Epitaxial growth method and epitaxial wafer

Abstract

Embodiments of the present application disclose an epitaxial growth method and an epitaxial wafer. The epitaxial growth method comprises: performing a minority carrier lifetime test on a first epitaxial wafer, to obtain a 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 a slit carrier gas introduced into a reaction chamber; and based on the first gas flow rate of the slit carrier gas, manufacturing to obtain a second epitaxial wafer.

Description

Epitaxial growth methods and epitaxial wafers

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411447580.9, filed in China on October 16, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of semiconductor manufacturing technology, and in particular to epitaxial growth methods and epitaxial wafers. Background Technology

[0004] Epitaxial growth technology is a technique that enables the growth of an epitaxial layer on a polished wafer. The grown epitaxial layer has a different conductivity, resistivity, and structure than the polished wafer, which can meet the production requirements of a variety of different semiconductor devices and greatly improve the flexibility and performance of semiconductor device design.

[0005] With the rapid development of semiconductor technology, the requirements for the quality of epitaxial wafers are becoming increasingly stringent, especially regarding the minority carrier lifetime (MCLT) level. It is known that the MCLT level of an epitaxial wafer is significantly related to the content of metal impurities within its chamber. During epitaxial growth, if the content of metal impurities in the reaction chamber is too high, it will result in an epitaxial wafer with excessively high metal impurity levels, thus affecting the MCLT level of the epitaxial wafer. Summary of the Invention

[0006] In view of this, embodiments of this application aim to provide an epitaxial growth method and an epitaxial wafer; capable of obtaining an epitaxial wafer with an MCLT greater than or equal to 2200us.

[0007] The technical solution of this application embodiment is implemented as follows:

[0008] In a first aspect, embodiments of this application provide an epitaxial growth method, the epitaxial growth method comprising:

[0009] The minority carrier lifetime of the first epitaxial wafer is measured to obtain the minority carrier lifetime of the first epitaxial wafer.

[0010] When the minority carrier lifetime of the first epitaxial wafer is less than a set first threshold, the first gas flow rate of the slit carrier gas introduced into the reaction chamber is determined.

[0011] A second epitaxial wafer is fabricated 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 μs.

[0012] In some examples, the first gas flow rate of the slit carrier gas is 20 slm to 35 slm.

[0013] In some examples, the epitaxial growth method further includes:

[0014] Based on the resistivity at different locations on the epitaxial layer of the second epitaxial wafer, a first characteristic value characterizing the resistivity uniformity of the epitaxial layer of the second epitaxial wafer is obtained.

[0015] When the first characteristic value is greater than the set second threshold, the first power ratio and the second power ratio during 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 at the center position above the reaction chamber to the sum of the power of the heating components at different positions above; the second power ratio is the ratio of the power of the heating component at the center position below the reaction chamber to the sum of the power of the heating components at different positions below.

[0016] Based on the adjusted first power ratio and second power ratio, the second epitaxial wafer is remanufactured.

[0017] 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%.

[0018] In some examples, 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.

[0019] In some examples, when the first feature value is greater than a set second threshold, adjusting the first power ratio and the second power ratio during the epitaxial growth process based on the resistivity at the center and edge of the epitaxial layer on the second epitaxial wafer includes:

[0020] When the first feature value is greater than the second threshold

[0021] If the resistivity at the center of the epitaxial layer of the second epitaxial wafer is greater than the resistivity at the edge, increase the first power ratio and the second power ratio; or

[0022] When the resistivity at the center of the epitaxial layer of the second epitaxial wafer is less than the resistivity at the edge of the epitaxial layer of the second epitaxial wafer, the first power ratio and the second power ratio are reduced.

[0023] In some examples, the epitaxial growth method further includes:

[0024] 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, a second gas flow rate of the slit carrier gas introduced into the reaction chamber is determined; 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.

[0025] Based on the second gas flow rate, the second epitaxial wafer is remanufactured again; wherein, the first characteristic value of the remanufactured second epitaxial wafer is specified.

