Epitaxial growth method and epitaxial wafer

Abstract

The invention relates to an epitaxial growth method and an epitaxial wafer. In one aspect, there is provided an epitaxial growth method for a heavily doped substrate without a back sealing film, the method comprising: placing the heavily doped substrate on a pedestal of a reaction chamber; main hydrogen is introduced into the reaction chamber through the first gas inlet, and auxiliary hydrogen is introduced into the area, located below the base, of the reaction chamber through the second gas inlet; baking the reaction chamber at a preset temperature; reaction gas is introduced into the reaction chamber through the first gas inlet, an epitaxial layer is formed on the heavily doped substrate through the deposition reaction, and at least in the baking and deposition reaction period, the flow of the main hydrogen is larger than or equal to 55 slm, or the flow of the auxiliary hydrogen is smaller than or equal to 18 slm. As a result, the resistivity uniformity of the epitaxial layer formed on the substrate can be improved.

Description

Technical Field

[0001] The present disclosure relates to the field of semiconductor processing and manufacturing technology, and in particular, to an epitaxial growth method and an epitaxial wafer. Background Art

[0002] Heavily doped substrates are key materials in semiconductor manufacturing. They change the electrical properties of silicon substrates by introducing high-concentration doping elements into them, thereby providing a basis for the manufacture of high-performance semiconductor devices.

[0003] For heavily doped substrates without a back-sealing film on the back, such as low temperature oxide (LTO) films, gas phase self-doping is likely to occur during epitaxial growth. Specifically, due to the high doping level of the heavily doped substrate, at the high temperature of the epitaxial process, the dopant in the substrate is easily released from the back of the substrate into the reaction chamber and will grow again in the epitaxial layer with the reaction gas.

[0004] Gas phase self-doping will cause the resistivity of the edge of the grown epitaxial layer to be lower than that of the center, thereby deteriorating the resistivity uniformity of the entire epitaxial layer, thereby affecting the quality of the epitaxial wafer. Summary of the invention

[0005] This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

[0006] The object of the present disclosure is to provide an epitaxial growth method capable of improving the resistivity uniformity of an epitaxial layer formed on a heavily doped substrate without a back seal.

[0007] In order to achieve the above object, according to one aspect of the present disclosure, a method for epitaxial growth of a heavily doped substrate without a back sealing film is provided, comprising:

[0008] placing a heavily doped substrate on a susceptor in a reaction chamber;

[0009] introducing main hydrogen gas into the reaction chamber through the first gas inlet and introducing auxiliary hydrogen gas into the area of ​​the reaction chamber below the susceptor through the second gas inlet;

[0010] baking the reaction chamber at a predetermined temperature; and

[0011] A reaction gas is introduced into the reaction chamber through the first gas inlet to form an epitaxial layer on the heavily doped substrate through a deposition reaction.

[0012] Wherein, at least during the baking and deposition reaction, the flow rate of the main hydrogen gas is greater than or equal to 55 slm, or the flow rate of the auxiliary hydrogen gas is less than or equal to 18 slm.

[0013] In some embodiments, at least during the baking and deposition reactions, the flow rate of the main hydrogen gas may be greater than or equal to 55 slm and the flow rate of the auxiliary hydrogen gas may be less than or equal to 18 slm.

[0014] In some embodiments, when the flow rate of the main hydrogen gas is greater than or equal to 55 slm at least during the baking and deposition reactions, the flow rate of the main hydrogen gas may be 55 slm to 65 slm, and the flow rate of the auxiliary hydrogen gas may be greater than or equal to 13 slm.

[0015] In some embodiments, when the flow rate of the auxiliary hydrogen gas is less than or equal to 18 slm at least during the baking and deposition reactions, the flow rate of the auxiliary hydrogen gas may be 13 slm to 18 slm, and the flow rate of the main hydrogen gas may be less than or equal to 65 slm.

[0016] In some embodiments, at least during the baking and deposition reactions, the flow rate of the main hydrogen gas may be 55 slm to 65 slm and the flow rate of the auxiliary hydrogen gas may be 13 slm to 18 slm.

[0017] In some embodiments, at least during the baking and deposition reactions, the flow rate of the main hydrogen gas may be 60 slm and the flow rate of the auxiliary hydrogen gas may be 15 slm.

[0018] In some embodiments, the predetermined temperature may be 1130° C. to 1150° C., and the duration of the baking may be 80 s to 100 s.

[0019] In some embodiments, the temperature of the deposition reaction may be between 1110°C and 1118°C.

