CN114197039A - Method for epitaxially growing uniform graphene more than six inches on 4H-SiC substrate - Google Patents

Method for epitaxially growing uniform graphene more than six inches on 4H-SiC substrate Download PDF

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CN114197039A
CN114197039A CN202111516423.5A CN202111516423A CN114197039A CN 114197039 A CN114197039 A CN 114197039A CN 202111516423 A CN202111516423 A CN 202111516423A CN 114197039 A CN114197039 A CN 114197039A
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crucible
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insulation layer
graphene
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陈秀芳
邵辰
徐现刚
李晓蒙
郭枫林
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Shandong University
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Abstract

The invention relates to a method for epitaxially growing more than six-inch uniform graphene on a 4H-SiC substrate, which adopts a large-diameter furnace chamber high-temperature furnace and a heat preservation and insulation layer with a reasonable structure arranged on the periphery of a crucible, realizes that a radial temperature field in the growth process of the graphene is a flat temperature field under double-layer conditions, and obtains a high-quality, high-uniformity and graphene material with the diameter of more than six inches and distributed on the surface of the whole silicon surface by the flat temperature field, the control of the growth temperature and the temperature increase and decrease speed.

Description

Method for epitaxially growing uniform graphene more than six inches on 4H-SiC substrate
Technical Field
The invention relates to a method for epitaxially growing more than six-inch uniform graphene on a 4H-SiC substrate, belonging to the technical field of microelectronic materials.
Background
Graphene is a novel carbonaceous two-dimensional material with a single-layer honeycomb lattice structure formed by tightly stacking carbon atoms, is the thinnest material all over the world at present, has the strength 200 ten thousand times that of steel although the thickness is only one millionth of hair, and has wide application prospects in the fields of micro-nano electronic devices, large-scale integrated circuits and the like due to the fact that graphene has high carrier mobility, zero band gap, high thermal conductivity, ultrahigh electric conductivity and the like, so that the preparation and application of graphene are widely concerned by various social circles.
SiC can be directly used as an insulating substrate of graphene as a third-generation wide bandgap semiconductor material, so that the graphene prepared by the silicon carbide high-temperature pyrolysis method does not need to be transferred for the second time, and a high-quality graphene material with a large area and controllable layer number can be prepared.
At present, the technology of 2-4 inch SiC upper epitaxial graphene is relatively mature, for example, Chinese patent document CN101602503A (CN200910023384.8) discloses a method for epitaxially growing graphene on a 4H-SiC silicon surface, the method is carried out in a CVD furnace, hydrogen and propane are introduced before growth for hydrogen etching to remove surface scratches and form regular steps, then silane treatment is carried out to remove surface oxides, and the graphene is epitaxially grown on the silicon surface at about 1600 ℃ under the argon atmosphere of 900 mbar. Chinese patent document CN102433586A (CN201110293632.8) discloses a method for epitaxially growing wafer-level graphene on a 4H/6H-SiC silicon surface. The method is carried out in a CVD furnace, firstly, hydrogen etching is used for removing surface scratches and forming regular steps, silane is introduced for removing surface oxides caused by hydrogen etching, and the growth of graphene is completed at 1600 ℃ and under lower argon pressure. However, the technology for preparing graphene by SiC high-temperature pyrolysis with the size of more than six inches is rarely reported. The reason is that the larger the SiC wafer size, the larger the radial difference in temperature field, and the more difficult the uniformity and quality of the epitaxial graphene is to control. Even if the report that the graphene is prepared by the SiC high-temperature pyrolysis method with the size of more than six inches exists, the obtained graphene is not uniform and has poor quality. For example, chinese patent document CN102051677A (CN201010541290.2) discloses a method for growing graphene on a large-diameter 6H — SiC carbon surface. The method is carried out in a single crystal growth furnace, and 2-4 inches of uniform graphene is obtained on the carbon surface of a 6H-SiC wafer at the temperature of about 1750 ℃ under the condition of 900 mbar. For another example, chinese patent document CN104947184A (CN201501304046.7) discloses a method for epitaxially growing graphene on a large-diameter 4H/6H-SiC silicon surface substrate based on in-situ Si atmosphere. The method is carried out in a single crystal growth furnace, a groove is arranged at the center of a graphite crucible or the periphery of a wafer for placing Si powder or SiC powder, and hydrogen etching and growth temperature regulation are combined to obtain 2-4 inches of graphene.
