A full permanent magnet 615 mhz electron cyclotron resonance wide band gap semiconductor thin film deposition apparatus

Abstract

This invention discloses a 615 MHz electron cyclotron resonance wide bandgap semiconductor thin film deposition equipment with a permanent magnet, which belongs to the field of wide bandgap semiconductor thin film deposition equipment. It solves the problems of high energy consumption, magnetic field drift, long wavelength microwave standing wave interference, many thin film defects, and small wafer size of existing 2.45 GHz and 915 MHz excitation coil type electron cyclotron resonance equipment. This invention comprises a 615 MHz microwave feed unit, a six-layer synergistic standing wave suppression cavity, a non-excitation coil all-permanent magnet resonant magnetic field assembly, a three-layer isolated spray gas path, a substrate chassis, a vacuum unit, and an industrial control system. It employs a multi-layer staggered hollow permanent magnet array to output a constant resonant magnetic field matching the 615 MHz output, eliminating the need for an excitation power supply and coil water cooling, thus significantly reducing overall energy consumption. The six-layer structure specifically suppresses multiple standing waves of the 615 MHz long-wavelength microwave, and the three-layer isolated gas path prevents premature reactions from metal-organic sources. This equipment features a long uniform magnetic field range, uniform plasma distribution, and few thin film lattice defects, making it suitable for the industrial-scale epitaxial fabrication of wide-bandgap semiconductor single crystal thin films such as gallium oxide, diamond, and aluminum nitride up to 6 inches in diameter.

Description

Technical Field

[0001] This invention relates to the field of wide bandgap semiconductor thin film deposition equipment technology, and is particularly applicable to the epitaxial fabrication of single crystal thin films of third-generation and fourth-generation semiconductors such as gallium oxide, diamond, aluminum nitride, gallium nitride, and silicon carbide. Specifically, it is a coilless, all-permanent magnet electron cyclotron resonance metal-organic chemical vapor deposition equipment adapted to 615 MHz low-frequency microwaves. Background Technology

[0002] Electron cyclotron resonance metal-organic chemical vapor deposition (EMVCD) relies on the resonance effect of microwaves and magnetic fields to generate high-density, low-temperature plasma. It is a core piece of equipment for the epitaxial fabrication of third- and fourth-generation wide-bandgap semiconductor thin films, and possesses unique process advantages compared to traditional high-temperature MCVD equipment, conventional microwave plasma deposition equipment, radio frequency plasma equipment, and molecular beam epitaxy equipment.

[0003] First, low-temperature deposition characteristics. Traditional thermal deposition equipment has an epitaxial temperature of 850~1200℃, which easily causes thermal decomposition of materials with low decomposition temperature such as gallium oxide and indium nitride, and substrate warping; electron cyclotron resonance plasma can dissociate the reactive gas under low pressure, and the deposition temperature is reduced to 300~650℃, which is suitable for flexible, ultra-thin substrates that are not resistant to high temperatures. Nitride growth can replace ammonia gas, and the process is environmentally friendly and simple.

[0004] Second, it features low ion bombardment and low lattice damage. The plasma generation region is separated from the deposition region, and the ion energy is below 20 eV, avoiding lattice defects in the epitaxial layer and making it suitable for the fabrication of high-precision power devices and optoelectronic devices.

[0005] Third, 615 MHz low-frequency microwaves can further reduce ion damage. Mainstream mature equipment in the industry uses 2.45 GHz microwaves, while a small number of imported equipment use 915 MHz intermediate-frequency microwaves. 2.45 GHz microwave plasma ion energy is too high, only suitable for small wafers up to 2 inches, resulting in high dislocation density in thin films. 915 MHz microwaves still suffer from standing wave interference and a short period of uniform magnetic field. In contrast, 615 MHz microwaves have a gentle energy distribution, with substrate ion energy of only 2-8 eV, resulting in almost no radiation damage. Simultaneously, they are compatible with large wafers of 6-8 inches, significantly improving the quality and production scale of thin film products.