[0020] According to another aspect of the present disclosure, an epitaxial wafer is provided. The epitaxial wafer is prepared from a heavily doped substrate without a back sealing film using the epitaxial growth method according to any of the above embodiments. The resistivity uniformity of the epitaxial layer of the epitaxial wafer can be less than 2.5%.

[0021] According to another aspect of the present disclosure, an epitaxial wafer is provided, which is prepared from a heavily doped substrate without a back sealing film using the epitaxial growth method according to some of the above-mentioned embodiments. The resistivity uniformity of the epitaxial layer of the epitaxial wafer can be less than 2.5%, and the SFQR of the epitaxial wafer can be less than or equal to 30nm.

[0022] According to the above technical solution, by making the flow rate of the main hydrogen gas greater than or equal to 55 slm, or making the flow rate of the auxiliary hydrogen gas less than or equal to 18 slm, at least in the baking stage and the deposition stage, the escape of dopants released from the back side and edge of the substrate 1 to the front side of the substrate 1 can be effectively suppressed, thereby reducing gas phase self-doping and improving the resistivity uniformity of the epitaxial layer formed on the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The features and advantages of the embodiments of the present disclosure will become more easily understood through the following description with reference to the accompanying drawings. The drawings are not drawn to scale and some features may be exaggerated or reduced to show details of particular components.

[0024] In the attached picture:

[0025] Figure 1 The schematic diagram shows the self-doping process of a heavily doped substrate in an epitaxial process, wherein a susceptor and a portion of the substrate supported by the susceptor are shown.

[0026] Figure 2 is a flow chart of an epitaxial growth method according to an embodiment of the present disclosure.

[0027] Figure 3 FIG. 1 is a top view showing a schematic structure of a reaction chamber.

[0028] In the drawings, the same or corresponding technical features or components are represented by the same or corresponding reference numerals. DETAILED DESCRIPTION

[0029] The present disclosure is described in detail below with reference to the accompanying drawings by means of exemplary embodiments. It should be noted that the following detailed description of the present disclosure is only for illustrative purposes and is by no means a limitation of the present disclosure.

[0030] 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.

[0031] Generally, the epitaxial growth process may include a substrate loading phase, a stabilization phase, a temperature rising phase, a baking phase, a deposition phase, and a cleaning and cooling phase.

[0032] Specifically, in the substrate loading stage, the substrate is placed on a susceptor of a reaction chamber so that epitaxial growth can be performed thereon later; in the stabilization stage, the reaction chamber is heated to a first temperature and hydrogen is introduced into the reaction chamber to remove impurity gases in the reaction chamber and on the substrate; in the heating stage, the temperature of the reaction chamber is further increased to a second temperature; in the baking stage, the reaction chamber is continuously baked at the second temperature for a certain period of time; in the deposition stage, a reaction gas, such as trichlorosilane (TCS), is introduced into the reaction chamber to form an epitaxial layer on the substrate through a chemical deposition reaction at the second temperature; in the cleaning and cooling stage, the reaction gas is stopped from entering the reaction chamber and the reaction gas and by-products remaining in the reaction chamber are removed by hydrogen, and the temperature of the reaction chamber is reduced to prepare for the unloading of the formed epitaxial wafer.

[0033] A heavily doped substrate without a back-sealing film, such as an LTO film, is prone to self-doping during epitaxial growth. Figure 1 Here, self-doping is divided into two categories, namely solid phase self-doping ( Figure 1 ) and gas phase self-doping ( Figure 1 Solid phase self-doping refers to the phenomenon that the dopant F in the substrate 200 placed on the susceptor 100 diffuses upward from the substrate 200 to the epitaxial layer 201 at the high temperature of the epitaxial process. Gas phase self-doping refers to the phenomenon that the dopant F in the substrate 200 is released from the back and edge of the substrate 200 into the reaction chamber 300 at the high temperature of the epitaxial process and is diffused into the epitaxial layer 201 along with the reaction gas ( Figure 1 The phenomenon that the epitaxial layer 201 is grown again is shown by the hollow arrow E3 in the figure.

[0034] Gas phase self-doping will cause the resistivity of the edge of the grown epitaxial layer to be lower than that of the center. Even if the doping concentration of the substrate is too high and the resistivity of the entire epitaxial layer is affected, the edge of the epitaxial layer is still the area with the most serious resistivity deterioration. This makes the resistivity uniformity of the entire epitaxial layer worse, thus affecting the quality of the epitaxial wafer.

[0035] In this regard, according to an embodiment of the present disclosure, a method for epitaxial growth of a heavily doped substrate without a backing film is proposed. Figure 2 and Figure 3 , the epitaxial growth method is described in detail.