With the development of large-scale integrated circuits, and the larger the SiC wafer size is, the larger the radial difference of the temperature field is, the more difficult the uniformity and quality of epitaxial graphene is to be controlled, and the difficulty that the obtained graphene is not uniform and has poor quality is high.
Disclosure of Invention
Aiming at the defects of the prior art, particularly the difficulty of preparing graphene by a SiC high-temperature pyrolysis method with the size of more than six inches, the invention provides a method for epitaxially growing uniform graphene with the size of more than six inches on a 4H-SiC substrate. By the method provided by the invention, the high-quality and high-uniformity wafer-level graphene can be prepared on the 4H-SiC silicon surface with the size of more than six inches.
Interpretation of terms:
six-inch 4H — SiC: is single crystal 4H-SiC with a diameter of six inches, the size of the graphene grown on the substrate is also six inches, and 4H-SiC is a conventional shorthand expression of 4H crystal form SiC.
Carbon surface: refers to the surface of the silicon carbide substrate terminated with a layer of carbon atoms in the <000-1> direction.
Silicon surface: refers to the surface of a silicon carbide substrate terminated with an atomic layer of silicon in the <0001> direction.
The carbon and silicon faces of the SiC wafer are different polarity faces. Due to different arrangement and proportion of elements of different polarity planes, the material shows different physical and chemical properties.
The invention is realized by the following technical scheme:
a method for epitaxially growing more than six-inch uniform graphene on a 4H-SiC substrate comprises the following steps:
(1) grinding, polishing and cleaning the silicon surface of the 4H-SiC wafer with the diameter of more than six inches to ensure that the step shape in the whole area of the 4H-SiC wafer is regular and stably repeated;
(2) a large-diameter furnace chamber high-temperature furnace is used as a growth furnace, the diameter of the large-diameter furnace chamber is 5-8 times of that of the 4H-SiC wafer, the 4H-SiC wafer processed in the step (1) is horizontally placed on a graphite tray, the silicon surface faces downwards, the graphite tray is horizontally placed on a crucible base plate, a crucible top plate is covered above a crucible, a thickened heat-preservation and heat-insulation layer is arranged on the periphery of the crucible, and then the crucible top plate and the crucible top plate are placed in the high-temperature furnace chamber together;
(3) vacuumizing the furnace chamber of the high-temperature furnace, quickly heating to 1000-;
(4) and closing the argon, quickly moving the crucible upwards, quickly cooling to 500-700 ℃, closing the growth furnace, and naturally cooling to room temperature to obtain the graphene with the diameter of more than six inches.
Preferably, in the step (1), the surface of the silicon surface of the 4H-SiC wafer is polished by a chemical mechanical polishing method, and then is cleaned by a standard RCA process, and after processing, the surface roughness of the 4H-SiC wafer is less than 0.2nm, the flatness is less than 10 μm, and the thickness is 550 μm.
Preferably, in step (1), after processing, the silicon surface of the wafer is subjected to scanning test by using an Atomic Force Microscope (Atomic Force Microscope), and the total test range of 41 points is measured, wherein each point is 5 μm by 5 μm, so that the steps in the whole six-inch 4H-SiC wafer are ensured to be clearly visible, regular in shape and stably repeated.
Preferably, in step (2), the diameter of the large-diameter furnace chamber is 800mm to 1200 mm. The large-diameter furnace chamber can ensure that the radial temperature field in the diameter range of the wafer is a flat temperature field.
Further preferably, in the step (2), the diameter of the large-diameter furnace chamber is 1000 mm.