[0006] Fourth, it is compatible with multiple materials and processes. A single machine can switch between growing thin films such as aluminum nitride, gallium oxide, single-crystal diamond, and silicon carbide buffer layers without changing the core structure of the cavity, thus accommodating both scientific research and development as well as small- to medium-batch mass production.

[0007] Existing 2.45 GHz and 915 MHz electron cyclotron resonance deposition equipment suffer from multiple inherent technical defects:

[0008] 1. Magnetic field systems mostly use electromagnetic excitation coils, equipped with high-power DC power supplies and circulating water cooling, resulting in large overall size and high energy consumption; coil current temperature drift causes continuous fluctuations in the magnetic field, and a magnetic field deviation of ±10Gs can cause plasma extinction, resulting in poor process repeatability; ordinary integral permanent magnet rings have short magnetic field uniformity ranges, and the uniformity deviation of 6-inch wafer thin films exceeds 15%.

[0009] 2. The vacuum wavelength of 615 MHz microwaves is approximately four times that of 2.45 GHz microwaves. Long-wavelength microwaves easily generate axial and annular standing waves in the cavity, forming hot and cold plasma zones. Reflected microwaves can easily burn out the microwave source. Traditional single-matching structures cannot suppress long-wavelength standing waves, with a standing wave ratio higher than 1.5 and microwave coupling efficiency less than 70%. Existing cavity structures for 2.45 GHz and 915 MHz equipment cannot meet the standing wave suppression requirements of 615 MHz long-wavelength microwaves.

[0010] 3. In traditional single-layer spray gas supply, the metal-organic precursor reacts with the reactive gas in the gas phase in advance, generating particulate impurities. The number of thin film pinholes and lattice defects increases dramatically, which cannot meet the epitaxial layer standards of high-end power devices. Airflow disturbance causes large differences in composition between the wafer center and edge.

[0011] 4. Conventional closed-loop permanent magnet rings have a large radial magnetic field gradient, resulting in plasma density differences exceeding 40% on large-size wafers; without a matching microwave absorption structure, lateral stray microwaves exacerbate standing waves, further worsening the problem of uneven ion energy distribution.

[0012] Currently, there is a lack of integrated all-permanent magnet electronic cyclotron resonance deposition equipment that is compatible with 615 MHz low-frequency microwaves, has no excitation coil, can suppress long-wavelength standing waves, and has layered isolated gas supply. This makes it impossible to fully utilize the advantages of 615 MHz microwaves in terms of low temperature, low damage, and large-size deposition, thus limiting the industrialization of next-generation wide-bandgap semiconductors such as gallium oxide and diamond. Summary of the Invention

[0013] Purpose of the invention

[0014] To address the shortcomings of existing 2.45 GHz coil-excited electron cyclotron resonance (ECR) equipment and 915 MHz intermediate-frequency ECR equipment, such as high energy consumption, magnetic field drift, long-wavelength microwave standing wave interference, gas pre-reaction, and narrow magnetic field uniformity range, this invention provides a fully permanent magnet 615 MHz ECR wide bandgap semiconductor thin film deposition equipment. This eliminates the electromagnetic excitation coil and its supporting water-cooling unit, relying on a multi-layer staggered hollow permanent magnet array to match the 615 MHz resonant magnetic field. Combined with a six-layer synergistic standing wave suppression cavity and a three-layer isolated spray gas path, this achieves low-energy, high-uniformity, and high-stability wide bandgap semiconductor thin film epitaxial fabrication.

[0015] Technical solution

[0016] A 615 MHz electron cyclotron resonance wide bandgap semiconductor thin film deposition equipment with permanent magnets includes a microwave feed unit, a six-layer synergistic standing wave suppression cavity, a permanent magnet resonance magnetic field generating component, a three-layer isolated gas path spraying unit, a substrate support chassis, a vacuum unit, and an industrial control and monitoring system.

