阅读说明：本技术 一种微波等离子体-热丝复合化学气相沉积制备n型掺杂金刚石的装置和方法 (Device and method for preparing n-type doped diamond by microwave plasma-hot wire composite chemical vapor deposition ) 是由 李辉 刘胜 王浩丞 于大洋 张磊 申胜男 聂思媛 于 2020-07-07 设计创作，主要内容包括：本发明提供一种微波等离子体-热丝复合化学气相沉积制备n型掺杂金刚石的装置和方法,装置包括微波等离子体源系统、热灯丝反应室改进系统、真空抽气系统和尾气处理系统。微波等离子体源系统包括微波源、三螺钉阻抗调配器、波导模式转换器、天线单元、波导管以及石英窗。波导模式转换器通过三螺调配器与微波源连接。热灯丝反应室改进系统包括谐振腔、进气孔、沉积台、等离子体、惰性气体气孔、水冷通道、石墨内衬、热灯丝、镜面钢板、分区冷却管路和出气孔。波导管通过石英窗与谐振腔相连。本发明将MPCVD与HFCVD装置结合,用微波源作为反应热源,热灯丝作为退火热源,再配合石墨内衬维持退火温度,提高n型掺杂金刚石的制备效率及质量。(The invention provides a device and a method for preparing n-type doped diamond by microwave plasma-hot wire composite chemical vapor deposition. The microwave plasma source system comprises a microwave source, a three-screw impedance tuner, a waveguide mode converter, an antenna unit, a waveguide tube and a quartz window. The waveguide mode converter is connected with the microwave source through the three-screw tuner. The improved system of the hot filament reaction chamber comprises a resonant cavity, an air inlet hole, a deposition table, plasma, an inert gas air hole, a water cooling channel, a graphite lining, a hot filament, a mirror steel plate, a partition cooling pipeline and an air outlet hole. The waveguide is connected to the resonator through a quartz window. The invention combines the MPCVD device with the HFCVD device, uses a microwave source as a reaction heat source, uses a hot filament as an annealing heat source, and maintains the annealing temperature by matching with a graphite lining, thereby improving the preparation efficiency and the quality of the n-type doped diamond.)

1. A device for preparing n-type doped diamond by microwave plasma-hot filament composite chemical vapor deposition is characterized by comprising a microwave plasma source system, a hot filament reaction chamber improvement system, a vacuum pumping system and a tail gas treatment system; the microwave plasma source system comprises a microwave source, an impedance matching element, a waveguide mode converter, an antenna unit, a waveguide tube and a quartz window.

2. The apparatus according to claim 1, wherein the hot filament reaction chamber improvement system comprises a resonant cavity, an air inlet hole, a deposition table, inert gas holes, a water cooling channel, a liner, a hot filament, a heat insulation layer and an air outlet hole, the upper end of the side wall of the resonant cavity is provided with the air inlet hole, the lower end of the side wall is provided with the air outlet hole, the deposition table is of a hollow structure and is connected to the center of the resonant cavity, the inert gas holes are uniformly formed in the deposition table, the water cooling channel is formed in the deposition table and is communicated with the outside to take charge of introducing cooling water, the liner is of a cylinder shape and covers the side surface of the deposition table, the outer wall of the liner is uniformly connected with the hot filament in the circumferential direction, and the heat insulation layer is covered outside the hot filament.

3. The device for preparing n-type doped diamond by microwave plasma-hot wire composite chemical vapor deposition according to claim 2, further comprising a plurality of partitioned cooling pipelines, wherein the partitioned cooling pipelines are communicated with the water cooling channel and connected to the back of the deposition table to cool the deposition table, and the speed of water inlet and outlet can be adjusted by each partitioned cooling pipeline.

4. The apparatus for preparing n-type doped diamond according to claim 2, wherein the liner is a graphite liner with a silicon carbide coating.

5. The device for preparing n-type doped diamond according to claim 2, wherein the heat insulation layer is a mirror steel plate, which can reflect the heat of the hot filament and can also be used for heat insulation of the surface of the resonant cavity.

6. The apparatus for preparing n-doped diamond according to claim 1, wherein the impedance matching element is a three-screw impedance matching device or a multi-section impedance transformer.

7. A method for preparing n-type doped diamond by a microwave plasma-hot wire composite chemical vapor deposition device is characterized by comprising the following steps:

S1 growing the phosphorus element doped diamond by using an MPVCD device;

s2 cooling to some extent with cooling water;

s3 was subjected to an in-situ n-type phosphorous doped diamond slow anneal using an HFCVD apparatus.