[0036] like Figure 2 As shown in , the epitaxial growth method comprises:

[0037] Step S1: placing the heavily doped substrate on a base in a reaction chamber;

[0038] Step S2: introducing main hydrogen gas into the reaction chamber through the first gas inlet and introducing auxiliary hydrogen gas into the area of ​​the reaction chamber below the susceptor through the second gas inlet;

[0039] Step S3: baking the reaction chamber at a predetermined temperature; and

[0040] Step S4: introducing a reaction gas into the reaction chamber through the first gas inlet to form an epitaxial layer on the heavily doped substrate through a deposition reaction.

[0041] Wherein, at least during the baking and deposition reaction, that is, in step S3 and step S4, the flow rate of the main hydrogen gas is greater than or equal to 55 slm, or the flow rate of the auxiliary hydrogen gas is less than or equal to 18 slm.

[0042] Reference Figure 3 The reaction chamber 10 generally includes two gas inlets, namely, a first gas inlet 11 and a second gas inlet 12. Figure 3 , the direction of the first gas inlet 11 is exemplarily shown as being orthogonal to the direction of the second gas inlet 12. The first gas inlet 11 is also generally referred to as the main gas inlet, and is used to supply gas to the main area of ​​the reaction chamber 10, that is, mainly to supply gas above the heavily doped substrate 1 placed on the susceptor 20, and the gas includes hydrogen (i.e., the so-called main hydrogen gas (Main H2)), reaction gas, etc. The second gas inlet 12 is also generally referred to as the auxiliary gas inlet, and is mainly used to supply gas to the area of ​​the reaction chamber 10 located below the susceptor 20, and the gas includes hydrogen (i.e., the so-called auxiliary hydrogen gas (Slit H2)). The flow rates of the intake gases of the first gas inlet 11 and the second gas inlet 12 can be controlled, for example, by valves.

[0043] The main hydrogen gas and the auxiliary hydrogen gas are introduced into the reaction chamber 10 until after step S4, for example, until the cleaning and cooling stage of the epitaxial growth process mentioned above. Here, hydrogen can be used as a purge gas, for example, in step S2 and the cleaning and cooling stage, and as a carrier gas for the reaction gas, for example, in step S4.

[0044] In step S3 and step S4, the flow rate of the main hydrogen gas is controlled to be greater than or equal to 55 slm, or the flow rate of the auxiliary hydrogen gas is controlled to be less than or equal to 18 slm.

[0045] This is because the temperature of the baking stage and the deposition stage is higher than that of other process stages of the epitaxial growth process, for example, above 1120°C, and at the end of the deposition stage, the growth of the epitaxial layer is completed. Therefore, in the baking stage and the deposition stage, it is more likely that the dopant in the substrate 1 is released from its back and edge to cause gas phase self-doping, thereby affecting the resistivity uniformity of the epitaxial layer formed on the substrate 1. The inventors found that in the baking stage and the deposition stage, when the flow rate of the main hydrogen gas is greater than or equal to 55 slm, or when the flow rate of the auxiliary hydrogen gas is less than or equal to 18 slm, the dopant released from the back and edge of the substrate 1 cannot escape to the front of the substrate 1, but is released through the holes below the base 20 that penetrate the base 20. As a result, gas phase self-doping can be reduced, thereby improving the resistivity uniformity of the epitaxial layer formed on the substrate 1.

[0046] Furthermore, it is understandable that in other process stages of the epitaxial growth method except the baking stage and the deposition stage, the flow rate of the main hydrogen gas may be greater than or equal to 55 slm, or the flow rate of the auxiliary hydrogen gas may be less than or equal to 18 slm.

[0047] That is to say, in one or more process stages of the epitaxial growth method except the baking stage and the deposition stage, for example, in the entire epitaxial process, more specifically, from the beginning of introducing the main hydrogen gas and the auxiliary hydrogen gas into the reaction chamber 10 to the stopping of introducing the main hydrogen gas and the auxiliary hydrogen gas into the reaction chamber 10, the flow rate of the main hydrogen gas is greater than or equal to 55 slm, or the flow rate of the auxiliary hydrogen gas is less than or equal to 18 slm.

[0048] It can be understood that the reasons for determining the range of the flow rate of the main hydrogen gas and the range of the flow rate of the auxiliary hydrogen gas are similar to those discussed previously and will not be repeated here.