[0017] 1. Microwave feed unit: Coaxially mounted on the top of the cavity, it includes a high-power solid-state microwave source and a three-pin integrated tuning matching component. 615 MHz microwaves are vertically downward incident into the deposition cavity; the three tuning pins are evenly distributed along the circumference at 120°, and independently extend and retract to adjust the impedance, dynamically offsetting the microwave reflection caused by plasma load drift.

[0018] 2. Six-layer synergistic standing wave suppression cavity: The six-layer synergistic standing wave suppression structure along the microwave propagation direction from top to bottom consists of a frustum-shaped gradient buffer cavity, a staggered hollow permanent magnet array, a gradient porous homogenizing grid plate, a wave-damping air path chassis, a three-pin tuning assembly, and an inner wall low-frequency absorbing liner. The six-layer structure is specially adapted to 615 MHz long-wavelength microwaves, synergistically eliminating axial and annular multiple standing waves, with the overall standing wave ratio stably controlled below 1.3, and the microwave coupling efficiency increased to over 88%.

[0019] 3. Permanent Magnet Resonance Magnetic Field Generator: The excitation coil is completely eliminated, and the resonant magnetic field source is formed by axially stacking multiple layers of neodymium iron boron permanent magnet rings; the single-layer permanent magnet rings have uniformly hollowed-out notches, and the notches of adjacent permanent magnet rings are staggered vertically to widen the uniform range of the axial magnetic field; the entire permanent magnet array outputs a constant 220Gs magnetic field, which is precisely matched to the 615MHz electron cyclotron resonance condition; the permanent magnet array is covered with a ferromagnetic shielding ring to isolate external stray magnetic fields, and the inner wall of the shielding ring is fitted with a low-frequency absorbing composite liner to absorb the lateral stray microwaves of the cavity.

[0020] 4. Three-layer isolated gas path spray unit: It is divided into an upper process gas channel, a middle metal-organic source channel, and a lower inert protective gas channel. The three layers of gas are physically isolated throughout the process and mix only in the deposition area above the substrate, which prevents the precursor from reacting in the gas phase in advance and reduces thin film particle defects.

[0021] 5. Substrate support chassis: The bottom surface is provided with a continuous wave damping surface, and the wave undulation period matches the half wavelength of the 615 MHz microwave. The chassis has 45° angled spray vents to change the microwave reflection angle and reduce the standing wave at the bottom of the cavity. A wafer substrate tray is placed in the center of the chassis as a deposition station.

[0022] 6. Vacuum unit and industrial control monitoring system: The vacuum unit maintains a high vacuum environment by connecting the side wall of the cavity; the industrial control computer is connected to all sensors for microwave, magnetic field, gas, vacuum, and temperature, and has a built-in closed-loop control program to automatically adjust process parameters and fully store the deposition process curve.

[0023] Beneficial effects

[0024] 1. The all-permanent magnet coilless magnetic field system eliminates the need for excitation coils, high-power DC power supplies, and coil water-cooling units, reducing the overall size by 30% and reducing operating energy consumption by more than 40%; it has no current temperature drift and a constant magnetic field strength, solving the problems of low fault tolerance and easy plasma extinction in the 615 MHz resonant magnetic field, and the process repeatability is far superior to that of 2.45 GHz and 915 MHz coil excitation equipment.

[0025] 2. The axial magnetic field uniformity range of the multi-layer staggered hollow permanent magnet array is ≥120mm, the magnetic field fluctuation is within ±8Gs, the wafer radial magnetic field deviation is ≤3%, and the uniform deviation of the 6-inch substrate film thickness is controlled within ±3%. It is suitable for mass production of large-size gallium oxide and diamond wafers, making up for the shortcoming of the existing 2.45 GHz equipment which is only suitable for 2-inch substrates.