Preferably, in step (2), the diameter of the graphite tray is matched to the size of the 4H-SiC wafer.
Preferably, in step (2), the bottom of the crucible top plate does not contact the wafer when the crucible top plate is placed.
Preferably, in the step (2), the thickened thermal insulation layer is arranged on the periphery of the crucible, specifically, the thickened thermal insulation layer is arranged on the bottom, the outer side of the side wall and the top of the top plate of the crucible, the thickness of the thickened thermal insulation layer on the bottom of the crucible is 400-.
Further preferably, the thickness of the crucible bottom thickening heat preservation and insulation layer is 600mm, the thickness of the side wall thickening heat preservation and insulation layer is 300mm, and the thickness of the crucible top plate top thickening heat preservation and insulation layer is 400 mm.
Preferably, in step (2), the radial diameter of the heat-insulating layer at the bottom of the crucible is equal to the outer diameter of the heat-insulating layer at the side wall. The inner diameter of the side wall heat preservation and insulation layer is larger than the outer diameter of the crucible, the difference is 2-20mm, and the radial diameter of the upper heat preservation and insulation layer of the crucible is equal to the inner diameter of the side wall heat preservation and insulation layer. The thickness of the heat preservation and insulation layer at the upper part, the side wall and the bottom of the crucible can obtain a flat temperature field.
Preferably, in step (2), the thermal insulation layer is a porous graphite thermal insulation layer.
Preferably, in step (3), the furnace chamber of the high-temperature furnace is vacuumized and vacuumized to a degree of less than or equal to 10-4Pa, the rapid heating rate is 10-100 ℃/min, the argon flow is 10-100sccm, and the slow heating rate is 1-10 ℃/min.
More preferably, in the step (3), the argon gas is high-purity argon gas with the purity of more than or equal to 99.999 percent
Further preferably, in the step (3), the temperature is rapidly increased to 1100 ℃, and the temperature increase rate is 100 ℃/min; and introducing argon gas with the flow rate of 60sccm and the pressure of 900mbar, slowly heating to 1300 ℃, keeping the temperature at the heating rate of 5 ℃/min for 120min, and finishing the growth of the graphene.
Preferably, according to the present invention, in the step (4), the temperature reduction rate is 200-.
In the method of the present invention, all the equipment and raw materials are known, and the prior art can be referred to without particular limitation.
According to the method, a large-diameter furnace chamber high-temperature furnace is adopted, a heat insulation layer is arranged on the periphery of a crucible, a radial temperature field in the graphene growth process is a flat temperature field under double-layer conditions, and high-quality and high-uniformity graphene with the diameter of more than six inches and the number of graphene layers uniformly distributed on the surface of the whole silicon surface is obtained through the flat temperature field, the control of growth temperature and the temperature rising and falling speed; the heat insulation layer is made of porous graphite material, the porous graphite has obvious impedance to heat flow and shows smaller heat conductivity coefficient, the temperature in the heat insulation layer is promoted to rise uniformly and slowly, a radial temperature field in the graphene growth process is obtained and is a flat temperature field, and as shown in figure 1, the flat temperature field is more suitable for growing the graphene with the size of six inches and more. According to the atomic structure of the SiC silicon surface, the radial temperature distribution in the crucible is improved in a combined manner, the large-diameter furnace chamber high-temperature furnace is used as a growth furnace, the heat preservation and insulation layer is arranged on the periphery of the crucible, in addition, the growth temperature is adjusted and the temperature rise and fall speed is controlled in a combined manner, the coverage rate of the obtained graphene material in 41 points tested is 100%, the layer number is uniform, the quality is high, and the half-peak width of a 2D peak in a Raman test is less than or equal to 60cm-1. In the existing method for epitaxially growing graphene, a radial temperature field in the growth process of graphene is a convex temperature field, so that graphene with uniform layer number and high quality and with the size of six inches or more cannot be obtained; therefore, the method overcomes the defects of the prior art, is simple and feasible, and can finally obtain the graphene material with large area, high quality and good uniformity.
