Heating device, CVD equipment and method
By designing a heating device including coil components, graphite disks and thermal pads in CVD devices, the problem of uneven distribution of wafer temperature during the CVD process of cold walls is solved, and the high -quality growth of the two -dimensional material thin film is realized.
Patent Information
- Application Number
- CN202411463808.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-18
- Publication Date
- 2025-01-24
AI Technical Summary
During cold wall chemical vapor deposition (CVD), due to the skin effect of electromagnetic induction, the temperature distribution of graphite disk and wafer surface is uneven, affecting the thickness uniformity and quality of the two-dimensional material film.
Design a heating device, including a coil assembly, a graphite disk and a thermal pad. The coil assembly is used to generate a magnetic field around the chamber of the CVD equipment. The graphite disk generates heat under the action of the magnetic field. The thermal pad is used to support the wafer and The wafer is heated more evenly through heat conduction and heat radiation.
Through this heating device, the uniformity of the wafer temperature distribution is improved, thereby improving the thickness uniformity and quality of the two-dimensional material film and ensuring high-quality growth of the film.
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Figure CN119351993A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to the technical field of chemical vapor deposition preparation, and in particular to a heating device, a CVD equipment and a method. Background Art
[0002] When using a cold wall chemical vapor deposition (CVD) reactor to prepare thin films of two-dimensional materials (such as graphene, molybdenum disulfide, MXene, etc.), the uniformity of the wafer temperature distribution is directly related to the thickness uniformity and quality of the film. Due to the skin effect of electromagnetic induction, when a high-frequency electric field or electromagnetic wave passes through a conductor, the energy is mainly concentrated near the surface of the conductor. Therefore, the skin effect makes the temperature distribution of the graphite disk and the wafer surface very uneven, with higher temperatures near the edge and lower temperatures near the middle, thus affecting the thickness uniformity and quality of the film. Summary of the invention
[0003] The purpose of the present disclosure is to provide a heating device, a CVD apparatus and a method to improve the thickness uniformity and quality of a two-dimensional material film.
[0004] Based on the above purpose, the present disclosure provides a heating device, which is applied to a chamber of a CVD device, and includes:
[0005] A coil assembly, the coil assembly comprising a coil and a power supply device, the coil being used to be arranged on the circumferential outer surface of the chamber, and the power supply device being used to supply power to the coil so as to generate a magnetic field in the chamber;
[0006] a graphite disk, the graphite disk being installed in the chamber, the graphite disk being capable of generating heat under the action of a magnetic field; and
[0007] A thermally conductive gasket, the thermally conductive gasket is located on the graphite disk, the thermally conductive gasket is coaxially arranged with the graphite disk, and the diameter of the thermally conductive gasket is smaller than the diameter of the graphite disk; the thermally conductive gasket is used to support a wafer, wherein the diameter of the wafer is larger than the diameter of the thermally conductive gasket, the wafer comprises a first region and a second region, the first region can be in direct contact with the thermally conductive gasket, and a gap is arranged between the second region and the graphite disk.
[0008] In one embodiment of the present disclosure, the radius of the thermally conductive gasket is 0.3 to 0.9 times the radius of the graphite disk.
[0009] In one embodiment of the present disclosure, the radius of the thermally conductive gasket is 0.35 to 0.8 times the radius of the wafer.
[0010] In one embodiment of the present disclosure, the thickness of the thermally conductive gasket is 0.5-1 mm.
[0011] In one embodiment of the present disclosure, the axial dimension of the coil is greater than the axial dimension of the graphite disk.
[0012] In one embodiment of the present disclosure, the center of the coil and the center of the graphite disk are in the same plane, wherein the center of the coil is a point on the axis of the coil, the distances from the point to both ends of the coil are equal, and the plane is perpendicular to the axis of the graphite disk.
[0013] In one embodiment of the present disclosure, the coil is spirally wound on the circumferential outer surface of the chamber, and the pitches of the coils are equal.
[0014] In one embodiment of the present disclosure, the thermally conductive gasket is made of graphite.
[0015] In one embodiment of the present disclosure, the heating device further includes a supporting platform, which is installed below the graphite disk and is used to support the graphite disk.
[0016] Based on the above purpose, the present disclosure further provides a CVD device, including a chamber and the heating device, wherein the coil is arranged on the circumferential outer surface of the chamber, and the graphite disk is installed in the chamber.
