Growth method for reducing Pit defect on epitaxial surface of silicon carbide

Abstract

The invention discloses a growth method for reducing a Pit defect on a silicon carbide epitaxial surface, which comprises the following steps of: after epitaxial growth is completed, increasing the air flotation flow of a base, increasing the temperature in a reaction chamber, reducing the pressure in the reaction chamber and increasing the hydrogen flow, and entering an etching stage; hydrogen chloride gas is introduced discontinuously in the etching stage, and at least one introduction time period and an interruption time period after the introduction time period are included; the thermal instability of SiC at high temperature / low pressure is utilized, efficient decomposition is achieved through an H2 / HCl synergistic etching system, sub-damage and dislocation are reduced while the etching rate is increased, the thickness of the removed epitaxial layer can be accurately controlled, the Pit defect of the surface layer of the epitaxial layer is reduced, the crystallization quality of the epitaxial layer is kept, and the subsequent power device preparation requirement is met.

Description

Technical Field

[0001] The present invention belongs to the technical field of silicon carbide epitaxy, and in particular relates to a growth method for reducing pit defects on the surface of silicon carbide epitaxy. Background Art

[0002] Compared to traditional Si devices, 4H-SiC, with its excellent material properties such as wide bandgap, high breakdown electric field, and high thermal conductivity, has demonstrated revolutionary advantages in high-voltage and high-power applications such as new energy vehicles, rail transit, and smart grids. In particular, it has gradually replaced silicon-based IGBT devices in high-voltage applications above 1200V. However, the excellent performance of the device is highly dependent on the preparation of high-quality epitaxial layers. During the SiC epitaxial growth process (typically using chemical vapor deposition (CVD)), various crystal defects are inevitably generated. The presence of these defects can seriously degrade the device's electrical performance and long-term reliability.

[0003] Early research and technological breakthroughs focused primarily on fatal defects that directly lead to device failure. For example, triangle defects can cause device short circuits or premature breakdown; carrot defects severely impact carrier transport and blocking properties; and stacking faults reduce carrier mobility, increase conduction losses, and potentially degrade the forward voltage of bipolar devices. In recent years, with the continuous advancement of epitaxial growth technology, technologies to control these fatal defects have rapidly developed and matured. However, the impact of non-fatal defects such as pit defects on device performance has gradually become apparent, posing new challenges that restrict device performance and reliability.

[0004] Pit (small pit) defects are small depressions or pits on the surface of the SiC epitaxial layer. Figure 1 As shown, these pits are typically micron or submicron in size, less than 20nm in depth, and possess diverse morphologies. The presence of pit defects can increase device leakage current, thereby impacting long-term device reliability. Therefore, optimizing processes and effectively reducing pit defects on epitaxial surfaces are crucial for the development of silicon carbide. Summary of the Invention

[0005] The present invention addresses the deficiencies in the prior art and provides a growth method for reducing pit defects on the epitaxial surface of silicon carbide.

[0006] In order to achieve the above objectives, the technical solution of the present invention is:

[0007] A growth method for reducing pit defects on a silicon carbide epitaxial surface comprises the following steps:

[0008] 1) Complete epitaxial growth of silicon carbide in a reaction chamber, with the epitaxial thickness being greater than the target thickness; during epitaxial growth, the substrate is placed on a susceptor in the reaction chamber, and the susceptor remains in an air-floating state;

[0009] 2) After the epitaxial growth is completed, the growth source is turned off, the flotation flow rate of the susceptor is increased, the temperature in the reaction chamber is increased, the pressure in the reaction chamber is reduced, and the hydrogen flow rate is increased before entering the etching phase; the etching phase comprises discontinuously introducing hydrogen chloride gas, including at least one introduction period and an interruption period after the introduction period; the etching phase etches the epitaxial layer to a target thickness;

[0010] 3) After etching is completed, turn off the hydrogen chloride source, reduce the flotation flow of the susceptor, reduce the hydrogen flow, increase the pressure of the reaction chamber to atmospheric pressure, and reduce the temperature of the reaction chamber to room temperature in a hydrogen atmosphere;

[0011] 4) Turn off the hydrogen flow and flotation flow, fill the reaction chamber with inert gas, open the reaction chamber and take out the epitaxial wafer.

