A method and apparatus for improving the uniformity of silicon carbide crystal growth
By using a movable crucible and flow guide hood during silicon carbide crystal growth, the temperature field of the seed crystal and raw materials can be independently controlled, solving the problem of uneven growth rate and achieving higher growth uniformity and lower defect density.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING TIANKE HEDA SEMICON CO LTD
- Filing Date
- 2024-12-18
- Publication Date
- 2026-06-26
AI Technical Summary
Traditional silicon carbide single crystal furnaces have difficulties in achieving uniform growth rate, leading to defects in the crystal, such as screw dislocations, edge dislocations, basal plane dislocations, and excessive resistivity, mainly due to the difficulty in effectively controlling the temperature gradient at the growth interface.
The design employs a movable crucible and flow guide hood, which controls the uniform supply of raw material airflow through horizontal and vertical movement, independently controls the seed crystal and raw material temperature field, and ensures the stability of the temperature gradient at the growth interface.
It improves the uniformity of silicon carbide crystal growth, reduces the difference in growth rate between the crystal center and the periphery, enhances the rate uniformity of different growth stages, and reduces defect density.
Smart Images
Figure CN122279733A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor technology, and particularly relates to a method and apparatus for improving the uniformity of silicon carbide crystal growth. Background Technology
[0002] The commonly used method for preparing silicon carbide single crystals is PVT (physical vapor deposition). The sublimation of silicon carbide raw materials, the transport of vapor phase components, and the growth of silicon carbide crystals are all affected by radial and axial temperature gradients. The shape of the growth interface and the growth rate are significantly related to the temperature gradient at the growth interface. The axial temperature gradient provides the growth driving force, and an appropriate temperature gradient is beneficial for ensuring a uniform growth rate; therefore, controlling the axial temperature gradient is a key factor in ensuring a uniform growth rate. The radial temperature gradient, on the other hand, leads to uneven growth rates between the center and the periphery of the crystal surface.
[0003] In traditional silicon carbide single crystal furnaces, the growth rate uniformity is tested by controlling the temperature gradient near the growth interface. However, the temperature gradient at different locations on the growth interface is not easy to control directly and can only be improved to a certain extent by optimizing the temperature field. Poor temperature uniformity manifests as difficulty in ensuring the growth interface is level and the growth rate is difficult to control, resulting in more defects in the silicon carbide single crystal, such as screw dislocations, edge dislocations, basal plane dislocations, inclusions, and excessive resistivity. Summary of the Invention
[0004] The purpose of this invention is to provide a method and apparatus for improving the uniformity of silicon carbide crystal growth. The method of this invention improves the uniformity of raw material supply to the crystal center and the periphery, reduces the difference in growth rate between the crystal center and the periphery, and improves the uniformity of crystal growth rate at different growth stages.
[0005] This invention provides a method for improving the uniformity of silicon carbide crystal growth, comprising the following steps:
[0006] A) The silicon carbide raw material is loaded into a movable crucible, and the outlet of the movable crucible is provided with a flow guide hood, the outlet area of which is smaller than the outlet area of the crucible.
[0007] Fix the seed crystal to the surface of the seed crystal base;
[0008] B) Keep the seed crystal base fixed, heat the silicon carbide raw material in the crucible, move the crucible evenly in the horizontal direction, so that the raw material gas flow generated by heating the raw material is uniformly grown on the seed crystal surface through the flow guide hood outlet. When the crystal thickness increases by Δh, keep the crucible in the horizontal direction still, move the crucible in the vertical direction by Δh, keep the distance between the flow guide hood outlet and the crystal surface unchanged, until the growth of silicon carbide crystal is completed.
[0009] Preferably, the outlet area of the flow guide is 1% to 10% of the seed crystal area.
[0010] Preferably, the crucible moves at a speed of 1 to 500 mm / min in the horizontal direction.
[0011] Preferably, the crucible moves horizontally in the horizontal direction by moving left and right, moving forward and backward, or moving in a horizontal circle.
[0012] Preferably, Δh is 1 to 1000 μm.
[0013] Preferably, the distance between the outlet of the flow guide and the surface of the seed crystal is 0.1 to 10 mm.
[0014] Preferably, the silicon carbide crystal growth is carried out under a protective atmosphere, which includes argon and nitrogen, the silicon carbide crystal growth temperature is 2000-2400°C, and the silicon carbide crystal growth pressure is 200-2000 Pa.
[0015] This invention provides an apparatus for improving the uniformity of silicon carbide crystal growth, comprising an independent feeding device and an independent growth device;
[0016] The independent feeding device includes a movable tray, on which a crucible is placed. A flow guide is provided at the outlet of the crucible, and the outlet area of the flow guide is smaller than the outlet area of the crucible. A heating device is fixedly provided on the outer wall of the crucible.
[0017] The independent growth device includes a seed crystal base, on the surface of which a seed crystal is fixed, and a growth zone boundary is provided around the seed crystal base.
[0018] Preferably, the outer wall of the crucible is provided with a heat insulation layer;
[0019] The outer wall of the flow guide is provided with a heat insulation layer.
[0020] Preferably, the shape of the outlet of the flow guide is rectangular, square, circular, or elliptical.
[0021] This invention provides a method for improving the uniformity of silicon carbide crystal growth, comprising the following steps: A) loading silicon carbide raw material into a movable crucible, wherein the outlet of the movable crucible is provided with a flow guide hood, and the outlet area of the flow guide hood is smaller than the outlet area of the crucible; fixing a seed crystal on the surface of a seed crystal base; B) keeping the seed crystal base fixed, heating the silicon carbide raw material in the crucible, and moving the crucible uniformly in the horizontal direction so that the raw material gas flow generated by heating the raw material passes through the outlet of the flow guide hood and grows uniformly on the surface of the seed crystal. When the crystal thickness increases by Δh, keeping the crucible stationary in the horizontal direction, the crucible is moved vertically by Δh, keeping the distance between the outlet of the flow guide hood and the crystal surface constant, until the growth of the silicon carbide crystal is completed. This invention separately controls the temperature of the seed crystal and the raw material, reducing the coupling between the temperature field of the seed crystal and the temperature field of the raw material, and solving the problem of difficult growth rate control caused by the difficulty in controlling the temperature gradient in traditional silicon carbide single crystal furnaces. The raw material region can move in both the horizontal and vertical directions. The horizontal and vertical movement of the raw material region transforms the control of growth rate uniformity into the control of the uniformity of the horizontal and vertical movement rates of the raw material region. Relatively speaking, the control of the uniformity of the horizontal and vertical movement rates of the raw material region is easier to control, thereby improving the uniformity of raw material supply to the crystal center and surrounding areas, reducing the difference in growth rate between the crystal center and surrounding areas, and improving the uniformity of crystal growth rate at different growth stages. Attached Figure Description
[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0023] Figure 1 This is a schematic diagram of the silicon carbide crystal growth apparatus used in Embodiment 1 of the present invention;
[0024] Figure 1 In the diagram, 1 is the seed crystal base, 2 is the seed crystal, 3 is the growth zone boundary, 4 is the flow guide, 5 is the heat insulation layer, 6 is the heating coil, 7 is the tray, 8 is the silicon carbide raw material, 9 is the coil support, 10 is the furnace body, and 11 is the crucible.
[0025] Figure 2 This is a schematic diagram of the silicon carbide crystal growth apparatus used in Embodiment 2 of the present invention;
[0026] Figure 2In the diagram, 1 is the seed crystal base, 2 is the seed crystal, 3 is the growth zone boundary, 4 is the flow guide, 5 is the heat insulation layer, 6 is the heating coil, 7 is the tray, 8 is the silicon carbide raw material, 9 is the coil support, 10 is the furnace body, and 11 is the crucible.
[0027] Figure 3 This is a schematic diagram of the silicon carbide crystal growth apparatus used in the comparative example of this invention.
[0028] Figure 3 In the diagram, 1 is the seed crystal base, 2 is the seed crystal, 3 is the crucible, 4 is the insulation layer, 5 is the heating coil, 6 is the tray, 7 is the silicon carbide raw material, 8 is the coil support, and 9 is the furnace body. Detailed Implementation
[0029] This invention provides a method for improving the uniformity of silicon carbide crystal growth, comprising the following steps:
[0030] A) The silicon carbide raw material is loaded into a movable crucible, and the outlet of the movable crucible is provided with a flow guide hood, the outlet area of which is smaller than the outlet area of the crucible.
[0031] Fix the seed crystal to the surface of the seed crystal base;
[0032] B) Keep the seed crystal base fixed, heat the silicon carbide raw material in the crucible, move the crucible evenly in the horizontal direction, so that the raw material gas flow generated by heating the raw material is uniformly grown on the seed crystal surface through the flow guide hood outlet. When the crystal thickness increases by Δh, keep the crucible in the horizontal direction still, move the crucible in the vertical direction by Δh, keep the distance between the flow guide hood outlet and the crystal surface unchanged, until the growth of silicon carbide crystal is completed.
[0033] In this invention, the silicon carbide growth apparatus includes an independent feeding device and an independent growth device. The independent feeding device is located below the independent growth device, and there is a certain distance between the two. The independent feeding device can move independently.
[0034] In this invention, the independent growth device includes a seed crystal base, on the surface of which a seed crystal is fixed, and a growth zone boundary is provided at the lower edge of the seed crystal base.
[0035] In this invention, the seed crystal base can be made of graphite, or it can be graphite, tantalum carbide, tungsten carbide or titanium carbide with a coating. The seed crystal is fixed on the surface of the seed crystal base. The seed crystal base and the seed crystal are fixed by adhesive or by mechanical force.
[0036] The growth region boundary is preferably made of graphite, but it can also be coated graphite, tantalum carbide, tungsten carbide or titanium carbide. The interior space of the growth boundary is the growth region of silicon carbide crystal.
[0037] During the growth of silicon carbide crystals, it is preferable to monitor the temperature of the seed crystal substrate to maintain the temperature at a set temperature value. The set temperature value is preferably (2000~2400)℃±5℃, more preferably (2100~2300)℃±5℃, such as 2000℃±5℃, 2050℃±5℃, 2100℃±5℃, 2150℃±5℃, 2200℃±5℃, 2250℃±5℃, 2300℃±5℃, 2350℃±5℃, 2400℃±5℃, and preferably a range of values with any of the above values as the upper or lower limit.
[0038] In this invention, the independent feeding device includes a movable tray, on which a crucible is fixedly mounted. A flow guide is provided at the outlet of the crucible, and the outlet area of the flow guide is smaller than the outlet area of the crucible. A heating device is fixedly mounted on the outer wall of the crucible.
[0039] In this invention, the movable tray is used to support the crucible and provide the crucible with a moving speed in the horizontal and vertical directions. The tray is preferably made of metal and needs to withstand a high temperature of 800°C. The surface is protected by a coating. The coating is preferably a silicon carbide coating, tantalum carbide coating, tungsten carbide coating, titanium carbide tungsten carbide coating, titanium carbide coating, etc. The tray can move horizontally or vertically at the same time, and the non-uniformity of the moving speed is ≤0.001mm / h.
[0040] In this invention, the crucible is fixed on the tray and has the same moving direction and moving speed as the tray. The crucible is preferably made of graphite, but it can also be graphite with a coating, tantalum carbide, tungsten carbide, or titanium carbide.
[0041] In this invention, a flow guide shroud is provided at the outlet of the crucible. The flow guide shroud is preferably made of graphite, but can also be coated graphite, tantalum carbide, tungsten carbide, titanium carbide, etc. The flow guide shroud can collect the evaporated gaseous components into a relatively small outlet area, providing a stable supply of gaseous components. This maintains a stable temperature gradient between the flow guide shroud outlet and the seed crystal substrate, ensuring uniform growth. This invention does not impose special restrictions on the shape of the flow guide shroud outlet, as long as the gaseous phase at the outlet can uniformly traverse the growth interface. In one embodiment of this invention, the outlet of the flow guide shroud is rectangular; in another embodiment, the outlet of the flow guide shroud is circular. The outlet area of the flow guide shroud is preferably 1% to 10% of the seed crystal area, more preferably 2% to 8%, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, preferably within a range where any of the above values are the upper or lower limits.
[0042] In this invention, a heating device is provided on the outer wall of the crucible, and the heating device is fixed relative to the crucible. In one embodiment of this invention, the heating device can be fixed to the surface of the tray by a bracket and has the same moving direction and moving speed as the crucible. In another embodiment of this invention, the heating device is a medium-frequency induction heating coil.
[0043] In this invention, the outer wall of the crucible is also provided with a heat-insulating device, such as... Figure 1 As shown, preferably, the outer wall of the flow guide is also provided with a heat insulation device, such as... Figure 2 As shown. The insulation device is preferably an insulation layer made of graphite.
[0044] This invention involves loading silicon carbide raw material into a crucible, fixing a seed crystal on a seed crystal base, placing the loaded growth apparatus inside a furnace, and evacuating the furnace body to a pressure of <50 Pa. After evacuation, a protective gas is introduced into the furnace body, preferably argon and nitrogen. The flow rate of argon is preferably 0–200 L / min, more preferably 10–200 L / min, and most preferably 50–150 L / min. The flow rate of nitrogen is preferably 0–20 L / min, more preferably 5–15 L / min. The furnace pressure is preferably 200-2000 Pa, more preferably 500-1500 Pa. The seed crystal substrate heating is activated to maintain the temperature at (2000-2400)℃ ± 5℃. Simultaneously, the intermediate frequency coil on the crucible is activated to heat the raw material area. When the raw material area temperature reaches 2000-2400℃, the outlet of the flow guide hood in the raw material area is moved to the edge of the seed crystal. The distance between the outlet of the flow guide hood and the surface of the seed crystal is preferably 0.1-10 mm, more preferably 1-8 mm, such as 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, or 2 mm. The preferred values are 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm, and 10mm, and are preferably values within the range of the above values that are not at their upper or lower limits. The air deflector can move at a uniform speed in the horizontal plane, such as moving horizontally left and right, forward and backward, or in a horizontal circle. The preferred moving speed is 1 to 500 mm / min, more preferably 10 to 400 mm / min, and most preferably... The flow rate is 50–300 mm / min to achieve uniform growth at the growth interface. As the crystal thickness increases, the flow guide outlet moves vertically accordingly. After each pass of the growth interface, assuming the crystal thickness increases by Δh, the flow guide outlet moves vertically by Δh, which is preferably 1–1000 μm, more preferably 10–800 μm, and most preferably 100–500 μm. This keeps the distance between the flow guide outlet and the crystal surface stable. Generally, growth is completed after 100–400 hours. After growth, the intermediate frequency coil heating, substrate heating, and protective gas are turned off, and the furnace is cooled for 10–50 hours, preferably 20–40 hours, to reduce the furnace temperature to below 50°C.
[0045] This invention provides a method for improving the uniformity of silicon carbide crystal growth, comprising the following steps: A) loading silicon carbide raw material into a movable crucible, wherein the outlet of the movable crucible is provided with a flow guide hood, and the outlet area of the flow guide hood is smaller than the outlet area of the crucible; fixing a seed crystal on the surface of a seed crystal base; B) keeping the seed crystal base fixed, heating the silicon carbide raw material in the crucible, and moving the crucible uniformly in the horizontal direction so that the raw material gas flow generated by heating the raw material passes through the outlet of the flow guide hood and grows uniformly on the surface of the seed crystal. When the crystal thickness increases by Δh, keeping the crucible stationary in the horizontal direction, the crucible is moved vertically by Δh, keeping the distance between the outlet of the flow guide hood and the crystal surface constant, until the growth of the silicon carbide crystal is completed. This invention separately controls the temperature of the seed crystal and the raw material, reducing the coupling between the temperature field of the seed crystal and the temperature field of the raw material, and solving the problem of difficult growth rate control caused by the difficulty in controlling the temperature gradient in traditional silicon carbide single crystal furnaces. The raw material region can move in both the horizontal and vertical directions. The horizontal and vertical movement of the raw material region transforms the control of growth rate uniformity into the control of the uniformity of the horizontal and vertical movement rates of the raw material region. Relatively speaking, the control of the uniformity of the horizontal and vertical movement rates of the raw material region is easier to control, thereby improving the uniformity of raw material supply to the crystal center and surrounding areas, reducing the difference in growth rate between the crystal center and surrounding areas, and improving the uniformity of crystal growth rate at different growth stages.
[0046] To further illustrate the present invention, the following detailed description of a method for improving the uniformity of silicon carbide crystal growth provided by the present invention is provided in conjunction with embodiments, but it should not be construed as limiting the scope of protection of the present invention.
[0047] Example 1
[0048] use Figure 1 The silicon carbide crystal growth apparatus shown.
[0049] Detailed operation steps:
[0050] The furnace body was evacuated to a pressure of <50 Pa. After evacuation, protective gases, namely argon and nitrogen, were introduced into the furnace body at flow rates of 100 L / min and 10 L / min, respectively. The furnace pressure was 1000 Pa. The substrate heating was turned on to maintain the temperature at 2000℃. At the same time, the intermediate frequency coil was turned on to heat the raw material area. When the temperature of the raw material area reached 2200℃, the outlet of the flow guide in the raw material area was moved to the edge of the seed crystal. The distance between the outlet of the flow guide and the surface of the seed crystal was 1 mm. The flow guide was moved horizontally left and right and back and forth on the horizontal plane to ensure that the gas from the outlet of the flow guide was evenly distributed on the surface of the seed crystal. The moving speed was 20 mm / min. For every 200 μm increase in crystal thickness, the outlet of the flow guide was moved downward by 200 μm in the vertical direction to ensure that the distance between the outlet of the flow guide and the crystal surface remained unchanged and stable. After 200 h, the growth was completed. After growth is complete, turn off the intermediate frequency coil heating, turn off the substrate heating, turn off the protective gas, and cool for 20 hours to reduce the furnace temperature to less than 50 degrees Celsius.
[0051] The specific parameters of the silicon carbide crystals grown in Example 1 are: TSD≤50, TED≤2000, BPD≤100, and resistivity range 0.020±0.02.
[0052] Example 2
[0053] Adopting such Figure 2 The silicon carbide crystal growth apparatus shown.
[0054] The specific operating steps are the same as in Example 1.
[0055] The specific parameters of the silicon carbide crystals grown in Example 2 are: TSD≤30, TED≤1500, BPD≤80, and resistivity range 0.020±0.015.
[0056] In the growth apparatus used in Example 2, the insulation layer structure is in contact with the flow guide hood, increasing the insulation capacity and improving the feeding efficiency. The flow guide hood outlet is designed as a rectangle to make the feeding more uniform.
[0057] Comparative Example
[0058] use Figure 3 The growth apparatus shown.
[0059] The specific operating steps are as follows:
[0060] The furnace is evacuated until the internal pressure reaches <50 Pa. After evacuation, a protective gas, argon and nitrogen, is introduced into the furnace at flow rates of 100 L / min and 10 L / min respectively, maintaining an internal pressure of 1000 Pa. The substrate heating is then activated to maintain the temperature at 2000℃, while the intermediate frequency coil is simultaneously activated to heat the raw material zone. When the raw material zone temperature reaches 2200℃, the tray begins to move upwards (the coil is fixed by a coil support and does not move). The tray moves at a rate of 1 mm / h. After 200 hours, growth is complete. After growth, the intermediate frequency coil heating, substrate heating, and protective gas are turned off, and the furnace is allowed to cool for 20 hours, reducing the internal temperature to below 50℃.
[0061] The specific parameters of the silicon carbide crystals obtained by comparative growth are: TSD≤150, TED≤3000, BPD≤200, and resistivity range 0.020±0.03.
[0062] In the comparative example, the gaseous components of silicon carbide raw material evaporated at high temperature directly reach the seed crystal surface for growth, without control over the transport of gaseous components. As the tray moves upward and the crystal growth interface moves downward, the temperature field inside the crucible changes significantly, which is not conducive to stable and uniform crystal growth. The temperature field environment near the growth interface can only be controlled by factors such as external insulation felt structure, lifting, and air pressure. The uniformity of the temperature gradient at the growth interface is not easy to control, and the uniformity of the growth rate is difficult to guarantee.
[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for improving the uniformity of silicon carbide crystal growth, comprising the following steps: A) The silicon carbide raw material is loaded into a movable crucible, and the outlet of the movable crucible is provided with a flow guide hood, the outlet area of which is smaller than the outlet area of the crucible. Fix the seed crystal to the surface of the seed crystal base; B) Keep the seed crystal base fixed, heat the silicon carbide raw material in the crucible, move the crucible evenly in the horizontal direction, so that the raw material gas flow generated by heating the raw material is uniformly grown on the seed crystal surface through the flow guide hood outlet. When the crystal thickness increases by Δh, keep the crucible in the horizontal direction still, move the crucible in the vertical direction by Δh, keep the distance between the flow guide hood outlet and the crystal surface unchanged, until the growth of silicon carbide crystal is completed.
2. The method according to claim 1, characterized in that, The outlet area of the flow guide is 1% to 10% of the seed crystal area.
3. The method according to claim 1, characterized in that, The crucible moves at a speed of 1 to 500 mm / min in the horizontal direction.
4. The method according to claim 1, characterized in that, The crucible can move horizontally in the left-right, forward-backward, or in a horizontal circular motion.
5. The method according to claim 1, characterized in that, Δh ranges from 1 to 1000 μm.
6. The method according to claim 1, characterized in that, The distance between the outlet of the flow guide and the surface of the seed crystal is 0.1 to 10 mm.
7. The method according to claim 1, characterized in that, The silicon carbide crystal is grown under a protective atmosphere, which includes argon and nitrogen. The growth temperature of the silicon carbide crystal is 2000–2400°C, and the growth pressure is 200–2000 Pa.
8. An apparatus for improving the uniformity of silicon carbide crystal growth, comprising an independent feeding device and an independent growth device; The independent feeding device includes a movable tray, on which a crucible is placed. A flow guide is provided at the outlet of the crucible, and the outlet area of the flow guide is smaller than the outlet area of the crucible. A heating device is fixedly provided on the outer wall of the crucible. The independent growth device includes a seed crystal base, on the surface of which a seed crystal is fixed, and a growth zone boundary is provided around the seed crystal base.
9. The apparatus according to claim 8, characterized in that, The outer wall of the crucible is provided with a heat insulation layer; The outer wall of the flow guide is provided with a heat insulation layer.
10. The apparatus according to claim 8, characterized in that, The shape of the air deflector outlet is rectangular, square, circular, or elliptical.