CN117107351A - CVD method for repairing surface cracks of large-size diamond monocrystal wafer - Google Patents
CVD method for repairing surface cracks of large-size diamond monocrystal wafer Download PDFInfo
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- 229910003460 diamond Inorganic materials 0.000 title claims abstract description 36
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- 239000013078 crystal Substances 0.000 claims abstract description 148
- 238000000034 method Methods 0.000 claims abstract description 41
- 230000008439 repair process Effects 0.000 claims abstract description 24
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 14
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 14
- 238000010438 heat treatment Methods 0.000 claims description 13
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 10
- 238000000259 microwave plasma-assisted chemical vapour deposition Methods 0.000 claims description 8
- 238000002791 soaking Methods 0.000 claims description 7
- 238000004140 cleaning Methods 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- 239000003337 fertilizer Substances 0.000 claims description 2
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- 238000003698 laser cutting Methods 0.000 abstract description 5
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- 239000012535 impurity Substances 0.000 description 3
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- 238000005498 polishing Methods 0.000 description 3
- 239000002131 composite material Substances 0.000 description 2
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- 238000005260 corrosion Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
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- 229910021641 deionized water Inorganic materials 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
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- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/02—Elements
- C30B29/04—Diamond
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
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- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
- C23C16/26—Deposition of carbon only
- C23C16/27—Diamond only
- C23C16/274—Diamond only using microwave discharges
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
- C23C16/455—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for introducing gases into reaction chamber or for modifying gas flows in reaction chamber
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
- C23C16/50—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating using electric discharges
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
- C30B25/02—Epitaxial-layer growth
- C30B25/14—Feed and outlet means for the gases; Modifying the flow of the reactive gases
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Abstract
The invention belongs to the technical field of surface repair of monocrystalline diamond, and particularly relates to a CVD method for repairing surface cracks of a large-size diamond monocrystalline wafer. The method of the invention uses large-size diamond single crystal as seed crystal, adopts CVD method to repair the crack extending to the surface inside the seed crystal, and after the surface of the seed crystal is etched at high temperature by H-O plasma, the surface of the seed crystal is etched by CH 4 And N 2 Filling cracks and grooves exposed on the surface of the seed crystal by adjusting the filling amount and the heat preservation time, and simultaneously realizing improvement of the surface quality of the seed crystal by utilizing the transverse epitaxial growth of the diamond, therebyThe purpose of repairing cracks is achieved. The method directly solves the problem that the large-size diamond single crystal wafer is unfavorable for growth due to surface cracks. After the epitaxial layer reaches a certain thickness, the epitaxial layer can be separated and made into new seed crystals by laser cutting, and the surface quality of the new seed crystals is good, so that the effectiveness and stability of the repair process are proved, and the repair process has higher application prospect and economic value.
Description
Technical Field
The invention belongs to the technical field of surface repair of monocrystalline diamond, and particularly relates to a CVD method for repairing surface cracks of a large-size diamond monocrystalline wafer.
Background
Diamond is a special material that integrates many excellent properties due to its wide band gap, high thermal conductivity, breakdown field strength, extremely high carrier mobility and charge mobility (electron mobility of CVD diamond)>3000cm 2 V.s), which enables the diamond semiconductor device to operate in very harsh environments such as high frequency, high power, high voltage, and strong radiation, is an ideal material for manufacturing high power, high temperature, high frequency devices, and is referred to as a "final semiconductor material".
In addition, diamond has high spectral transmission performance in a wide wavelength range from ultraviolet to far infrared, and is an optical window material of a high-power infrared laser and a detector. Meanwhile, the material has the performances of acid resistance, alkali resistance and corrosion resistance to various corrosive gases, and is an excellent corrosion-resistant material.