[0012] Optionally, in step 2), the temperature in the reaction chamber during the etching stage is 1700° C. to 1750° C., and the pressure in the reaction chamber is 30 mbar to 80 mbar.

[0013] Optionally, in step 2), the hydrogen flow rate in the etching stage is 250 slm to 350 slm.

[0014] Optionally, in step 2), the flotation flow rate in the etching stage is 2000 sccm to 2500 sccm.

[0015] Optionally, in step 2), one of the input period and one of the interruption period is considered as one cycle, and the etching stage includes multiple cycles.

[0016] Optionally, the flow rate of hydrogen chloride during the introduction period is 1500 to 2000 sccm, and the duration is 10 seconds to 1 minute; the flow rate of hydrogen chloride during the interruption period is 0, and the duration is 30 seconds to 2 minutes.

[0017] Optionally, the thickness of the surface layer of the epitaxial layer removed in the etching stage is 0.1 μm to 0.2 μm.

[0018] Optionally, the epitaxial growth conditions in step 1) include: hydrogen flow rate of 80 slm to 200 slm, flotation flow rate of 500 scmm to 1000 scmm, reaction chamber temperature of 1600° C. to 1650° C., and reaction chamber pressure of 150 mbar to 250 mbar.

[0019] Optionally, in step 3), the temperature of the reaction chamber is lowered to 1000°C to 1200°C within 5 minutes to 15 minutes, while the flotation flow rate of the base is reduced to 50 sccm to 150 sccm, the hydrogen flow rate is reduced to 50 slm to 150 slm, the pressure of the reaction chamber is increased to atmospheric pressure, and then the temperature of the reaction chamber is lowered to room temperature.

[0020] A silicon carbide epitaxial wafer obtained by the above-mentioned growth method for reducing pit defects on the surface of silicon carbide epitaxial wafer, wherein the distribution density of pit defects on the surface of the epitaxial wafer is less than 0.1 / cm 2 .

[0021] The beneficial effects of the present invention are:

[0022] After the epitaxial growth is completed, an etching stage is introduced. Utilizing the thermal instability of SiC at high temperature and low pressure, an H2 / HCl collaborative etching system is used to achieve efficient decomposition. Through HCl's dynamic bond weakening-repair mechanism and its strong etching action, the Si-C bonds on the epitaxial layer surface are destroyed. Selective etching is then achieved in the pure H2 stage, increasing the etching rate while reducing sub-damage and dislocations. The introduction of HCl also reduces the probability of silicon droplets during the etching process. Simultaneously, the small plate is lifted by air flotation, and etching uniformity is enhanced through a higher rotation speed. Controlling the H2 / HCl collaborative process allows for precise control of the thickness of the removed epitaxial layer, ensuring the roughness of the epitaxial layer surface after treatment. This reduces pit defects on the epitaxial layer surface without the need for CMP (chemical mechanical polishing) and maintains the crystallinity of the epitaxial layer, meeting the requirements for subsequent power device fabrication.

[0023] Other features and advantages of the present invention will be set forth in the following description, and in part will be obvious from the description, or may be learned by practicing the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the morphology of pit defects in the prior art;

[0025] Figure 2 Schematic diagram of the process conditions of the growth method of Example 1;

[0026] Figure 3 The pits defect distribution diagram of three epitaxial wafers obtained by the growth method of Example 1 (SICA detection);

[0027] Figure 4 Surface roughness test images of three epitaxial wafers obtained by the growth method of Example 1;

[0028] Figure 5 This is the pits defect distribution diagram of the epitaxial wafer obtained by the growth method of Comparative Example 1 (SICA detection);

[0029] Figure 6 This is the pits defect distribution diagram of the epitaxial wafer obtained by the growth method of Example 2 (SICA detection);

[0030] Figure 7Surface roughness test images of three epitaxial wafers obtained by the growth method of Example 2;

[0031] Figure 8 This is the pits defect distribution diagram of the epitaxial wafer obtained by the growth method of Example 3 (SICA detection);

[0032] Figure 9 Surface roughness test images of three epitaxial wafers obtained by the growth method of Example 3;