[0049] By introducing the main hydrogen gas and the auxiliary hydrogen gas in the above-mentioned flow range into the reaction chamber in the process stages other than the baking stage and the deposition stage of the epitaxial growth method, for the process stages where dopants may be released from the back side and edge of the substrate, that is, the process stages where the temperature is high and the dopants in the substrate are released from the back side and edge of the substrate, the released dopants can be effectively suppressed from escaping to the front side of the substrate, thereby more effectively reducing gas phase self-doping and thus more effectively improving the resistivity uniformity of the epitaxial layer formed on the substrate.

[0050] In some embodiments, at least during the baking and deposition reactions, the flow rate of the main hydrogen gas may be greater than or equal to 55 slm and the flow rate of the auxiliary hydrogen gas may be less than or equal to 18 slm.

[0051] When the flow rate of the main hydrogen gas is greater than or equal to 55 slm, and when the flow rate of the auxiliary hydrogen gas is less than or equal to 18 slm, the dopant released from the back and edge of the substrate can be suppressed from escaping to the front of the substrate, and when the flow rates of the main hydrogen gas and the auxiliary hydrogen gas simultaneously meet the above conditions, compared with the case where only one of them meets the above corresponding conditions, the dopant released from the back and edge of the substrate can be more effectively suppressed from escaping to the front of the substrate. As a result, gas phase self-doping can be more effectively reduced, and thus the resistivity uniformity of the epitaxial layer formed on the substrate can be more effectively improved.

[0052] In some embodiments, when the flow rate of the main hydrogen gas is greater than or equal to 55 slm at least during the baking and deposition reactions, the flow rate of the main hydrogen gas may be 55 slm to 65 slm, and the flow rate of the auxiliary hydrogen gas may be greater than or equal to 13 slm.

[0053] This is because when the flow rate of the main hydrogen gas is greater than or equal to 55 slm, the resistivity uniformity of the epitaxial layer formed on the substrate can be improved for reasons similar to those stated above; and if the flow rate of the main hydrogen gas is greater than 65 slm or the flow rate of the auxiliary hydrogen gas is less than 13 slm, the surface flatness of the formed epitaxial wafer will deteriorate. That is, by making the flow rates of the main hydrogen gas and the auxiliary hydrogen gas within the above range, not only can the resistivity uniformity of the epitaxial layer be improved, but also the surface flatness of the epitaxial wafer can be made good.

[0054] In some embodiments, when the flow rate of the auxiliary hydrogen gas is less than or equal to 18 slm at least during the baking and deposition reactions, the flow rate of the auxiliary hydrogen gas may be 13 slm to 18 slm, and the flow rate of the main hydrogen gas may be less than or equal to 65 slm.

[0055] This is because when the flow rate of the auxiliary hydrogen gas is less than or equal to 18 slm, the resistivity uniformity of the epitaxial layer formed on the substrate can be improved for reasons similar to those stated above; and if the flow rate of the auxiliary hydrogen gas is less than 13 slm or the flow rate of the main hydrogen gas is greater than 65 slm, the surface flatness of the formed epitaxial wafer will deteriorate. That is, by making the flow rates of the main hydrogen gas and the auxiliary hydrogen gas within the above range, not only can the resistivity uniformity of the epitaxial layer be improved, but also the surface flatness of the epitaxial wafer can be made good.

[0056] In some embodiments, at least during the baking and deposition reactions, the flow rate of the main hydrogen gas may be 55 slm to 65 slm and the flow rate of the auxiliary hydrogen gas may be 13 slm to 18 slm.

[0057] In this case, since the flow rate of the main hydrogen gas is greater than or equal to 55 slm and the flow rate of the auxiliary hydrogen gas is less than or equal to 18 slm, compared with the case where only one of the main hydrogen gas and the auxiliary hydrogen gas satisfies the above corresponding conditions, the dopant released from the back and edge of the substrate to the front of the substrate can be more effectively suppressed, thereby more effectively improving the resistivity uniformity of the epitaxial layer formed on the substrate. In addition, since the flow rate of the main hydrogen gas is less than or equal to 65 slm and the flow rate of the auxiliary hydrogen gas is greater than or equal to 13 slm, the surface of the formed epitaxial wafer can have good flatness.

[0058] In some embodiments, the temperature of the deposition reaction in step S4 may be 1110°C to 1118°C.

[0059] This is because when the temperature of the deposition reaction is less than 1110°C, the resistivity uniformity of the epitaxial wafer formed will deteriorate, and when the temperature of the deposition reaction is greater than 1118°C, the surface flatness of the epitaxial layer formed on the substrate will deteriorate. When the temperature of the deposition reaction is between 1110°C and 1118°C, the resistivity uniformity of the epitaxial layer formed on the substrate can be improved, and the surface flatness of the epitaxial wafer can be improved.

