Epitaxial growth method and epitaxial wafer

Abstract

The embodiment of the invention discloses an epitaxial growth method and an epitaxial wafer, and the method comprises the steps: carrying out the minority carrier lifetime test of a first epitaxial wafer, and obtaining the minority carrier lifetime of the first epitaxial wafer; when the minority carrier lifetime of the first epitaxial wafer is less than a set first threshold value, determining a first gas flow of a slit carrier gas introduced into a reaction chamber; and manufacturing a second epitaxial wafer based on the first gas flow of the slit carrier gas.

Description

Technical Field

[0001] The disclosed embodiments relate to the field of semiconductor manufacturing technology, and in particular to an epitaxial growth method and an epitaxial wafer. Background Art

[0002] Epitaxial growth technology is a technology that can achieve the growth of an epitaxial layer on a polished wafer. The conductivity type, resistivity and structure of the grown epitaxial layer are different from those of the polished wafer. It can meet the production requirements of a variety of different semiconductor devices and greatly improve the flexibility and performance of semiconductor device design.

[0003] With the rapid development of semiconductor industry technology, the requirements for epitaxial wafer quality are getting higher and higher, especially for the minority carrier lifetime (MCLT) level of epitaxial wafers. It is known that the MCLT level of epitaxial wafers has an important relationship with the content of metal impurities in them. During the epitaxial growth process, if the content of metal impurities in the reaction chamber is too high, the epitaxial wafers produced will have too high metal impurities, which will affect the MCLT level of the epitaxial wafers. Summary of the invention

[0004] In view of this, the embodiments of the present disclosure are intended to provide an epitaxial growth method and an epitaxial wafer, which can obtain an epitaxial wafer with a MCLT greater than or equal to 2200us.

[0005] The technical solution of the embodiment of the present disclosure is implemented as follows: In a first aspect, an embodiment of the present disclosure provides an epitaxial growth method, the epitaxial growth method comprising: Performing a minority carrier lifetime test on the first epitaxial wafer to obtain the minority carrier lifetime of the first epitaxial wafer; When the minority carrier lifetime of the first epitaxial wafer is less than a set first threshold, determining a first gas flow rate of the slit carrier gas introduced into the reaction chamber; Based on the first gas flow rate of the slit carrier gas, a second epitaxial wafer is manufactured; wherein the minority carrier lifetime of the second epitaxial wafer is greater than or equal to 2200 us.

[0006] In some examples, the first gas flow rate of the slit carrier gas is 20 slm to 35 slm.

[0007] In some examples, the epitaxial growth method further includes: Based on the resistivity at different positions on the epitaxial layer of the second epitaxial wafer, obtaining a first characteristic value characterizing the resistivity uniformity of the epitaxial layer of the second epitaxial wafer; When the first characteristic value is greater than a set second threshold value, the first power ratio and the second power ratio in the epitaxial growth process are adjusted according to the resistivity at the center position and the resistivity at the edge position of the epitaxial layer of the second epitaxial wafer; wherein the first power ratio is the ratio of the power of the heating component located at the center position above the reaction chamber to the sum of the powers of the heating components located at different positions above the reaction chamber; the second power ratio is the ratio of the power of the heating component located at the center position below the reaction chamber to the sum of the powers of the heating components located at different positions below the reaction chamber; Based on the adjusted first power ratio and second power ratio, the second epitaxial wafer is remanufactured.

[0008] In some examples, the adjustment range of the first power ratio is 66% to 82%, and the adjustment range of the second power ratio is 16% to 20%.

[0009] In some examples, when the first power ratio increases or decreases synchronously with the second power ratio, and the first power ratio is adjusted by a first adjustment amount and the second power ratio is adjusted by a second adjustment amount, the ratio of the first adjustment amount to the second adjustment amount is in the range of 3:1 to 5:1.

[0010] In some examples, when the first characteristic value is greater than a set second threshold, adjusting the first power ratio and the second power ratio in the epitaxial growth process according to the resistivity at the center position and the resistivity at the edge position of the epitaxial layer of the second epitaxial wafer includes: When the first characteristic value is greater than the second threshold, When the resistivity at the center position of the epitaxial layer of the second epitaxial wafer is greater than the resistivity at the edge position, increasing the first power ratio and the second power ratio; or When the resistivity at the center position of the epitaxial layer of the second epitaxial wafer is smaller than the resistivity at the edge position of the epitaxial layer of the second epitaxial wafer, the first power ratio and the second power ratio are reduced.

[0011] In some examples, the epitaxial growth method further includes: After the second epitaxial wafer is remanufactured, when the first characteristic value of the epitaxial layer of the second epitaxial wafer is greater than the second threshold value, determining a second gas flow rate of the slit carrier gas introduced into the reaction chamber; wherein the second gas flow rate is less than the first gas flow rate, and the second gas flow rate is 20 slm to 35 slm; Based on the second gas flow rate, the second epitaxial wafer is re-manufactured; wherein the first characteristic value of the second epitaxial wafer re-manufactured is obtained.