[0033] Figure 10 This is the pits defect distribution diagram of the epitaxial wafer obtained by the growth method of Example 4 (SICA detection);

[0034] Figure 11 Surface roughness test images of three epitaxial wafers obtained by the growth method of Example 4;

[0035] Figure 12 This is the pits defect distribution diagram of the epitaxial wafer obtained by the growth method of Example 5 (SICA detection);

[0036] Figure 13 This is a surface roughness test image of three epitaxial wafers obtained by the growth method of Example 5. DETAILED DESCRIPTION

[0037] The present invention will be further explained below with reference to the accompanying drawings and specific examples. Although preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in the art or in the product specifications shall be followed.

[0038] The embodiment's method for reducing pit defects on the surface of silicon carbide epitaxial growth involves performing precise micro-etching of the epitaxial layer surface in situ within a reaction chamber after the silicon carbide epitaxial growth is completed, followed by cooling and wafer removal. The etching process employed, under high-temperature, low-pressure conditions, employs alternating HCl / H2 etching, coupled with high-flow flotation, effectively eliminating pit defects on the epitaxial layer surface while maintaining the epitaxial layer's crystalline quality.

[0039] Silicon carbide epitaxial growth can be achieved using known growth processes, including substrate cleaning and etching, and the growth of buffer and epitaxial layers. For example, after a standard cleaning, the silicon carbide substrate is placed on a susceptor (i.e., a small plate used to support the substrate) within a reaction chamber. The reaction chamber is evacuated, and then hydrogen is introduced. The temperature is raised, and the plate is floated using, for example, argon to maintain the floated state while the substrate is etched. Growth and doping sources are then introduced, and the buffer and epitaxial layers are sequentially grown under appropriate growth conditions.

[0040] Growth sources include carbon and silicon sources. Common silicon carbide growth materials can be used. Silicon sources include, but are not limited to, TCS (SiHCl3), and carbon sources include, but are not limited to, ethylene (C2H4). Doping sources can include, but are not limited to, high-purity nitrogen (N2) or trimethylaluminum.

[0041] To reduce pit defects, epitaxial growth is conducted based on the formation mechanism of pit defects. By optimizing epitaxial process parameters, the growth temperature or the C / Si ratio is lowered, thereby reducing pit defects. For example, epitaxial growth conditions include: a hydrogen flow rate of 80 slm to 200 slm, a flotation flow rate of 500 scmm to 1000 scmm, a reaction chamber temperature of 1600°C to 1650°C, and a reaction chamber pressure of 150 mbar to 250 mbar. The epitaxial thickness is greater than the target thickness to reserve a sufficient amount for removal in the subsequent etching stage.

[0042] After the epitaxial growth is completed, the growth source and doping source are turned off, the flotation flow of the base is increased, the temperature in the reaction chamber is raised, the pressure in the reaction chamber is lowered, and the hydrogen flow is increased before entering the etching stage. Hydrogen chloride gas is introduced discontinuously during the etching stage. Specifically, hydrogen is continuously introduced into the reaction chamber, and within 2 to 3 minutes, the hydrogen flow rate is increased from 80slm to 200slm in the epitaxial stage to 250slm to 350slm. At the same time, the small disk flotation (argon) flow rate is increased from 500 to 1000scmm in the epitaxial stage to 2000 to 2500sccm; the pressure is reduced from 150mbar to 250mbar in the epitaxial stage to 30mbar to 80mbar; and the temperature is increased from 1600 to 1650°C in the epitaxial stage to 1700 to 1750°C. After the above conditions remain constant, hydrogen chloride gas is introduced. The discontinuity mentioned here means that during the etching stage, hydrogen chloride gas is introduced intermittently, and there is at least one introduction period and an interruption period after the introduction period. Furthermore, with one introduction period and one interruption period as a cycle, the etching stage can be similar to a pulse, including multiple consecutive cycles, to form a periodic pulse etching environment. The hydrogen chloride flow rate during the introduction period is 1500-2000sccm, and the duration is 10s-1min; the hydrogen chloride flow rate during the interruption period is 0, and the duration is 30s-2min. The number of cycles can be adjusted according to the actual etching thickness requirements to accurately control the thickness of the removed epitaxial layer and ultimately achieve the target thickness of the epitaxial wafer. For the purpose of effectively eliminating pits defects with a depth of 3-20nm, the number of cycles can be, for example, 3 to 8, removing 0.1-0.2μm epitaxial surface layer.