[0060] In addition, the autodoping may also affect the target value of the resistivity of the epitaxial layers formed on each substrate obtained from different positions of the crystal rod.

[0061] The dopant concentration inside the crystal rod may be different along its longitudinal direction and radial direction, so the dopant concentration of the substrate obtained at different positions of the crystal rod may also be different. Therefore, when self-doping occurs, the target value of the resistivity of the epitaxial layer formed on each substrate obtained from different positions of the crystal rod will be different, resulting in a large difference in the resistance of the final product obtained from the crystal rod.

[0062] In this regard, in some embodiments, the predetermined temperature for baking in step S3 may be 1130° C. to 1150° C., and the duration of baking may be 80 s to 100 s.

[0063] This is because if the predetermined baking temperature is less than 1130°C, the tendency of dopants in the substrate to release outward is slow, and it is difficult to release the dopants in the outermost layer of the substrate (including the back surface, the front surface and the edge surface) in advance during the baking stage. If the predetermined baking temperature is greater than 1150°C, it is easy to cause haze defects. Moreover, if the baking duration is less than 80s, it is also difficult to accelerate the tendency of dopants in the substrate to release outward, which is not conducive to releasing the dopants in the outermost layer of the substrate in advance during the baking stage. If the baking duration is greater than 100s, it is also easy to cause haze defects.

[0064] When the predetermined baking temperature is 1130°C to 1150°C and the baking duration is 80s to 100s, the tendency of dopants in the substrate to be released outward can be accelerated, prompting the dopants in the outermost layer of the substrate to be released in advance during the baking stage and fully volatilized before the deposition stage of step S4. As a result, the self-doping in the deposition stage can be reduced, thereby reducing the influence of the difference in dopant concentration on the resistivity of the epitaxial layers formed on each substrate obtained from different positions of the crystal rod, so that the difference between the target values ​​of the resistivity of each epitaxial layer formed is reduced, and thus the difference between the resistances of the final product obtained by the crystal rod can be reduced. In addition, when the predetermined baking temperature is 1130°C to 1150°C and the baking duration is 80s to 100s, the risk of causing Haze can also be avoided.

[0065] An epitaxial wafer can be prepared by the epitaxial growth method. In the embodiment of the present disclosure, the resistivity uniformity of the epitaxial layer of the epitaxial wafer can be less than 8.5%, and can be further less than 2.5%.

[0066] In some embodiments, the resistivity uniformity of the epitaxial layer of the epitaxial wafer may be less than 2.5%, and the SFQR of the epitaxial wafer may be less than or equal to 30 nm.

[0067] Resistivity uniformity refers to the consistency of resistivity at different positions of the epitaxial layer, which can be measured by a variety of methods, including four-probe test, Hall effect measurement, etc. In this article, resistivity uniformity can be obtained, for example, in the following manner: first, excluding the area 5 mm away from the edge of the epitaxial layer, sampling is performed at a point in the center, four points at half the radius, and four points at the edge of the epitaxial layer, and then the ratio of the difference between the maximum and minimum values ​​of the resistivity of each sampled point to the sum of the maximum and minimum values ​​is calculated.

[0068] <Preliminary Study on Epitaxial Growth Method>

[0069] Epitaxial wafers according to Examples A1 to A3 and Comparative Examples A1 to A5 were prepared according to the epitaxial growth method of the above-mentioned embodiment. Except for the flow rates of the main hydrogen gas and the auxiliary hydrogen gas, these epitaxial wafers were prepared according to the same process conditions. Specifically, in the stabilization stage, the power of the heating lamp is 40KW, and the heating time is 10s; in the heating stage, the reaction chamber is heated to 1120°C; in the baking stage, the temperature is maintained at 1120°C, and the baking time is 30s; in the deposition stage, the temperature is maintained at 1120°C, and the TCS flow rate is 8slm; in the cleaning stage, the temperature is maintained at 1120°C, and the cleaning time is 10s; in the cooling stage, the power of the heating lamp is 5KW, and the cooling time is 10s, and auxiliary gases such as hydrogen chloride (HCL) are not introduced in the entire process stage.

[0070] Table 1

[0071] project Main hydrogen (slm) Auxiliary hydrogen (slm) Resistivity uniformity SFQR(nm) Example A1 60 20 7.64％ 30 Example A2 50 15 8.23％ 29 Example A3 60 15 6.14％ 30 Comparative Example A1 50 20 14.17％ 28 Comparative Example A2 60 10 6.52％ 35 Comparative Example A3 70 15 5.91％ 34 Comparative Example A4 70 10 5.85％ 38 Comparative Example A5 80 10 5.67％ 45

[0072] Table 1 shows the flow rates of main hydrogen gas and auxiliary hydrogen gas introduced into the reaction chamber during the baking stage and the deposition stage when epitaxial wafers are prepared according to Examples A1 to A3 and Comparative Examples A1 to A5, as well as the corresponding resistivity uniformity of the epitaxial layer of the prepared epitaxial wafers and the corresponding flatness of the epitaxial wafers represented by SFQR.