[0026] 3. The six-layer dedicated standing wave suppression structure is adapted to 615 MHz long-wavelength microwaves. The multi-layer structure eliminates multiple microwave reflections, avoids microwave source burnout, significantly improves microwave energy utilization, and ensures uniform plasma density throughout the cavity, thus solving the problem of long-wavelength standing wave distortion in 2.45 GHz and 915 MHz equipment.

[0027] 4. Three-layer physical isolation gas supply eliminates premature reaction of metal-organic sources, reduces the number of thin film pinholes and lattice defects by 60%, and significantly improves the quality of epitaxial layers and the yield of finished products for power devices.

[0028] 5. The modular structure facilitates disassembly and maintenance, and the fully automated closed-loop control allows for switching between gallium oxide, diamond, and aluminum nitride thin film growth on a single device by simply adjusting process parameters, without requiring modifications to the magnetic field hardware, thus adapting to continuous industrial production. Attached Figure Description

[0029] This invention comprises 8 accompanying drawings, all with consistent labeling:

[0030] 1. 360° revolution 2. 615 MHz solid-state microwave source 3. Frustum-shaped gradient buffer cavity 4. Multi-layer ring permanent magnet array 5. Ferromagnetic shielding ring 6. Gradient porous homogenizing grid plate 7. Upper layer process gas path 8. Middle layer metal-organic source gas path 9. Wave damping gas path chassis 10. Coaxial conversion waveguide 11. Impedance matching device 12. Gas curtain purge channel 13. Outer conductor 14. Dielectric sealing window 15. Water cooling channel 16. Three-pin integrated tuning matching assembly 17. Coated finished product discharge station 18. Vacuum detection assembly 19. Vacuum sealing flange 20. Industrial control monitoring 21. Computer; 22. Annular permanent magnet yoke; 23. Permanent magnet shell; 24. Top layer permanent magnet ring; 25. Middle layer permanent magnet ring; 26. Hollowed-out through hole; 27. Permanent magnet laminate layer; 28. Bottom layer permanent magnet ring; 29. ​​Central positioning mandrel; 30. Substrate feed gate; 31. Outer magnetic yoke iron ring; 32. Low-frequency wave-absorbing composite liner; 33. Adjustable metal tuning pin; 34. Staggered hollowed-out permanent magnet array; 35. Wave-damped spray chassis; 36. Substrate tray; 37. Lifting support shaft; 38. Rotating bearing platform; 39. Heat insulation layer and transmission base; 40. Overall machine base; 40. Small-amplitude radial reciprocating swing unit.

[0031] Figure 1 This is a three-dimensional schematic diagram of the overall assembly of the present invention;

[0032] Figure 2 This is a cross-sectional perspective view of the integrated target assembly of the 615 MHz microwave source and the all-permanent magnet magnetic circuit of the present invention.

[0033] Figure 3 This is a schematic diagram of the radial cross-sectional magnetic field distribution of the all-permanent magnet magnetic circuit assembly of the present invention;

[0034] Figure 4 This is a three-dimensional exploded view of the multi-layer stacked permanent magnet magnetic confinement cavity of the present invention;

[0035] Figure 5 This is a schematic diagram of the gas diffusion distribution in the multi-stage flow uniform plate of the present invention.

[0036] Figure 6 This is a schematic diagram of the axial full cross-sectional structure of the reaction chamber of the present invention;

[0037] Figure 7 This is an exploded perspective view of the substrate rotating support stage of the present invention;

[0038] Figure 8 This is a schematic diagram of the layered assembly of the magnet, flow uniform plate, and substrate stage inside the cavity of the present invention. Detailed Implementation

