CN117144328A - Method for preparing gallium nitride film based on patterned graphene mask - Google Patents
Method for preparing gallium nitride film based on patterned graphene mask Download PDFInfo
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- CN117144328A CN117144328A CN202310435684.7A CN202310435684A CN117144328A CN 117144328 A CN117144328 A CN 117144328A CN 202310435684 A CN202310435684 A CN 202310435684A CN 117144328 A CN117144328 A CN 117144328A
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- 229910002601 GaN Inorganic materials 0.000 title claims abstract description 122
- JMASRVWKEDWRBT-UHFFFAOYSA-N Gallium nitride Chemical compound [Ga]#N JMASRVWKEDWRBT-UHFFFAOYSA-N 0.000 title claims abstract description 121
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 105
- 229910021389 graphene Inorganic materials 0.000 title claims abstract description 105
- 238000000034 method Methods 0.000 title claims abstract description 63
- 239000000758 substrate Substances 0.000 claims abstract description 28
- 238000005530 etching Methods 0.000 claims abstract description 17
- 238000001259 photo etching Methods 0.000 claims abstract description 11
- 238000005229 chemical vapour deposition Methods 0.000 claims abstract description 10
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 claims abstract description 10
- 229910052751 metal Inorganic materials 0.000 claims abstract description 7
- 239000002184 metal Substances 0.000 claims abstract description 7
- 238000004140 cleaning Methods 0.000 claims abstract description 6
- 230000000379 polymerizing effect Effects 0.000 claims abstract description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 8
- 229910052594 sapphire Inorganic materials 0.000 claims description 8
- 239000010980 sapphire Substances 0.000 claims description 8
- XCZXGTMEAKBVPV-UHFFFAOYSA-N trimethylgallium Chemical compound C[Ga](C)C XCZXGTMEAKBVPV-UHFFFAOYSA-N 0.000 claims description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 7
- 239000001301 oxygen Substances 0.000 claims description 7
- 229910052760 oxygen Inorganic materials 0.000 claims description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 6
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- 238000001020 plasma etching Methods 0.000 claims description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 3
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 239000001257 hydrogen Substances 0.000 claims description 3
- 229910052739 hydrogen Inorganic materials 0.000 claims description 3
- 230000006911 nucleation Effects 0.000 claims description 3
- 238000010899 nucleation Methods 0.000 claims description 3
- 239000007789 gas Substances 0.000 claims description 2
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims 1
- 229910001882 dioxygen Inorganic materials 0.000 claims 1
- 239000013078 crystal Substances 0.000 abstract description 5
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- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
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- 235000012239 silicon dioxide Nutrition 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
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Classifications
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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
- C23C16/22—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
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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
- C23C16/22—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
- C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
- C23C16/301—AIII BV compounds, where A is Al, Ga, In or Tl and B is N, P, As, Sb or Bi
- C23C16/303—Nitrides
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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
- 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
- C23C16/56—After-treatment
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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
- C30B25/04—Pattern deposit, e.g. by using masks
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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
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/40—AIIIBV compounds wherein A is B, Al, Ga, In or Tl and B is N, P, As, Sb or Bi
- C30B29/403—AIII-nitrides
- C30B29/406—Gallium nitride
Abstract
The invention relates to a method for preparing a gallium nitride film based on a patterned graphene mask, which comprises the steps of growing a plurality of graphene layers on the surface of a substrate layer by adopting a plasma enhanced chemical vapor deposition method; preparing a patterned hexagonal graphene mask structure from the graphene layer through photoetching and etching; and (3) carrying out inorganic cleaning on the mask structure to remove oxide left by etching in the window area, growing a gallium nitride epitaxial layer in two steps by adopting a metal organic chemical vapor deposition method, nucleating and growing the gallium nitride on the window of the hexagonal mask in the first step, and polymerizing the gallium nitride in the second step towards the center of the mask in the transverse growth mode to obtain the complete gallium nitride film. By adopting the technical scheme provided by the invention, the growth mode of gallium nitride is changed by regulating and controlling the growth parameters such as temperature, pressure, V/III ratio and the like, and the grown gallium nitride is finally combined laterally to obtain the high-quality gallium nitride film. The result shows that the patterned hexagonal graphene mask can effectively reduce the high dislocation density of gallium nitride caused by mismatch, relax the stress of gallium nitride and improve the crystal quality of gallium nitride.