[0073] In Examples A1 and A3, the flow rate of the main hydrogen gas is greater than 55 slm, and in Examples A2 and A3, the flow rate of the auxiliary hydrogen gas is less than 18 slm, and the resistivity uniformity of the epitaxial layer is less than 8.5%. In Comparative Example A1, the flow rate of the main hydrogen gas is less than 55 slm and the flow rate of the auxiliary hydrogen gas is greater than 18 slm, and the resistivity uniformity of the epitaxial layer is 14.17%, which is greater than 8.5%. Therefore, when the flow rate of the main hydrogen gas is greater than or equal to 55 slm, or the flow rate of the auxiliary hydrogen gas is less than or equal to 18 slm, the resistivity uniformity of the epitaxial layer formed on the substrate can be improved.

[0074] Moreover, in Example A3, the flow rate of the main hydrogen gas is greater than 55 slm and the flow rate of the auxiliary hydrogen gas is less than 18 slm, and the resistivity uniformity of the epitaxial layer is 6.14%. In Example A1, the flow rate of the main hydrogen gas is greater than 55 slm, but the flow rate of the auxiliary hydrogen gas is greater than 18 slm; in Example A2, the flow rate of the auxiliary hydrogen gas is less than 18 slm, but the flow rate of the main hydrogen gas is less than 55 slm, and the resistivity uniformity of the epitaxial layer is 7.64% and 8.23%, respectively, both less than 6.14%. Therefore, when the flow rate of the main hydrogen gas is greater than 55 slm and the flow rate of the auxiliary hydrogen gas is less than 18 slm, the resistivity uniformity of the epitaxial layer formed on the substrate can be more effectively improved.

[0075] In Examples A1 and A3, the flow rate of the main hydrogen is in the range of 55slm to 65slm, and the flow rate of the auxiliary hydrogen is greater than 13slm, the resistivity uniformity of the epitaxial layer is less than 8.5%, and the SFQR of the epitaxial wafer is 30nm. In Comparative Example A1, the flow rate of the auxiliary hydrogen is greater than 13slm, but the flow rate of the main hydrogen is less than 55slm, the SFQR of the epitaxial wafer is less than 30nm, but the resistivity uniformity of the epitaxial layer is greater than 8.5%. In Comparative Example A2, the flow rate of the main hydrogen is in the range of 55slm to 65slm, but the flow rate of the auxiliary hydrogen is less than 13slm, the resistivity uniformity of the epitaxial layer is less than 8.5%, but the SFQR of the epitaxial wafer is greater than 30nm. In Comparative Example A3, the flow rate of the auxiliary hydrogen is greater than 13slm, but the flow rate of the main hydrogen is greater than 65slm, the resistivity uniformity of the epitaxial layer is less than 8.5%, but the SFQR of the epitaxial wafer is greater than 30nm. In comparative examples A4 and A5, the flow rate of the main hydrogen gas is greater than 65 slm and the flow rate of the auxiliary hydrogen gas is less than 13 slm, the resistivity uniformity of the epitaxial layer is less than 8.5%, but the SFQR of the epitaxial wafer is greater than 30 nm. Therefore, when the flow rate of the main hydrogen gas is within the range of 55 slm to 65 slm, and the flow rate of the auxiliary hydrogen gas is greater than or equal to 13 slm, not only the resistivity uniformity of the epitaxial layer can be improved, but also the surface of the epitaxial wafer can have good flatness.