[0012] In some examples, the epitaxial growth method further includes: Detecting the thickness of the epitaxial layer of the second epitaxial wafer to obtain a second characteristic value characterizing the thickness uniformity of the epitaxial layer of the second epitaxial wafer; When the second characteristic value is greater than a set third threshold, the gas flow ratio during the epitaxial growth process is adjusted; wherein the gas flow ratio is the ratio of the gas flow of the reaction gas at the center position of the reaction chamber to the gas flow of the first gas inlet in the reaction chamber.

[0013] In some examples, when the second characteristic value is greater than a set third threshold, adjusting the gas flow ratio during the epitaxial growth process includes: When the thickness at the center of the epitaxial layer is less than the thickness at the edge, increasing the gas flow ratio; or When the thickness at the center of the epitaxial layer is greater than the thickness at the edge, the gas flow ratio is reduced.

[0014] In a second aspect, an embodiment of the present disclosure provides an epitaxial wafer, which is manufactured according to the epitaxial growth method described in the first aspect, and has a minority carrier lifetime greater than or equal to 2200µs.

[0015] In some examples, the first characteristic value of the epitaxial wafer is less than or equal to 2.7%, and the second characteristic value is less than or equal to 0.65%, wherein the first characteristic value is used to characterize the resistivity uniformity of the epitaxial layer of the epitaxial wafer, and the second characteristic value is used to characterize the thickness uniformity of the epitaxial layer of the epitaxial wafer.

[0016] The embodiments of the present disclosure provide an epitaxial growth method and an epitaxial wafer. In the present disclosure, the gas flow rate of the slit carrier gas is adjusted through the MCLT of the first epitaxial wafer, so that the slit carrier gas with a first gas flow rate is introduced into the reaction chamber, thereby reducing the metal impurity content in the epitaxial layer of the second epitaxial wafer, and finally improving the MCLT of the second epitaxial wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the structure of a reaction chamber used in an epitaxial growth process provided in an embodiment of the present disclosure; Figure 2 A schematic diagram of a process of an epitaxial growth method provided in one embodiment of the present disclosure; Figure 3When the slit carrier gas provided in the embodiment of the present disclosure is hydrogen, the MCLT corresponding to different first gas flow rates of the slit carrier gas; Figure 4 The first characteristic value corresponding to different first gas flow rates of the slit carrier gas provided in the embodiment of the present disclosure; Figure 5 A schematic diagram of a method for calculating a first eigenvalue provided by an embodiment of the present disclosure; Figure 6 A schematic diagram of a method for calculating a first eigenvalue provided by another embodiment of the present disclosure; Figure 7 A schematic diagram of a method for calculating a second eigenvalue provided by an embodiment of the present disclosure; Figure 8 A flow chart of an epitaxial growth method provided in accordance with another embodiment of the present disclosure. DETAILED DESCRIPTION

[0018] The technical solutions in the present disclosure will be described clearly and completely below in conjunction with the accompanying drawings in the present disclosure.

[0019] It should be noted that, for the sake of clarity, not all features of a specific implementation are described and illustrated in the specification and drawings. Furthermore, in order to avoid unnecessary details that obscure the technical solution focused on by the present disclosure, only the device structure and method steps closely related to the technical solution of the present disclosure are described and illustrated in the specification and drawings, while other details that are not closely related to the technical content of the present disclosure and are known to those skilled in the art are omitted.

[0020] In addition, the epitaxial growth process mentioned in the present disclosure may include a loading stage of a polished wafer, a heating stage, a baking stage, a vapor deposition stage, and an unloading stage of the epitaxial wafer.

[0021] As mentioned above, when the content of metal impurities in the reaction chamber is too high, the metal content of the epitaxial wafer produced will also be too high, which will in turn affect the MCLT level of the epitaxial wafer. In the related art, before the epitaxial growth begins, it is necessary to first confirm the content of metal impurities in the reaction chamber. If the content of metal impurities does not meet the requirements, it is necessary to clean the interior of the reaction chamber or even replace other reaction chambers. It is often necessary to replace the reaction chamber multiple times, and the operation cycle of the entire process is long.

