electromagnetic wave generated by the microwave power supply (1); The microwave resonator (8) is used for converging electromagnetic waves, the microwave resonator (8) has an upper focus and a lower focus, the upper focus corresponds to the position of the frustum-shaped groove, and the lower focus corresponds to the surface position of the substrate.

6. The microwave plasma chemical vapor deposition apparatus according to claim 5, characterized in that, The radius of the groove bottom is r₁, and r₁ = 0.25λ.

7. The microwave plasma chemical vapor deposition apparatus according to claim 1, characterized in that, The air inlets (83) are provided in multiple ways, and all the air inlets (83) are symmetrically distributed along the half-axis of length c; the exhaust ports (84) are provided in multiple ways, and all the exhaust ports (84) are symmetrically distributed along the half-axis of length c. The microwave resonant cavity (8) includes a first cavity (86) and a second cavity (87) arranged along the z-direction. A sealing groove is formed between the first cavity (86) and the second cavity (87). The quartz window (7) is embedded in the sealing groove. The quartz window (7) is sealed to the first cavity (86) and the second cavity (87) respectively by a sealing member (6).

8. The microwave plasma chemical vapor deposition apparatus according to claim 1, characterized in that, The supporting component includes a bracket (9) and a height-adjustable tuning structure (10). The bracket (9) is disposed on the height-adjustable tuning structure (10). The height-adjustable tuning structure (10) is located at the center of the bottom plane (88). The height-adjustable tuning structure (10) and the microwave resonant cavity (8) are insulated and isolated by high thermal conductivity silicon carbide ceramic. The bracket (9) and the microwave resonant cavity (8) are connected by a DC power supply and form a current loop.

9. The microwave plasma chemical vapor deposition apparatus according to claim 8, characterized in that, The microwave plasma chemical vapor deposition apparatus further includes a bias electrode and a pulsed bias power supply (20). The bias electrode is disposed on the support (9), and the pulsed bias power supply (20) is disposed outside the microwave resonant cavity (8). One end of the pulsed bias power supply (20) is connected to the bias electrode, and the other end of the pulsed bias power supply (20) is connected to the microwave resonant cavity (8).

10. The microwave plasma chemical vapor deposition apparatus according to any one of claims 1-9, characterized in that, The microwave resonant cavity (8) is provided with an observation window on its side, which is used to observe the state of the plasma inside the microwave resonant cavity (8) and measure the temperature of the substrate.

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