[0076] In Examples A2 and A3, the flow rate of the auxiliary hydrogen is in the range of 13slm to 18slm, and the flow rate of the main hydrogen is less than 65slm, the resistivity uniformity of the epitaxial layer is less than 8.5%, and the SFQR of the epitaxial wafer is less than or equal to 30nm. In Comparative Example A1, the flow rate of the main hydrogen is less than 65slm, but the flow rate of the auxiliary hydrogen is greater than 18slm, the SFQR of the epitaxial wafer is less than 30nm, but the resistivity uniformity of the epitaxial layer is greater than 8.5%. In Comparative Example A2, the flow rate of the main hydrogen is less than 65slm, but the flow rate of the auxiliary hydrogen is less than 13slm, the resistivity uniformity of the epitaxial layer is less than 8.5%, but the SFQR of the epitaxial wafer is greater than 30nm. In Comparative Example A3, the flow rate of the auxiliary hydrogen is in the range of 13slm to 18slm, but the flow rate of the main hydrogen is greater than 65slm, the resistivity uniformity of the epitaxial layer is less than 8.5%, but the SFQR of the epitaxial wafer is greater than 30nm. In comparative examples A4 and A5, the flow rate of the main hydrogen gas is greater than 65 slm and the flow rate of the auxiliary hydrogen gas is less than 13 slm, the resistivity uniformity of the epitaxial layer is less than 8.5%, but the SFQR of the epitaxial wafer is greater than 30 nm. Therefore, when the flow rate of the auxiliary hydrogen gas is within the range of 13 slm to 18 slm and the flow rate of the main hydrogen gas is less than 65 slm, not only the resistivity uniformity of the epitaxial layer can be improved, but also the surface of the epitaxial wafer can have good flatness.

[0077] In Example A3, the flow rate of the main hydrogen gas is in the range of 55 slm to 65 slm and the flow rate of the auxiliary hydrogen gas is in the range of 13 slm to 18 slm, the resistivity uniformity of the epitaxial layer is 6.14%, and the SFQR of the epitaxial wafer is equal to 30 nm. In Example A1, the flow rate of the main hydrogen gas is in the range of 55 slm to 65 slm, but the flow rate of the auxiliary hydrogen gas is greater than 18 slm, the SFQR of the epitaxial wafer is equal to 30 nm, but the resistivity uniformity of the epitaxial layer is greater than 6.14%. In Example A2, the flow rate of the auxiliary hydrogen gas is in the range of 13 slm to 18 slm, but the flow rate of the main hydrogen gas is less than 55 slm, the SFQR of the epitaxial wafer is less than 30 nm, but the resistivity uniformity of the epitaxial layer is greater than 6.14%. Therefore, when the flow rate of the main hydrogen gas is in the range of 55slm to 65slm and the flow rate of the auxiliary hydrogen gas is in the range of 13slm to 18slm, not only can the surface of the formed epitaxial wafer have good flatness, but the resistivity uniformity of the epitaxial layer formed on the substrate can also be more effectively improved.

[0078] The epitaxial wafers according to Example B1 and Comparative Examples B1 and B2 were prepared according to the same process conditions as those described above with respect to Examples A1 to A3, except for the deposition temperature, with the same flow rates of main hydrogen and auxiliary hydrogen.

[0079] Table 2

[0080] project Deposition temperature (℃) Resistivity uniformity SFQR(nm) Example B1 1115 5.26 29 Comparative Example B1 1105 7.51 27 Comparative Example B2 1125 4.78 38

[0081] Table 2 shows the deposition temperature when preparing the epitaxial wafer according to Example B1 and Comparative Examples B1 and B2, as well as the corresponding resistivity uniformity of the epitaxial layer of the prepared epitaxial wafer and the corresponding flatness of the epitaxial wafer represented by SFQR.

[0082] In Example B1, the deposition temperature is in the range of 1110°C to 1118°C, the resistivity uniformity of the epitaxial layer is 5.26%, and the SFQR of the epitaxial wafer is 29nm. In Comparative Example B1, the deposition temperature is less than 1110°C, the SFQR of the epitaxial wafer is 27nm, but the resistivity uniformity of the epitaxial layer is 7.51%, which is worse than 5.26%. In Comparative Example B2, the deposition temperature is greater than 1118°C, the resistivity uniformity of the epitaxial layer is 4.78%, but the SFQR of the epitaxial wafer is 38nm, which is worse than 27nm. Therefore, when the deposition temperature is in the range of 1110°C to 1118°C, not only can the resistivity uniformity of the epitaxial layer formed on the substrate be improved, but also the surface of the epitaxial wafer can have good flatness.

[0083] The epitaxial wafers according to Example C1 and Comparative Examples C1 and C2 were prepared according to the same process conditions as those described above with respect to Examples A1 to A3, except for the baking temperature, with the same flow rates of main hydrogen and auxiliary hydrogen.

[0084] Table 3

[0085]

[0086] Table 3 shows the baking temperature and baking time when preparing the corresponding epitaxial wafers according to Example C1 and Comparative Examples C1 and C2 for each silicon substrate obtained from different positions of the crystal rod, the resistivity target value of the epitaxial layer of the epitaxial wafer prepared according to the silicon substrate obtained from the head, middle and tail of the crystal rod, respectively, and the corresponding Haze.