The invention has the following advantages:
1. according to the method, a large-diameter furnace chamber high-temperature furnace is adopted, a heat insulation layer is arranged on the periphery of a crucible, a radial temperature field in the graphene growth process is a flat temperature field under double-layer conditions, and high-quality and high-uniformity graphene with the diameter of more than six inches and the number of graphene layers uniformly distributed on the surface of the whole silicon surface is obtained through the flat temperature field, the control of growth temperature and the temperature rising and falling speed.
2. The diameter of the high-temperature furnace with the large-diameter furnace chamber is 5-8 times of the diameter of a six-inch wafer. The large-diameter furnace chamber can ensure that a radial temperature field in the diameter range of the wafer is a flat temperature field, and the growth uniformity of graphene is improved.
3. The method of the invention arranges the heat preservation and insulation layer at the periphery of the crucible, the thickness of the heat preservation and insulation layer at the bottom of the crucible is 400-plus-600 mm, the thickness of the heat preservation and insulation layer at the side wall is 200-plus-300 mm, and the thickness of the heat preservation and insulation layer at the upper part of the crucible is 400-plus-600 mm. The thickened heat insulation layer can optimize the distribution of a radial temperature field, ensure that the radial temperature field in the crucible is a flat temperature field, and improve the growth uniformity of graphene.
4. The method provided by the invention combines the accurate control of the temperature, the temperature rise and reduction rate and the pressure of the furnace chamber, can be used for preparing the graphene material with high quality and uniformity and the size of more than six inches on the 4H-SiC with the size of more than six inches, and is simple, feasible, convenient and efficient. The six-inch wafer-level graphene prepared by the method can effectively improve the size and the integration level of a single device. In addition, the method has great application prospect in graphene photoelectric detectors, optical Q-switch switches and high-performance MOSFETs.
Drawings
FIG. 1 is a simulated temperature field generated using VR-PVT software. (a) The simulated temperature field (without the thickened thermal insulation layer) of the comparative example 1, and the simulated temperature field (with the thickened thermal insulation layer) optimized by the growth conditions of the invention are shown in the specification.
FIG. 2 is a diagram showing the arrangement of a crucible and a thickened heat-insulating layer in a furnace chamber of a high-temperature furnace. In the figure, 1, a thickened heat preservation and insulation layer is arranged on the top of a crucible top plate, 2, a thickened heat preservation and insulation layer is arranged on the side wall, 3, a thickened heat preservation and insulation layer is arranged on the bottom of a crucible, 4, a crucible top plate, 5, six-inch 4H-SiC wafers, 6, a graphite tray, 7, a crucible chassis, 8 and a furnace chamber.
FIG. 3 is a diagram of six inch 4H-SiC silicon face substrate dot pick-up and dot pick-up locations; 41 points in total;
FIG. 4 is an Atomic Force Microscope (Atomic Force Microscope) topography of a six inch 4H-SiC silicon surface substrate after processing of example 1 at the point 1 location (a) and the point 41 location (b); the test area was 5 μm by 5 μm;
FIG. 5 is a Raman spectrum of graphene obtained by epitaxial growth on a six-inch 4H-SiC silicon surface substrate in different positions in example 1; 2D Peak (2700 cm) in Raman spectrogram of graphene-1) According to the empirical formula FWHM (2D) ═ 45(1/N)) +88cm-1The number of layers of graphene, the D peak (1350 cm) can be characterized-1) The strength of (a) can characterize the defect degree of graphene;
fig. 6 is a schematic diagram of a six-inch graphene sample obtained in example 1.
Fig. 7 is a raman spectrum of graphene obtained in comparative example 1.
Detailed Description
The growing method of the present invention will be further described below with reference to examples and drawings, but is not limited thereto.
The high-temperature furnace used in the examples was a commercially available high-temperature furnace.