[0022] like Figure 1 As shown, the reaction chamber 10 used in the epitaxial growth process generally includes two gas inlets, namely, a first gas inlet 101 and a second gas inlet 102. Figure 1, the direction of the first gas inlet 101 is exemplarily shown as being orthogonal to the direction of the second gas inlet 102. The first gas inlet 101 is also generally referred to as the main gas inlet, and is used to provide gas to the main area of ​​the reaction chamber 10, that is, mainly to provide gas above the polished wafer W placed on the base 103, and the gas includes hydrogen (i.e., the so-called main hydrogen (Main H2)), reaction gas, and dopant gas, etc. The second gas inlet 102 is also generally referred to as the auxiliary gas inlet, and is mainly used to provide gas to the area below the base 103 in the reaction chamber 10, and the gas includes hydrogen (i.e., the so-called slit hydrogen (Slit H2)). The gas flow rates of the first gas inlet 101 and the second gas inlet 102 can be controlled, for example, by valves. It should be noted that in the present disclosure, the introduction of main hydrogen and slit hydrogen into the reaction chamber 10 will continue throughout the entire epitaxial growth process.

[0023] In some examples, slit hydrogen can be used as a purge gas, as well as a carrier gas.

[0024] The inventors found that the reaction chamber can be cleaned by simply increasing the gas flow rate of the slit hydrogen, thereby improving the MCLT level of the epitaxial wafer. This is mainly because the slit hydrogen can purge the area below the susceptor 103, thereby inhibiting the diffusion of metal impurities in the area below the susceptor 103 to the area above the susceptor 103, thereby affecting the metal impurity content in the epitaxial wafer.

[0025] Based on this, see Figure 2 The present disclosure provides an epitaxial growth method, which specifically includes the following steps: S201, testing the minority carrier lifetime of the first epitaxial wafer to obtain the minority carrier lifetime of the first epitaxial wafer; S202, when the minority carrier lifetime of the first epitaxial wafer is less than a set first threshold, determining a first gas flow rate of the slit carrier gas introduced into the reaction chamber; S203 , manufacturing a second epitaxial wafer based on the first gas flow rate of the slit carrier gas; wherein the minority carrier lifetime of the second epitaxial wafer is greater than or equal to 2200 us.

[0026] First, in step S201, a MCLT test is performed on the first epitaxial wafer to obtain the MCLT of the first epitaxial wafer. It can be understood that the MCLT of the first epitaxial wafer can represent the current content of metal impurities in the reaction chamber.

[0027] In some examples, the MCLT of the first epitaxial wafer can be obtained by the conductivity decay method (CDM), that is, injecting non-equilibrium carriers into the epitaxial layer of the first epitaxial wafer, and then measuring the decay of the conductivity of the epitaxial layer of the first epitaxial wafer over time, so as to determine the MCLT of the first epitaxial wafer. Of course, in the present disclosure, other methods can also be used to obtain the MCLT of the first epitaxial wafer, such as the surface photovoltage method (SPV), that is, using light to irradiate the surface of the epitaxial layer of the first epitaxial wafer to generate a photovoltage signal, and then obtaining the corresponding MCLT by measuring the decay time of the photovoltage signal.

[0028] In step S202, when the set first threshold refers to the critical value of the minority carrier lifetime of the epitaxial wafer, it is determined according to the use requirements of the semiconductor device corresponding to the epitaxial wafer.

[0029] In some examples, the slit carrier gas may be hydrogen or other gas that can perform a purge function.

[0030] It can be understood that when the MCLT of the first epitaxial wafer is greater than the first threshold value, in order to make the MCLT level of the second epitaxial wafer meet the requirements in the present disclosure, the gas flow rate of the slit carrier gas is adjusted so that the slit carrier gas with a first gas flow rate is introduced into the reaction chamber 10, thereby suppressing the diffusion of metal impurities in the area below the base 203 to the area above the base 103, so as to reduce the metal impurity content in the epitaxial layer of the second epitaxial wafer, and ultimately improve the MCLT of the second epitaxial wafer.

[0031] for Figure 1 In the technical solution shown, in some possible implementations, the first gas flow rate of the slit carrier gas is 20 slm to 35 slm.

[0032] In the present disclosure, the first gas flow rate of the slit carrier gas is set to 20slm to 35slm, because this can further purge the metal impurities in the area below the susceptor 103 out of the reaction chamber 10, and prevent the metal impurities in the area below the susceptor 103 from diffusing to the area above the susceptor 103. On the one hand, if the first gas flow rate of the slit carrier gas is too small, the metal impurities in the area below the susceptor 103 cannot be completely purged out of the reaction chamber 10. On the other hand, if the first gas flow rate of the slit carrier gas is too large, the edge flatness of the second epitaxial wafer may be deteriorated. This is mainly because the increase in the first gas flow rate of the slit carrier gas may change the gas flow pattern inside the reaction chamber 20, thereby causing the reaction gas to be unevenly distributed on the surface of the polished wafer W, so as to affect the growth rate of the edge position of the second epitaxial wafer, thereby affecting the edge flatness. In addition, the increase in the first gas flow rate of the slit carrier gas may change the heat transfer efficiency inside the reaction chamber 103, resulting in uneven temperature distribution, thereby causing the growth rates of the center position and the edge position of the epitaxial layer to be inconsistent, thereby affecting the edge flatness.