[0017] Based on the above purpose, the present disclosure further provides a CVD method, the CVD method is based on the CVD device, and the CVD method comprises:
[0018] Providing a wafer, wherein the diameter of the wafer is greater than the diameter of the thermally conductive pad, and the wafer comprises a first region and a second region;
[0019] Placing the wafer on the thermally conductive pad, wherein the first region is in direct contact with the thermally conductive pad, and a gap is set between the second region and the graphite disk;
[0020] The power supply device supplies power to the coil to generate a magnetic field in the chamber;
[0021] The graphite disk generates heat under the action of the magnetic field. The heat generated by the graphite disk is transferred to the first area of the wafer through the thermal pad by heat conduction, and is transferred to the second area of the wafer by heat radiation.
[0022] The beneficial effects of the present disclosure are mainly:
[0023] The heating device provided by the present disclosure is installed in the chamber of the CVD equipment when in use, and the wafer is placed on the thermally conductive pad, and the first area of the wafer is in direct contact with the thermally conductive pad. When the power supply device supplies power to the coil, for example, after the power supply device passes a high-frequency alternating current into the coil, the graphite disk generates an eddy current due to electromagnetic induction, thereby generating heat. Due to the existence of the skin effect, the temperature of the area near the edge of the graphite disk is higher, while the temperature of the area near the middle is lower, that is, the temperature of the area of the graphite disk corresponding to the thermally conductive pad is lower. Since the first area of the wafer is in direct contact with the thermally conductive pad, the first area can be directly heat-conducted by the thermally conductive pad, and since the gap between the second area of the wafer and the graphite disk is set, the second area is heat-radiated by the graphite disk; since the efficiency of direct heat conduction is higher than the efficiency of heat radiation, the temperature of the first area of the wafer corresponding to the area with a lower temperature of the graphite disk rises faster by direct heat conduction, and at the same time, the temperature rise of the second area of the wafer corresponding to the area with a higher temperature of the graphite disk is mitigated by heat radiation, so that the overall heating of the wafer is more uniform. The reaction gas in the chamber undergoes a chemical reaction on the uniformly heated wafer, and the reaction products are deposited and grown relatively evenly on the wafer to form a two-dimensional material film. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] In order to more clearly illustrate the specific embodiments of the present disclosure or the technical solutions in the prior art, the drawings required for use in the specific embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.
[0025] Figure 1 A schematic diagram of the structure of a heating device provided in an embodiment of the present disclosure;
[0026] Figure 2 for Figure 1 A cross-sectional view along line AA;
[0027] Figure 3 A schematic diagram of a wafer heated by a heating device provided in an embodiment of the present disclosure;
[0028] Figure 4 Isothermal distribution diagram in the chamber of the CVD device provided by the embodiment of the present disclosure;
[0029] Figure 5 A temperature field distribution diagram of a wafer heated by a CVD device provided in an embodiment of the present disclosure;
[0030] Figure 6 This is a schematic diagram of a visualized photo of a graphene wafer prepared in Example 1 of the present disclosure;
[0031] Figure 7 This is a Raman spectrum of the graphene wafer prepared in Example 1 of the present disclosure;
[0032] Figure 8 This is a schematic diagram of the surface resistance characterization of the graphene wafer prepared in Example 1 of the present disclosure;
[0033] Fig. 9 This is an atomic force microscope image of the central area of the graphene wafer prepared in Example 1 of the present disclosure;
[0034] Fig.10 This is an atomic force microscope image of the edge area of the graphene wafer prepared in Example 1 of the present disclosure;
[0035] Fig.11 is the isothermal distribution diagram in the chamber of the common CVD equipment in Comparative Example 1;
[0036] Fig.12 The temperature field distribution diagram of the wafer heated by the common CVD equipment in Comparative Example 1;
[0037] Fig.13 Graphs showing temperature curves at different radial positions of the wafer in Example 1 and Comparative Example 1;
[0038] Fig.14 This is a Raman spectrum of the graphene wafer prepared in Comparative Example 1;
[0039] Fig.15 Schematic diagram of the surface resistance characterization of the graphene wafer prepared in Comparative Example 1;
[0040] Fig.16 This is an atomic force microscope image of the central area of the graphene wafer prepared in Comparative Example 1;
[0041] Fig.17 This is an atomic force microscope image of the edge area of the graphene wafer prepared in Comparative Example 1;
[0042] Fig.18 A flow chart of a graphene CVD preparation method provided in an embodiment of the present disclosure.