A six inch diameter 4H-SiC wafer was used with the conductivity type N-type or semi-insulating. The surface deviation is positive, the deviation error is within 0.2 degrees, the thickness is 450-550 μm, and the surface deviation is provided by a new generation semiconductor material research institute of Shandong university.
Example 1
A method for epitaxially growing more than six-inch uniform graphene on a 4H-SiC substrate comprises the following steps:
(1) grinding, polishing and cleaning a silicon surface of a 4H-SiC wafer with the diameter of six inches to ensure that the surface roughness of the silicon surface is less than 0.2nm and the flatness is less than 10 mu m, thus obtaining the 4H-SiC wafer with the thickness of 550 mu m; scanning and testing the silicon surface of the wafer by using an Atomic Force Microscope (Atomic Force Microscope), wherein 41 points are tested in total, the distribution of the test points is shown in figure 3, the test range of each point is 5 microns by 5 microns, the regular and stable repetition of the step shape in the whole six-inch 4H-SiC wafer is ensured, and the test result is shown in figure 4;
(2) a large-diameter furnace chamber high-temperature furnace is used as a growth furnace, the diameter of the large-diameter furnace chamber is 1000mm, the 4H-SiC wafer processed in the step (1) is horizontally placed on a six-inch graphite tray, the silicon surface faces downwards, the graphite tray is horizontally placed on a crucible base plate, a crucible top plate is covered above a crucible, the bottom of the crucible top plate is not contacted with the wafer, a heat preservation and insulation layer is arranged on the periphery of the crucible, and then the crucible top plate and the crucible top plate are together placed in the high-temperature furnace chamber; the thickened heat-insulating layer is arranged on the periphery of the crucible, and specifically, the thickened heat-insulating layer is arranged on the bottom, the outer side of the side wall and the top of the top plate of the crucible; the thickness of crucible bottom thickening heat preservation insulating layer is 600mm, and the thickness of lateral wall thickening heat preservation insulating layer is 300mm, and the thickness of crucible top dish top thickening heat preservation insulating layer is 400mm, and crucible bottom thickening heat preservation insulating layer radial diameter equals lateral wall thickening heat preservation insulating layer external diameter. The inner diameter of the thickened heat-insulation layer on the side wall is larger than the outer diameter of the crucible, the difference value is 10mm, and the radial diameter of the thickened heat-insulation layer on the upper part of the crucible is equal to the inner diameter of the thickened heat-insulation layer on the side wall. The arrangement of the crucible and the thickened heat-insulating layer in the high-temperature furnace is shown in figure 2;
(3) the furnace chamber of the high-temperature furnace is vacuumized to 10 DEG-4Pa, heating up to 1100 ℃ rapidly, wherein the heating rate is 100 ℃/min; introducing argon gas with the flow rate of 60sccm and the pressure of 900mbar, slowly heating to 1300 ℃, keeping the temperature at the heating rate of 5 ℃/min for 120min, and finishing the growth of graphene;
(4) closing argon, rapidly moving the crucible upwards, rapidly cooling to 600 ℃, wherein the cooling rate is 300 ℃/min; and (4) closing the growth furnace, stopping heating, and naturally cooling to room temperature. The graphene sample in the crucible graphite tray was then removed.
The number of layers of the graphene material obtained in this example was 2. The raman spectrum test is performed on the graphene sample, the test result is shown in fig. 5, and as can be seen from fig. 5, the 2D peak of the graphene is significant, and the half-peak width is between 45 and 60cm-1The D peak intensity of the graphene is basically 0, which indicates that the prepared graphene has few defects and high quality; 2D Peak (2700 cm)-1) The width is uniform, which shows that the graphene obtained in the embodiment has high uniformity.
The graphene sample obtained in this example is shown in fig. 6, and the diameter of the graphene sample is six inches.