[0026] In some examples, the epitaxial growth method further includes:

[0027] The thickness of the epitaxial layer of the second epitaxial wafer is detected to obtain a second characteristic value characterizing the thickness uniformity of the epitaxial layer of the second epitaxial wafer;

[0028] When the second characteristic value is greater than the set third threshold, the airflow ratio during the epitaxial growth process is adjusted; wherein, the airflow ratio is the ratio of the gas flow rate of the reaction gas at the center position of the reaction chamber to the gas flow rate of the first air inlet in the reaction chamber.

[0029] In some examples, adjusting the airflow ratio during the epitaxial growth process when the second characteristic value is greater than a set third threshold includes:

[0030] When the thickness at the center of the epitaxial layer is less than the thickness at the edge, the airflow ratio is increased; or

[0031] When the thickness at the center of the epitaxial layer is greater than the thickness at the edge, the airflow ratio is reduced.

[0032] Secondly, embodiments of this application provide an epitaxial wafer, which is manufactured according to the epitaxial growth method described in the first aspect, and the minority carrier lifetime of the epitaxial wafer is greater than or equal to 2200 μs.

[0033] 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.

[0034] This application provides an epitaxial growth method and an epitaxial wafer. In this application, by adjusting the gas flow rate of the slit carrier gas through the MCLT of the first epitaxial wafer, 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 ultimately improving the MCLT of the second epitaxial wafer. Attached Figure Description

[0035] Figure 1 is a schematic diagram of the reaction chamber used in the epitaxial growth process provided in an embodiment of this application;

[0036] Figure 2 is a schematic flowchart of an epitaxial growth method provided in an embodiment of this application;

[0037] Figure 3 shows the MCLT corresponding to different first gas flow rates of the slit carrier gas when the slit carrier gas is hydrogen, according to the embodiments of this application.

[0038] Figure 4 shows the first characteristic values ​​corresponding to different first gas flow rates of the slit carrier gas provided in the embodiments of this application;

[0039] Figure 5 is a schematic diagram of a method for calculating a first feature value provided in an embodiment of this application;

[0040] Figure 6 is a schematic diagram of a method for calculating a first feature value provided in another embodiment of this application;

[0041] Figure 7 is a schematic diagram of a method for calculating a second feature value provided in an embodiment of this application;

[0042] Figure 8 is a flowchart of an epitaxial growth method provided in another embodiment of this application. Detailed Implementation

[0043] The technical solutions in this application will now be clearly and completely described with reference to the accompanying drawings.

[0044] It should be noted that, for clarity, not all features of a particular embodiment are described or shown in the specification and drawings. Furthermore, to avoid unnecessary details obscuring the technical solutions of interest in this application, only the device structures and method steps closely related to the technical solutions of this application are described and shown in the specification and drawings, while other details that are not closely related to the technical content of this application and are known to those skilled in the art are omitted.

[0045] Furthermore, the epitaxial growth process mentioned in this application may include a loading stage of polished wafers, a heating stage, a baking stage, a vapor deposition stage, and an unloading stage of epitaxial wafers.

[0046] As mentioned earlier, excessively high levels of metal impurities in the reaction chamber can lead to excessively high metal content in the resulting epitaxial wafers, thus affecting the MCLT level of the epitaxial wafers. In related technologies, the metal impurity content in the reaction chamber needs to be confirmed before epitaxial growth begins. If the metal impurity content does not meet the requirements, the inside of the reaction chamber needs to be cleaned or even replaced with another reaction chamber, often resulting in multiple replacements of the reaction chamber and a long operation cycle for the entire process.

[0047] As shown in Figure 1, the reaction chamber 10 used in the epitaxial growth process typically includes two gas inlets: a first gas inlet 101 and a second gas inlet 102. In Figure 1, the direction of the first gas inlet 101 is shown exemplarily as orthogonal to the direction of the second gas inlet 102. The first gas inlet 101, also commonly referred to as the main gas inlet, is used to supply gas to the main region of the reaction chamber 10, that is, primarily to the area above the polished wafer W placed on the substrate 103. This gas includes hydrogen (commonly known as main hydrogen (Main H2)), reactive gases, and dopant gases, etc. The second gas inlet 102, also commonly referred to as the secondary gas inlet, primarily supplies gas to the region of the reaction chamber 10 located below the substrate 103. This gas includes hydrogen (commonly known as 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 this application, the introduction of main hydrogen gas and slit hydrogen gas into the reaction chamber 10 will continue throughout the entire epitaxial growth process.