[0043] The following are the descriptions of the reference numerals:
[0044] 101 - chamber;
[0045] 102-coil;
[0046] 103-graphite disk;
[0047] 104-thermal conductive pad;
[0048] 105-wafer;
[0049] 1051-1st area;
[0050] 1052-Second area;
[0051] 106-carrying platform. DETAILED DESCRIPTION
[0052] The technical solution of the present disclosure will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present disclosure.
[0053] In the description of the present disclosure, it should be noted that, if the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present disclosure and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present disclosure. In addition, if the terms "first", "second", "third" appear, they are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.
[0054] In the description of the present disclosure, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.
[0055] See also Figures 1 to 18As shown, this embodiment provides a heating device, which is applied to the chamber 101 of the CVD device. The heating device includes a coil assembly, a graphite disk 103 and a thermally conductive pad 104. The coil assembly includes a coil 102 and a power supply device. The coil 102 is used to be arranged on the circumferential outer surface of the chamber 101. The power supply device is used to supply power to the coil 102 to generate a magnetic field in the chamber 101; the graphite disk 103 is used to be installed in the chamber 101, and the graphite disk 103 can generate heat under the action of the magnetic field; the thermally conductive pad 104 is used to generate heat in the chamber 101. The thermal gasket 104 is located on the graphite disk 103, and the thermally conductive gasket 104 is coaxially arranged with the graphite disk 103, and the diameter of the thermally conductive gasket 104 is smaller than the diameter of the graphite disk 103; the thermally conductive gasket 104 is used to support the wafer 105, wherein the diameter of the wafer 105 is larger than the diameter of the thermally conductive gasket 104, and the wafer 105 includes a first area 1051 and a second area 1052, the first area 1051 can directly contact the thermally conductive gasket 104, and a gap is set between the second area 1052 and the graphite disk 103.
[0056] The heating device provided in this embodiment is installed in the chamber 101 of the CVD device when in use, and the wafer is placed on the thermally conductive pad 104, so that the first region 1051 of the wafer is in direct contact with the thermally conductive pad 104. After the power supply device supplies power to the coil 102, for example, after the power supply device passes a high-frequency alternating current into the coil 102, the graphite disk 103 generates an eddy current due to electromagnetic induction, thereby generating heat. Due to the existence of the skin effect, the temperature of the area near the edge of the graphite disk 103 is higher, while the temperature of the area near the middle is lower, that is, the temperature of the area of the graphite disk 103 corresponding to the thermally conductive pad 104 is lower. Since the first region 1051 of the wafer is in direct contact with the thermal pad 104, the first region 1051 can be directly heat-conducted by the thermal pad 104, and since the gap between the second region 1052 of the wafer and the graphite disk 103 is set, the second region 1052 is heat-radiated by the graphite disk 103; since the efficiency of direct heat conduction is higher than the efficiency of heat radiation, the temperature of the first region 1051 of the wafer corresponding to the region with a lower temperature of the graphite disk 103 rises faster through direct heat conduction, and at the same time, the temperature rise of the second region 1052 of the wafer corresponding to the region with a higher temperature of the graphite disk 103 is mitigated through heat radiation, so that the overall heating of the wafer is more uniform. The reaction gas in the chamber 101 undergoes a chemical reaction on the uniformly heated wafer, and the reaction product is deposited and grown on the wafer to form a two-dimensional material film, such as a graphene film, a molybdenum disulfide film, and a MXene film.
[0057] Therefore, the heating device provided in this embodiment improves the uniformity of wafer temperature distribution through a heating method that combines heat conduction and heat radiation, which is beneficial to improving the uniformity and quality of the two-dimensional material film.
[0058] Computer simulation revealed that the skin depth is approximately 5 mm within the experimental temperature range.
[0059] When placing the wafer 105 , the axis of the wafer 105 and the axis of the thermal pad 104 should coincide as much as possible to ensure uniform heating of the wafer.
[0060] When the axis of the wafer 105 coincides with the axis of the thermal pad 104, see Figure 3 As shown, the area within the dotted line is the first area 1051 of the wafer 105, and the shape of the first area 1051 is circular. The area between the dotted line and the solid line is the second area 1052 of the wafer 105, and the shape of the second area 1052 is annular. Along the radial direction of the wafer 105, the first area 1051 is located in the second area 1052, and the first area 1051 and the second area 1052 are coaxially arranged.
[0061] In one embodiment, the radius of the thermally conductive pad 104 is 0.3 to 0.9 times the radius of the graphite disk 103. On the basis of coaxially arranging the thermally conductive pad 104 and the graphite disk 103, the thermally conductive pad 104 can cover as much as possible the inner region of the graphite disk 103 where the temperature is lower due to the skin effect. In the inner region, the heat of the graphite disk 103 is thermally conducted to the first region 1051 of the wafer through the thermally conductive pad 104, while the region located outside the inner region has a higher temperature due to the skin effect, and there is no thermally conductive pad 104 in this region, so that the graphite disk 103 heats the second region 1052 of the wafer through thermal radiation.
[0062] In one embodiment, the radius of the thermally conductive pad 104 is 0.35 to 0.8 times the radius of the wafer 105. By selecting different radii of the thermally conductive pad 104, first regions of different sizes can be heated by direct thermal conduction.
[0063] For example, when the radius of the wafer is R, the area of the first region 1051 is π×(0.35R) 2 ~π×(0.8R) 2 .
[0064] In one embodiment, the thickness of the thermal pad 104 is 0.5-1 mm, which is conducive to further enhancing the effect of heat conduction, and at the same time, the distance between the wafer and the graphite disk 103 will not be too far, so as to ensure the effect of heat radiation, thereby further reducing the temperature difference between the first area 1051 and the second area 1052 of the wafer, and enhancing the uniformity of the wafer temperature distribution.
[0065] It should be understood that for the same CVD equipment, the radius of the graphite disk 103 is usually determined, so the first radius range of the thermal pad 104 can be calculated. At the same time, the second radius range of the thermal pad 104 can also be obtained according to the radius of the wafer to be processed. In the actual calculation process, the first radius range and the second radius range can be combined to select a more suitable radius range of the thermal pad 104. In addition, the radius range of the wafer to be processed can also be selected so that the radius of the wafer to be processed, the radius of the thermal pad 104 and the radius of the graphite disk 103 match each other, so as to produce a higher quality film.
[0066] In one embodiment, the axial dimension of the coil 102 is larger than the axial dimension of the graphite disk 103. This can ensure that the entire graphite disk 103 is located in the magnetic field as much as possible, ensuring that the entire graphite disk 103 is heated to generate a higher amount of heat, thereby increasing the reaction temperature.
[0067] In one embodiment, the center of the coil 102 and the center of the graphite disk 103 are in the same plane, wherein the center of the coil 102 is a point on the axis of the coil 102 , the distance between the point and both ends of the coil 102 is equal, and the plane is perpendicular to the axis of the graphite disk 103 .
[0068] In this embodiment, the graphite disk 103 is a cylindrical structure with uniform mass. The center of the graphite disk 103 is the geometric center, and the geometric center coincides with the center of gravity of the graphite disk 103 .
[0069] Since the center of the coil 102 and the center of the graphite disk 103 are in the same plane, the overall heat distribution of the graphite disk 103 can be guaranteed to be uniform, which is beneficial to enhancing the effects of heat conduction and heat radiation, and further improving the uniformity of wafer temperature distribution.
[0070] In one embodiment, the coil 102 is spirally wound on the circumferential outer surface of the chamber 101, and the pitches of the coil 102 are equal. This can make the magnetic field strength more uniform, which is further conducive to improving the uniformity of heating.
[0071] Exemplarily, the coil 102 of this embodiment has four turns, and the distance between two adjacent turns is equal.
[0072] In one embodiment, the thermal conductive pad 104 is made of graphite.
[0073] It should be noted that the thermally conductive pad 104 may also be made of other thermally conductive insulating materials.
[0074] In one embodiment, see Figure 2 As shown, the heating device further includes a supporting platform 106 , which is installed below the graphite disk 103 and is used to support the graphite disk 103 .
[0075] In some embodiments, the carrier platform 106 can be installed under the graphite disk 103 in a liftable manner. By adjusting the position of the carrier platform 106, the wafer 105 can be placed on the thermal pad 104, and the wafer with the two-dimensional material film grown thereon can also be taken out.
[0076] Exemplarily, the supporting platform 106 may be a crucible platform.
[0077] This embodiment further provides a CVD device, including a chamber 101 and a heating device provided in this embodiment, wherein a coil 102 is disposed on a circumferential outer surface of the chamber 101 , and a graphite disk 103 is installed in the chamber 101 .
[0078] The CVD equipment provided in this embodiment uses the heating device provided in this embodiment, which improves the uniformity of wafer temperature distribution through a heating method that combines heat conduction and heat radiation, thereby helping to improve the uniformity and quality of two-dimensional material films.
[0079] When in use, the wafer is placed on the thermally conductive pad 104 in the chamber 101, and the first region 1051 of the wafer is in direct contact with the thermally conductive pad 104. When the power supply device supplies power to the coil 102, for example, after the power supply device passes a high-frequency alternating current into the coil 102, the graphite disk 103 generates an eddy current due to electromagnetic induction, thereby generating heat. Due to the existence of the skin effect, the temperature of the region near the edge of the graphite disk 103 is higher, while the temperature of the region near the middle is lower, that is, the temperature of the region of the graphite disk 103 corresponding to the thermally conductive pad 104 is lower. Since the first region 1051 of the wafer is in direct contact with the thermal pad 104, the first region 1051 can be directly heat-conducted by the thermal pad 104, and since the gap between the second region 1052 of the wafer and the graphite disk 103 is set, the second region 1052 is heat-radiated by the graphite disk 103; since the efficiency of direct heat conduction is higher than the efficiency of heat radiation, the temperature of the first region 1051 of the wafer corresponding to the region with a lower temperature of the graphite disk 103 rises faster through direct heat conduction, and at the same time, the temperature rise of the second region 1052 of the wafer corresponding to the region with a higher temperature of the graphite disk 103 is mitigated through heat radiation, so that the overall heating of the wafer is more uniform. The reaction gas in the chamber 101 undergoes a chemical reaction on the uniformly heated wafer, and the reaction product is deposited and grown on the wafer to form a two-dimensional material film in a relatively uniform manner.
[0080] In one embodiment, the chamber 101 is formed by the inner cavity of a quartz tube. Exemplarily, the cross-section of the quartz tube is circular, and the quartz tube is coaxially arranged with the graphite disk 103 .
[0081] When the coil 102 is energized, it is equivalent to an energized solenoid. According to the magnetic effect of the current, a magnetic field is generated in the inner cavity of the quartz tube. Then, according to the magnetocaloric effect, the graphite disk 103 can generate heat under the action of the magnetic field.
[0082] The following is a detailed description with specific implementation methods.
[0083] Example 1
[0084] The CVD equipment provided in this embodiment is used to grow a graphene film on a sapphire wafer with a diameter of 150 mm to form a graphene wafer. After finite element simulation and testing, the height of the graphite disk 103 used is 10 mm, the diameter of the graphite disk 103 is 155 mm, the thickness of the thermal pad 104 is 0.5 mm, and the diameter of the thermal pad 104 is 110 mm.
[0085] See also Figure 4 and Figure 5 As shown, during operation of the CVD device provided in this embodiment, the temperature field has better uniformity, the wafer as a whole is heated more evenly, and there will not be a phenomenon where the temperature of the center of the wafer is significantly lower than that of the peripheral part.
[0086] For the prepared graphene wafer, its uniformity can usually be evaluated by three methods: visual inspection or optical microscope observation, Raman spectrum and surface resistance measurement. The visualization picture, Raman spectrum and surface resistance results of the prepared graphene wafer are shown in the figure. Figures 6 to 8 As shown. Figure 6 It can be seen that the prepared graphene wafer image is uniform. Raman characterization is performed on it, and tests are performed at different positions of the wafer (Ⅰ, Ⅱ, Ⅲ, Ⅳ and Ⅴ) to characterize the overall uniformity. The Raman spectrum characterization results are shown in Figure 7 As shown. Figure 7 It can be seen that the defect peaks at the five positions Ⅰ~Ⅴ are extremely small, indicating that the graphene wafer has a high crystal quality and a very small defect density, which further indicates that the prepared graphene has a high quality.