[0043] In the SiC epitaxial growth process, SiC decomposes slowly due to its highly stable physical and chemical properties. However, it decomposes more readily under high temperature and low pressure. Therefore, the etching phase increases the temperature and reduces the pressure within the reaction chamber compared to the epitaxial phase. Since H2 reacts readily with C to form CxHx, and HCl reacts with Si to form SiCl, accelerating the decomposition of SiC, the addition of H2+HCl is more effective. During the HCl addition phase, the strong etching action quickly destroys the Si-C bonded lattice structure on the epitaxial wafer surface, making the epitaxial layer surface more susceptible to etching. However, this strong etching action can damage the epitaxial layer surface lattice structure, resulting in dislocations or sub-damage. Therefore, intermittent HCl addition is beneficial. By alternating small amounts of HCl to disrupt the epitaxial layer surface structure, followed by H2-assisted selective etching, the epitaxial layer surface is micro-etched without adding new dislocations or damage. Furthermore, the introduction of HCl reduces the formation of "silicon droplets" on the epitaxial wafer surface, improving the quality of the epitaxial layer.

[0044] During the etching phase, increasing the flotation flow rate of the small plate to 1.5-2 times that of conventional processes accelerates the rotation speed of the epitaxial wafer on the small plate, which promotes uniform etching of the epitaxial wafer surface. Overall, this process acts similarly to chemical mechanical polishing of the epitaxial wafer surface. By controlling the etching phase time and etching efficiency, the thickness of the epitaxial layer on the epitaxial wafer surface is reduced, thereby reducing pits on the epitaxial wafer surface and maintaining excellent surface roughness.

[0045] After etching is complete, the hydrogen chloride source is turned off, and the temperature of the reaction chamber is lowered to 1000°C to 1200°C over 5 to 15 minutes. Simultaneously, the susceptor flotation flow rate is reduced to 50 sccm to 150 sccm, the hydrogen flow rate is reduced to 50 slm to 150 slm, the reaction chamber pressure is raised to atmospheric pressure, and the reaction chamber temperature is lowered to room temperature in a hydrogen atmosphere. Subsequently, the hydrogen flow rate and the small plate flotation flow rate are turned off, and an inert gas is introduced to replace the hydrogen in the reaction chamber. The reaction chamber is evacuated and maintained for 3 to 10 minutes. Subsequently, the reaction chamber is filled with inert gas to atmospheric pressure, the reaction chamber is opened, and the epitaxial wafer is removed. The inert gas described here is a gas corresponding to an element in Group 0 of the periodic table, such as argon.

[0046] Example 1

[0047] The silicon carbide film growth method using TCS+ethylene, the main parameters change as follows Figure 2 The steps are described in detail below.

[0048] Step 1: Select an 8-inch silicon carbide substrate with a silicon surface that is 4° tilted toward the <11-20> direction, perform standard cleaning, and then place the substrate on a small plate in the reaction chamber.

[0049] Step 2: Evacuate the reaction chamber to a vacuum state, then introduce hydrogen, maintain the hydrogen flow rate at 200 slm, and the reaction chamber pressure at 200 mbar. Raise the temperature of the reaction chamber from room temperature to 1650°C, set the small plate flotation (argon) flow rate at 800 slm, and perform constant temperature etching for 10 minutes. Change the hydrogen flow rate in the reaction chamber to 200 slm and the temperature to 1650°C. After the pressure stabilizes, introduce TCS (SiHCl3) gas + ethylene (C2 H4) gas into the reaction chamber, set the TCS flow rate to 40 slm, the C / Si ratio to 1, the doping source to high-purity nitrogen, the growth thickness to ~0.5 μm, and the doping concentration to ~1E18 / cm 3 buffer layer; keep the temperature, pressure and hydrogen flow constant, control the TCS flow rate to 280slm, C / Si to 1.2, and the doping concentration to 1E16 / cm 3 , grow to a target thickness of +0.1um, and an epitaxial layer with a target doping concentration.