Description
Technical Field
The invention belongs to the technical field of semiconductors, and particularly relates to a method for growing gallium nitride by using a patterned hexagonal graphene mask.
Background
The third-generation semiconductor material represented by gallium nitride has excellent performances of wide band gap, high breakdown electric field, high electron mobility and the like, and has wide application in the fields of optoelectronic devices, radio frequency devices, power devices and the like. However, gallium nitride does not exist in nature and it requires artificial synthesis. Gallium nitride is typically available in a heteroepitaxial manner due to the lack of a homogeneous substrate for gallium nitride in view of cost. However, there is a problem in that the difference in lattice constant and thermal expansion coefficient between the hetero-substrate and gallium nitride seriously affects the crystal quality of gallium nitride, and dislocation density and stress of gallium nitride are at high levels, which hinders the performance and development of gallium nitride-based devices. The dislocation density of gallium nitride can be effectively reduced by inserting the mask layer. The mask layer is often a single-layer mask made of silicon dioxide or silicon nitride and other dielectric materials or a multi-layer dielectric mask structure combined by multiple materials. While such masks serve to reduce dislocation, the thickness and amorphous state of the dielectric mask can present low angle grain boundaries and introduce additional stress problems to the gallium nitride. Furthermore, the good stability of the dielectric mask allows for the growth to remain in the sample, which will affect the properties of gallium nitride, such as electrical and thermal conductivity. On the other hand, there is a lateral epitaxy technology of patterning heterogeneous substrates at present, namely, the substrates are prepared into patterned structures with periodical depth differences through an etching process, in such structures, the substrates play a role of a mask, the lateral combination of the blocking of the substrates and dislocation is a main reason for the reduction of dislocation density of gallium nitride, and the reduction degree of dislocation density is influenced by the depth of grooves. Therefore, we propose a method for growing gallium nitride by using patterned hexagonal graphene mask, because gallium nitride with unique surface non-dangling bond characteristic is difficult to nucleate on the patterned hexagonal graphene mask as a mask layer, weak van der Waals force between the patterned hexagonal graphene mask and the gallium nitride layer can overcome the influence of mismatch, dislocation density and stress of the grown gallium nitride are greatly reduced, the crystal quality of the gallium nitride is improved, and the method has wide application prospect.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention provides a method for preparing a gallium nitride film with good uniformity based on a patterned graphene mask, which can effectively improve the crystal quality of the gallium nitride film on a heterogeneous substrate and reduce the high dislocation density and high stress of heteroepitaxial gallium nitride.
The technical scheme for achieving the purpose of the invention is to provide a method for preparing a gallium nitride film based on a patterned graphene mask, wherein a plasma enhanced chemical vapor deposition method is adopted to grow a plurality of graphene layers on the surface of a substrate layer; preparing a patterned hexagonal graphene mask structure from the graphene layer through photoetching and etching; and (3) carrying out inorganic cleaning on the mask structure to remove oxide left by etching in the window area, growing a gallium nitride epitaxial layer in two steps by adopting a metal organic chemical vapor deposition method, carrying out nucleation growth on the window of the hexagonal mask in the first step of gallium nitride, and polymerizing the gallium nitride in the second step of lateral growth towards the center of the mask to obtain the complete gallium nitride film.
The substrate layer is sapphire-based gallium nitride.
According to the method for preparing the gallium nitride film based on the patterned graphene mask, the process condition of growing the multilayer graphene layer by the plasma enhanced chemical vapor deposition method is that the ion source power is 80w, the growth temperature is 800 ℃, the growth time is 90min, and the growth gas is methane, hydrogen and argon.
According to the method for preparing the gallium nitride film based on the patterned graphene mask, the patterned hexagonal graphene mask structure is prepared by adopting photoetching and oxygen plasma etching, and the process conditions of the oxygen plasma etching are 200sccm of oxygen airflow flux, power is 400w and etching time is 80s. The window width of the hexagonal graphene mask structure is 3-5 microns, and the mask width is 15-25 microns.