The large-size diamond single crystal wafer is rare in number and high in price, and can be used for preparing cultivation diamonds with the diameter of more than 4 Kla and researching diamond functionalization application. Typically, CVD replication is performed with a small number of large-sized single-crystal wafers as seed to increase single-crystal wafer reserves. Because of the large size of the single crystal wafer, the seed crystal is easy to crack or even break due to stress release in the process of continuous temperature rise or unstable process control in the repeated growth process or the later cutting and separating process. In the subsequent use of the single crystal wafer with cracks as a seed crystal, polycrystal is easily generated at the cracks due to secondary nucleation, and the polycrystal forms penetrating impurities along with the extension of the growth time, so that the quality of the single crystal is seriously affected. In this case, when the single crystal is cut and separated again, the seed crystal having the original crack is likely to be damaged by the extension of the crack. Currently, no clear processing method is available for cracked single crystal wafers, and random test growth is generally adopted to verify whether the cracked single crystal wafers can be reused or not, and even the cracked single crystal wafers are directly limited to waste materials, so that great loss and waste are caused.
Therefore, the inventor discriminates the crack according to the state of the crack and the width of the 'groove' with the exposed surface, and designs a CVD process method aiming at crack repair for single crystal wafers with uniform cracks and flatter 'grooves', and the effective recycling of large-size diamond single crystal wafers with cracks is realized by controlling the adding mode of reaction gas and corresponding temperature interval and adjusting process parameters.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention provides a CVD repair method for a large-size diamond single crystal wafer with surface cracks, and the repair and stable growth of the surface cracks of the large-size single crystal wafer are realized by controlling the addition mode of reaction gas and a corresponding temperature interval and adjusting process parameters.
In order to achieve the technical purpose, the invention adopts the following technical scheme:
a CVD method for repairing surface cracks of a large-size diamond single crystal wafer comprises the following steps:
(1) Seed crystal pretreatment:
selecting a CVD diamond single crystal wafer with cracks on the surface (grooves are formed at the cracks) as a seed crystal, directly cleaning the seed crystal or firstly heating and soaking the seed crystal, cleaning the seed crystal, and wiping the seed crystal clean;
(2) And (3) assembling:
placing the seed crystal in the step (1) into a molybdenum sheet for assembly;
(3) Single wafer surface repair and growth using MPCVD equipment:
a. opening MPCVD equipment, placing molybdenum sheet with seed crystal in step (2), and vacuumizing to 1×10 -2 Below mbar, then simultaneously introducing H 2 、CO 2 Setting the microwave power to be 4.3-4.8 kw and the air pressure to be 175-195mbar, the temperature is 900-1000 ℃, and the temperature is kept for 60-90min;
b. adjusting the microwave power to 3.5-4 kw and the air pressure to 160-180 mbar, gradually reducing the temperature due to the reduction of the microwave power and the air pressure, and introducing CH when the temperature reaches 700-750 DEG C 4 Maintaining for 2-3 hours;
c. adjusting CH 4 Flow is simultaneously introduced into N 2 Adjusting the microwave power to be 4-4.5 kw, the air pressure to be 170-190 mbar, and the temperature to be 800-900 ℃ and keeping for 8-10h;
d. adjusting the microwave power to 5-5.5 kw and the air pressure to 190-210 mbar, and adjusting CH 4 And CO 2 And adjusting the flow rate to 950-1050 ℃ and stably growing to obtain the fertilizer.
Specifically, the diamond single crystal wafer used in step (1) is a diamond single crystal wafer of crystallographic orientation (100) having dimensions of 16mm×16mm×0.7mm, 15mm×15mm×0.5mm, or 15mm×15mm×0.7mm.
Specifically, in the step (1), heating and soaking are that the seed crystal is sequentially heated and soaked in acetone and alcohol, the heating temperature is 60-80 ℃, the heating time is 2-3 hours, the acetone and the alcohol are all analytically pure, and the mass fraction of the alcohol is more than 99.7%.
Specifically, during the assembly in the step (2), the surface of the seed crystal in the step (1) with cracks (the cracks form a groove) is selected as a growth surface, and the surface is placed at the center of a molybdenum sheet, and the size of the molybdenum sheet is phi 50mm multiplied by 4mm.
Specifically, in the step (3) a, H is introduced after vacuumizing 2 、CO 2 The flow rates are 400-500sccm and 10-12sccm respectively.