[0050] Step 3: After the epitaxial layer growth is completed, the growth source gas and the doping source are turned off, and hydrogen is continuously introduced into the reaction chamber. In addition, within 2 minutes, the hydrogen flow rate is increased to 300slm. At the same time, the small disk flotation (argon) flow rate is increased to 2000sccm; the pressure is reduced to 50mbar; the temperature is increased to 1700°C and kept constant. Subsequently, hydrogen chloride (HCl) is intermittently introduced in a pulse-like manner, with an HCl flow rate of 1500sccm, that is, HCl is introduced instantaneously and kept constant for 30s (i.e., the introduction period), then HCl is turned off, and after 1min (i.e., the interruption period), HCl is introduced instantaneously again and kept constant for 30s (i.e., the introduction period), and so on. Four cycles are repeated to form a periodic pulse etching environment to etch the surface of the epitaxial layer.

[0051] Step 4: Turn off the HCl source and reduce the temperature to 1000-1200°C within 10 minutes. At the same time, reduce the small plate flotation flow rate to 100 seem and the hydrogen flow rate to 100 slm. Raise the reaction chamber pressure to atmospheric pressure and then reduce the reaction chamber temperature to room temperature in a hydrogen atmosphere.

[0052] Step 5: Turn off the hydrogen flow and the small plate flotation flow, introduce argon to replace the hydrogen in the reaction chamber, evacuate the reaction chamber and maintain it for 5 minutes, then fill the reaction chamber with argon to atmospheric pressure, open the reaction chamber, and take out the epitaxial wafer.

[0053] The above growth method was used to continuously grow three 8-inch epitaxial wafers, and the pits defect distribution diagram (SICA detection) is shown as follows: Figure 3 As shown, the surface roughness is Figure 4 shown.

[0054] Comparative Example 1

[0055] Comparative Example 1 uses a TCS+ethylene silicon carbide epitaxial growth method, and the steps are as follows:

[0056] Step 1 and step 2 are the same as in Example 1, and an epitaxial layer is grown to a target thickness and a target doping concentration.

[0057] Step 3: After the epitaxial layer growth is completed, turn off the growth source gas and doping source, and within 10 minutes, reduce the temperature to 1000-1200°C. At the same time, reduce the small plate flotation flow rate to 100 sccm, reduce the hydrogen flow rate to 100 slm, increase the reaction chamber pressure to atmospheric pressure, and then reduce the reaction chamber temperature to room temperature in a hydrogen atmosphere.

[0058] Step 4: Turn off the hydrogen flow and the small plate flotation flow, introduce argon to replace the hydrogen in the reaction chamber, evacuate the reaction chamber and maintain it for 5 minutes, then fill the reaction chamber with argon to atmospheric pressure, open the reaction chamber, and take out the epitaxial wafer.

[0059] The above method is used to grow an 8-inch epitaxial wafer, and its pits defect distribution diagram (SICA detection) is as follows Figure 5 shown.

[0060] Depend on Figure 5 It can be seen that the number of pits defects in the epitaxial wafer of Comparative Example 1, which did not undergo the etching stage after epitaxial layer growth, was 656. Figure 3 It can be seen that in Example 1, after the etching process of the epitaxial layer growth, the pit defects of three consecutive epitaxial wafers are 20, 26 and 26 respectively, which are all less than 30. Converted into distribution density, the distribution density of pit defects is 0.068 pcs / cm 2 、0.088pcs / cm 2 、0.088pcs / cm 2 , all less than 0.1pcs / cm 2 , significantly reducing the surface defects of silicon carbide epitaxial films.

[0061] Depend on Figure 4 It can be seen that in Example 1, through the etching stage process after the epitaxial layer growth, the surface roughness Rq of three consecutive epitaxial wafers are 0.179 nm, 0.172 nm and 0.149 nm, respectively, all less than 0.2 nm, and the surface of the epitaxial wafer maintains excellent roughness.