According to the method for preparing the gallium nitride film based on the patterned graphene mask, provided by the invention, the process conditions of nucleation growth of the gallium nitride in the window of the hexagonal mask in the first step are that the growth temperature is 950-1000 ℃, the pressure is 450-550 Torr, the V/III is 2000-2500, the ammonia gas is 15-20 slm, and the trimethyl gallium is 25-35 sccm; the second step of lateral growth of gallium nitride is to polymerize towards the mask center under the technological conditions of 1000-1100 deg.c, 250-350 Torr pressure, 3500-4000V/III, 50-60 slm ammonia gas and 55-65 sccm trimethyl gallium.
According to the method for preparing the gallium nitride film based on the patterned graphene mask, a sample is placed in hydrochloric acid with the temperature of 60 ℃ and the concentration of 38%, soaked for 10 minutes, and the mask structure is subjected to inorganic cleaning.
In the invention, the complete multilayer graphene obtained by a plasma enhanced chemical vapor deposition method is prepared into a patterned hexagonal graphene mask by photoetching, etching and other processes, and gallium nitride is grown by two-step growth parameters. The advantages of the invention are mainly divided into the following three parts:
1. the method can directly grow the graphene on the target substrate by adopting the plasma enhanced chemical vapor deposition method, and effectively avoids the problem of damage of the graphene caused by pollution and human factors.
2. Because the graphene material has the advantages, the graphene material is a good mask material due to the fact that the surface of the graphene lacks a dangling bond, and the effect of blocking gallium nitride dislocation of a substrate is achieved; the Van der Waals force of the graphene mask layer and the epitaxial gallium nitride layer can overcome the influence of lattice mismatch, and the stress of gallium nitride is improved; the graphene has excellent physical and chemical properties, so that the graphene has good electric and thermal conductivity, and the stability and heat dissipation performance of the gallium nitride-based device can be effectively improved; meanwhile, the ultrathin thickness of the graphene does not cause the problem of small-angle grain boundaries of gallium nitride.
3. Compared with a one-dimensional grating strip mask, the patterned hexagonal mask has six window areas, and the gallium nitride merging and film forming speed is higher; due to the anisotropy of gallium nitride, the surface of the gallium nitride film grown on the one-dimensional grating strip mask can be uneven, the patterned hexagonal graphene mask provided by the invention can regulate and control the growth in multiple directions, and the gallium nitride film has good uniformity.
Drawings
Fig. 1 is a schematic structural diagram of a gallium nitride film grown by using a graphene mask according to an embodiment of the present invention;
fig. 2 is a schematic plan view of a graphene mask layer arranged by a hexagonal pattern according to an embodiment of the present disclosure;
FIG. 3 is a schematic diagram of a window and a mask width structure of a mask layer according to an embodiment of the present invention;
wherein: 1 is a gallium nitride epitaxial layer, 2 is a graphene mask layer, 3 is a gallium nitride/sapphire composite substrate layer, 4 is a graphene mask region, and 5 is a window region;
FIG. 4 is a graph of a graphene Raman spectrum of a mask region and a window region of a patterned hexagonal graphene mask structure provided by an embodiment of the present invention;
fig. 5 is an electron microscope image of a patterned hexagonal graphene mask structure after a first growth step of gallium nitride according to an embodiment of the present invention;
fig. 6 is a diagram of a scanning electron microscope (a) and a diagram of a cathode fluorescence spectrum (b) of a patterned hexagonal graphene mask structure provided by an embodiment of the present invention after a second growth step of gallium nitride;
fig. 7 is a raman spectrum diagram of graphene in a mask region after a patterned hexagonal graphene mask structure provided by an embodiment of the present invention grows in a second step of gallium nitride;
FIG. 8 is a Raman spectrum diagram of a substrate gallium nitride and an epitaxial gallium nitride after growth of a patterned hexagonal graphene mask structure according to an embodiment of the present invention;
FIG. 9 is a Raman spectrum diagram of wet transfer graphene provided by an embodiment of the invention;
fig. 10 is a mirror diagram of a wet transfer graphene mask structure according to an embodiment of the present invention;
fig. 11 is a scanning electron microscope (a) image and a cathode fluorescence spectrum image (b) image of gallium nitride after a wet transfer graphene mask is grown according to an embodiment of the present invention.