[0048] In some examples, slit hydrogen can be used as a purge gas, as well as as a carrier gas.

[0049] The applicant discovered that simply increasing the flow rate of hydrogen gas in the slit can clean the reaction chamber, thereby improving the MCLT level of the epitaxial wafer. This is mainly because the hydrogen gas in the slit can purge the area below the substrate 103, thereby inhibiting the diffusion of metal impurities from the area below the substrate 103 to the area above the substrate 103, thus affecting the metal impurity content in the epitaxial wafer.

[0050] Based on this, referring to Figure 2, this application embodiment provides an epitaxial growth method, which specifically includes the following steps:

[0051] S201. The minority carrier lifetime of the first epitaxial wafer is tested to obtain the minority carrier lifetime of the first epitaxial wafer.

[0052] S202. When the minority carrier lifetime of the first epitaxial wafer is less than a set first threshold, determine the first gas flow rate of the slit carrier gas introduced into the reaction chamber.

[0053] S203. 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 2200µs.

[0054] First, in step S201, the first epitaxial wafer is subjected to MCLT testing to obtain the MCLT of the first epitaxial wafer. It is understood that the MCLT of the first epitaxial wafer can characterize the current content of metal impurities in the reaction chamber.

[0055] In some examples, the MCLT of the first epitaxial wafer can be obtained using the Conductivity Decay Method (CDM). This involves 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 over time to determine the MCLT. Of course, other methods can also be used to obtain the MCLT of the first epitaxial wafer in this application, such as the Surface Photovoltage Method (SPV). This method uses light to irradiate the surface of the epitaxial layer of the first epitaxial wafer to generate a photovoltage signal, and then measures the decay time of the photovoltage signal to obtain the corresponding MCLT.

[0056] In step S202, when the first threshold is set to refer to the critical value of the minority carrier lifetime of the epitaxial wafer, it is determined according to the usage requirements of the semiconductor device corresponding to the epitaxial wafer.

[0057] In some examples, the slit carrier gas can be hydrogen or other gases that can serve a purging function.

[0058] Understandably, when the MCLT of the first epitaxial wafer is greater than the first threshold, in order to ensure that the MCLT level of the second epitaxial wafer meets the requirements, the gas flow rate of the slit carrier gas is adjusted so that the slit carrier gas with the first gas flow rate is introduced into the reaction chamber 10, thereby suppressing the diffusion of metal impurities in the region below the base 203 to the region above the base 103, thereby reducing the metal impurity content in the epitaxial layer of the second epitaxial wafer, and ultimately improving the MCLT of the second epitaxial wafer.

[0059] For the technical solution shown in Figure 1, in some possible implementations, the first gas flow rate of the slit carrier gas is 20 slm to 35 slm.

[0060] In this application, the first gas flow rate of the slit carrier gas is set to 20 slm to 35 slm. This is because it can further purge metal impurities in the region below the substrate 103 from the reaction chamber 10, preventing metal impurities in the region below the substrate 103 from diffusing to the region above the substrate 103. On the one hand, if the first gas flow rate of the slit carrier gas is too small, it will not be able to completely purge metal impurities in the region below the substrate 103 from the reaction chamber 10. On the other hand, if the first gas flow rate of the slit carrier gas is too large, it may cause deterioration of the edge flatness of the second epitaxial wafer. This is mainly because increasing the first gas flow rate of the slit carrier gas may change the gas flow pattern inside the reaction chamber 20, resulting in uneven distribution of the reactive gas on the surface of the polished wafer W, thus affecting the growth rate at the edge of the second epitaxial wafer and consequently affecting the edge flatness. In addition, increasing 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, which in turn leads to inconsistent growth rates at the center and edge of the epitaxial layer, thus affecting the edge flatness.