[0033] See also Figure 3 , which shows the MCLT of the second epitaxial wafer when the slit carrier gas is hydrogen and the corresponding first gas flow rates are 5slm, 10slm, 20slm, 30slm and 40slm respectively. Figure 3 It can be seen that when the slit carrier gas is hydrogen and the corresponding first gas flow rate is 5slm and 10slm respectively, the MCLT of the second epitaxial wafer is about 1800µs and 2100µs respectively. When the slit carrier gas is hydrogen and the corresponding first gas flow rate is 20slm to 35slm, the MCLT of the second epitaxial wafer is greater than 2200µs. When the slit carrier gas is hydrogen and the corresponding first gas flow rate is 40slm, although the MCLT of the second epitaxial wafer is greater than 2200µs, when the first gas flow rate of the slit carrier gas is large during the specific implementation process, the edge flatness of the second epitaxial wafer will deteriorate.

[0034] In the present disclosure, although the MCLT level of the second epitaxial wafer is improved by introducing the slit carrier gas with the first gas flow rate into the reaction chamber 10, the increase in the gas flow rate of the slit carrier gas will have a negative impact on the resistivity distribution and thickness distribution at different positions on the epitaxial layer of the second epitaxial wafer. Therefore, in the present disclosure, after the MCLT level of the second epitaxial wafer meets the requirements, the resistivity distribution and thickness distribution at different positions on the epitaxial layer need to be detected. Figure 1 In some possible implementations of the technical solution shown, the epitaxial growth method further includes: Based on the resistivity at different positions on the epitaxial layer of the second epitaxial wafer, obtaining a first characteristic value characterizing the resistivity uniformity of the epitaxial layer of the second epitaxial wafer; When the first characteristic value is greater than a set second threshold value, the first power ratio and the second power ratio in the epitaxial growth process are adjusted according to the resistivity at the center position and the resistivity at the edge position on the epitaxial layer of the second epitaxial wafer; wherein the first power ratio is the ratio of the power of the heating component located at the center position above the reaction chamber to the sum of the powers of the heating components located at different positions above; the second power ratio is the ratio of the power of the heating component located at the center position below the reaction chamber to the sum of the powers of the heating components located at different positions below; Based on the adjusted first power ratio and second power ratio, a second epitaxial wafer is remanufactured.

[0035] It should be noted that the second threshold refers to the upper limit of the first characteristic value characterizing the resistivity uniformity of the epitaxial layer of the second epitaxial wafer. When the first characteristic value characterizing the resistivity uniformity of the epitaxial layer of the second epitaxial wafer exceeds the second threshold, it indicates that the resistivity distribution of the epitaxial layer is uneven. Specifically, the second threshold can be determined according to actual conditions.

[0036] The inventors also found that if Figure 4 As shown, when the first gas flow rate of the slit carrier gas is increased, the resistivity uniformity of the epitaxial layer becomes worse, especially the resistivity at the edge of the epitaxial layer is significantly lower than the resistivity at the center. This is mainly because the introduction of the slit carrier gas into the reaction chamber 10 with the first gas flow rate will promote the diffusion of the dopant gas to the edge of the epitaxial layer. Therefore, after the second epitaxial wafer is manufactured based on the first gas flow rate of the slit carrier gas and the MCLT of the second epitaxial wafer is greater than the second threshold, it is still necessary to detect the resistivity uniformity of the epitaxial layer. It should be noted that the resistivity uniformity of the epitaxial layer in the present disclosure refers to the fact that the resistivity at different positions on the epitaxial layer is not much different, that is, the difference between the resistivity at different positions is within a set range.

[0037] It should be noted that in the present disclosure, the resistivity uniformity of the epitaxial layer can be obtained by the following method, for example: Figure 5As shown, 9 measurement points are selected on the epitaxial layer, one of the 9 measurement points is located at the center of the epitaxial layer, 4 measurement points are located at half of the radius, and the remaining 4 measurement points are located at the edge. It should be noted that in the present disclosure, the edge position on the epitaxial layer refers to a position close to the center position along the radial direction of the epitaxial layer and 5mm, 6mm or 10mm away from the outermost edge of the epitaxial layer. In the specific implementation process, after the resistivity of the above-mentioned 9 measurement points is obtained, based on the ratio of the difference between the maximum and minimum values ​​of the measured resistivity and the sum of the maximum and minimum values, the first characteristic value for characterizing the resistivity uniformity of the epitaxial layer of the second epitaxial wafer can be obtained, which is specifically calculated according to the following formula:

[0038] in, a represents the first eigenvalue; Indicates the maximum value of resistivity; Indicates the minimum value of resistivity.