8. The method for preparing n-type doped diamond according to claim 7,

the specific process of step S1 is: (1) after the resonant cavity is vacuumized by a suction pump, the mixed gas of hydrogen and methane with certain purity required by the reaction is introduced into the resonant cavity, and simultaneously PH is introduced₃Gas, which is prepared for doping phosphorus element in diamond; (2) turning on a microwave source, under the action of microwave energy, carrying out molecular ionization on gas molecules, and generating plasma above a deposition table; (3) carbon and phosphorus groups in the plasma are continuously deposited and gradually accumulated, so that a phosphorus element doped diamond film, namely n-type doped diamond, is formed;

the specific process of step S2 is: the water cooling channel guides cooling water into the subarea cooling pipelines, wherein different pipelines can adjust the speed of water inlet and outlet, and the cooling effect of different temperature areas is uniform by matching with the effect of large heat exchange of inert gas pores, so that the substrate is kept within the temperature of the diamond growth process;

The specific process of step S3 is: turning off the microwave source, stopping cooling, and turning on the hot filament; the hot filament is rapidly heated and maintains proper annealing temperature under vacuum atmosphere by matching with the graphite lining so as to remove residual stress in the n-type doped diamond and improve the anti-cracking impact performance of the n-type doped diamond; meanwhile, the bond energy of the phosphorus-hydrogen bond is lower than that of a carbon-carbon bond and a carbon-phosphorus bond, so that the phosphorus-hydrogen bond can be broken on the premise of not damaging the carbon-carbon bond and the carbon-phosphorus bond by reasonably controlling the annealing temperature and the annealing time by utilizing the excellent temperature control performance of the hot filament; the n-type doped diamond can complete the dehydrogenation process, and after the annealing in the vacuum environment is finished, the n-type doped diamond is cooled to the normal temperature along with the furnace.

9. The method for preparing N-doped diamond according to claim 8, wherein the mixed gas of hydrogen and methane with a purity of 7N is introduced into the resonant cavity in step S1, and simultaneously PH with a purity of 5N is introduced₃And gas is prepared for doping phosphorus element in the diamond.

10. The method for preparing n-type doped diamond according to claim 8, wherein in the step S2, He gas is introduced into the inert gas pores.

Technical Field

The invention belongs to the technical field of growth of monocrystalline diamond films, and particularly relates to a device and a method for preparing n-type doped diamond by microwave plasma-hot wire composite chemical vapor deposition.

Background

The diamond film has the advantages of high hardness, high strength, good thermal conductivity, small thermal expansion coefficient, excellent optical performance, high chemical stability, strong radiation resistance, high sound propagation speed, good dielectric performance, wide transmission waveband, large forbidden bandwidth, small dielectric coefficient and the like. Therefore, the material has wide application in the fields of high-power semiconductor devices, high-power microwave windows, infrared optical window materials and the like. Among them, n-type diamond has higher carrier mobility, and can realize n-type conduction at room temperature, which is also the key to develop bipolar devices. Phosphorus is the only element generally accepted for obtaining room temperature n-type conductivity in n-type diamond films.

There are four major cvd (chemical vapor deposition) diamond film deposition techniques currently in wide use worldwide, namely thermal filament chemical vapor deposition (HFCVD), direct current assisted plasma chemical vapor deposition (DC-PACVD), microwave plasma chemical vapor deposition (microwaveplasma cvd, MPCVD), and direct current arc plasma jet chemical vapor deposition (dcarcplasma jet cvd). The MPCVD method is based on the principle that microwave-excited deposition gas is used to generate glow discharge in a reaction chamber, so that the molecules of the reaction gas are ionized to generate plasma, and then deposition is carried out to obtain the diamond film. Many factors in the preparation process of diamond can affect the preparation efficiency and quality, such as: carbon source concentration, substrate temperature, reaction gas pressure, and the like. Generally, the MPCVD method has the advantages of high plasma density, no discharge electrode pollution, good controllability and the like, but the temperature control performance is slightly insufficient compared with HFCVD. And the common substrate cooling method also influences the temperature uniformity of the substrate, thereby reducing the quality of the diamond. Meanwhile, hydrogen elements in the n-type doped diamond can be combined with phosphorus elements in a phosphorus-hydrogen bond mode, impurities in the diamond are passivated, and the conductivity is reduced. These factors all affect the preparation of large area, high quality doped diamond, especially n-type doped diamond, with existing equipment.