Detailed Description
According to the invention, gallium nitride grows on the patterned hexagonal graphene mask through a metal organic chemical vapor deposition method. Firstly, growing a plurality of layers of complete graphene on a gallium nitride/sapphire composite substrate by a plasma enhanced chemical vapor deposition method. Then, the multilayer graphene is prepared into a patterned hexagonal mask structure through photoetching, etching and other processes. And finally, growing gallium nitride on the patterned hexagonal graphene mask by a metal organic chemical vapor deposition method. Trimethylgallium (TMGa) and ammonia (NH) 3 ) Ga source and N source are provided separately to synthesize GaN. The growth parameters of gallium nitride are divided into two steps: the first step growth parameters select a low growth temperature, a high growth pressure, and a low V/III ratio to promote three-dimensional growth of gallium nitride. The second step of growth parameters are that the growth temperature and the ratio of V/III are increased based on the first step of growth, and the growth pressure is reduced to promote the lateral growth of gallium nitride to be combined. In the invention, the patterned graphene mask is in a hexagonal shape, the width of a window area is 4 mu m, the width of a mask area is 20 mu m, and the shape of the graphene mask, the ratio of the window to the mask and the like can be properly adjusted for different growth methods.
The technical scheme of the invention is further described below with reference to the accompanying drawings and examples.
Embodiment one: the embodiment provides a method for growing gallium nitride based on a patterned hexagonal graphene mask, which comprises the following steps:
the gallium nitride based on the commercial sapphire is conventionally cleaned and dried, and the complete multilayer graphene is obtained on the surface of the gallium nitride by a plasma enhanced chemical vapor deposition method, wherein the growth conditions of the graphene are as follows: the ion source power was 60w, the growth temperature was 800 ℃, and the growth rates of methane, hydrogen and argon were 10sccm, 2sccm and 2sccm, respectively, for 90min.
Carrying out photoetching and etching on a sample, and preparing the sample into a patterned hexagonal graphene mask, wherein the method comprises the following specific steps of: (1) Spin-coating and pre-baking, namely coating AZ5214 photoresist on the surface of a graphene layer, adsorbing a sample in vacuum, spin-coating at a spin-coating rate of 600rad/min for 30s after 600rad/min, and then placing the sample on a hot plate at 95 ℃ for pre-baking for 90s; (2) And exposing and developing, and exposing for 6.5s in a hard mode of the MA6 ultraviolet photoetching machine. After exposure is completed, the sample is subjected to development treatment, and the sample is developed for 40 seconds by using a developing solution matched with the AZ5214 photoresist; (3) Etching the graphene in the window area, etching the graphene in the window area by using oxygen plasma of a March photoresist remover, setting the oxygen flow flux and the power to 200sccm and 400W, setting the etching time to 80s, and forming a hexagonal graphene mask layer on the gallium nitride surface of the substrate.
And growing a gallium nitride epitaxial layer on the graphene mask layer by a metal organic chemical vapor deposition method, and using two-step growth parameters. The first step of growth is carried out at 970 ℃, the pressure is 500Torr, the V/III is 2100, the ammonia gas is 16.1slm, the trimethyl gallium is 30sccm, and the growth time is 25 minutes; the second step of growth temperature is 1050 ℃, the pressure is 300 Torr, the V/III is 3600, the ammonia gas is 55slm, the trimethyl gallium is 60sccm, and the growth time is 180 minutes.
Referring to fig. 1, a schematic structural diagram of a gallium nitride film grown by a graphene mask provided in this embodiment includes a gallium nitride epitaxial layer 1, a graphene mask layer 2 and a substrate layer 3 which is a gallium nitride/sapphire composite substrate layer, and growing multiple layers of complete graphene on the gallium nitride/sapphire composite substrate 3 by a plasma enhanced chemical vapor deposition method; preparing the multilayer graphene into a graphene mask layer 2 with a patterned hexagonal structure through photoetching, etching and other processes; and growing the gallium nitride epitaxial layer 1 on the grapheme mask with the patterned hexagonal structure by a metal organic chemical vapor deposition method.