Example 2
A method for epitaxially growing more than six-inch uniform graphene on a 4H-SiC substrate comprises the following steps:
(1) grinding, polishing and cleaning a silicon surface of a 4H-SiC wafer with the diameter of six inches to ensure that the surface roughness of the silicon surface is less than 0.2nm and the flatness is less than 10 mu m, thus obtaining the 4H-SiC wafer with the thickness of 550 mu m; scanning and testing the silicon surface of the wafer by using an Atomic Force Microscope (Atomic Force Microscope), wherein 41 points are tested in total, the distribution of the test points is shown in figure 3, the test range of each point is 5 micrometers by 5 micrometers, and the regular and stable repetition of the step shape in the whole six-inch 4H-SiC wafer is ensured;
(2) a large-diameter furnace chamber high-temperature furnace is used as a growth furnace, the diameter of the large-diameter furnace chamber is 1000mm, the 4H-SiC wafer processed in the step (1) is horizontally placed on a six-inch graphite tray, the silicon surface faces downwards, the graphite tray is horizontally placed on a crucible base plate, a crucible top plate is covered above a crucible, the bottom of the crucible top plate is not contacted with the wafer, a heat preservation and insulation layer is arranged on the periphery of the crucible, and then the crucible top plate and the crucible top plate are together placed in the high-temperature furnace chamber; the thickened heat-insulating layer is arranged on the periphery of the crucible, and specifically, the thickened heat-insulating layer is arranged on the bottom, the outer side of the side wall and the top of the top plate of the crucible; the thickness of crucible bottom thickening heat preservation insulating layer is 500mm, and the thickness of lateral wall thickening heat preservation insulating layer is 200mm, and the thickness of crucible top dish top thickening heat preservation insulating layer is 500mm, and crucible bottom thickening heat preservation insulating layer radial diameter equals lateral wall thickening heat preservation insulating layer external diameter. The inner diameter of the thickened heat-insulation layer on the side wall is larger than the outer diameter of the crucible, the difference value is 10mm, and the radial diameter of the thickened heat-insulation layer on the upper part of the crucible is equal to the inner diameter of the thickened heat-insulation layer on the side wall. The arrangement of the crucible and the thickened heat-insulating layer in the high-temperature furnace is shown in figure 2;
(3) the furnace chamber of the high-temperature furnace is vacuumized to 10 DEG-4Pa, quickly heating to 1000 ℃, wherein the heating rate is 90 ℃/min; introducing argon gas with the flow rate of 100sccm and the pressure controlled at 1000mbar, slowly heating to 1200 ℃, keeping the temperature at the heating rate of 1 ℃/min for 60min, and finishing the growth of graphene;
(4) closing argon, rapidly moving the crucible upwards, rapidly cooling to 700 ℃, wherein the cooling rate is 200 ℃/min; and (4) closing the growth furnace, stopping heating, and naturally cooling to room temperature. The graphene sample in the crucible graphite tray was then removed.
Graphene material obtained by atomic force microscope characterizationThe material shape and appearance are regular. The 2D peak half-value width of the graphene material obtained by Raman spectrum test characterization is between 15 and 45cm-1And the number of layers is uniform and is 1-2 layers of graphene. The D peak intensity of the graphene is basically 0, which shows that the prepared graphene has few defects and high quality.