[0061] Referring to Figure 3, it shows the MCLT of the second epitaxial wafer when the slit carrier gas is hydrogen and the corresponding first gas flow rates are 5 slm, 10 slm, 20 slm, 30 slm, and 40 slm. As can be seen from Figure 3, when the slit carrier gas is hydrogen and the corresponding first gas flow rates are 5 slm and 10 slm, the MCLT of the second epitaxial wafer is approximately 1800 μs and 2100 μs, respectively. When the slit carrier gas is hydrogen and the corresponding first gas flow rate is between 20 slm and 35 slm, the MCLT of the second epitaxial wafer is greater than 2200 μs. When the slit carrier gas is hydrogen and the corresponding first gas flow rate is 40 slm, although the MCLT of the second epitaxial wafer is greater than 2200 μs, in practical implementation, a higher first gas flow rate of the slit carrier gas can cause a deterioration in the edge flatness of the second epitaxial wafer.

[0062] In this application, although the MCLT level of the second epitaxial wafer is improved by introducing a slit carrier gas with a first gas flow rate into the reaction chamber 10, the increased gas flow rate of the slit carrier gas will negatively affect the resistivity distribution and thickness distribution at different locations on the epitaxial layer of the second epitaxial wafer. Therefore, in this application, after the MCLT level of the second epitaxial wafer meets the requirements, it is still necessary to detect the resistivity distribution and thickness distribution at different locations on the epitaxial layer. Therefore, for the technical solution shown in Figure 1, in some possible embodiments, the epitaxial growth method further includes:

[0063] Based on the resistivity at different locations on the epitaxial layer of the second epitaxial wafer, a first characteristic value characterizing the resistivity uniformity of the epitaxial layer of the second epitaxial wafer is obtained.

[0064] When the first characteristic value is greater than the set second threshold, the first power ratio and the second power ratio during 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 at the center position above the reaction chamber to the sum of the power of the heating components at different positions above; the second power ratio is the ratio of the power of the heating component at the center position below the reaction chamber to the sum of the power of the heating components at different positions below.

[0065] Based on the adjusted first and second power ratios, a second epitaxial wafer was remanufactured.

[0066] 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 not uniform. Specifically, the second threshold can be determined according to the actual situation.

[0067] The applicant also discovered, as shown in Figure 4, that increasing the flow rate of the first gas in the slit carrier gas led to a decrease in the resistivity uniformity of the epitaxial layer. In particular, the resistivity at the edges of the epitaxial layer was significantly lower than that at the center. This is mainly because introducing the slit carrier gas into the reaction chamber 10 at the first gas flow rate promotes the diffusion of dopant gas towards the edges of the epitaxial layer. Therefore, after fabricating a second epitaxial wafer based on the first gas flow rate of the slit carrier gas and ensuring that the MCLT of the second epitaxial wafer is greater than the second threshold, it is still necessary to test the resistivity uniformity of the epitaxial layer. It should be noted that the resistivity uniformity of the epitaxial layer in this application refers to the resistivity at different locations on the epitaxial layer being relatively similar, meaning that the difference in resistivity between different locations is within a set range.

[0068] It should be noted that the resistivity uniformity of the epitaxial layer in this application can be obtained by the following method, for example, as shown in Figure 5, nine measurement points are selected on the epitaxial layer. One of these nine measurement points is located at the center of the epitaxial layer, four measurement points are located at half the radius, and the remaining four measurement points are located at the edge. It should be noted that in this application, the edge location on the epitaxial layer refers to a location close to the center along the radial direction of the epitaxial layer and 5 mm, 6 mm, or 10 mm away from the outermost edge of the epitaxial layer. In specific implementation, after obtaining the resistivity of the above nine measurement points, based on the ratio of the difference between the maximum and minimum resistivity values ​​and the sum of the maximum and minimum resistivity values, a first characteristic value for characterizing the resistivity uniformity of the epitaxial layer of the second epitaxial wafer can be obtained, specifically calculated according to the following formula:

[0069] Where a represents the first eigenvalue; R max R represents the maximum resistivity. min This represents the minimum resistivity.

[0070] Of course, in the specific implementation process, as shown in Figure 6, five measurement points can be selected on the epitaxial layer. One of these five measurement points is located at the center of the epitaxial layer, and the other four measurement points are located at the edge of the epitaxial layer. Then, based on the ratio of the difference between the maximum and minimum resistivity values ​​and the sum of the maximum and minimum resistivity values, a first characteristic value for characterizing the resistivity uniformity of the epitaxial layer of the second epitaxial wafer can be obtained.