Disclosure of Invention

Aiming at the problems, the invention provides a device for preparing diamond by microwave plasma-hot wire composite chemical vapor deposition, which combines an MPCVD device and a HFCVD device to reduce the P-H bond concentration of n-type doped diamond and comprises a microwave plasma source system, a hot wire reaction chamber improvement system, a vacuum pumping system and a tail gas treatment system.

The microwave plasma source system is responsible for providing growth groups such as carbon hydrogen and the like for the growth of the diamond and comprises a microwave source, an impedance adjusting element, a waveguide mode converter, an antenna unit, a waveguide tube and a quartz window. The waveguide mode converter is arranged right above the resonant cavity and is connected with the microwave source through the impedance adjusting element. The waveguide tube is connected with the resonant cavity through the quartz window.

The hot filament reaction chamber improvement system comprises a resonant cavity, an air inlet hole, a deposition table, a plasma, an inert gas air hole, a water cooling channel, a lining, a hot filament, a heat insulation layer and an air outlet hole. The resonant cavity is in a sleeve shape, an air inlet hole is formed in the upper end of the side wall of the resonant cavity, and an air outlet hole is formed in the lower end of the side wall. The gas inlet hole is responsible for introducing mixed gas required by reactions of hydrogen, methane, phosphine and the like. The deposition table is erected in the center of the resonant cavity and is of a hollow structure, and a plurality of inert gas holes are uniformly distributed on the deposition table. The plasma is positioned above the deposition table and is obtained by the molecular ionization of reaction gas, and carbon and phosphorus groups in the plasma are continuously deposited and gradually accumulated, so that the diamond film is formed. The water cooling channel is positioned inside the lower end of the deposition table and is responsible for introducing cooling water. The lining is positioned in the resonant cavity and covers the side surface of the deposition table. The hot filament is arranged around the inner lining in a circle, and the heat insulation layer is arranged around the hot filament in a circle. And the gas outlet is positioned at the bottom of the resonant cavity and is responsible for discharging gas after reaction.

The vacuum pumping system comprises a pipeline and a suction pump. The air pump is responsible for vacuumizing the cavity before the reaction starts and for pumping out reaction gas after the reaction starts.

And the tail gas treatment system is connected behind the vacuum pumping system and is responsible for treating the harmful gas after reaction.

Preferably, the impedance matching element is a three-screw impedance matching device or a multi-section impedance transformer.

Preferably, a sealing ring is used for sealing between the quartz window and the resonant cavity.

Preferably, the sealing Ring is an O-Ring fluororubber Ring.

Preferably, the lining is a graphite lining with a SiC coating, and can protect the side wall of the cavity and prevent phosphorus-doped diamond from depositing on the wall of the cavity and polluting the cavity.

Preferably, the hot filament is rapidly heated, and the graphite lining is matched to maintain a proper annealing temperature in a vacuum atmosphere.

Preferably, the heat insulation layer is a mirror steel plate, which can reflect the heat light of the hot filament and can also be used as a heat insulation layer on the surface of the resonant cavity.

Preferably, the device further comprises a partition cooling pipeline, wherein the partition cooling pipeline is an inlet and outlet pipeline with several different pipe diameters positioned on the back surface of the deposition table. During operation, cooling water enters from the water cooling channel and then is guided into the partition cooling pipeline, wherein the water inlet and outlet speeds can be adjusted through different pipelines, so that different areas on the substrate can be cooled to different degrees, the cooling uniformity is realized, and the growth quality of the diamond is improved.

Preferably, the deposition table is distributed with a plurality of He air holes, and a small amount of uniform He gas is added between the deposition table and the growth material, so that the He gas does not participate in the reaction, and the heat exchange can be greatly increased.

Further, the invention provides a method for preparing n-type doped diamond by using a microwave plasma-hot wire composite chemical vapor deposition device, which comprises the following specific working steps:

s1 growing the phosphorus element doped diamond by using an MPVCD device;

s2 cooling to some extent with cooling water;

s3 was subjected to an in-situ n-type phosphorous doped diamond slow anneal using an HFCVD apparatus.