[0087] The surface resistance of the prepared graphene wafer as a whole is characterized by using a probe test system (e.g., a four-probe electrical test system) to illustrate the conductivity and uniformity of graphene. The test results are as follows: Figure 8 As shown. The statistical analysis of the test data shows that the average sheet resistance of the graphene wafer prepared in this embodiment is 1400Ω / sq, and the sheet resistance deviation at all positions is within ±25%, which proves that it has good uniformity. Figure 8 It can be seen that there are about 100 locations with a sheet resistance of 1250Ω / sq, which is close to the average value, and only a few locations have resistance values that are significantly different from the average value. For example, there are only about 10 locations with a resistance value of 2250Ω / sq.
[0088] It should be understood that for the direct preparation of graphene on c-plane sapphire wafers, when the CVD growth temperature reaches 1300°C, steps will appear on the wafer surface. The steps are very sensitive to temperature, and the temperature uniformity can be reflected by the step morphology and width at different positions on the surface.
[0089] from Fig. 9 and Fig.10 It can be seen that the steps of the central part and the edge part of the graphene wafer prepared in this embodiment are more uniform and the quality is better.
[0090] In summary, the graphene wafer sample obtained in Example 1 has high uniformity.
[0091] Comparative Example 1
[0092] A graphene film is grown on a sapphire wafer with a diameter of 150 mm using a conventional CVD device, in which the graphite disk has a height of 10 mm and a diameter of 155 mm. The sapphire wafer is directly placed on the graphite disk.
[0093] See also Fig.11 and Fig.12 As shown, during the operation of conventional CVD equipment, the uniformity of the temperature field is poor, the wafer as a whole is heated unevenly, and there is a phenomenon that the temperature in the center of the wafer is significantly lower than that in the peripheral part.
[0094] contrast Figure 4 and Figure 5 The temperature field uniformity and the wafer heating uniformity in Example 1 are significantly higher than those in Comparative Example 1.
[0095] Further, see Fig.13 As shown, the gray curve 1 with an opening upward represents the temperature of different positions of the wafer of comparative example 1 along the radial direction outward from the center of the circle, and the black curve 2 with an opening downward represents the temperature of different positions of the wafer of embodiment 1 along the radial direction outward from the center of the circle.
[0096] First, let's look at curve 1. Due to the skin effect, the temperature of the area near the edge of the graphite disk is higher, while the temperature of the area near the middle is lower. Therefore, when the wafer in comparative example 1 is placed directly on the graphite disk, the temperature of the wafer in the center of the graphite disk is significantly lower than the temperature of the wafer near the edge of the graphite disk through heat conduction. Therefore, the wafer in comparative example 1 is heated very unevenly.
[0097] Looking at curve 2 again, the first region 1051 of the wafer in Example 1 is in direct contact with the thermal pad 104, and the first region 1051 can be directly heat-conducted by the thermal pad 104. Due to the gap between the second region 1052 of the wafer and the graphite disk 103, the second region 1052 is heat-radiated by the graphite disk 103. Since the efficiency of direct heat conduction is higher than the efficiency of heat radiation, the temperature of the first region 1051 of the wafer corresponding to the region with a lower temperature of the graphite disk 103 rises faster by direct heat conduction. For example, in a circular region with a radius of 40 mm, the temperature of the wafer in Example 1 is higher than that of the wafer in Comparative Example 1. At the same time, by heat radiation, the temperature rise of the second region 1052 of the wafer originally corresponding to the region with a higher temperature of the graphite disk 103 is mitigated. For example, in an annular region with a radius greater than 55 mm, the temperature of the wafer in Example 1 is significantly lower than that of the wafer in Comparative Example 1, and is closer to the temperature of its circular region, so that the overall heating of the wafer is more uniform.
[0098] It should be understood that in Example 1, since the position where the wafer contacts the edge of the thermal pad 104 is also in the area close to the edge of the graphite disk 103, the circumferential portion corresponding to the radius of 55 mm on the wafer in Example 1 may be affected by both heat conduction and skin effect, so the temperature of this circle may be the highest temperature portion of the entire wafer. Nevertheless, it will not affect the overall heating uniformity of the wafer.
[0099] See also Fig.14 As shown, the defect peaks at the five positions Ⅰ to Ⅴ are relatively high, indicating that the graphene wafer in Comparative Example 1 has poor crystallization quality and a large defect density due to uneven heating.
[0100] The surface resistance of the graphene wafer in Comparative Example 1 was tested by the same test method as in Example 1. The test results are as follows: Fig.15 As shown. The test data were statistically analyzed. The average sheet resistance of the graphene wafer prepared in Example 1 was 1400Ω / sq, but the sheet resistance deviation at all positions was within the range of ±40%, which was a large deviation range, indicating that the uniformity of the graphene film was poor. Fig.15 The red and black areas in the figure have a sheet resistance of 0, indicating that the temperature in this area is too high and the steps formed are too large to grow graphene films.