[0039] Of course, in the specific implementation process, Figure 6 As shown, 5 measurement points are selected on the epitaxial layer, one of the 5 measurement points is located at the center of the epitaxial layer and the other 4 measurement points are located at the edge of the epitaxial layer, and then according to the ratio of the difference between the maximum and minimum values ​​of the resistivity and the sum of the maximum and minimum values ​​obtained by measurement, a first characteristic value for characterizing the resistivity uniformity of the epitaxial layer of the second epitaxial wafer can be obtained.

[0040] In the specific implementation process, after obtaining the first characteristic value, when the first characteristic value is greater than the set second threshold value, it is characterized that the resistivity at different positions on the epitaxial layer of the second epitaxial wafer is uneven, so it is necessary to adjust the first power ratio and the second power ratio in the epitaxial growth process. It should be noted that the first power ratio is the ratio of the power of the heating component located at the center position above the reaction chamber to the sum of the powers of the heating components located at different positions above; the second power ratio is the ratio of the power of the heating component located at the center position below the reaction chamber to the sum of the powers of the heating components located at different positions below. For example, the first power ratio is 72%, which means that the ratio of the power of the heating component located at the center position above the reaction chamber to the sum of the powers of the heating components located at different positions above is 72%. The first power ratio is 17.5%, which means that the ratio of the power of the heating component located at the center position below the reaction chamber to the sum of the powers of the heating components located at different positions below is 17.5%.

[0041] It is understandable that during the epitaxial growth process, multiple heating components are arranged above and below the reaction chamber to provide a high temperature environment for the epitaxial growth process. Therefore, in the present disclosure, when the resistivity at different positions on the epitaxial layer of the second epitaxial wafer is uneven, the resistivity of the epitaxial layer is adjusted by adjusting the power corresponding to the heating components arranged above and below the reaction chamber.

[0042] For the above-mentioned implementation, in some examples, the adjustment range corresponding to the first power ratio is 66% to 82%, and the adjustment range corresponding to the second power ratio is 16% to 20%.

[0043] By controlling the adjustment range of the first power ratio and the second power ratio, the diffusion of dopants during the epitaxial growth process can be controlled, thereby helping to achieve a more uniform doping distribution and improve the uniformity of resistivity.

[0044] Optionally, when the first power ratio and the second power ratio increase or decrease synchronously, and the first power ratio is adjusted by the first adjustment amount and the second power ratio is adjusted by the second adjustment amount, the ratio of the first adjustment amount to the second adjustment amount is in the range of 3:1 to 5:1.

[0045] Specifically, when the resistivity at different positions on the epitaxial layer of the second epitaxial wafer is uneven, the corresponding first power ratio is 74% and the second power ratio is 18%. When the first power ratio and the second power ratio are increased synchronously according to the actual situation, and the ratio of the first adjustment amount of the first power ratio to the second adjustment amount of the second power ratio is 4:1, the adjusted first power ratio is 76% and the second power ratio is 18.5%. In the present disclosure, the first power ratio and the second power ratio are increased or decreased synchronously, which can avoid excessive temperature difference between the upper and lower parts of the reaction chamber during the adjustment process, so as to prevent defects such as slip and dislocation from occurring in the epitaxial layer.

[0046] Optionally, when the first characteristic value is greater than a set second threshold value, adjusting the first power ratio and the second power ratio in the epitaxial growth process according to the resistivity at the center position and the resistivity at the edge position of the epitaxial layer of the second epitaxial wafer includes: When the first eigenvalue is greater than the second threshold, When the resistivity at the center position of the epitaxial layer of the second epitaxial wafer is greater than the resistivity at the edge position, increasing the first power ratio and the second power ratio; or When the resistivity at the center position of the epitaxial layer of the second epitaxial wafer is smaller than the resistivity at the edge position of the epitaxial layer of the second epitaxial wafer, the first power ratio and the second power ratio are reduced.

[0047] It can be understood that when the resistivity at the center position of the epitaxial layer of the second epitaxial wafer is greater than the resistivity at the edge position, it means that the doping concentration of the dopant at the center position of the epitaxial layer is lower than the doping concentration of the dopant at the edge position. Therefore, in the specific implementation process, the first power ratio and the second power ratio are increased, thereby improving the temperature distribution at the center position of the epitaxial layer, thereby increasing the growth rate at the center position and increasing the doping concentration of the dopant. On the contrary, when the resistivity at the center position of the epitaxial layer of the second epitaxial wafer is less than the resistivity at the edge position, it means that the doping concentration of the dopant at the center position of the epitaxial layer is greater than the doping concentration of the dopant at the edge position, therefore, in the specific implementation process, the first power ratio and the second power ratio are reduced.