Still further, the specific process of step S1 is: (1) after the resonant cavity is vacuumized by a suction pump, the mixed gas of hydrogen and methane with certain purity required by the reaction is introduced into the resonant cavity, and meanwhile, the PH with certain purity is introduced₃And gas is prepared for doping phosphorus element in the diamond. (2) The microwave source is turned on, and the gas molecules are subjected to molecular ionization under the action of microwave energy to generate plasma above the deposition table. (3) Carbon and phosphorus groups in the plasma are continuously deposited and gradually accumulated, so that a phosphorus element doped diamond film, namely n-type doped diamond, is formed.

Still further, the specific process of step S2 is: cooling water is guided into the subarea cooling pipelines through the water cooling channels, wherein the water inlet and outlet speeds of different pipelines can be adjusted, and the cooling effect of different temperature areas is uniform by matching with the effect of large-amplitude heat exchange of the inert gas holes. Thereby maintaining the substrate within the diamond growth process temperature.

Still further, the specific process of step S3 is: the microwave source was turned off, cooling was stopped, and the hot filament was turned on. The hot filament is rapidly heated and maintains proper annealing temperature under vacuum atmosphere by matching with the graphite lining so as to remove residual stress in the n-type doped diamond and improve the anti-burst impact performance of the n-type doped diamond. Meanwhile, the bond energy of the phosphorus-hydrogen bond is lower than that of a carbon-carbon bond and a carbon-phosphorus bond, and the phosphorus-hydrogen bond can be broken on the premise of not damaging the carbon-carbon bond and the carbon-phosphorus bond by reasonably controlling the annealing temperature and the annealing time by utilizing the excellent temperature control performance of the hot filament. The n-type doped diamond can complete the dehydrogenation process, and after the annealing is finished in the vacuum environment, the n-type doped diamond is cooled to the normal temperature along with the furnace.

In the above method for preparing N-type doped diamond by microwave plasma-hot wire composite chemical vapor deposition, in step S1, a mixed gas of hydrogen and methane with a purity of 7N is introduced into the resonant cavity, and simultaneously PH with a purity of 5N is introduced₃And gas is prepared for doping phosphorus element in the diamond.

In the above method for preparing n-type doped diamond by microwave plasma-hot wire composite chemical vapor deposition, in step S2, He gas is introduced into the inert gas holes.

In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:

1 this device has adopted the graphite inside lining that has the SiC coating, does not influence the molecular ionization of reacting gas and protects the cavity lateral wall and do not deposit phosphorus and mix the diamond for the unpicking and washing of device is more convenient. And the existence of the graphite lining protects the inner wall of the resonant cavity and components thereof from high temperature during reaction, and prevents phosphorus atoms from polluting the cavity.

2 the apparatus combines an MPCVD apparatus with an HFCVD apparatus. A microwave source is used as a reaction heat source during diamond growth. The hot filament is used for annealing the diamond, and the graphite lining is matched to maintain proper annealing temperature in the vacuum atmosphere, so that the preparation efficiency and the preparation quality of the n-type doped diamond are improved.

3 the device innovatively adopts hot filament annealing to finish the dehydrogenation process of the n-type doped diamond, thereby improving the electrical property of the n-type diamond film.

4 this device adopts the hot light of mirror surface steel sheet reflection hot filament, and the secondary has increased the heat, improves energy utilization and rates, and mirror surface steel sheet has also reduced the surface temperature of resonant cavity as the insulating layer on resonant cavity surface simultaneously.

5 the device adopts a subarea cooling pipeline aiming at the characteristics of high middle temperature and low peripheral temperature of the microwave plasma, thereby realizing different degrees of cooling of different areas on the substrate. Particularly, the heat exchange effect is greatly improved by matching with the inert gas holes, and the preparation efficiency and the preparation quality of the n-type doped diamond are further improved.

6 this device possesses tail gas processing system for whole preparation process is pollution-free, belongs to environment friendly device.

Drawings

FIG. 1 is a schematic view of the overall structure of the present invention;

FIG. 2 is a partial schematic view of the present invention;

fig. 3 is a flow chart of n-type doped diamond preparation.

In the figure, 1-a microwave source, 2-a three-screw impedance tuner, 3-an antenna unit, 4-a waveguide tube, 5-a quartz window, 6-a resonant cavity, 7-an air inlet, 8-plasma, 9-an inert gas air hole, 10-a deposition table, 11-a water cooling channel, 12-a lining, 13-a hot filament, 14-a mirror steel plate, 15-a partition cooling pipeline, 16-an air outlet, 17-an air suction pump and 18-a tail gas treatment device.

Detailed Description

The invention is described in further detail below with reference to the attached drawing figures: