Method for improving doping concentration uniformity of p-type silicon carbide epitaxial wafer

Abstract

The application belongs to the technical field of silicon carbide epitaxial growth, and discloses a method for improving the doping concentration uniformity of a P-type silicon carbide epitaxial wafer, which comprises the following steps: after hydrogen gas with a preset flow rate is introduced into a reaction chamber, a silicon carbide substrate is placed in the reaction chamber, the input flow rate of the hydrogen gas is kept unchanged, the temperature and the pressure of the reaction chamber are respectively adjusted to a preset etching temperature and a preset etching pressure, the surface of the silicon carbide substrate is etched, a silicon carbide substrate after surface etching is obtained, ethylene gas and trichlorosilane gas are input into the reaction chamber through the lower channel of a layered gas distribution box, trimethylaluminum gas is input into the reaction chamber through the upper channel of the layered gas distribution box, the silicon carbide substrate after surface etching is made to grow an epitaxial layer, and a P-type silicon carbide epitaxial wafer with uniform doping concentration is prepared; the reaction gases are separately input through the layered gas distribution box, the P-type silicon carbide epitaxial wafer with uniform doping concentration is prepared, and the doping concentration uniformity of the P-type silicon carbide epitaxial wafer is improved.

Description

Technical Field

[0001] This application relates to the field of silicon carbide epitaxial growth technology, and more specifically, to a method for improving the uniformity of doping concentration in P-type silicon carbide epitaxial wafers. Background Technology

[0002] Silicon carbide (SiC), a key wide-bandgap semiconductor material, has become a core material for manufacturing high-voltage, high-frequency, and high-temperature high-power devices due to its unique advantages such as large bandgap, high breakdown field strength, high thermal conductivity, and high electron saturation drift velocity. It widely supports modern industrial applications such as new energy vehicle drive systems, 5G communication base stations, rail transit traction devices, and smart grid power transmission and distribution equipment. In the manufacturing process of SiC power devices, both N-type and P-type chips rely on high-quality 4H-SiC epitaxial films (i.e., SiC epitaxial wafers) as a basic platform. These epitaxial wafers are doped with specific impurity elements to form the required electrical properties. Under current technological conditions, the thickness uniformity and doping concentration uniformity of N-type 4H-SiC epitaxial films have achieved a high level of control, maintaining a stable fluctuation range within 3%, fully meeting the performance requirements of most unipolar devices. However, there are still significant bottlenecks in the uniformity control of P-type 4H-SiC epitaxial films. The uniformity of their thickness and doping concentration distribution is difficult to achieve an ideal state. In particular, for bipolar devices such as insulated gate bipolar transistors, their stringent process requirements necessitate better uniformity performance.

[0003] When growing P-type 4H-SiC epitaxial films using a horizontal silicon carbide high-temperature epitaxial furnace, the doping concentration generally exhibits a V-shaped distribution characteristic, with a lower concentration in the central region and a higher concentration at the edges. The fundamental reason for this phenomenon lies in the temperature matching defect during the P-type doping process: high-quality crystallization of 4H-SiC epitaxial films requires a process temperature above 1600℃, while the aluminum element in the P-type dopant trimethylaluminum is chemically highly reactive and can be largely incorporated into the silicon carbide lattice at a process temperature of 1400℃, far below the minimum temperature threshold required for crystallization. Inside the reaction chamber, the temperature distribution exhibits a gradient characteristic, with a higher temperature in the center and a lower temperature at the edges. To ensure that the edge region reaches the crystallization temperature (approximately 1600℃), the temperature in the central region must be increased to above 1630℃. According to the principles of gas reaction kinetics, when reactant gases such as ethylene, trichlorosilane, and trimethylaluminum are premixed in the inlet pipe and enter the reaction chamber, aluminum atoms readily replace silicon atoms and form stable covalent bonds with carbon atoms at the substrate edge region under the high temperature of 1600℃. However, in the central region, the carbon-silicon bond strength is significantly enhanced due to the further increase in temperature, making it difficult for aluminum atoms to effectively embed into the crystal structure. This results in a significantly lower doping concentration at the center compared to the edge. Although existing technologies attempt to reduce the steepness of the V-shaped distribution by optimizing process parameters such as gas flow rate and temperature distribution, they cannot fundamentally eliminate the concentration difference between the center and the edge. This leads to a severe lack of doping uniformity in single epitaxial wafers, greatly limiting the reliability and mass production feasibility of high-performance P-type silicon carbide devices.

[0004] Therefore, in order to solve the technical problem that the existing P-type silicon carbide epitaxial wafer preparation method first mixes trimethylaluminum gas with ethylene gas and trichlorosilane gas, so that aluminum atoms replace silicon atoms and combine with carbon atoms under high temperature, resulting in uneven distribution of aluminum atoms and thus uneven doping concentration distribution of the prepared P-type silicon carbide epitaxial wafer, there is an urgent need for a method to improve the doping concentration uniformity of P-type silicon carbide epitaxial wafers. Summary of the Invention

[0005] The purpose of this application is to provide a method for improving the doping concentration uniformity of P-type silicon carbide epitaxial wafers. This method involves introducing ethylene gas and trichlorosilane gas into the reaction chamber via the lower channel of a layered gas homogenizer, and introducing trimethylaluminum gas into the reaction chamber via the upper channel of the layered gas homogenizer to promote silicon carbide substrate growth. This results in the preparation of P-type silicon carbide epitaxial wafers with uniform doping concentration. This addresses the problem in existing P-type silicon carbide epitaxial wafer preparation methods that first mix trimethylaluminum gas with ethylene gas and trichlorosilane gas, causing aluminum atoms to replace silicon atoms and combine with carbon atoms at high temperatures, leading to uneven aluminum atom distribution and thus uneven doping concentration distribution in the prepared P-type silicon carbide epitaxial wafers. By using a dual-channel gas input method in the layered gas homogenizer to input the dopant gas and main reaction gas in layers, the premature local reaction caused by traditional mixed input is avoided, thus improving the doping concentration uniformity of the P-type silicon carbide epitaxial wafer.

[0006] In a first aspect, this application provides a method for improving the doping concentration uniformity of a P-type silicon carbide epitaxial wafer, utilizing a layered gas equalization box to prepare a P-type silicon carbide epitaxial wafer with uniform doping concentration. The layered gas equalization box includes a gas equalization box and an upper channel and a lower channel disposed inside the gas equalization box. The method for improving the doping concentration uniformity of the P-type silicon carbide epitaxial wafer includes:

[0007] Vacuuming is performed on the reaction chamber of the epitaxial furnace;

[0008] After introducing hydrogen gas at a predetermined flow rate into the reaction chamber, the silicon carbide substrate is placed in the reaction chamber.

[0009] Keeping the hydrogen input flow rate constant, the temperature and pressure of the reaction chamber are adjusted to a preset etching temperature and a preset etching pressure, respectively, to etch the surface of the silicon carbide substrate to obtain a silicon carbide substrate with surface etching.

[0010] Ethylene gas and trichlorosilane gas are introduced into the reaction chamber through the lower channel of the layered gas equalization box, and trimethylaluminum gas is introduced into the reaction chamber through the upper channel of the layered gas equalization box to promote the growth of epitaxial layers on the silicon carbide substrate after surface etching, thereby preparing a P-type silicon carbide epitaxial wafer with uniform doping concentration.

[0011] The method for improving the doping concentration uniformity of P-type silicon carbide epitaxial wafers provided in this application can prepare P-type silicon carbide epitaxial wafers with uniform doping concentration. By introducing ethylene gas and trichlorosilane gas into the reaction chamber through the lower channel of the layered gas homogenizer, and introducing trimethylaluminum gas into the reaction chamber through the upper channel of the layered gas homogenizer, the growth of the epitaxial layer on the silicon carbide substrate is promoted, and a P-type silicon carbide epitaxial wafer with uniform doping concentration is prepared. This method solves the problem in existing P-type silicon carbide epitaxial wafer preparation methods that first mix trimethylaluminum gas with ethylene gas and trichlorosilane gas, causing aluminum atoms to replace silicon atoms and combine with carbon atoms under high temperature, resulting in uneven distribution of aluminum atoms and thus uneven doping concentration distribution in the prepared P-type silicon carbide epitaxial wafer. By using the dual-channel gas input method of the layered gas homogenizer to input the dopant gas and the main reaction gas in layers, the premature local reaction caused by traditional mixed input is avoided, thus improving the doping concentration uniformity of the P-type silicon carbide epitaxial wafer.

[0012] Optionally, after introducing hydrogen gas at a predetermined flow rate into the reaction chamber, the silicon carbide substrate is placed in the reaction chamber, including:

[0013] The reaction chamber is adjusted to a preset preheating temperature, and hydrogen gas is introduced into the reaction chamber at a preset flow rate.

[0014] The gas pressure in the reaction chamber is adjusted to atmospheric pressure, and the silicon carbide substrate is placed in the reaction chamber.

[0015] Optionally, the preset preheating temperature is 850~950℃; the preset flow rate is 100~300slm.

[0016] Optionally, the preset etching temperature is 1650°C; the preset etching pressure is 100 mbar.

[0017] Optionally, ethylene gas and trichlorosilane gas are introduced into the reaction chamber through the lower channel of the layered gas homogenizer, and trimethylaluminum gas is introduced into the reaction chamber through the upper channel of the layered gas homogenizer to promote the growth of an epitaxial layer on the surface-etched silicon carbide substrate, thereby preparing a P-type silicon carbide epitaxial wafer with uniform doping concentration, comprising:

[0018] Keep the temperature, pressure, and hydrogen flow rate constant;

[0019] Based on preset ethylene flow rate, preset trichlorosilane flow rate, and preset trimethylaluminum flow rate, ethylene gas and trichlorosilane gas are introduced into the reaction chamber through the lower channel of the layered gas equalization box, and trimethylaluminum gas is introduced into the reaction chamber through the upper channel of the layered gas equalization box to promote the growth of an epitaxial layer on the surface-etched silicon carbide substrate, thereby obtaining an epitaxially grown silicon carbide epitaxial wafer.

[0020] The gas pressure in the reaction chamber is adjusted to atmospheric pressure, and after the reaction chamber cools down naturally to the preset extraction temperature, the epitaxial silicon carbide wafer grown after epitaxial growth is taken out from the reaction chamber to obtain a P-type silicon carbide epitaxial wafer with uniform doping concentration.

[0021] The method for improving the doping concentration uniformity of P-type silicon carbide epitaxial wafers provided in this application can achieve the preparation of P-type silicon carbide epitaxial wafers with varying doping concentrations. By utilizing the structural characteristics of the layered gas distribution box, two gases form a layered gas flow in the reaction chamber. This avoids premature consumption of trimethylaluminum in the central high-temperature region and stabilizes the gas flow field on the substrate surface through the carbon source gas flow in the lower channel, promoting the uniform incorporation of aluminum atoms into the lattice in various regions of the substrate. This effectively alleviates the V-shaped distribution defect caused by excessive edge doping and insufficient center doping.

[0022] Optionally, the preset ethylene flow rate includes a preset first ethylene flow rate and a preset second ethylene flow rate; the preset trichlorosilane flow rate includes a preset first trichlorosilane flow rate and a preset second trichlorosilane flow rate; the preset trimethylaluminum flow rate includes a preset first trimethylaluminum flow rate and a preset second trimethylaluminum flow rate; based on the preset ethylene flow rate, the preset trichlorosilane flow rate, and the preset trimethylaluminum flow rate, ethylene gas and trichlorosilane gas are introduced into the reaction chamber through the lower channel of the layered gas equalization box, and trimethylaluminum gas is introduced into the reaction chamber through the upper channel of the layered gas equalization box to promote the growth of an epitaxial layer on the surface-etched silicon carbide substrate, resulting in an epitaxially grown silicon carbide epitaxial wafer, comprising:

[0023] Based on the preset first ethylene inlet flow rate, the preset first trichlorosilane inlet flow rate, and the preset first trimethylaluminum inlet flow rate, combined with the preset first growth time, ethylene gas and trichlorosilane gas are introduced into the reaction chamber through the lower channel of the layered gas equalization box, and trimethylaluminum gas is introduced into the reaction chamber through the upper channel of the layered gas equalization box, so as to promote the growth of the buffer layer on the surface-etched silicon carbide substrate, and obtain a silicon carbide substrate with a buffer layer grown.

[0024] Based on the preset second ethylene inlet flow rate, the preset second trichlorosilane inlet flow rate, and the preset second trimethylaluminum inlet flow rate, combined with the preset second growth time, the ethylene gas and the trichlorosilane gas are introduced into the reaction chamber through the lower channel of the layered gas equalization box, and the trimethylaluminum gas is introduced into the reaction chamber through the upper channel of the layered gas equalization box, so as to promote the growth of the epitaxial layer on the silicon carbide substrate with the buffer layer, and obtain the epitaxially grown silicon carbide epitaxial wafer.

[0025] The method for improving the doping concentration uniformity of P-type silicon carbide epitaxial wafers provided in this application can achieve the preparation of P-type silicon carbide epitaxial wafers with varying doping concentrations. By controlling the gas flow rate and growth time in stages, the aluminum doping process is optimized. Through the design of a layered gas distribution box combined with staged flow control, the gas distribution and reaction kinetics are optimized, effectively suppressing the formation of a V-shaped distribution of doping concentration.

[0026] Optionally, the preset first ethylene flow rate is 20~100 sccm; the preset second ethylene flow rate is 50~200 sccm; the preset first trichlorosilane flow rate is 50~200 sccm; the preset second trichlorosilane flow rate is 100~400 sccm; the preset first trimethylaluminum flow rate is 100~300 sccm; and the preset second trimethylaluminum flow rate is 5~60 sccm.

[0027] Optionally, the preset first growth time is 5-10 min; the preset second growth time is 10-20 min.

[0028] Optionally, the preset extraction temperature is 900°C.

[0029] Optionally, ethylene gas and trichlorosilane gas are introduced into the reaction chamber through the lower channel of the layered gas homogenizer, and trimethylaluminum gas is introduced into the reaction chamber through the upper channel of the layered gas homogenizer to promote the growth of an epitaxial layer on the surface-etched silicon carbide substrate. After obtaining a P-type silicon carbide epitaxial wafer with uniform doping concentration, the process further includes:

[0030] The doping concentration of the P-type silicon carbide epitaxial wafer is tested to ensure that the doping concentration of the P-type silicon carbide epitaxial wafer is uniform.

[0031] Beneficial Effects: The method for improving the doping concentration uniformity of P-type silicon carbide epitaxial wafers provided in this application introduces ethylene gas and trichlorosilane gas into the reaction chamber through the lower channel of the layered gas homogenizer, and trimethylaluminum gas into the reaction chamber through the upper channel of the layered gas homogenizer, to promote the growth of epitaxial layers on silicon carbide substrates, thereby preparing P-type silicon carbide epitaxial wafers with uniform doping concentration. This solves the problem in existing P-type silicon carbide epitaxial wafer preparation methods that first mix trimethylaluminum gas with ethylene gas and trichlorosilane gas, causing aluminum atoms to replace silicon atoms and combine with carbon atoms under high temperature, resulting in uneven distribution of aluminum atoms and thus uneven doping concentration distribution in the prepared P-type silicon carbide epitaxial wafers. By using the dual-channel gas input method of the layered gas homogenizer to input the dopant gas and the main reaction gas in layers, the premature local reaction caused by traditional mixed input is avoided, thus improving the doping concentration uniformity of P-type silicon carbide epitaxial wafers. Attached Figure Description

[0032] Figure 1 This is a flowchart illustrating a method for improving the doping concentration uniformity of a P-type silicon carbide epitaxial wafer provided in an embodiment of this application.

[0033] Figure 2 This is a schematic diagram of the structure of the layered gas equalization box according to an embodiment of this application.

[0034] Figure 3 This is a schematic diagram of the doping concentration distribution of a P-type silicon carbide epitaxial wafer according to an embodiment of this application.

[0035] Figure 4 This is a schematic diagram of the doping concentration distribution of a P-type silicon carbide epitaxial wafer after reducing the hydrogen flow rate, according to an embodiment of this application.

[0036] Figure 5 This is a schematic diagram of the doping concentration distribution of a P-type silicon carbide epitaxial wafer prepared using traditional methods.

[0037] Labeling explanation: 1. Air distribution box; 2. Lower channel; 3. Upper channel; 4. Upper air inlet pipe; 5. Lower air inlet pipe. Detailed Implementation

[0038] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0039] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0040] Please refer to Figure 1 , Figure 1 This application discloses a method for improving the doping concentration uniformity of a P-type silicon carbide epitaxial wafer in some embodiments. It utilizes a layered gas homogenizing box to prepare a P-type silicon carbide epitaxial wafer with uniform doping concentration. The layered gas homogenizing box (specific structure shown in...) Figure 2 (As shown) includes a gas equalization box 1 and an upper channel 3 and a lower channel 2 disposed inside the gas equalization box; the method for improving the doping concentration uniformity of the P-type silicon carbide epitaxial wafer includes:

[0041] Step S1: Vacuum the reaction chamber of the epitaxial furnace;

[0042] Step S2: After introducing hydrogen gas at a preset flow rate into the reaction chamber, place the silicon carbide substrate in the reaction chamber.

[0043] Step S3: Keep the hydrogen input flow rate constant, and adjust the temperature and pressure of the reaction chamber to the preset etching temperature and preset etching pressure respectively to etch the surface of the silicon carbide substrate to obtain the surface-etched silicon carbide substrate.

[0044] In step S4, ethylene gas and trichlorosilane gas are introduced into the reaction chamber through the lower channel of the layered gas homogenizer, and trimethylaluminum gas is introduced into the reaction chamber through the upper channel of the layered gas homogenizer to promote the growth of epitaxial layers on the silicon carbide substrate after surface etching, thereby preparing a P-type silicon carbide epitaxial wafer with uniform doping concentration (the doping concentration refers to the P-type doping concentration).

[0045] This method for improving the doping concentration uniformity of P-type silicon carbide epitaxial wafers involves introducing ethylene and trichlorosilane gases into the reaction chamber via the lower channel of a layered gas homogenizer, and introducing trimethylaluminum gas into the reaction chamber via the upper channel of the layered gas homogenizer. This promotes the growth of the epitaxial layer on the silicon carbide substrate, resulting in a P-type silicon carbide epitaxial wafer with uniform doping concentration. This method addresses the problem in existing P-type silicon carbide epitaxial wafer preparation methods that first mix trimethylaluminum gas with ethylene and trichlorosilane gases, causing aluminum atoms to replace silicon atoms and combine with carbon atoms at high temperatures, leading to uneven aluminum atom distribution and thus uneven doping concentration distribution in the prepared P-type silicon carbide epitaxial wafer. By using a dual-channel gas input method in the layered gas homogenizer, the dopant gas and the main reaction gas are input separately, avoiding premature local reactions caused by traditional mixed inputs and improving the doping concentration uniformity of the P-type silicon carbide epitaxial wafer.

[0046] Specifically, such as Figure 2 As shown, Figure 2 This is a schematic diagram of the layered gas distribution box. Arrows indicate the gas flow direction. In practical applications, the upper inlet pipe 4 and the lower inlet pipe 5 serve as the inlets for the upper channel 3 and lower channel 2, respectively. Ethylene gas and trichlorosilane gas (carbon source and silicon source) are first introduced into the lower inlet pipe 5 and then into the reaction chamber via the lower channel 2. Trimethylaluminum gas (P-type dopant) is first introduced into the upper inlet pipe 4 and then into the reaction chamber via the upper channel 3. This layered input strategy keeps different types of reactive gases separate before entering the reaction chamber, thus avoiding premature mixing and preventing aluminum atoms from combining with carbon atoms first, which would lead to uneven distribution of aluminum atoms in the reaction chamber. This layered input strategy allows trimethylaluminum gas to diffuse more independently and in a more controlled manner onto the silicon carbide substrate surface after entering the reaction chamber, thereby promoting more uniform embedding of aluminum atoms into the silicon carbide lattice across the entire substrate surface.

[0047] Therefore, this layered gas homogenizing box effectively isolates the premature mixing of trimethylaluminum gas with ethylene and trichlorosilane gases in space, and also slows down the rate of chemical reaction between trimethylaluminum gas, ethylene gas, and trichlorosilane gas in the reaction chamber, which is equivalent to suppressing the rate at which Al atoms are incorporated into the 4H-SiC epitaxial film lattice. In this way, Al atoms have more kinetic energy to move above the center of the silicon carbide substrate, combine with C atoms, and then incorporate into the 4H-SiC epitaxial film lattice. This can compensate for the low doping concentration at the center of the 4H-SiC epitaxial wafer, leveling out the P-type doping concentration between the edge and center of the 4H-SiC epitaxial wafer, thereby solving the V-shaped distribution problem of doping concentration in P-type silicon carbide epitaxial wafers.

[0048] In some alternative embodiments, the single-channel ports of the upper and lower channels can be adjusted to multi-channel ports (i.e., multiple gas outlets), so that the gas flow rate at different gas output positions can be adjusted according to the actual situation during silicon carbide substrate growth. For example, baffles or valves can be set at each gas outlet to control the gas flow rate, so as to ensure the uniformity of doping concentration of P-type silicon carbide epitaxial wafers; or, the upper and lower channels can be adjusted to left and right channels respectively (the upper and lower gas inlets are adjusted to left and right gas inlets), thereby achieving more ways of separate input.

[0049] Specifically, in step S1, a vacuum operation is performed on the reaction chamber to remove residual gas and impurities, providing a clean reaction environment for subsequent epitaxial growth. The vacuum level should reach 1E-4~9E-4 mbar to ensure that the reaction chamber is leak-proof.

[0050] Specifically, in step S2, after introducing hydrogen gas at a preset flow rate into the reaction chamber, the silicon carbide substrate is placed in the reaction chamber, including:

[0051] Adjust the reaction chamber to the preset preheating temperature and introduce hydrogen gas at a preset flow rate into the reaction chamber;

[0052] Adjust the gas pressure in the reaction chamber to atmospheric pressure, and place the silicon carbide substrate in the reaction chamber.

[0053] In step S2, the reaction chamber is adjusted to a preset preheating temperature and hydrogen gas is introduced at a preset flow rate (within a certain range, the higher the hydrogen flow rate, the more uniform the doping concentration of the final silicon carbide epitaxial wafer). This reduces the temperature difference between the substrate and the ambient temperature when the substrate enters the reaction chamber, effectively reducing the thermal stress caused by sudden temperature changes and preventing damage or defects to the substrate. After the hydrogen flow rate stabilizes, the gas pressure in the reaction chamber is adjusted to atmospheric pressure (i.e., 960 mbar). Performing the substrate placement operation under atmospheric pressure provides a more stable and controllable operating environment, reduces the difficulty of operation, and minimizes the potential impact of the external environment on the cleanliness of the reaction chamber, ensuring the accuracy and safety of the substrate placement process.

[0054] The preset preheating temperature is 850~950℃; the preset flow rate is 100~300slm.

[0055] Specifically, in step S3, while maintaining a continuous flow of hydrogen, the reaction chamber is heated to a preset etching temperature and adjusted to a preset etching pressure to etch the surface of the silicon carbide substrate, thereby removing the surface defect layer and activating the active sites on the substrate surface, resulting in an etched silicon carbide substrate. The preset etching temperature is 1650°C; the preset etching pressure is 100 mbar.

[0056] Specifically, in step S4, ethylene gas and trichlorosilane gas are introduced into the reaction chamber through the lower channel of the layered gas homogenizer, and trimethylaluminum gas is introduced into the reaction chamber through the upper channel of the layered gas homogenizer to promote the growth of an epitaxial layer on the silicon carbide substrate after surface etching, thereby preparing a P-type silicon carbide epitaxial wafer with uniform doping concentration, including:

[0057] Keep the temperature, pressure, and hydrogen flow rate constant;

[0058] Based on the preset ethylene flow rate, the preset trichlorosilane flow rate, and the preset trimethylaluminum flow rate, ethylene gas and trichlorosilane gas are introduced into the reaction chamber through the lower channel of the layered gas equalization box, and trimethylaluminum gas is introduced into the reaction chamber through the upper channel of the layered gas equalization box to promote the growth of an epitaxial layer on the silicon carbide substrate after surface etching, thereby obtaining an epitaxial silicon carbide wafer.

[0059] The gas pressure in the reaction chamber is adjusted to atmospheric pressure, and after the reaction chamber cools down naturally to the preset extraction temperature, the epitaxial silicon carbide wafer grown on the reaction chamber is taken out to obtain a P-type silicon carbide epitaxial wafer with uniform doping concentration.

[0060] In step S4, maintaining stable temperature, pressure, and hydrogen flow rate provides a constant physicochemical environment for epitaxial growth, avoiding the adverse effects of growth condition fluctuations on the uniformity of the epitaxial layer. Based on preset ethylene, trichlorosilane, and trimethylaluminum flow rates, and utilizing the channels of the layered gas distribution box for input separation, the carbon source, silicon source, and dopant can reach the substrate surface in a precise and stable ratio and distribution. The precise control of the flow rate of trimethylaluminum as a dopant directly determines the number of doped atoms, while the design of the layered gas distribution box ensures the uniform distribution of the dopant across the entire substrate surface, thus fundamentally guaranteeing the high uniformity of the doping concentration in the epitaxial layer. Furthermore, after epitaxial growth, by adjusting the gas pressure in the reaction chamber to atmospheric pressure and allowing natural cooling to the preset extraction temperature, thermal stress, defects, or surface contamination that may be introduced by rapid cooling or improper operation are effectively avoided. These factors could potentially disrupt the uniformity of the formed epitaxial layer. The epitaxially grown silicon carbide wafer is then removed from the reaction chamber, yielding a P-type silicon carbide epitaxial wafer with uniform doping concentration.

[0061] Specifically, the preset ethylene flow rate includes a preset first ethylene flow rate and a preset second ethylene flow rate; the preset trichlorosilane flow rate includes a preset first trichlorosilane flow rate and a preset second trichlorosilane flow rate; the preset trimethylaluminum flow rate includes a preset first trimethylaluminum flow rate and a preset second trimethylaluminum flow rate; in step S4, based on the preset ethylene flow rate, the preset trichlorosilane flow rate, and the preset trimethylaluminum flow rate, ethylene gas and trichlorosilane gas are introduced into the reaction chamber through the lower channel of the layered gas equalization box, and trimethylaluminum gas is introduced into the reaction chamber through the upper channel of the layered gas equalization box, so as to promote the growth of an epitaxial layer on the surface-etched silicon carbide substrate, and obtain an epitaxially grown silicon carbide epitaxial wafer, including:

[0062] Based on the preset first ethylene inlet flow rate, the preset first trichlorosilane inlet flow rate, and the preset first trimethylaluminum inlet flow rate, combined with the preset first growth time, ethylene gas and trichlorosilane gas are introduced into the reaction chamber through the lower channel of the layered gas equalization box, and trimethylaluminum gas is introduced into the reaction chamber through the upper channel of the layered gas equalization box, so as to promote the growth of buffer layer on the silicon carbide substrate after surface etching, and obtain silicon carbide substrate with buffer layer grown.

[0063] Based on the preset second ethylene inlet flow rate, the preset second trichlorosilane inlet flow rate, and the preset second trimethylaluminum inlet flow rate, combined with the preset second growth time, ethylene gas and trichlorosilane gas are introduced into the reaction chamber through the lower channel of the layered gas equalization box, and the trimethylaluminum gas is introduced into the reaction chamber through the upper channel of the layered gas equalization box, so as to promote the growth of epitaxial layer on silicon carbide substrate with buffer layer, and obtain silicon carbide epitaxial wafer after epitaxial growth.

[0064] In step S4, the growth process of the P-type silicon carbide epitaxial wafer is divided into two stages: buffer layer growth and epitaxial layer growth. In the buffer layer growth stage, a buffer layer is formed on the etched silicon carbide substrate using preset first ethylene flow rate, preset first trichlorosilane flow rate, and preset first trimethylaluminum flow rate, combined with a preset first growth time. This buffer layer effectively absorbs and alleviates the lattice mismatch stress between the substrate and the epitaxial layer, and acts as a barrier to prevent micro-defects (such as dislocations and stacking faults) in the substrate from extending to the subsequently grown epitaxial layer. The presence of the buffer layer lays a solid foundation for the subsequent growth of a high-quality epitaxial layer. Next, in the epitaxial layer growth stage, based on preset second ethylene flow rate, preset second trichlorosilane flow rate, and preset second trimethylaluminum flow rate, combined with a preset second growth time, the epitaxial layer continues to grow on the silicon carbide substrate with the buffer layer. At this point, since the buffer layer has optimized the growth interface, the epitaxial layer can be grown under more stable conditions, thereby obtaining better crystal quality and more uniform doping distribution.

[0065] The preset flow rates are as follows: first ethylene flow rate: 20-100 sccm; second ethylene flow rate: 50-200 sccm; first trichlorosilane flow rate: 50-200 sccm; second trichlorosilane flow rate: 100-400 sccm; first trimethylaluminum flow rate: 100-300 sccm; second trimethylaluminum flow rate: 5-60 sccm; and the preset extraction temperature: 900℃. The preset first growth time is 5-10 min; and the preset second growth time is 10-20 min.

[0066] Specifically, in step S4, ethylene gas and trichlorosilane gas are introduced into the reaction chamber through the lower channel of the layered gas homogenizer, and trimethylaluminum gas is introduced into the reaction chamber through the upper channel of the layered gas homogenizer to promote the growth of an epitaxial layer on the silicon carbide substrate after surface etching. After obtaining a P-type silicon carbide epitaxial wafer with uniform doping concentration, the process further includes:

[0067] The doping concentration of P-type silicon carbide epitaxial wafers was tested to ensure that the doping concentration of P-type silicon carbide epitaxial wafers was uniform.

[0068] In step S4, the doping concentration distribution of the epitaxial wafer is quantitatively analyzed to provide objective data support for determining whether the epitaxial wafer truly meets the requirement of uniform doping concentration. If the test results show that the doping concentration uniformity does not meet the standard, corrective measures can be taken promptly, such as adjusting the growth parameters of subsequent batches or screening out defective products to prevent them from entering subsequent device manufacturing stages. Thus, this testing step transforms uniformity from an expected value into a verifiable indicator, significantly improving the quality control level of the production process.

[0069] In practical applications, such as Figure 3 , Figure 4 , Figure 5 As shown, Figure 3 This is a schematic diagram of the doping concentration distribution of a P-type silicon carbide epitaxial wafer according to an embodiment of this application (a preparation method using a layered gas homogenizer to pre-separate the input gas). Figure 4 This is a schematic diagram of the doping concentration distribution of a P-type silicon carbide epitaxial wafer after reducing the hydrogen flow rate (using a layered gas equalization box to pre-separate the input gas but reducing the hydrogen flow rate in the preparation method of this application). Figure 5 This diagram illustrates the doping concentration distribution of a P-type silicon carbide epitaxial wafer prepared using a conventional method (a method that does not use a layered gas equalization box for pre-separation of the input gas). In this diagram, a represents the doping concentration distribution curve of the P-type silicon carbide epitaxial wafer prepared according to the embodiments of this application; b represents the doping concentration distribution curve of the P-type silicon carbide epitaxial wafer prepared according to the embodiments of this application after reducing the hydrogen flow rate (hydrogen flow rate of 100 slm); and c represents the doping concentration distribution curve of the P-type silicon carbide epitaxial wafer prepared using the conventional method (hydrogen flow rate of 100 slm). Figure 3 , Figure 4 and Figure 5 The horizontal axis represents the pre-set measurement points (specifically, the measurement points are set at the edge-center-another edge), and the vertical axis represents the doping concentration, in units of E15cm. -3 .Depend on Figure 3 , Figure 4 It can be seen that, using the method for improving the doping concentration uniformity of P-type silicon carbide epitaxial wafers provided in this application (hydrogen flow rate of 120 slm), the average doping concentration of the prepared P-type silicon carbide epitaxial wafers is 9.82E15cm. -3 The doping concentration non-uniformity was 1.13%. Using the method for improving the doping concentration uniformity of P-type silicon carbide epitaxial wafers provided in this application (hydrogen flow rate of 100 slm), the average doping concentration of the P-type silicon carbide epitaxial wafers prepared after reducing the hydrogen flow rate was 9.22E15cm. -3The doping concentration non-uniformity is 1.56%. Therefore, using a hydrogen flow rate of 120 slm can drive more Al atoms to move above the center of the SiC substrate and combine with C atoms, which helps to further improve the uniformity of the p-type 4H-SiC doping concentration. Figure 4 , Figure 5 As can be seen, using the method for improving the doping concentration uniformity of P-type silicon carbide epitaxial wafers provided in this application (hydrogen flow rate of 100 slm), the average doping concentration of the P-type silicon carbide epitaxial wafers prepared after reducing the hydrogen flow rate is 9.22E15cm. -3 The doping concentration non-uniformity was 1.56%. Using the traditional preparation method (hydrogen flow rate of 100 slm), the average doping concentration of the prepared P-type silicon carbide epitaxial wafer was 8.43E15cm. -3 The doping concentration non-uniformity is 23.85%. Therefore, the method for improving the doping concentration uniformity of P-type silicon carbide epitaxial wafers using the layered gas equalization box and the method provided in the embodiments of this application can flatten the doping concentration at the edge and center of the P-type silicon carbide epitaxial wafer, thus solving the V-shaped distribution problem of doping concentration in P-type silicon carbide epitaxial wafers.

[0070] As described above, the method for improving the doping concentration uniformity of the P-type silicon carbide epitaxial wafer involves evacuating the reaction chamber of the epitaxial furnace, introducing hydrogen gas at a predetermined flow rate into the reaction chamber, placing the silicon carbide substrate in the reaction chamber, maintaining a constant hydrogen gas flow rate, and adjusting the temperature and pressure of the reaction chamber to predetermined etching temperatures and pressures to etch the surface of the silicon carbide substrate, resulting in a surface-etched silicon carbide substrate. Ethylene gas and trichlorosilane gas are then introduced into the reaction chamber through the lower channel of the layered gas homogenizer, while trimethylaluminum gas is introduced through the upper channel of the layered gas homogenizer to promote the growth of the epitaxial layer on the surface-etched silicon carbide substrate, thus preparing a P-type silicon carbide epitaxial wafer with uniform doping concentration. Therefore, by using ethylene gas and trichlorosilane... Gas is introduced into the reaction chamber through the lower channel of the layered gas homogenizer, and trimethylaluminum gas is introduced into the reaction chamber through the upper channel of the layered gas homogenizer to promote the growth of epitaxial layers on the silicon carbide substrate, thus preparing a P-type silicon carbide epitaxial wafer with uniform doping concentration. This solves the problem of uneven aluminum atom distribution caused by mixing trimethylaluminum gas with ethylene gas and trichlorosilane gas in the existing P-type silicon carbide epitaxial wafer preparation method, which causes aluminum atoms to replace silicon atoms and combine with carbon atoms under high temperature, resulting in uneven doping concentration distribution of the prepared P-type silicon carbide epitaxial wafer. By using the dual-channel gas input method of the layered gas homogenizer to input the dopant gas and the main reaction gas in layers, the premature local reaction caused by the traditional mixed input is avoided, thus improving the doping concentration uniformity of the P-type silicon carbide epitaxial wafer.

[0071] In this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, without necessarily requiring or implying any such actual relationship or order between these entities or operations.

[0072] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for improving the doping concentration uniformity of a P-type silicon carbide epitaxial wafer, using a layered gas distribution box to produce a P-type silicon carbide epitaxial wafer having a uniform doping concentration, characterized by, The layered uniform gas box comprises a uniform gas box and upper and lower channels arranged inside the uniform gas box; The method for improving the uniformity of the doping concentration of the P-type silicon carbide epitaxial wafer comprises: Performing vacuumizing operation on the reaction chamber of the epitaxial furnace; After introducing hydrogen gas with preset flow rate into the reaction chamber, placing silicon carbide substrate in the reaction chamber; Keeping the input flow rate of hydrogen gas unchanged, respectively adjusting the temperature and pressure of the reaction chamber to preset etching temperature and preset etching pressure, so as to etch the surface of the silicon carbide substrate, and obtain silicon carbide substrate after surface etching; Introducing ethylene gas and trichlorosilane gas into the reaction chamber through the lower channel of the layered uniform gas box, and introducing trimethylaluminum gas into the reaction chamber through the upper channel of the layered uniform gas box, so as to promote the growth of epitaxial layer on the silicon carbide substrate after surface etching, and obtain P-type silicon carbide epitaxial wafer with uniform doping concentration.

2. The method for improving the doping concentration uniformity of a P-type silicon carbide epitaxial wafer according to claim 1, wherein After introducing hydrogen gas with preset flow rate into the reaction chamber, placing silicon carbide substrate in the reaction chamber, comprising: Adjusting the reaction chamber to preset preheating temperature, and introducing hydrogen gas with preset flow rate into the reaction chamber; Adjusting the gas pressure of the reaction chamber to atmospheric pressure, and placing silicon carbide substrate in the reaction chamber.

3. The method for improving the doping concentration uniformity of a P-type silicon carbide epitaxial wafer according to claim 2, wherein The preset preheating temperature is 850-950 ℃; and the preset flow rate is 100-300 slm.

4. The method for improving the doping concentration uniformity of a P-type silicon carbide epitaxial wafer according to claim 1, wherein The preset etching temperature is 1650 ℃; and the preset etching pressure is 100 mbar.

5. The method for improving the doping concentration uniformity of a P-type silicon carbide epitaxial wafer according to Claim 1, wherein Introducing ethylene gas and trichlorosilane gas into the reaction chamber through the lower channel of the layered uniform gas box, and introducing trimethylaluminum gas into the reaction chamber through the upper channel of the layered uniform gas box, so as to promote the growth of epitaxial layer on the silicon carbide substrate after surface etching, and obtain P-type silicon carbide epitaxial wafer with uniform doping concentration, comprising: Keeping the temperature, pressure and hydrogen input flow rate unchanged; Based on preset ethylene input flow rate, preset trichlorosilane input flow rate and preset trimethylaluminum input flow rate, introducing ethylene gas and trichlorosilane gas into the reaction chamber through the lower channel of the layered uniform gas box, and introducing trimethylaluminum gas into the reaction chamber through the upper channel of the layered uniform gas box, so as to promote the growth of epitaxial layer on the silicon carbide substrate after surface etching, and obtain silicon carbide epitaxial wafer after epitaxial growth; Adjusting the gas pressure of the reaction chamber to atmospheric pressure, and waiting for the reaction chamber to naturally cool down to preset extraction temperature, and then taking out the silicon carbide epitaxial wafer after epitaxial growth from the reaction chamber, and obtaining P-type silicon carbide epitaxial wafer with uniform doping concentration.

6. The P-type silicon carbide epitaxial wafer's doping concentration uniformity improvement method according to claim 5, wherein The preset ethylene input flow rate comprises preset first ethylene input flow rate and preset second ethylene input flow rate; and the preset trichlorosilane input flow rate comprises preset first trichlorosilane input flow rate and preset second trichlorosilane input flow rate. The preset trimethylaluminum input flow rate comprises preset first trimethylaluminum input flow rate and preset second trimethylaluminum input flow rate. Based on the preset ethylene flow rate, the preset trichlorosilane flow rate and the preset trimethylaluminum flow rate, the ethylene gas and the trichlorosilane gas are input into the reaction chamber through the lower passage of the layered gas distribution box, and the trimethylaluminum gas is input into the reaction chamber through the upper passage of the layered gas distribution box to promote the growth of the epitaxial layer on the surface-etched silicon carbide substrate, thereby obtaining the silicon carbide epitaxial wafer after epitaxial growth, comprising: Based on the preset first ethylene flow rate, the preset first trichlorosilane flow rate and the preset first trimethylaluminum flow rate, and in combination with the preset first growth time, the ethylene gas and the trichlorosilane gas are input into the reaction chamber through the lower passage of the layered gas distribution box, and the trimethylaluminum gas is input into the reaction chamber through the upper passage of the layered gas distribution box to promote the growth of the buffer layer on the surface-etched silicon carbide substrate, thereby obtaining the silicon carbide substrate with the grown buffer layer; Based on the preset second ethylene flow rate, the preset second trichlorosilane flow rate and the preset second trimethylaluminum flow rate, and in combination with the preset second growth time, the ethylene gas and the trichlorosilane gas are input into the reaction chamber through the lower passage of the layered gas distribution box, and the trimethylaluminum gas is input into the reaction chamber through the upper passage of the layered gas distribution box to promote the growth of the epitaxial layer on the silicon carbide substrate with the grown buffer layer, thereby obtaining the silicon carbide epitaxial wafer after epitaxial growth.

7. The method for improving the doping concentration uniformity of a P-type silicon carbide epitaxial wafer according to claim 6, wherein The preset first ethylene flow rate is 20-100sccm; the preset second ethylene flow rate is 50-200sccm; the preset first trichlorosilane flow rate is 50-200sccm; the preset second trichlorosilane flow rate is 100-400sccm; the preset first trimethylaluminum flow rate is 100-300sccm; and the preset second trimethylaluminum flow rate is 5-60sccm.

8. The method for improving the doping concentration uniformity of an P-type silicon carbide epitaxial wafer according to claim 6, wherein, The preset first growth time is 5-10min; and the preset second growth time is 10-20min.

9. The method for improving the doping concentration uniformity of a P-type silicon carbide epitaxial wafer according to Claim 5, wherein The preset extraction temperature is 900℃.

10. The method for improving the doping concentration uniformity of a P-type silicon carbide epitaxial wafer according to Claim 1, wherein After the ethylene gas and the trichlorosilane gas are input into the reaction chamber through the lower passage of the layered gas distribution box, and the trimethylaluminum gas is input into the reaction chamber through the upper passage of the layered gas distribution box to promote the growth of the epitaxial layer on the surface-etched silicon carbide substrate, the P-type silicon carbide epitaxial wafer with uniform doping concentration is prepared, and the method further comprises: The P-type silicon carbide epitaxial wafer is subjected to doping concentration testing to ensure that the doping concentration of the P-type silicon carbide epitaxial wafer is uniform.

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