Example 3
A method for epitaxially growing more than six-inch uniform graphene on a 4H-SiC substrate comprises the following steps:
(1) grinding, polishing and cleaning a silicon surface of a 4H-SiC wafer with the diameter of six inches to ensure that the surface roughness of the silicon surface is less than 0.2nm and the flatness is less than 10 mu m, thus obtaining the 4H-SiC wafer with the thickness of 550 mu m; scanning and testing the silicon surface of the wafer by using an Atomic Force Microscope (Atomic Force Microscope), wherein 41 points are tested in total, the distribution of the test points is shown in figure 3, the test range of each point is 5 micrometers by 5 micrometers, and the regular and stable repetition of the step shape in the whole six-inch 4H-SiC wafer is ensured;
(2) a large-diameter furnace chamber high-temperature furnace is used as a growth furnace, the diameter of the large-diameter furnace chamber is 1000mm, the 4H-SiC wafer processed in the step (1) is horizontally placed on a six-inch graphite tray, the silicon surface faces downwards, the graphite tray is horizontally placed on a crucible base plate, a crucible top plate is covered above a crucible, the bottom of the crucible top plate is not contacted with the wafer, a heat preservation and insulation layer is arranged on the periphery of the crucible, and then the crucible top plate and the crucible top plate are together placed in the high-temperature furnace chamber; the thickened heat-insulating layer is arranged on the periphery of the crucible, and specifically, the thickened heat-insulating layer is arranged on the bottom, the outer side of the side wall and the top of the top plate of the crucible; the thickness of crucible bottom thickening heat preservation insulating layer is 400mm, and the thickness of lateral wall thickening heat preservation insulating layer is 250mm, and the thickness of crucible top dish top thickening heat preservation insulating layer is 600mm, and crucible bottom thickening heat preservation insulating layer radial diameter equals lateral wall thickening heat preservation insulating layer external diameter. The inner diameter of the thickened heat-insulation layer on the side wall is larger than the outer diameter of the crucible, the difference value is 10mm, and the radial diameter of the thickened heat-insulation layer on the upper part of the crucible is equal to the inner diameter of the thickened heat-insulation layer on the side wall. The arrangement of the crucible and the thickened heat-insulating layer in the high-temperature furnace is shown in figure 2;
(3) the furnace chamber of the high-temperature furnace is vacuumized to 10 DEG-4Pa, quickly heating to 1050 ℃, wherein the heating rate is 50 ℃/min; introducing argon gas into the reactor,controlling the flow rate to be 10sccm and the pressure to be 800mbar, then slowly heating to 1400 ℃, controlling the heating rate to be 10 ℃/min, and keeping the temperature for 90min to finish the growth of the graphene;
(4) closing argon, rapidly moving the crucible upwards, rapidly cooling to 500 ℃, wherein the cooling rate is 250 ℃/min; and (4) closing the growth furnace, stopping heating, and naturally cooling to room temperature. The graphene sample in the crucible graphite tray was then removed.
And characterizing the obtained graphene material by an atomic force microscope. The 2D peak half-value width of the obtained graphene material is between 30 and 60cm by Raman spectrum test characterization-1And the number of layers is uniform and is double-layer graphene. The D peak intensity of the graphene is basically 0, which shows that the prepared graphene has few defects and high quality.
Through the descriptions of examples 1, 2 and 3, in combination with the characterization results of the graphene materials of the examples, it can be seen that: by applying the method disclosed by the invention, the high-quality and high-uniformity wafer-level graphene can be prepared on the six-inch 4H-SiC, and the wider application of the graphene in the field of electronic devices is facilitated.
Comparative example 1
The method for epitaxially growing more than six inches of uniform graphene on a 4H-SiC substrate is the same as that in example 1, except that:
step (2) adopting a large-diameter furnace chamber high-temperature furnace as a growth furnace, wherein the diameter of the large-diameter furnace chamber is 1000mm, horizontally placing the 4H-SiC wafer processed in the step (1) on a six-inch graphite tray, placing the graphite tray on a crucible chassis, covering a crucible top plate above the crucible, and placing the crucible top plate in the furnace chamber of the high-temperature furnace without contacting the wafer at the bottom of the crucible top plate;
the other was carried out as in example 1.
The Raman spectrum of the graphene obtained in this comparative example is shown in FIG. 7, and it can be seen from FIG. 7 that points 1 and 17 are 1350cm-1And an obvious defect peak (D peak) exists, and the half-width of the 2D peak of the graphene in the three tested points is different and has non-uniform thickness.