[0062] Example 2

[0063] The silicon carbide film growth method using TCS+ethylene is as follows:

[0064] Step 1 and step 2 are the same as in Example 1. An epitaxial layer is grown to a target thickness of +0.15 μm and a doping concentration of the target doping concentration.

[0065] Step 3: After the epitaxial layer growth is completed, the growth source gas and the doping source are turned off, and hydrogen is continuously introduced into the reaction chamber. In addition, within 2 minutes, the hydrogen flow rate is increased to 300slm. At the same time, the small disk flotation (argon) flow rate is increased to 2000sccm; the pressure is reduced to 60mbar; the temperature is increased to 1720°C and kept constant. Subsequently, hydrogen chloride (HCl) is intermittently introduced in a pulse-like manner, with an HCl flow rate of 1500sccm, that is, HCl is introduced instantaneously and kept constant for 1min (i.e., the introduction period), then HCl is turned off, and after 1min (i.e., the interruption period), HCl is introduced instantaneously again and kept constant for 1min (i.e., the introduction period), and so on. Repeat five cycles to form a periodic pulse etching environment to etch the surface of the epitaxial layer.

[0066] Step 4 and step 5 are the same as in Example 1.

[0067] The above growth method was used to continuously grow three 8-inch epitaxial wafers, and the pits defect distribution diagram (SICA detection) is shown as follows: Figure 6 As shown in the figure, it can be seen that in Example 2, after the etching process of the epitaxial layer growth, the pit defects of three consecutive epitaxial wafers are 25, 19, and 23 respectively. Converted into distribution density, the distribution density of pit defects is 0.084 pcs / cm 2 、0.064pcs / cm 2 、0.078pcs / cm 2 , significantly reducing the surface defects of silicon carbide epitaxial films.

[0068] Depend on Figure 7 It can be seen that in Example 2, through the etching stage process after the epitaxial layer growth, the surface roughness Rq of three consecutive epitaxial wafers are 0.146nm, 0.151nm and 0.148nm, respectively, which are all less than 0.2nm. The surface of the epitaxial wafer maintains excellent roughness.

[0069] Example 3

[0070] The silicon carbide film growth method using TCS+ethylene is as follows:

[0071] Step 1 and step 2 are the same as in Example 1. An epitaxial layer is grown to a target thickness of +0.10 μm and a doping concentration of the target doping concentration.

[0072] Step 3: After the epitaxial layer growth is completed, the growth source gas and the doping source are turned off, and hydrogen is continuously introduced into the reaction chamber. In addition, within 2 minutes, the hydrogen flow rate is increased to 300slm. At the same time, the small disk flotation (argon) flow rate is increased to 2500sccm; the pressure is reduced to 80mbar; the temperature is increased to 1750°C and kept constant. Subsequently, hydrogen chloride (HCl) is intermittently introduced in a pulse-like manner, with an HCl flow rate of 1500sccm, that is, HCl is introduced instantaneously and kept constant for 10s (i.e., the introduction period), then HCl is turned off, and after 30s (i.e., the interruption period), HCl is introduced instantaneously again and kept constant for 10s (i.e., the introduction period), and so on. Repeat three cycles to form a periodic pulse etching environment to etch the epitaxial layer surface.

[0073] Step 4 and step 5 are the same as in Example 1.

[0074] The above growth method was used to continuously grow three 8-inch epitaxial wafers, and the pits defect distribution diagram (SICA detection) is shown as follows: Figure 8 As shown in the figure, it can be seen that in Example 3, after the etching process of the epitaxial layer growth, the pit defects of three consecutive epitaxial wafers are 25, 17, and 26 respectively. Converted into distribution density, the distribution density of pit defects is 0.085 pcs / cm 2 、0.058pcs / cm 2 、0.088pcs / cm 2 , significantly reducing the surface defects of silicon carbide epitaxial films.

[0075] Depend on Figure 9 It can be seen that in Example 3, through the etching stage process after the epitaxial layer growth, the surface roughness Rq of three consecutive epitaxial wafers are 0.148nm, 0.153nm and 0.155nm, respectively, all less than 0.2nm, and the epitaxial wafer surface maintains excellent roughness.