Referring to fig. 2 and 3, a schematic plan view of a graphene mask layer arranged by a hexagonal pattern and a schematic view of a window and a mask width structure of the mask layer provided by the present embodiment are respectively shown, a black coverage portion is a graphene mask region 4, a white exposed region is a window region 5, and as can be seen from fig. 3, the hexagonal graphene mask layer structure provided by the present embodiment has a window region width of 4 micrometers and a mask region width of 20 micrometers.
Referring to fig. 4, in the graphene raman graph of the mask region and the window region in this embodiment, 3 characteristic peaks (D peak, G peak and 2D peak) of graphene exist in the mask region, and signals of the three characteristic peaks do not exist in the window region, which indicates that the preparation of the mask structure is completed.
Referring to fig. 5, in order to obtain an electron microscope image of gallium nitride after the first step of growth parameters, the gallium nitride epitaxial layer preferentially nucleates and grows in the window area and covers the whole window area.
Referring to fig. 6, (a) is an electron microscope image after epitaxial layer growth, and (b) is a cathode fluorescence spectrometer image; as can be seen from the graph (a), after the second growth step, gallium nitride grows laterally and polymerizes towards the center of the mask region, the distribution of threading dislocation on the gallium nitride surface appears to be consistent with that of the window, and many dislocations can still be seen in the unmixed substrate region, which means that the graphene mask successfully acts as a mask, effectively blocking dislocations from the substrate. Estimating the dislocation density of gallium nitride to be about 8.5X10 according to the number of dislocation black spots in the cathode fluorescence spectrum of the (b) chart 7 cm -2 。
Referring to fig. 7, a raman spectrum of graphene in the mask region after growing gallium nitride with the second step of growth parameters is shown in fig. 7, and it can be seen that no characteristic peak signal of graphene exists in the raman spectrum, which indicates that graphene is decomposed during the growth process and is not in the sample.
Referring to FIG. 8, an E of gallium nitride is shown as a Raman diagram of a substrate gallium nitride and epitaxial gallium nitride 2 The (high) peak is very sensitive to stress, and can intuitively detect the stress of gallium nitride, namely unstressed gallium nitride E 2 (high) peak position 568cm -1 . E of gallium nitride after growth 2 The (high) peak is 570.44cm -1 Reduced to 569.5cm -1 The stress of gallium nitride is relaxed from 0.57Gpa to 0.35Gpa.
Embodiment two: after conventional cleaning and blow-drying of commercially available sapphire-based gallium nitride, the multilayer graphene deposited on the copper foil by chemical vapor deposition is transferred onto a target substrate by a wet method. The wet transfer process comprises the following steps: (1) Spin-coating polymethyl methacrylate (PMMA) on the surface of a copper foil covered with graphene; (2) Immersing the PMMA-coated sample in an ion etching agent to completely etch and fall off the copper foil; (3) The PMMA/graphene is supported by a silicon substrate, repeatedly cleaned in deionized water and then transferred to a target substrate; (4) Drying the sample until the graphene is tightly attached to the target substrate; (5) And (3) immersing the dried sample in an acetone solution to remove PMMA, putting the sample into an ethanol solution to remove acetone, drying again, and completing transfer.
Referring to fig. 9, a raman spectrum of the wet transfer graphene is shown, and three raman characteristic peaks of D peak, G peak and 2D peak of the graphene can be seen from fig. 9. Compared with the multilayer graphene obtained by plasma chemical vapor deposition, the wet transfer graphene has better crystal quality and shows a defect D peak with lower intensity.
According to the conditions provided in the first embodiment, the sample is subjected to photoetching and etching processes, and the wet transfer graphene layer is prepared into a patterned hexagonal mask structure with a window width of 4 microns and a mask width of 20 microns.
Referring to fig. 10, a mirror image of a hexagonal mask after fabrication is shown, the contrast difference between the mask surfaces can be seen, which illustrates the non-uniformity and imperfections in the mask surface topography, which may be caused by contamination of the transfer process or by human handling.