Specifically, in the step (3) b, CH is introduced 4 The flow rate of (2) is 4-5 sccm, which is about H 2 1% of the flow.
Specifically, in step (3) c, CH is adjusted 4 The flow rate is 10-15 sccm, which is about H 2 2-3% of flow, at this time, N is introduced 2 The concentration of (2) is 15.3-15.6ppm.
Specifically, in step (3) d, CH is adjusted 4 The flow rate is 26-33 sccm, which is about H 2 6.5% of flow, N 2 The concentration is 15ppm, and the CO is regulated 2 The flow is 3-5 sccm, about H 2 1% of the flow.
Specifically, in the step (3) d, the stable growth time is 50-60 h.
Specifically, the MPCVD equipment used in the step (3) is CYRANNUS system in Germany, and the working parameters are 6 kw-2.45 GHz.
Specifically, H as described in step (3) 2 、N 2 The purity of (C) is greater than 99.999%, CH 4 、CO 2 The purity of (2) is more than 99.995%.
Furthermore, the invention also provides a large-size CVD diamond single crystal wafer prepared by the method.
Preferably, in step (3) a of the present invention, the seed crystal having cracks cannot be subjected to surface polishing treatment by H at 900 to 1000 ℃ 2 And CO 2 And forming H, O plasma to etch the surface of the seed crystal for 60-90min, so as to reduce the micro defect density of the surface of the seed crystal, especially at the crack, reduce the risk of polycrystal penetration at the crack in the growth process, and improve the quality of the surface of the whole seed crystal.
Preferably, in step (3) b of the present invention, a small amount of CH is introduced first 4 And for a certain period of time, with the aim of preventing CO 2 Defects, namely etching pits, are formed on the surface of the seed crystal due to long-time etching, and the defect density at cracks is sufficiently reduced, because of CH 4 The concentration is low enough that the seed crystal is not nucleated on the surface of the seed crystal for a certain period of time, and the CO 2 But also has a certain neutralization effect, so the surface morphology of the whole seed crystal can be greatly improved.
Preferably, in step (3) c of the present invention, N is introduced after the seed surface morphology has been sufficiently treated 2 The method aims at filling and repairing cracks in a low-speed longitudinal growth and lateral growth acceleration mode, inhibiting secondary nucleation and polycrystalline growth and further realizing complete coverage.
Preferably, in the step (3) d of the present invention, the flow rate of each gas is adjusted to a stable growth value, and the growth is performed on the surface where the crack is completely repaired, and after the epitaxial layer reaches a certain thickness, a new large-size seed crystal can be prepared by a laser cutting separation technology, and the specific cutting method is as follows: and (3) sticking a single crystal growth surface on a clamp, ensuring that the bottom surface of the single crystal is vertical to the clamp, fixing the clamp on a cutter tool, adjusting the Z-axis alignment focal length, finely adjusting an adjusting screw on the clamp to enable the edge of the single crystal to coincide with a datum line, taking the upper, middle and lower three points as datum points, setting cutting parameters, cutting edge polycrystal by pressing a start key, rotating the clamp to enable the edge polycrystal to be vertical to the laser direction after cutting off the edge polycrystal, and cutting the single crystal according to the same operation method to obtain the prepared epitaxial layer.
Compared with the prior art, the invention has the beneficial effects that:
1. the method of the invention uses large-size diamond single crystal as seed crystal, adopts CVD method to repair the crack extending to the surface inside the seed crystal, and after the surface of the seed crystal is etched at high temperature by H-O plasma, the surface of the seed crystal is etched by CH 4 And N 2 And (3) adjusting the ventilation quantity and the heat preservation time, filling the crack groove exposed on the surface of the seed crystal, and simultaneously utilizing the transverse epitaxial growth of the diamond to improve the surface quality of the seed crystal so as to achieve the purpose of repairing the crack. The method directly solves the problem that the large-size diamond single crystal wafer is unfavorable for growth due to surface cracks. When the epitaxial layer reaches a certain thickness, the epitaxial layer can be separated and made into new seed crystals by laser cutting, and the surface quality of the new seed crystals is good, so that the effectiveness and stability of the repair process are proved.