[0087] In Example C1, the baking temperature is in the range of 1130°C to 1150°C and the baking time is in the range of 80s to 100s, and the resistivity target values ​​of the epitaxial wafers corresponding to the head, middle and tail of the crystal rod, respectively, tend to be consistent, and the Haze is 0.25ppm. In Comparative Example C1, the baking temperature is less than 1130°C and the baking time is less than 80s, and the Haze is 0.21ppm, but there are significant differences in the resistivity target values ​​of the epitaxial wafers corresponding to the head, middle and tail of the crystal rod, respectively. In Comparative Example C2, the baking temperature is greater than 1150°C and the baking time is greater than 100s, and the resistivity target values ​​of the epitaxial wafers corresponding to the head, middle and tail of the crystal rod, respectively, tend to be consistent, but the Haze is 0.43ppm, which is significantly worse than 0.25ppm. Therefore, when the predetermined baking temperature is 1130°C to 1150°C and the baking duration is 80s to 100s, not only can the difference between the target values ​​of the resistivity of the epitaxial layers formed on various substrates obtained from different positions of the crystal rod be reduced, but also the risk of causing Haze can be avoided.

[0088] 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.

[0089] The features mentioned and / or shown in the above description of the exemplary embodiments of the present disclosure may be combined in the same or similar manner into one or more other embodiments, combined with the features in other embodiments or substituted for the corresponding features in other embodiments. The technical solutions obtained by these combinations or substitutions shall also be deemed to be included in the protection scope of the present disclosure.

Claims

1. An epitaxial growth method for a heavily doped substrate without a backing film, characterized in that: include: placing the heavily doped substrate on a susceptor in a reaction chamber; introducing main hydrogen gas into the reaction chamber through a first gas inlet and introducing auxiliary hydrogen gas into a region of the reaction chamber below the susceptor through a second gas inlet; baking the reaction chamber at a predetermined temperature; as well as introducing a reaction gas into the reaction chamber through the first gas inlet to form an epitaxial layer on the heavily doped substrate through a deposition reaction, Wherein, at least during the baking and the deposition reaction, the flow rate of the main hydrogen gas is greater than or equal to 55 slm, or the flow rate of the auxiliary hydrogen gas is less than or equal to 18 slm.

2. The epitaxial growth method according to claim 1, characterized in that: At least during the baking and the deposition reaction, the flow rate of the main hydrogen gas is greater than or equal to 55 slm and the flow rate of the auxiliary hydrogen gas is less than or equal to 18 slm.

3. The epitaxial growth method according to claim 1, characterized in that: In the case where the flow rate of the main hydrogen gas is greater than or equal to 55 slm at least during the baking and the deposition reaction, the flow rate of the main hydrogen gas is 55 slm to 65 slm, and the flow rate of the auxiliary hydrogen gas is greater than or equal to 13 slm.

4. The epitaxial growth method according to claim 1, characterized in that: In the case where the flow rate of the auxiliary hydrogen gas is less than or equal to 18 slm at least during the baking and the deposition reaction, the flow rate of the auxiliary hydrogen gas is 13 slm to 18 slm, and the flow rate of the main hydrogen gas is less than or equal to 65 slm.

5. The epitaxial growth method according to claim 1, characterized in that: At least during the baking and the deposition reaction, the flow rate of the main hydrogen gas is 55 slm to 65 slm and the flow rate of the auxiliary hydrogen gas is 13 slm to 18 slm.

6. The epitaxial growth method according to claim 5, characterized in that: At least during the baking and the deposition reaction, the flow rate of the main hydrogen gas is 60 slm and the flow rate of the auxiliary hydrogen gas is 15 slm.

7. The epitaxial growth method according to any one of claims 1 to 6, characterized in that: The predetermined temperature is 1130° C. to 1150° C., and the baking duration is 80 s to 100 s.

8. The epitaxial growth method according to any one of claims 1 to 6, characterized in that: The temperature of the deposition reaction is 1110°C to 1118°C.

9. An epitaxial wafer, characterized in that: The epitaxial wafer is prepared from a heavily doped substrate without a back sealing film using the epitaxial growth method according to any one of claims 1 to 8, and the resistivity uniformity of the epitaxial layer of the epitaxial wafer is less than 2.5%.

10. An epitaxial wafer, characterized in that: The epitaxial wafer is prepared by using the epitaxial growth method according to any one of claims 3 to 6 from a heavily doped substrate without a back sealing film, the resistivity uniformity of the epitaxial layer of the epitaxial wafer is less than 2.5%, and the SFQR of the epitaxial wafer is less than or equal to 30nm.

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