Samples were grown in a two-step process under the conditions provided in example one, with results of the growth being shown in fig. 11, (a) for a scanning electron microscope image and (b) for a cathode fluorescence spectrum image. It can be seen that the growth of gallium nitride is not performed in a lateral epitaxial mode, but the mask region and the window region are grown together, and the surface morphology of the grown gallium nitride is uneven due to the non-uniformity of the graphene in the mask region, so that a plurality of pits are left. On the other hand, the cathode fluorescence spectrum image shows that the surface threading dislocation of gallium nitride has no regularity, and the graphene does not play a role of a mask.
The multilayer complete graphene grown by adopting the plasma chemical vapor deposition method avoids pollution and artificial damage of the graphene, and is prepared into patternsAnd a hexagonal mask layer and a gallium nitride epitaxial layer are grown. The gallium nitride epitaxial layer preferentially nucleates in the window region and grows vertically in three dimensions. And then the gallium nitride grows laterally and polymerizes towards the mask center under the control of growth parameters. The results show that the graphene mask is decomposed during the growth of gallium nitride, but gallium nitride is still grown in a lateral epitaxial mode, the surface threading dislocation distribution of gallium nitride is consistent with the window distribution, and the dislocation density is reduced to 10 7 On the order of magnitude. On the other hand, the stress of gallium nitride is obviously relaxed, E 2 The (high) peak is 570.44cm -1 Reduced to 569.5cm -1 Reducing from 0.57GPa to 0.35GPa. Therefore, the invention greatly improves the problems of high dislocation density and high stress of heteroepitaxial gallium nitride, can effectively improve the performance of gallium nitride-based devices, and has application prospect in the semiconductor industry.
Claims (7)
1. A method for preparing a gallium nitride film based on a patterned graphene mask is characterized by comprising the following steps: growing a plurality of graphene layers on the surface of the substrate layer by adopting a plasma enhanced chemical vapor deposition method; preparing a patterned hexagonal graphene mask structure from the graphene layer through photoetching and etching; and (3) carrying out inorganic cleaning on the mask structure to remove oxide left by etching in the window area, growing a gallium nitride epitaxial layer in two steps by adopting a metal organic chemical vapor deposition method, nucleating and growing the gallium nitride on the window of the hexagonal mask in the first step, and polymerizing the gallium nitride in the second step towards the center of the mask in the transverse growth mode to obtain the complete gallium nitride film.
2. The method for preparing the gallium nitride film based on the patterned graphene mask according to claim 1, wherein the method comprises the following steps: the substrate layer is sapphire-based gallium nitride.
3. The method for preparing the gallium nitride film based on the patterned graphene mask according to claim 1, wherein the method comprises the following steps: the process condition of growing the multi-layer graphene layer by the plasma enhanced chemical vapor deposition method is that the ion source power is 80w, the growth temperature is 800 ℃, the growth time is 90min, and the growth gases are methane, hydrogen and argon.
4. The method for preparing the gallium nitride film based on the patterned graphene mask according to claim 1, wherein the method comprises the following steps: and preparing a patterned hexagonal graphene mask structure by adopting photoetching and oxygen plasma etching, wherein the process condition of the oxygen plasma etching is 200sccm of oxygen gas flow, the power is 400w, and the etching time is 80s.
5. The method for preparing the gallium nitride film based on the patterned graphene mask according to claim 1, wherein the method comprises the following steps: the window width of the hexagonal graphene mask structure is 3-5 microns, and the mask width is 15-25 microns.
6. The method for preparing the gallium nitride film based on the patterned graphene mask according to claim 1, wherein the method comprises the following steps: the first step of nucleation growth of gallium nitride in a window of a hexagonal mask has the process conditions of growth temperature of 950-1000 ℃, pressure of 450-550 Torr, V/III of 2000-2500, ammonia gas of 15-20 slm and trimethyl gallium of 25-35 sccm; the second step of lateral growth of gallium nitride is to polymerize towards the mask center under the technological conditions of 1000-1100 deg.c, 250-350 Torr pressure, 3500-4000V/III, 50-60 slm ammonia gas and 55-65 sccm trimethyl gallium.
7. The method for preparing the gallium nitride film based on the patterned graphene mask according to claim 1, wherein the method comprises the following steps: the sample is placed in hydrochloric acid with the temperature of 60 ℃ and the concentration of 38 percent, soaked for 10 minutes, and the mask structure is subjected to inorganic cleaning.
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