2. According to the method, different reaction gases are added in different growth stages, and the gas proportion, the gas type and the corresponding temperature of each stage are controlled, so that cracks on the surface of the seed crystal are filled and repaired to a certain extent, the probability that polycrystal penetration impurities are easy to form at the cracks due to high defect density is greatly reduced, smooth transition of the growth surface state is realized, and the crystallization quality and the growth time are ensured.
3. The method directly solves the problem that the diamond single crystal wafer cannot grow and is wasted because of a certain degree of cracks, avoids the risk that the cracks are easy to extend again in the processing process, greatly reduces the loss rate and high cost of the large-size single crystal wafer, and has higher application prospect and economic value.
Drawings
FIG. 1 is a cracked seed crystal in step (1) of example 1;
FIG. 2 is an enlarged view of a portion of the "trench" formed at the crack of the seed crystal in step (1) of example 1;
FIG. 3 is a photograph of a single crystal after repair of step (1) in example 1;
FIG. 4 is a state after repair of an original crack in the diamond single crystal prepared in example 1;
FIG. 5 is a 500-time metallographic photograph of the diamond single crystal prepared in example 1 after repair of the original crack;
FIG. 6 is a photograph of a large-size seed crystal after repair of example 2;
FIG. 7 is a state diagram at the center of the seed crystal after repair in example 2;
FIG. 8 is a graph of the state of the edge of the seed crystal after repair in example 2.
Detailed Description
The present invention will be described in further detail below in order to make the objects, technical solutions and effects of the present invention more clear and distinct. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The MPCVD equipment used in the specific embodiment of the invention is CYRANNUS system in Germany, and the working parameter is 6 kw-2.45 GHz.
Example 1
The CVD method for repairing the surface cracks of the large-size diamond monocrystal wafer specifically comprises the following steps:
(1) Seed crystal pretreatment:
using a large-size CVD diamond single crystal wafer with cracks (grooves are formed at the positions of the cracks) on the surface as a seed crystal, wherein the size of the seed crystal is 15mm multiplied by 0.5mm, the crystallographic orientation is (100), firstly, heating and soaking the seed crystal in acetone and alcohol in sequence, wherein the acetone and the alcohol are analytically pure, the mass fraction of the alcohol is more than 99.7%, the heating temperature is 65 ℃, the heating and soaking time is 3 hours, taking out the seed crystal, washing the seed crystal with deionized water, and cleaning the surface of the seed crystal with a dust-free wiping rod;
(2) And (3) assembling:
for the seed crystal in the step (1), the surface with cracks (the cracks form a groove) is taken as a growth surface, and the surface is placed on a molybdenum sheet (the molybdenum sheet is phi 50mm multiplied by 4mm in size) in a centering way;
(3) Single wafer surface repair and growth:
a. opening MPCVD equipment, placing molybdenum sheet with seed crystal in step (2), and vacuumizing to 1×10 -2 Below mbar, then simultaneously introducing H 2 、CO 2 The flow rates are 400sccm and 10sccm respectively, the microwave power is set to be 4.5kw, the air pressure is set to be 185mbar, the temperature is set to be 950 ℃, and the temperature is maintained for 80 minutes;
b. adjusting the microwave power to 4kw and the air pressure to 175mbar, gradually decreasing the temperature due to the decrease of the microwave power and the air pressure, and introducing CH when the temperature reaches 750 DEG C 4 The flow is 4sccm and is kept for 2 hours;
c. improving CH 4 The flow rate is 15sccm, at this time, N is introduced 2 The concentration is 15.3-15.6ppm, the microwave power is adjusted to be 4.3kw, the air pressure is adjusted to be 180mbar, the temperature is adjusted to be 850 ℃, and the microwave power is kept for 10 hours;
d. adjusting the microwave power to 5kw and the air pressure to 195mbar, and adjusting CH 4 Flow rate of 28sccm to N 2 The concentration is 15ppm, and the CO is regulated 2 The flow is 3.5sccm, the temperature is 980 ℃, and the growth is stable for 55 hours, thus obtaining the composite material.