[0039] Example 1: 6-inch gallium oxide thin film deposition machine

[0040] The top of the device is equipped with a 615 MHz solid-state microwave source, connected to a three-pin integrated tuning and matching assembly. The three tuning pins are evenly distributed along a 120° circumference. The microwave enters the main cavity through an 8° frustum-shaped buffer cavity, the height of which is 1 / 4 of the vacuum wavelength of the 615 MHz microwave, eliminating feed impedance reflection. In the middle of the cavity, multiple layers of neodymium iron boron permanent magnet rings are axially stacked, with 10 rectangular perforations in each ring. Adjacent rings have perforations staggered by 35° to output a constant 220 Gs magnetic field matching the 615 MHz electron cyclotron resonance condition. A 1 mm thick low-frequency absorbing composite liner is attached to the inner wall of the ferromagnetic shielding ring outside the permanent magnet array. Below the permanent magnet array, a gradient porous homogenizing grid plate, 1 / 16 the wavelength of the 615 MHz microwave, is filled with 0.5 mm permeable micropores to convert specular microwave reflection into diffuse reflection, weakening axial standing waves. The device features a three-layer isolation gas path beneath the grid: an upper layer for oxygen process gas, a middle layer for gallium oxide metal-organic source gas, and a lower layer for argon protective gas. These three gas paths are completely isolated, with mixing and reaction occurring only above the substrate. The bottom wave-damping gas path chassis has a wave period equal to half the wavelength of a 615 MHz microwave. The chassis has 45° angled spray nozzles, delivering gas obliquely to the wafer surface while simultaneously altering the microwave reflection angle to eliminate strong standing waves at the bottom. The cavity is equipped with an inlet gate, outlet station, vacuum unit, and industrial control monitoring computer, enabling automatic parameter control throughout the entire process. The equipment operates with a stable VSWR of 1.25, magnetic field fluctuations of ±6 Gs, a uniform thickness deviation of ±2.6% for a 6-inch gallium oxide film, no particle defects, and continuous stable operation for 720 hours without parameter drift. Energy consumption is reduced by 42% compared to traditional 2.45 GHz coil excitation equipment.

[0041] Example 2: Single-crystal diamond thin film deposition machine

[0042] The permanent magnet array maintains a resonant magnetic field of 220Gs, and the three-layer gas path ratio is adjusted. The middle layer is introduced with a carbon source metal-organic precursor, the upper layer is introduced with hydrogen etching gas, and the lower layer is introduced with argon protective gas. The industrial control system is equipped with a diamond-specific process program, with a magnetic field uniformity range of 130mm, which is suitable for continuous deposition on 4-inch diamond substrates.

[0043] Example 3: Aluminum nitride thin film deposition machine

[0044] Without modifying the magnetic field, cavity, or gas path hardware, aluminum nitride epitaxial growth can be switched simply by modifying the microwave power, gas flow rate, and cavity vacuum parameters through the industrial control system, making it highly adaptable to various processes.

Claims

1. A fully permanent magnet 615 MHz electron cyclotron resonance wide bandgap semiconductor thin film deposition apparatus, characterized in that, include: Microwave feed unit, six-layer synergistic standing wave suppression cavity, all permanent magnet resonance magnetic field generating component, three-layer isolated gas path spray unit, substrate support chassis, vacuum unit, industrial control monitoring system; The microwave feed unit is coaxially mounted at the top of the cavity and includes a solid-state microwave source and a three-pin integrated tuning and matching component. The microwave is vertically incident into the cavity downwards. The six-layer synergistic standing wave suppression cavity is arranged with six standing wave suppression units from top to bottom along the microwave propagation direction, namely, a frustum-shaped buffer cavity, a staggered hollow permanent magnet array, a gradient porous homogenizing grid plate, a wave damping air path chassis, a three-pin tuning component, and a low-frequency absorbing composite liner. The permanent magnet resonant magnetic field generating component has no excitation coil and is composed of multiple layers of annular permanent magnet rings stacked axially. Adjacent permanent magnet rings have circumferentially open notches and are staggered vertically. The entire permanent magnet array provides a stable and constant magnetic field, which is suitable for electron cyclotron resonance conditions. The permanent magnet array is covered with a ferromagnetic shielding ring on the outside, and a low-frequency absorbing composite liner is attached to the inner wall of the shielding ring. The three-layer isolated gas path spraying unit is independently set with an upper process gas channel, a middle metal-organic source gas channel, and a lower protective gas channel. The three layers of gas are physically isolated throughout the process and mix only in the deposition area above the substrate. The bottom surface of the substrate support chassis is provided with a wave damping surface, and the chassis is provided with 45° angled spray air holes. A wafer substrate tray is placed on top of the chassis. The vacuum unit is connected to the side wall of the cavity, and the industrial control monitoring system is connected to the microwave source, magnetic field detection sensor, gas flow controller, vacuum gauge and temperature sensor through signal lines to collect the process parameters of the whole process in real time.