[0071] In practical implementation, after obtaining the first characteristic value, if the first characteristic value is greater than a set second threshold, it indicates that the resistivity at different locations on the epitaxial layer of the second epitaxial wafer is not uniform. Therefore, it is necessary to adjust the first power ratio and the second power ratio during 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, a first power ratio of 72% 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%. A first power ratio of 17.5% 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%.

[0072] It is understandable that during epitaxial growth, multiple heating components are arranged above and below the reaction chamber to provide a high-temperature environment for the epitaxial growth process. Therefore, in this application, when the resistivity at different locations on the epitaxial layer of the second epitaxial wafer is not uniform, the resistivity of the epitaxial layer is adjusted by adjusting the power of the heating components arranged above and below the reaction chamber.

[0073] In some examples of the above implementation methods, 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%.

[0074] 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, which helps to achieve a more uniform doping distribution and improve the uniformity of resistivity.

[0075] Optionally, 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.

[0076] Specifically, when the resistivity is uneven at different locations on the epitaxial layer of the second epitaxial wafer, the corresponding first power ratio is 74% and the second power ratio is 18%. When the first and second power ratios are increased synchronously according to actual conditions, 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 becomes 76% and the second power ratio becomes 18.5%. In this application, the synchronous increase or decrease of the first and second power ratios can avoid excessive temperature differences between the upper and lower parts of the reaction chamber during the adjustment process, thereby preventing defects such as slip and dislocations in the epitaxial layer.

[0077] Optionally, when the first characteristic value is greater than a set second threshold, the first power ratio and the second power ratio during the epitaxial growth process are adjusted according to the resistivity at the center and the edge of the epitaxial layer on the second epitaxial wafer, including:

[0078] When the first feature value is greater than the second threshold

[0079] If the resistivity at the center of the epitaxial layer of the second epitaxial wafer is greater than the resistivity at the edge, increase the first power ratio and the second power ratio; or

[0080] When the resistivity at the center of the epitaxial layer of the second epitaxial wafer is less than the resistivity at the edge of the epitaxial layer of the second epitaxial wafer, the first power ratio and the second power ratio are reduced.

[0081] Understandably, when the resistivity at the center of the epitaxial layer of the second epitaxial wafer is greater than that at the edge, it indicates that the doping concentration of the dopant at the center is lower than that at the edge. Therefore, in practical implementation, increasing the first power ratio and the second power ratio can improve the temperature distribution at the center of the epitaxial layer, thereby increasing the growth rate at the center and increasing the doping concentration of the dopant. Conversely, when the resistivity at the center of the epitaxial layer of the second epitaxial wafer is less than that at the edge, it indicates that the doping concentration of the dopant at the center is greater than that at the edge. Therefore, in practical implementation, decreasing the first power ratio and the second power ratio is necessary.

[0082] In some examples of the above-described implementation methods, the epitaxial growth method further includes:

[0083] 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, the second gas flow rate of the slit carrier gas introduced into the reaction chamber is determined; 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.

[0084] Based on the second gas flow rate, a second epitaxial wafer is remanufactured; wherein, the first characteristic value of the remanufactured second epitaxial wafer is specified.

[0085] It should be noted that if, after adjusting the first and second power ratios, the resistivity at different locations on the epitaxial layer of the remanufactured second epitaxial wafer is still non-uniform, the flow rate of the slit carrier gas introduced into the reaction chamber 10 needs to be reduced. The slit carrier gas should be introduced into the reaction chamber at the second gas flow rate, and the second epitaxial wafer should be remanufactured again. Understandably, after remanufacturing the second epitaxial wafer, if the MCLT of the second epitaxial wafer is greater than or equal to 2000 μs, it is still necessary to reconfirm the resistivity uniformity at different locations on the epitaxial layer of the second epitaxial wafer.