Claims (10)

1. A method for epitaxially growing more than six-inch uniform graphene on a 4H-SiC substrate comprises the following steps:
(1) grinding, polishing and cleaning the silicon surface of the 4H-SiC wafer with the diameter of more than six inches to ensure that the step shape in the whole area of the 4H-SiC wafer is regular and stably repeated;
(2) a large-diameter furnace chamber high-temperature furnace is used as a growth furnace, the diameter of the large-diameter furnace chamber is 5-8 times of that of the 4H-SiC wafer, the 4H-SiC wafer processed in the step (1) is horizontally placed on a graphite tray, the silicon surface faces downwards, the graphite tray is horizontally placed on a crucible base plate, a crucible top plate is covered above a crucible, a thickened heat-preservation and heat-insulation layer is arranged on the periphery of the crucible, and then the crucible top plate and the crucible top plate are placed in the high-temperature furnace chamber together;
(3) vacuumizing the furnace chamber of the high-temperature furnace, quickly heating to 1000-;
(4) and closing the argon, quickly moving the crucible upwards, quickly cooling to 500-700 ℃, closing the growth furnace, and naturally cooling to room temperature to obtain the graphene with the diameter of more than six inches.
2. The method as claimed in claim 1, wherein in the step (1), the surface of the silicon surface of the 4H-SiC wafer is polished by chemical mechanical polishing, then the wafer is cleaned by standard RCA process, and the processed silicon surface of the wafer is scanned and tested by using an Atomic Force Microscope (Atomic Force Microscope) for 41 points in total, wherein each point is tested within the test range of 5 μm by 5 μm, the surface roughness of the processed 4H-SiC wafer is less than 0.2nm, the flatness is less than 10 μm, and the thickness is 450-.
3. The method of claim 1, wherein in step (2), the diameter of the large diameter furnace chamber is 800mm to 1200 mm.
4. The method of claim 1, wherein in step (2), the diameter of the large diameter furnace chamber is 1000mm, and the diameter of the graphite tray matches the size of the 4H-SiC wafer.
5. The method as claimed in claim 1, wherein in the step (2), the step of providing the thickened thermal insulation layer at the periphery of the crucible comprises providing the thickened thermal insulation layer at the bottom, outside the sidewall and top of the top plate of the crucible, wherein the thickness of the thickened thermal insulation layer at the bottom of the crucible is 600mm, the thickness of the thickened thermal insulation layer at the sidewall is 300mm, and the thickness of the thickened thermal insulation layer at the top of the top plate of the crucible is 600 mm; preferably, the thickness of crucible bottom thickening heat preservation insulating layer is 600mm, and the thickness of lateral wall thickening heat preservation insulating layer is 300mm, and the thickness of crucible top dish top thickening heat preservation insulating layer is 400 mm.
6. The method according to claim 1, wherein in the step (2), the radial diameter of the heat preservation and insulation layer at the bottom of the crucible is equal to the outer diameter of the heat preservation layer at the side wall; the inner diameter of the side wall heat preservation and insulation layer is larger than the outer diameter of the crucible, the difference value is 2-20mm, and the radial diameter of the upper heat preservation and insulation layer of the crucible is equal to the inner diameter of the side wall heat preservation and insulation layer; the thickness of the heat preservation and insulation layer at the upper part, the side wall and the bottom of the crucible can obtain a flat temperature field.
7. The method according to claim 1, wherein in step (2), the thermal insulation layer is a porous graphite thermal insulation layer.
8. The method of claim 1, wherein in step (3), the furnace chamber of the high temperature furnace is evacuated to a vacuum degree of 10 or less-4Pa, the rapid heating rate is 10-100 ℃/min, the argon flow is 10-100sccm, and the slow heating rate is 1-10 ℃/min.
9. The method of claim 1, wherein in step (3), the argon gas is high-purity argon gas with a purity of 99.999% or more; rapidly heating to 1100 deg.C at a heating rate of 100 deg.C/min; and introducing argon gas with the flow rate of 60sccm and the pressure of 900mbar, slowly heating to 1300 ℃, keeping the temperature at the heating rate of 5 ℃/min for 120min, and finishing the growth of the graphene.
10. The method as claimed in claim 1, wherein the temperature reduction rate in step (4) is 200 ℃ to 300 ℃/min.
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