The seed crystal with cracks cannot be subjected to surface polishing treatment, and the seed crystal is subjected to H at 900-1000 DEG C 2 And CO 2 And H, O plasma is formed to carry out plasma etching on the surface of the seed crystal, so that the micro defect density of the surface of the seed crystal, especially at the crack position, is reduced, the risk of polycrystal penetration at the crack position in the growth process is reduced, and the aim of improving the surface quality of the whole seed crystal is fulfilled.
Specifically, in the method, the temperature is adjusted, and H, O plasma is utilized to carry out intermittent plasma etching on the surface of the seed crystal.
I.e. when the temperature is 750 ℃, a small amount of CH is introduced 4 Held in parallelFor a certain time, aim at preventing CO 2 Defects, namely etching pits, are formed on the surface of the seed crystal due to long-time etching, and the defect density at cracks is sufficiently reduced, because of CH 4 The concentration is low enough that the seed crystal is not nucleated on the surface of the seed crystal for a certain period of time, and the CO 2 But also has a certain neutralization effect, so the surface morphology of the whole seed crystal can be greatly improved.
After the surface morphology of the seed crystal is fully treated, N is introduced into 2 Filling and repairing cracks in a low-speed longitudinal growth and lateral growth accelerating mode, and inhibiting secondary nucleation and polycrystalline growth, so that complete coverage is realized. And finally, regulating the flow of each gas to a stable growth value, and growing on the surface of which the crack is completely repaired for 50 hours.
H described in step (3) 2 、N 2 The purity of (C) is greater than 99.999%, CH 4 、CO 2 The purity of (2) is more than 99.995%.
Preferably, in the step (3) d of the present invention, the flow rate of each gas is adjusted to a stable growth value, and the growth is performed on the surface where the crack is completely repaired, and after the epitaxial layer reaches a certain thickness, a new large-size seed crystal can be prepared by a laser cutting separation technology, and the specific cutting method is as follows: and (3) sticking a single crystal growth surface on a clamp, ensuring that the bottom surface of the single crystal is vertical to the clamp, fixing the clamp on a cutter tool, adjusting the Z-axis alignment focal length, finely adjusting an adjusting screw on the clamp to enable the edge of the single crystal to coincide with a datum line, taking the upper, middle and lower three points as datum points, setting cutting parameters, cutting edge polycrystal by pressing a start key, rotating the clamp to enable the edge polycrystal to be vertical to the laser direction after cutting off the edge polycrystal, and cutting the single crystal according to the same operation method to obtain the prepared epitaxial layer.
The method of the embodiment is implemented by H 2 、CO 2 Plasma etching the crack, and then using a certain proportion of CH 4 Repairing the crack (forming a groove at the crack) under the high-temperature condition, and realizing filling and covering of the crack by inhibiting longitudinal growth and accelerating transverse growth. When the repaired single crystal is cut and separated by laser, the original seed crystal is thickened to ensureThe repairing layer covers the original crack defect, improves the surface quality of the large-size seed crystal and ensures that the seed crystal can be recycled.
The seed crystal with the crack before growth is shown in fig. 1, the state of a groove at the crack of the seed crystal is shown in fig. 2, the prepared single crystal is shown in fig. 3, the state after original crack repair in the prepared single crystal is shown in fig. 4, and a metallographic photograph after crack repair is shown in fig. 5.
As can be seen from fig. 4 and fig. 5, the cracks on the surface of the single crystal wafer are well repaired, the epitaxial layer obtained by growth has better partial quality, the surface step flow is smoothly transited, no visible impurity defect exists, the further growth condition is met, the growth process of the embodiment is feasible, and the repair of the crack surface can be completed through 3 times of the same test, so that the method has higher repeatability.