[0048] For the above-mentioned embodiments, in some examples, the epitaxial growth method further includes: After the second epitaxial wafer is remanufactured, when the first characteristic value of the epitaxial layer of the second epitaxial wafer is greater than the second threshold value, determining a second gas flow rate of the slit carrier gas introduced into the reaction chamber; wherein the second gas flow rate is less than the first gas flow rate, and the second gas flow rate is 10 slm to 35 slm; Based on the second gas flow rate, a second epitaxial wafer is re-manufactured; wherein the first characteristic value of the second epitaxial wafer re-manufactured is obtained.

[0049] It should be noted that, when the resistivity at different positions on the epitaxial layer of the remanufactured second epitaxial wafer is still uneven after adjusting the first power ratio and the second power ratio, it is necessary to reduce the gas flow rate of the slit carrier gas introduced into the reaction chamber 10, introduce the slit carrier gas into the reaction chamber at the second gas flow rate, and remanufacture the second epitaxial wafer again. It can be understood that after the second epitaxial wafer is remanufactured again, when the MCLT of the second epitaxial wafer is greater than or equal to 2000µs, it is still necessary to reconfirm the resistivity uniformity at different positions on the epitaxial layer of the second epitaxial wafer.

[0050] In some possible implementations, the epitaxial growth method further includes: Detecting the thickness of the epitaxial layer of the second epitaxial wafer to obtain a second characteristic value characterizing the thickness uniformity of the epitaxial layer of the second epitaxial wafer; When the second characteristic value is greater than a set third threshold, the gas flow ratio during the epitaxial growth process is adjusted; wherein the gas flow ratio is the ratio of the gas flow of the reaction gas at the center position of the reaction chamber to the gas flow of the first gas inlet in the reaction chamber.

[0051] In some examples, the second characteristic value characterizing the thickness uniformity of the epitaxial layer of the second epitaxial wafer can be obtained by the following method. Figure 7 As shown, multiple measurement points are selected on any diameter of the epitaxial layer. In order to ensure the accuracy of the measurement results, for example, 31 measurement points can be selected, and then according to the ratio of the difference between the maximum and minimum values ​​of the measured thickness and the sum of the maximum and minimum values, a second characteristic value for characterizing the thickness uniformity of the epitaxial layer of the second epitaxial wafer can be obtained, which is specifically calculated according to the following formula:

[0052] in, b represents the second eigenvalue; Indicates the maximum value of thickness; Indicates the minimum value of thickness.

[0053] Of course, in some examples, Figure 5 As shown, 9 measurement points are selected on the epitaxial layer, one of the 9 measurement points is located at the center of the epitaxial layer, 4 measurement points are located at half of the radius, and the remaining 4 measurement points are located at the edge. Then, according to the ratio of the difference between the maximum and minimum values ​​of the measured thickness and the sum of the maximum and minimum values, a second characteristic value for characterizing the thickness uniformity of the epitaxial layer of the second epitaxial wafer can be obtained. Or as Figure 6 As shown, 5 measurement points are selected on the epitaxial layer, one of the 5 measurement points is located at the center of the epitaxial layer and the other 4 measurement points are located at the edge positions, and then according to the ratio of the difference between the maximum and minimum values ​​of the measured thickness and the sum of the maximum and minimum values, a second characteristic value for characterizing the thickness uniformity of the epitaxial layer of the second epitaxial wafer can be obtained.

[0054] It should be noted that the second threshold refers to the upper limit of the second characteristic value characterizing the thickness uniformity of the epitaxial layer of the second epitaxial wafer. When the second characteristic value characterizing the thickness uniformity of the epitaxial layer of the second epitaxial wafer is greater than the third threshold, it indicates that the thickness distribution of the second epitaxial wafer is uneven or the flatness does not meet the requirements, so it is necessary to adjust the thickness distribution of the epitaxial layer by adjusting the gas flow ratio during the epitaxial growth process. Specifically, the third threshold can be determined according to actual conditions.

[0055] In the present disclosure, the gas flow ratio refers to the ratio of the gas flow of the reaction gas at the center of the epitaxial layer to the gas flow of the reaction gas through the first gas inlet 101 in the reaction chamber. For example, a gas flow ratio of 45% means that the gas flow of the reaction gas at the center of the epitaxial layer accounts for 45% of the gas flow of the reaction gas through the first gas inlet 101 in the reaction chamber, that is, 65% of the gas flow of the reaction gas diffuses to the edge of the epitaxial layer.

[0056] Specifically, in some examples, when the second characteristic value is greater than a set third threshold, adjusting the gas flow ratio during the epitaxial growth process includes: When the thickness at the center of the epitaxial layer is less than the thickness at the edge, increasing the gas flow ratio; or When the thickness at the center of the epitaxial layer is greater than the thickness at the edge, the gas flow ratio is reduced.