[0086] In some possible implementations, the epitaxial growth method further includes:

[0087] The thickness of the epitaxial layer of the second epitaxial wafer is measured to obtain a second characteristic value characterizing the thickness uniformity of the epitaxial layer of the second epitaxial wafer;

[0088] When the second characteristic value is greater than the set third threshold, the airflow ratio during the epitaxial growth process is adjusted; wherein, the airflow ratio is the ratio of the gas flow rate of the reaction gas at the center position of the reaction chamber to the gas flow rate of the first air inlet in the reaction chamber.

[0089] 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. For example, as shown in Figure 7, multiple measurement points are selected on any diameter of the epitaxial layer. To ensure the accuracy of the measurement results, for example, 31 measurement points can be selected. Then, based on the ratio of the difference between the maximum and minimum thicknesses and the sum of the maximum and minimum thicknesses, the second characteristic value characterizing the thickness uniformity of the epitaxial layer of the second epitaxial wafer can be obtained, specifically calculated according to the following formula:

[0090] Where b represents the second eigenvalue; T max T represents the maximum thickness. min This represents the minimum thickness.

[0091] Of course, in some examples, as shown in Figure 5, nine measurement points can be selected on the epitaxial layer. One of these nine measurement points is located at the center of the epitaxial layer, four are located at half the radius of the epitaxial layer, and the remaining four are located at the edge. Then, based on the ratio of the difference between the maximum and minimum thickness values ​​and the sum of the maximum and minimum thickness values, a second characteristic value for characterizing the thickness uniformity of the epitaxial layer of the second epitaxial wafer can be obtained. Alternatively, as shown in Figure 6, five measurement points can be selected on the epitaxial layer. One of these five measurement points is located at the center of the epitaxial layer, and the remaining four are located at the edge. Then, based on the ratio of the difference between the maximum and minimum thickness values ​​and the sum of the maximum and minimum thickness values, a second characteristic value for characterizing the thickness uniformity of the epitaxial layer of the second epitaxial wafer can be obtained.

[0092] 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 not uniform or that the flatness does not meet the requirements. Therefore, 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 the actual situation.

[0093] In this application, the gas flow ratio refers to the ratio of the gas flow rate of the reactant gas at the center of the epitaxial layer to the gas flow rate of the reactant gas entering the first inlet 101 of the reaction chamber. For example, a gas flow ratio of 45% means that the gas flow rate of the reactant gas at the center of the epitaxial layer accounts for 45% of the gas flow rate entering the first inlet 101 of the reaction chamber, which means that 65% of the gas flow rate of the reactant gas diffuses to the edge of the epitaxial layer.

[0094] Specifically, in some examples, when the second characteristic value is greater than a set third threshold, the airflow ratio during the epitaxial growth process is adjusted, including:

[0095] When the thickness at the center of the epitaxial layer is less than the thickness at the edge, increase the airflow ratio; or

[0096] When the thickness at the center of the epitaxial layer is greater than the thickness at the edge, the airflow ratio should be reduced.

[0097] Understandably, when the thickness at the center of the epitaxial layer is less than that at the edge, increasing the gas flow rate at the center can improve the growth rate of the epitaxial layer at that center, making it closer to the growth rate at the edge and reducing the thickness distribution difference. Conversely, when the thickness at the center of the epitaxial layer is greater than that at the edge, decreasing the gas flow rate can reduce the growth rate of the epitaxial layer at that center, thus reducing the thickness distribution difference between the center and the edge of the epitaxial layer.

[0098] Referring to Figure 8, which details the process flow steps of an epitaxial growth method provided in this application, as follows:

[0099] In step S801, the first flow rate of the slit carrier gas introduced into the reaction chamber is determined based on the MCLT level of the first epitaxial wafer.

[0100] In step S802, a second epitaxial wafer is fabricated based on the first flow rate of the slit carrier gas; 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 a first threshold, step S803 is executed.

[0101] 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 executed. 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 executed.

[0102] 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 adjusting the first power ratio and the second power ratio makes the first characteristic value characterizing the resistivity uniformity of the epitaxial layer of the second epitaxial wafer less than the second threshold, step S805 is executed. If adjusting the first power ratio and the second power ratio does not make the first characteristic value characterizing the resistivity uniformity of the epitaxial layer of the second epitaxial wafer less than the second threshold, the second flow rate of the slit carrier gas introduced into the reaction chamber is re-determined, and step S802 is executed again until the first characteristic value characterizing the resistivity uniformity of the epitaxial layer of the second epitaxial wafer is less than the second threshold.