Example 2
The CVD method for repairing the surface cracks of the large-size diamond monocrystal wafer specifically comprises the following steps:
(1) Seed crystal pretreatment:
using a large-size CVD diamond single crystal wafer with cracks (grooves are formed at the positions of the cracks) on the surface as a seed crystal, wherein the size of the seed crystal is 15mm multiplied by 0.5mm, the crystallographic orientation is (100), firstly, heating and soaking the seed crystal in acetone and alcohol in sequence, wherein the acetone and the alcohol are analytically pure, the mass fraction of the alcohol is more than 99.7%, the heating temperature is 80 ℃, the heating and soaking time is 2 hours, taking out the seed crystal, washing the seed crystal with deionized water, and cleaning the surface of the seed crystal with a dust-free wiping rod;
(2) And (3) assembling:
for the seed crystal in the step (1), the surface with cracks (the cracks form a groove) is taken as a growth surface, and the surface is placed on a molybdenum sheet (the molybdenum sheet is phi 50mm multiplied by 4mm in size) in a centering way;
(3) Single wafer surface repair and growth:
a. opening MPCVD equipment, placing molybdenum sheet with seed crystal in step (2), and vacuumizing to 1×10 -2 Below mbar, then simultaneously introducing H 2 、CO 2 The flow rates are 500sccm and 12sccm respectively, and the microwave power is set to be 4.3kw and the air pressure is set175mbar at 900℃for 60min;
b. adjusting the microwave power to 3.5kw and the air pressure to 160mbar, gradually decreasing the temperature due to the decrease of the microwave power and the air pressure, and introducing CH when the temperature reaches 700 DEG C 4 The flow is 5sccm and is kept for 3 hours; :
c. improving CH 4 The flow rate is 10sccm, at this time, N is introduced 2 The concentration is 15.3-15.6ppm, the microwave power is adjusted to 4kw, the air pressure is adjusted to 170mbar, the temperature is 800 ℃, and the microwave power is kept for 8 hours;
d. adjusting the microwave power to 5.5kw and the air pressure to 210mbar, and adjusting CH 4 Flow rate of 33sccm to give N 2 The concentration is 15ppm, and the CO is regulated 2 The flow is 5sccm, the temperature is 1050 ℃, and the growth time is 50 hours, thus obtaining the composite material.
The seed crystal with cracks cannot be subjected to surface polishing treatment, and H is required to be used at 900-1000 DEG C 2 And CO 2 And plasma etching is carried out on the surface of the seed crystal, so that the micro defect density of the surface of the seed crystal, especially at the crack position, is reduced, the risk of polycrystal penetration at the crack position in the growth process is reduced, and the aim of improving the surface quality of the whole seed crystal is fulfilled.
At 700 deg.C, a small amount of CH is introduced 4 And for a certain period of time, with the aim of preventing CO 2 Defects, namely etching pits, are formed on the surface of the seed crystal due to long-time etching, and the defect density at cracks is sufficiently reduced, because of CH 4 The concentration is low enough that the seed crystal is not nucleated on the surface of the seed crystal for a certain period of time, and the CO 2 But also has a certain neutralization effect, so the surface morphology of the whole seed crystal can be greatly improved. After the surface morphology of the seed crystal is fully treated, N is introduced into 2 Filling and repairing cracks in a low-speed longitudinal growth and lateral growth accelerating mode, and inhibiting secondary nucleation and polycrystalline growth, so that complete coverage is realized. And finally, regulating the flow of each gas to a stable growth value, and growing on the surface of which the crack is completely repaired for 50 hours.
H described in step (3) 2 、N 2 The purity of (C) is greater than 99.999%, CH 4 、CO 2 Is greater than the purity of99.995%。
The method of the embodiment is implemented by H 2 、CO 2 Plasma etching the crack, and then using a certain proportion of CH 4 Repairing the crack (forming a groove at the crack) under the high-temperature condition, and realizing filling and covering of the crack by inhibiting longitudinal growth and accelerating transverse growth. And 2 times of growth verification prove that the repair of the crack surface can be completed.