[0101] See also Fig.16 and Fig.17 As shown, the steps in the center part of the graphene wafer prepared in Comparative Example 1 are relatively small, but the steps in the edge part are obviously too large, which is not conducive to the growth of the graphene film.
[0102] It should be noted that the heating device provided in this embodiment is also suitable for heating large-sized (e.g., eight-inch and twelve-inch) wafers. At this time, the size of the graphite disk 103 and the radius and thickness of the thermal pad 104 can be adjusted accordingly. For large-sized wafers, there is no need to modify the magnetic field distribution of the electromagnetic induction coil, the structure is simple, and the heating efficiency is high. In addition, the heating device provided in this embodiment is more suitable for use in large-sized CVD reaction chambers, and is easy to process and easy to control.
[0103] This embodiment further provides a CVD method. The CVD method is based on the CVD device provided in this embodiment. The CVD method includes:
[0104] Providing a wafer, wherein the diameter of the wafer is greater than the diameter of the thermally conductive pad 104 , and the wafer includes a first region 1051 and a second region 1052 ;
[0105] The wafer is placed on the thermally conductive pad 104 , wherein the first region 1051 is in direct contact with the thermally conductive pad 104 , and a gap is set between the second region 1052 and the graphite disk 103 ;
[0106] The power supply device supplies power to the coil 102 to generate a magnetic field in the chamber 101;
[0107] The graphite disk 103 generates heat under the action of the magnetic field. The heat generated by the graphite disk 103 is transferred to the first area 1051 of the wafer through the thermal pad 104 by heat conduction, and is transferred to the second area 1052 of the wafer by heat radiation.
[0108] The CVD method provided in this embodiment can be used to prepare graphene. The first region 1051 of the wafer is directly contacted with the thermal pad 104, and the first region 1051 can be directly heat-conducted by the thermal pad 104. At the same time, a gap is set between the second region 1052 of the wafer and the graphite disk 103, and the second region 1052 is heat-radiated by the graphite disk 103. Since the efficiency of direct heat conduction is higher than the efficiency of heat radiation, the temperature of the first region 1051 of the wafer corresponding to the region with a lower temperature of the graphite disk 103 rises faster by direct heat conduction. At the same time, the temperature rise of the second region 1052 of the wafer corresponding to the region with a higher temperature of the graphite disk 103 is alleviated by heat radiation, so that the overall heating of the wafer is more uniform. The reaction gas in the chamber 101 undergoes a chemical reaction on the uniformly heated wafer, and the reaction product is deposited and grown on the wafer to form a graphene film in a relatively uniform manner, thereby preparing high-quality graphene.
[0109] For example, see Fig.18 As shown, the graphene CVD preparation method includes:
[0110] Step S102 , providing a wafer 105 , wherein the diameter of the wafer 105 is greater than the diameter of the thermal pad 104 , and the wafer 105 includes a first region 1051 and a second region 1052 .
[0111] When selecting the size of the wafer, calculation can be performed based on the fact that the radius of the thermal pad 104 is 0.35 to 0.8 times the radius of the wafer 105 , so that wafers within a suitable size range can be processed.
[0112] In this embodiment, the diameter of the wafer 105 is smaller than the diameter of the graphite disk 103 .
[0113] It should be understood that the thickness of the wafer is relatively thin, and the sum of the area of the first region 1051 and the area of the second region 1052 of the wafer is equal to the surface area of the side of the wafer facing the conductive pad.
[0114] Step S104 , placing the wafer on the thermally conductive pad 104 , wherein the first region 1051 is in direct contact with the thermally conductive pad 104 , and a gap is set between the second region 1052 and the graphite disk 103 .
[0115] When placing the wafer, the axis of the wafer basically coincides with the axis of the thermal pad 104, the first area 1051 of the wafer is circular in shape, and the second area 1052 of the wafer is annular. Along the radial direction of the wafer, the first area 1051 is located in the second area 1052, and the first area 1051 and the second area 1052 are coaxially arranged.
[0116] In step S106 , the power supply device supplies power to the coil 102 to generate a magnetic field in the chamber 101 .