[0057] It can be understood that when the thickness at the center of the epitaxial layer is less than the thickness at the edge, the gas flow rate of the reaction gas at the center can be increased by increasing the gas flow ratio, thereby increasing the growth rate of the epitaxial layer at the center, making it closer to the growth rate of the epitaxial layer at the edge, and reducing the thickness distribution difference. Conversely, when the thickness at the center of the epitaxial layer is greater than the thickness at the edge, the growth rate of the epitaxial layer at the center can be reduced by reducing the gas flow ratio, reducing the thickness distribution difference between the center and edge positions on the epitaxial layer.

[0058] See also Figure 8 , which shows in detail the process steps of an epitaxial growth method provided by the present disclosure, as follows: In step S801 , a first flow rate of a slit carrier gas introduced into a reaction chamber is determined according to the MCLT level of a first epitaxial wafer.

[0059] In step S802, based on the first flow rate of the slit carrier gas, a second epitaxial wafer is manufactured, wherein the MCLT of the second epitaxial wafer is greater than or equal to 2000 μs. When the MCLT of the second epitaxial wafer is less than the first threshold, step S803 is executed.

[0060] In step S803, the resistivity uniformity of the epitaxial layer of the second epitaxial wafer is confirmed. When the first characteristic value characterizing the resistivity uniformity of the epitaxial layer of the second epitaxial wafer is greater than the second threshold, step S804 is performed. When the first characteristic value characterizing the resistivity uniformity of the epitaxial layer of the second epitaxial wafer is less than the second threshold, step S805 is performed.

[0061] In step S804, the resistivity uniformity of the epitaxial layer of the second epitaxial wafer is controlled by adjusting the first power ratio and the second power ratio. If the first characteristic value characterizing the resistivity uniformity of the epitaxial layer of the second epitaxial wafer can be made smaller than the second threshold value by adjusting the first power ratio and the second power ratio, step S805 is executed. If the first characteristic value characterizing the resistivity uniformity of the epitaxial layer of the second epitaxial wafer cannot be made smaller than the second threshold value by adjusting the first power ratio and the second power ratio, the second flow rate of the slit carrier gas introduced into the reaction chamber is re-determined, and step S802 is re-executed until the first characteristic value characterizing the resistivity uniformity of the epitaxial layer of the second epitaxial wafer is smaller than the second threshold value.

[0062] In step S805, when the MCLT of the second epitaxial wafer and the resistivity uniformity of the epitaxial layer meet the requirements, the thickness uniformity of the epitaxial layer of the second epitaxial wafer is confirmed. When the second characteristic value characterizing the thickness uniformity of the epitaxial layer of the second epitaxial wafer is less than the set third threshold, step S806 is executed. When the second characteristic value characterizing the thickness uniformity of the epitaxial layer of the second epitaxial wafer is less than the set third threshold, step S807 is executed.

[0063] In step S806, the thickness uniformity of the epitaxial layer of the second epitaxial wafer is controlled by adjusting the gas flow ratio during the epitaxial growth process. If the second characteristic value characterizing the thickness uniformity of the epitaxial layer of the second epitaxial wafer is less than the set third threshold value by adjusting the gas flow ratio during the epitaxial growth process, step S807 is executed.

[0064] In step S807 , when the MCLT of the second epitaxial wafer, the resistivity uniformity of the epitaxial layer and the thickness uniformity of the epitaxial layer all meet the requirements, the production of the second epitaxial wafer is started.

[0065] In addition, the present disclosure also provides an epitaxial wafer, which is manufactured according to the epitaxial growth method of the aforementioned technical solution, and the minority carrier lifetime of the epitaxial wafer is greater than or equal to 2000µs.

[0066] In some examples, a first characteristic value of the epitaxial wafer is less than or equal to 2.7%, and a second characteristic value is less than or equal to 0.65%, wherein the first characteristic value is used to characterize the resistivity uniformity of the epitaxial layer of the epitaxial wafer, and the second characteristic value is used to characterize the thickness uniformity of the epitaxial layer of the epitaxial wafer.

[0067] In the present disclosure, the terms "first", "second", etc. are used only for the purpose of convenience of description and should not be regarded as limiting. In addition, although the present disclosure has been described with reference to exemplary embodiments, it should be understood that the present disclosure is not limited to the specific embodiments described and shown in detail herein. Those skilled in the art may make various changes to the exemplary embodiments without departing from the scope defined by the claims of the present disclosure.

[0068] It should be noted that the technical solutions described in the embodiments of the present disclosure can be combined arbitrarily without conflict.