Example 2 method the repaired large size seed crystal is shown in fig. 6, the repaired seed crystal center is shown in fig. 7, and the repaired seed crystal edge is shown in fig. 8.
As can be seen from fig. 7 and 8, the cracks originally exposed on the surface are well covered, the cracks on the surface of the seed crystal are not exposed again after laser cutting, the surface quality is further improved, and the condition of recycling is met.
The process method of the invention greatly reduces the loss rate and high cost of large-size single crystal wafers, improves the growth efficiency and the growth quantity, and the obtained single crystal products have excellent quality and higher application prospect and economic value.
While specific embodiments of the invention have been described above, it should be understood that the invention is not limited to the particular embodiments described above. Various changes or modifications may be made by one skilled in the art within the scope of the claims without affecting the spirit of the invention.
Claims (10)
1. The CVD method for repairing the surface cracks of the large-size diamond monocrystal wafer is characterized by comprising the following steps of:
(1) Seed crystal pretreatment:
selecting CVD diamond single crystal wafer with cracks on the surface as seed crystal, directly cleaning the seed crystal or firstly heating and soaking the seed crystal, cleaning the seed crystal, and wiping the seed crystal;
(2) And (3) assembling:
placing the seed crystal in the step (1) into a molybdenum sheet for assembly;
(3) Single wafer surface repair and growth using MPCVD equipment:
a. opening MPCVD equipment, placing molybdenum sheet with seed crystal in step (2), and vacuumizing to 1×10 -2 Below mbar, then simultaneously introducing H 2 、CO 2 Setting the microwave power to be 4.3-4.8 kw, the air pressure to be 175-195 mbar and the temperature to be 900-1000 ℃ and keeping for 60-90min;
b. adjusting the microwave power to 3.5-4 kw and the air pressure to 160-180 mbar, gradually reducing the temperature due to the reduction of the microwave power and the air pressure, and introducing CH when the temperature reaches 700-750 DEG C 4 Maintaining for 2-3 hours;
c. adjusting CH 4 Flow is simultaneously introduced into N 2 Adjusting the microwave power to be 4-4.5 kw, the air pressure to be 170-190 mbar, and the temperature to be 800-900 ℃ and keeping for 8-10h;
d. adjusting the microwave power to 5-5.5 kw and the air pressure to 190-210 mbar, and adjusting CH 4 And CO 2 And adjusting the flow rate to 950-1050 ℃ and stably growing to obtain the fertilizer.
2. The method according to claim 1, wherein the diamond single crystal wafer used in step (1) is a diamond single crystal wafer of crystallographic orientation (100) having dimensions of 16mm x 0.7mm, 15mm x 0.5mm or 15mm x 0.7mm.
3. The method of claim 1, wherein in the step (1), the seed crystal is heated and soaked in acetone and alcohol in sequence, the heating temperature is 60-80 ℃, and the heating time is 2-3 hours.
4. The method of claim 1, wherein the surface of the seed crystal having cracks in step (1) is selected as a growth surface and placed at the center of the molybdenum sheet, and the molybdenum sheet has a size of phi 50mm x 4mm at the time of assembly in step (2).
5. The method of claim 1, wherein in step (3) a, H is introduced after evacuation 2 、CO 2 The flow rates are 400-500sccm and 10-12sccm respectively.
6. The method of claim 1, wherein in step (3) b, CH is introduced 4 The flow rate of the water is 4-5 sccm.
7. The method of claim 1, wherein in step (3) c, CH is adjusted 4 The flow rate is 10-15 sccm.
8. The method of claim 1, wherein in step (3) d, CH is adjusted 4 The flow rate is 26-33 sccm, so that N 2 At a concentration of 15ppm, CO 2 The flow rate is 3-5 sccm.
9. The method of claim 1, wherein in step (3) d, the stable growth time is 50 to 60 hours.
10. The method of claim 1, wherein said H in step (3) 2 、N 2 The purity of (C) is greater than 99.999%, CH 4 、CO 2 The purity of (2) is more than 99.995%.
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