2. The all-permanent magnet 615 MHz electron cyclotron resonance wide bandgap semiconductor thin film deposition equipment according to claim 1, characterized in that, The multi-layer annular permanent magnet ring is made of neodymium iron boron permanent magnet material. Each layer of permanent magnet ring has 8 to 12 rectangular hollow notches evenly opened along the circumference, and the notches of adjacent two layers of permanent magnet ring are staggered by 30° to 45° in the circumference.

3. The all-permanent magnet 615 MHz electron cyclotron resonance wide bandgap semiconductor thin film deposition equipment according to claim 1, characterized in that, The frustum-shaped gradient buffer cavity has a cone angle of 8° and a cavity height of 1 / 4 of the 615 MHz microwave vacuum wavelength, which is used to eliminate the reflection of sudden impedance changes at the microwave feed interface.

4. The all-permanent magnet 615 MHz electron cyclotron resonance wide bandgap semiconductor thin film deposition equipment according to claim 1, characterized in that, The gradient porous homogenizing grid plate has a thickness of 1 / 16 of the 615 MHz microwave vacuum wavelength, and the grid plate has micron-sized air pores evenly distributed to convert the specular microwave reflection into diffuse reflection.

5. The all-permanent magnet 615 MHz electron cyclotron resonance wide bandgap semiconductor thin film deposition equipment according to claim 1, characterized in that, The low-frequency absorbing composite liner is made of ferrite composite absorbing material with a thickness of 0.8~1.2mm, and is attached to the inner wall of the ferromagnetic shielding ring to absorb lateral stray microwaves in the cavity.

6. The all-permanent magnet 615 MHz electron cyclotron resonance wide bandgap semiconductor thin film deposition apparatus according to claim 1, characterized in that, The wave undulation period of the wave damping air circuit chassis is equal to half the axial wavelength of the 615 MHz microwave cavity, and the 45° oblique spray air holes supply air towards the central region of the substrate.

7. The all-permanent magnet 615 MHz electron cyclotron resonance wide bandgap semiconductor thin film deposition apparatus according to claim 1, characterized in that, The three-pin integrated tuning and matching assembly includes three adjustable metal tuning pins evenly arranged along a 120° circumference. The extension and retraction length of the pins is independently controllable, dynamically compensating for plasma load impedance drift.

8. The all-permanent magnet 615 MHz electron cyclotron resonance wide bandgap semiconductor thin film deposition apparatus according to claim 1, characterized in that, The entire unit has no electromagnetic excitation coil or matching water-cooled coil heat dissipation system, and only a small cooling water circuit for the microwave source is set, which reduces the energy consumption of the entire unit by more than 40%.

9. The all-permanent magnet 615 MHz electron cyclotron resonance wide bandgap semiconductor thin film deposition apparatus according to claim 1, characterized in that, The axial magnetic field uniformity interval of the multilayer misaligned permanent magnet array is ≥120mm in length, and the magnetic field fluctuation is controlled within ±8Gs. It is suitable for epitaxial deposition of gallium oxide, diamond, and aluminum nitride wafers of 6 inches and below.

10. A fully permanent magnet 615 MHz electron cyclotron resonance wide bandgap semiconductor thin film deposition apparatus according to claim 1, characterized in that, The industrial control monitoring system has a built-in parameter closed-loop control program that can automatically adjust microwave power, gas flow rate of each channel, cavity vacuum degree, and store complete deposition process curves.

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