[0069] The above is only a specific embodiment of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. An epitaxial growth method, characterized in that: The epitaxial growth method comprises: Performing a minority carrier lifetime test on the first epitaxial wafer to obtain the minority carrier lifetime of the first epitaxial wafer; When the minority carrier lifetime of the first epitaxial wafer is less than a set first threshold, determining a first gas flow rate of the slit carrier gas introduced into the reaction chamber; Based on the first gas flow rate of the slit carrier gas, a second epitaxial wafer is manufactured; wherein the minority carrier lifetime of the second epitaxial wafer is greater than or equal to 2200 μs.

2. The epitaxial growth method according to claim 1, characterized in that: The first gas flow rate of the slit carrier gas is 20 slm to 35 slm.

3. The epitaxial growth method according to claim 1, characterized in that: The epitaxial growth method further comprises: Based on the resistivity at different positions on the epitaxial layer of the second epitaxial wafer, obtaining a first characteristic value characterizing the resistivity uniformity of the epitaxial layer of the second epitaxial wafer; When the first characteristic value is greater than a set second threshold value, the first power ratio and the second power ratio in the epitaxial growth process are adjusted according to the resistivity at the center position and the resistivity at the edge position of the epitaxial layer of the second epitaxial wafer; wherein the first power ratio is the ratio of the power of the heating component located at the center position above the reaction chamber to the sum of the powers of the heating components located at different positions above the reaction chamber; the second power ratio is the ratio of the power of the heating component located at the center position below the reaction chamber to the sum of the powers of the heating components located at different positions below the reaction chamber; Based on the adjusted first power ratio and second power ratio, the second epitaxial wafer is remanufactured.

4. The epitaxial growth method according to claim 3, characterized in that: The adjustment range of the first power ratio is 66% to 82%, and the adjustment range of the second power ratio is 16% to 20%.

5. The epitaxial growth method according to claim 4, characterized in that: When the first power ratio and the second power ratio increase or decrease synchronously, and the first power ratio is adjusted by a first adjustment amount and the second power ratio is adjusted by a second adjustment amount, the ratio of the first adjustment amount to the second adjustment amount is in the range of 3:1 to 5:

1.

6. The epitaxial growth method according to any one of claims 3 to 5, characterized in that: When the first characteristic value is greater than a set second threshold value, adjusting the first power ratio and the second power ratio in the epitaxial growth process according to the resistivity at the center position and the resistivity at the edge position of the epitaxial layer of the second epitaxial wafer, including: When the first characteristic value is greater than the second threshold, When the resistivity at the center position of the epitaxial layer of the second epitaxial wafer is greater than the resistivity at the edge position, increasing the first power ratio and the second power ratio; or When the resistivity at the center position of the epitaxial layer of the second epitaxial wafer is smaller than the resistivity at the edge position of the epitaxial layer of the second epitaxial wafer, the first power ratio and the second power ratio are reduced.

7. The epitaxial growth method according to claim 3, characterized in that: The epitaxial growth method further comprises: After the second epitaxial wafer is remanufactured, when the first characteristic value of the epitaxial layer of the second epitaxial wafer is greater than the second threshold value, determining a second gas flow rate of the slit carrier gas introduced into the reaction chamber; wherein the second gas flow rate is less than the first gas flow rate, and the second gas flow rate is 20 slm to 35 slm; Based on the second gas flow rate, the second epitaxial wafer is re-manufactured; wherein the first characteristic value of the second epitaxial wafer re-manufactured is obtained.

8. The epitaxial growth method according to claim 1, characterized in that: The epitaxial growth method further comprises: Detecting the thickness of the epitaxial layer of the second epitaxial wafer to obtain a second characteristic value characterizing the thickness uniformity of the epitaxial layer of the second epitaxial wafer; When the second characteristic value is greater than a set third threshold, the gas flow ratio during the epitaxial growth process is adjusted; wherein the gas flow ratio is the ratio of the gas flow of the reaction gas at the center position of the reaction chamber to the gas flow of the first gas inlet in the reaction chamber.

9. The epitaxial growth method according to claim 8, characterized in that: When the second characteristic value is greater than a set third threshold, adjusting the gas flow ratio during the epitaxial growth process includes: When the thickness at the center of the epitaxial layer is less than the thickness at the edge, increasing the gas flow ratio; or When the thickness at the center of the epitaxial layer is greater than the thickness at the edge, the gas flow ratio is reduced.

10. An epitaxial wafer, characterized in that: The epitaxial wafer is manufactured according to the epitaxial growth method according to any one of claims 1 to 9, and the minority carrier lifetime of the epitaxial wafer is greater than or equal to 2200µs.

11. The epitaxial wafer according to claim 10, characterized in that: The first characteristic value of the epitaxial wafer is less than or equal to 2.7%, and the second characteristic value is less than or equal to 0.65%, wherein the first characteristic value is used to characterize the resistivity uniformity of the epitaxial layer of the epitaxial wafer, and the second characteristic value is used to characterize the thickness uniformity of the epitaxial layer of the epitaxial wafer.

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