[0103] In step S805, after the MCLT and resistivity uniformity of the second epitaxial wafer 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.

[0104] 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 adjusting the gas flow ratio during the epitaxial growth process makes the second characteristic value characterizing the thickness uniformity of the epitaxial layer of the second epitaxial wafer less than a set third threshold, step S807 is executed.

[0105] 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 and manufacturing of the second epitaxial wafer begins.

[0106] In addition, this application also provides an epitaxial wafer, which is manufactured by the epitaxial growth method according to the aforementioned technical solution, and the minority carrier lifetime of the epitaxial wafer is greater than or equal to 2000 μs.

[0107] 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.

[0108] Throughout this application, the terms "first," "second," etc., are used merely for descriptive purposes and should not be considered restrictive. Furthermore, although this application has been described with reference to exemplary embodiments, it should be understood that this application is not limited to the specific embodiments described and shown herein. Various modifications to the exemplary embodiments can be made by those skilled in the art without departing from the scope defined by the claims of this application.

[0109] It should be noted that the technical solutions described in the embodiments of this application can be combined arbitrarily without conflict.

[0110] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An epitaxial growth method, the epitaxial growth method comprising: The minority carrier lifetime of the first epitaxial wafer is measured 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, the first gas flow rate of the slit carrier gas introduced into the reaction chamber is determined. A second epitaxial wafer is fabricated 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 μs.

2. The epitaxial growth method according to claim 1, wherein, 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, wherein, The epitaxial growth method further includes: Based on the resistivity at different locations on the epitaxial layer of the second epitaxial wafer, a first characteristic value characterizing the resistivity uniformity of the epitaxial layer of the second epitaxial wafer is obtained. When the first characteristic value is greater than the set second threshold, the first power ratio and the second power ratio during 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 at the center position above the reaction chamber to the sum of the power of the heating components at different positions above; the second power ratio is the ratio of the power of the heating component at the center position below the reaction chamber to the sum of the power of the heating components at different positions below. 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, wherein, 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%.

5. The epitaxial growth method according to claim 4, wherein, 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, wherein, When the first characteristic value is greater than a set second threshold, adjusting the first power ratio and the second power ratio during the epitaxial growth process based on the resistivity at the center and edge of the epitaxial layer on the second epitaxial wafer includes: When the first feature value is greater than the second threshold If the resistivity at the center of the epitaxial layer of the second epitaxial wafer is greater than the resistivity at the edge, increase the first power ratio and the second power ratio; or When the resistivity at the center of the epitaxial layer of the second epitaxial wafer is less than the resistivity at the edge 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, wherein, 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, a second gas flow rate of the slit carrier gas introduced into the reaction chamber is determined; 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 remanufactured again; wherein, the first characteristic value of the remanufactured second epitaxial wafer is specified.

8. The epitaxial growth method according to claim 1, wherein, The epitaxial growth method further includes: The thickness of the epitaxial layer of the second epitaxial wafer is detected 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 the set third threshold, the airflow ratio during the epitaxial growth process is adjusted; wherein, the airflow ratio is the ratio of the gas flow rate of the reaction gas at the center position of the reaction chamber to the gas flow rate of the first air inlet in the reaction chamber.

9. The epitaxial growth method according to claim 8, wherein, The step of adjusting the airflow ratio during the epitaxial growth process when the second characteristic value is greater than the set third threshold includes: When the thickness at the center of the epitaxial layer is less than the thickness at the edge, the airflow ratio is increased; or When the thickness at the center of the epitaxial layer is greater than the thickness at the edge, the airflow ratio is reduced.

10. An epitaxial wafer, said epitaxial wafer being manufactured by the epitaxial growth method according to any one of claims 1 to 9, said epitaxial wafer having a minority carrier lifetime greater than or equal to 2200 μs.

11. The epitaxial wafer according to claim 10, wherein, 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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