[0076] Example 4

[0077] The silicon carbide film growth method using TCS+ethylene is as follows:

[0078] Step 1 and step 2 are the same as in Example 1. An epitaxial layer is grown to a target thickness of +0.12 μm and a doping concentration of the target doping concentration.

[0079] Step 3: After the epitaxial layer growth is completed, the growth source gas and the doping source are turned off, and hydrogen is continuously introduced into the reaction chamber. In addition, within 2 minutes, the hydrogen flow rate is increased to 350slm. At the same time, the small disk flotation (argon) flow rate is increased to 2000sccm; the pressure is reduced to 40mbar; the temperature is increased to 1700°C and kept constant. Subsequently, hydrogen chloride (HCl) is intermittently introduced in a pulse-like manner, with an HCl flow rate of 1600sccm, that is, HCl is introduced instantaneously and kept constant for 1min (i.e., the introduction period), then HCl is turned off, and after 2min (i.e., the interruption period), HCl is introduced instantaneously again and kept constant for 1min (i.e., the introduction period), and so on. Four cycles are repeated to form a periodic pulse etching environment to etch the surface of the epitaxial layer.

[0080] Step 4 and step 5 are the same as in Example 1.

[0081] The above growth method was used to continuously grow three 8-inch epitaxial wafers, and the pits defect distribution diagram (SICA detection) is shown as follows: Figure 10 As shown in the figure, it can be seen that in Example 4, after the etching process of the epitaxial layer growth, the pit defects of three consecutive epitaxial wafers are 15, 17, and 24 respectively. Converted into distribution density, the distribution density of pit defects is 0.051 pcs / cm 2 、0.058pcs / cm 2 、0.081pcs / cm 2 , significantly reducing the surface defects of silicon carbide epitaxial films.

[0082] Depend on Figure 11 It can be seen that in Example 4, through the etching stage process after the epitaxial layer growth, the surface roughness Rq of three consecutive epitaxial wafers are 0.158nm, 0.152nm and 0.153nm, respectively, all less than 0.2nm, and the epitaxial wafer surface maintains excellent roughness.

[0083] Example 5

[0084] The silicon carbide film growth method using TCS+ethylene is as follows:

[0085] Step 1 and step 2 are the same as in Example 1. An epitaxial layer is grown to a target thickness of +0.10 μm and a doping concentration of the target doping concentration.

[0086] Step 3: After the epitaxial layer growth is completed, the growth source gas and the doping source are turned off, and hydrogen is continuously introduced into the reaction chamber. In addition, within 2 minutes, the hydrogen flow rate is increased to 250slm. At the same time, the small disk flotation (argon) flow rate is increased to 2000sccm; the pressure is reduced to 30mbar; the temperature is increased to 1750°C and kept constant. Subsequently, hydrogen chloride (HCl) is intermittently introduced in a pulse-like manner, with an HCl flow rate of 2000sccm, that is, HCl is introduced instantaneously and kept constant for 30s (i.e., the introduction period), then HCl is turned off, and after 1min (i.e., the interruption period), HCl is introduced instantaneously again and kept constant for 30s (i.e., the introduction period), and so on. Repeat two cycles to form a periodic pulse etching environment to etch the epitaxial layer surface.

[0087] Step 4 and step 5 are the same as in Example 1.

[0088] The above growth method was used to continuously grow three 8-inch epitaxial wafers, and the pits defect distribution diagram (SICA detection) is shown as follows: Figure 12 As shown in the figure, it can be seen that in Example 5, after the etching process of the epitaxial layer growth, the pit defects of three consecutive epitaxial wafers are 21, 15, and 23 respectively. Converted into distribution density, the distribution density of pit defects is 0.071 pcs / cm 2 、0.051pcs / cm 2 、0.071pcs / cm 2 , significantly reducing the surface defects of silicon carbide epitaxial films.

[0089] Depend on Figure 13 It can be seen that in Example 5, through the etching stage process after the epitaxial layer growth, the surface roughness Rq of three consecutive epitaxial wafers are 0.136nm, 0.157nm and 0.158nm, respectively, which are all less than 0.2nm. The surface of the epitaxial wafer maintains excellent roughness.