[0117] Exemplarily, after the power supply device supplies high-frequency alternating current to the coil 102 , the graphite disk 103 generates eddy current due to electromagnetic induction, and generates a magnetic field in the chamber 101 according to the magnetic effect of the current.
[0118] In step S108, the graphite disk 103 generates heat under the action of the magnetic field. The heat generated by the graphite disk 103 is transferred to the first area 1051 of the wafer through the thermal pad 104 by heat conduction, and is transferred to the second area 1052 of the wafer by heat radiation.
[0119] According to the magnetocaloric effect, the graphite disk 103 generates heat under the action of the magnetic field. Since the efficiency of direct heat conduction is higher than that of thermal radiation, the temperature of the first area 1051 of the wafer corresponding to the area with a lower temperature of the graphite disk 103 rises faster through direct heat conduction. At the same time, the temperature rise of the second area 1052 of the wafer corresponding to the area with a higher temperature of the graphite disk 103 is mitigated through thermal radiation, so that the overall heating of the wafer is more uniform. The reaction gas in the chamber 101 undergoes a chemical reaction on the uniformly heated wafer, and the reaction product is deposited and grown on the wafer more uniformly to form a graphene film, thereby preparing high-quality graphene.
[0120] Of course, the CVD method provided in this embodiment can also be used to prepare two-dimensional material films such as molybdenum disulfide and MXene.
[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them. Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present disclosure.
Claims
1. A heating device, characterized in that: Applicable to the chamber of a CVD device, the heating device comprises: A coil assembly, the coil assembly comprising a coil and a power supply device, the coil being used to be arranged on the circumferential outer surface of the chamber, and the power supply device being used to supply power to the coil so as to generate a magnetic field in the chamber; a graphite disk, the graphite disk being installed in the chamber, the graphite disk being capable of generating heat under the action of a magnetic field; and A thermally conductive gasket, the thermally conductive gasket is located on the graphite disk, the thermally conductive gasket is coaxially arranged with the graphite disk, and the diameter of the thermally conductive gasket is smaller than the diameter of the graphite disk; the thermally conductive gasket is used to support a wafer, wherein the diameter of the wafer is larger than the diameter of the thermally conductive gasket, the wafer comprises a first region and a second region, the first region can be in direct contact with the thermally conductive gasket, and a gap is arranged between the second region and the graphite disk.
2. The heating device according to claim 1, characterized in that The radius of the thermally conductive gasket is 0.3 to 0.9 times the radius of the graphite disk; preferably, the radius of the thermally conductive gasket is 0.35 to 0.8 times the radius of the wafer.
3. The heating device according to claim 1, characterized in that: The thickness of the thermally conductive pad is 0.5-1 mm.
4. The heating device according to claim 1, characterized in that The axial dimension of the coil is greater than the axial dimension of the graphite disk.
5. The heating device according to claim 1, characterized in that: The center of the coil and the center of the graphite disk are in the same plane, wherein the center of the coil is a point on the axis of the coil, the distances from the point to both ends of the coil are equal, and the plane is perpendicular to the axis of the graphite disk.
6. The heating device according to claim 1, characterized in that: The coil is spirally wound on the circumferential outer surface of the chamber, and the pitches of the coils are equal.
7. The heating device according to any one of claims 1 to 6, characterized in that: The thermal conductive pad is made of graphite.
8. The heating device according to any one of claims 1 to 6, characterized in that: It also includes a bearing platform, which is installed below the graphite disk and is used to support the graphite disk.
9. A CVD device, characterized in that: The invention comprises a chamber and the heating device according to any one of claims 1 to 8, wherein the coil is arranged on the circumferential outer surface of the chamber, and the graphite disk is installed in the chamber.
10. A CVD method, characterized in that: The CVD method is based on the CVD device according to claim 9, and the CVD method comprises: Providing a wafer, wherein the diameter of the wafer is greater than the diameter of the thermally conductive pad, and the wafer comprises a first region and a second region; Placing the wafer on the thermally conductive pad, wherein the first region is in direct contact with the thermally conductive pad, and a gap is set between the second region and the graphite disk; The power supply device supplies power to the coil to generate a magnetic field in the chamber; The graphite disk generates heat under the action of the magnetic field. The heat generated by the graphite disk is transferred to the first area of the wafer through the thermal pad by heat conduction, and is transferred to the second area of the wafer by heat radiation.