[0090] The above embodiments are only used to further illustrate a growth method of the present invention for reducing pit defects on the epitaxial surface of silicon carbide, but the present invention is not limited to the embodiments. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention fall within the scope of protection of the technical solution of the present invention.

Claims

1. A growth method for reducing pit defects on the surface of silicon carbide epitaxial growth, characterized in that: The following steps are involved: 1) Complete epitaxial growth of silicon carbide in a reaction chamber, with the epitaxial thickness being greater than the target thickness; during epitaxial growth, the substrate is placed on a susceptor in the reaction chamber, and the susceptor remains in an air-floating state; 2) After the epitaxial growth is completed, the growth source is turned off, the flotation flow rate of the susceptor is increased, the temperature in the reaction chamber is increased, the pressure in the reaction chamber is reduced, and the hydrogen flow rate is increased before entering the etching stage; The HCl gas is introduced discontinuously during the etching phase, including at least one introduction period and an interruption period after the introduction period; the epitaxial layer is etched to a target thickness during the etching phase; 3) After etching is completed, turn off the hydrogen chloride source, reduce the flotation flow of the susceptor, reduce the hydrogen flow, increase the pressure of the reaction chamber to atmospheric pressure, and reduce the temperature of the reaction chamber to room temperature in a hydrogen atmosphere; 4) Turn off the hydrogen flow and flotation flow, fill the reaction chamber with inert gas, open the reaction chamber and take out the epitaxial wafer.

2. The method for reducing pit defects on the surface of silicon carbide epitaxial growth according to claim 1, characterized in that: In step 2), the temperature in the reaction chamber during the etching stage is 1700° C. to 1750° C., and the pressure in the reaction chamber is 30 mbar to 80 mbar.

3. The method for reducing pit defects on the surface of silicon carbide epitaxial growth according to claim 1, characterized in that: In step 2), the hydrogen flow rate in the etching stage is 250 slm to 350 slm.

4. The method for reducing pit defects on the surface of silicon carbide epitaxial growth according to claim 1, characterized in that: In step 2), the flotation flow rate in the etching stage is 2000 sccm to 2500 sccm.

5. The method for reducing pit defects on the surface of silicon carbide epitaxial growth according to claim 1, wherein: In step 2), one of the input period and one of the interruption period is considered as one cycle, and the etching stage includes multiple cycles.

6. The method for reducing pit defects on the surface of silicon carbide epitaxial growth according to claim 1, characterized in that: The flow rate of hydrogen chloride during the introduction period is 1500 to 2000 sccm, and the duration is 10 seconds to 1 minute; the flow rate of hydrogen chloride during the interruption period is 0, and the duration is 30 seconds to 2 minutes.

7. The method for reducing pit defects on the surface of silicon carbide epitaxial growth according to claim 1, characterized in that: The thickness of the surface layer of the epitaxial layer removed in the etching stage is 0.1 μm to 0.2 μm.

8. The method for reducing pit defects on the surface of silicon carbide epitaxial growth according to claim 1, characterized in that: The conditions for the epitaxial growth in step 1) include: a hydrogen flow rate of 80 slm to 200 slm, a flotation flow rate of 500 sccm to 1000 sccm, a temperature in the reaction chamber of 1600° C. to 1650° C., and a pressure in the reaction chamber of 150 mbar to 250 mbar.

9. The method for reducing pit defects on the surface of silicon carbide epitaxial growth according to claim 1, wherein: In step 3), the temperature of the reaction chamber is lowered to 1000°C to 1200°C within 5 minutes to 15 minutes, while the flotation flow rate of the susceptor is reduced to 50 sccm to 150 sccm, the hydrogen flow rate is reduced to 50 slm to 150 slm, the pressure of the reaction chamber is increased to atmospheric pressure, and then the temperature of the reaction chamber is lowered to room temperature.

10. A silicon carbide epitaxial wafer, characterized in that: The silicon carbide epitaxial wafer is obtained by the growth method for reducing pit defects on the surface of silicon carbide epitaxial wafer according to any one of claims 1 to 9, and the distribution density of pit defects on the surface of the epitaxial wafer is less than 0.1 pcs / cm 2 .

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