Epitaxial growth method and epitaxial wafer

Abstract

The present disclosure relates to an epitaxial growth method and an epitaxial wafer. In one aspect, provided is an epitaxial growth method for a heavily doped substrate without a back seal film. The method comprises: placing the heavily doped substrate on a pedestal of a reaction chamber; introducing main hydrogen into the reaction chamber via a first gas inlet and auxiliary hydrogen into the region of the reaction chamber below the pedestal via a second gas inlet; baking the reaction chamber at a predetermined temperature; and introducing a reaction gas into the reaction chamber via the first gas inlet, so as to form an epitaxial layer on the heavily doped substrate by means of a deposition reaction, wherein, at least during baking and the deposition reaction, the flow rate of the main hydrogen is greater than or equal to 55 slm, or the flow rate of the auxiliary hydrogen is less than or equal to 18 slm.

Description

Epitaxial growth methods and epitaxial wafers

[0001] Cross-reference to related applications

[0002] This disclosure claims priority to Chinese Patent Application No. 202411494740.5, filed in China on October 24, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of semiconductor processing and manufacturing technology, and more specifically, to epitaxial growth methods and epitaxial wafers. Background Technology

[0004] Heavy doped substrates are key materials in semiconductor manufacturing. They are created by introducing high concentrations of doping elements into silicon substrates to alter their electrical properties, thereby providing a foundation for the manufacture of high-performance semiconductor devices.

[0005] For heavily doped substrates without a back seal, such as those with low-temperature oxide (LTO) films, vapor-phase self-doping is prone to occur during epitaxial growth. Specifically, due to the high doping degree of the heavily doped substrate, at the high temperatures of the epitaxial process, the dopant in the substrate is easily released from the back side of the substrate into the reaction chamber and will grow again in the epitaxial layer along with the reaction gas.

[0006] Vapor phase self-doping causes the resistivity at the edges of the grown epitaxial layer to be lower than that in the center. This results in poor resistivity uniformity of the entire epitaxial layer, thus affecting the quality of the epitaxial wafer. Summary of the Invention

[0007] This section provides a general overview of this disclosure, rather than a full disclosure of the entire scope or all features of this disclosure.

[0008] The purpose of this disclosure is to provide an epitaxial growth method that can improve the resistivity uniformity of epitaxial layers formed on heavily doped substrates without back seals.

[0009] To achieve the above objectives, according to one aspect of this disclosure, an epitaxial growth method for a heavily doped substrate without a back seal is provided, comprising:

[0010] The heavily doped substrate is placed on the base of the reaction chamber;

[0011] Main hydrogen gas is introduced into the reaction chamber through the first inlet and auxiliary hydrogen gas is introduced into the area of ​​the reaction chamber located below the base through the second inlet.

[0012] The reaction chamber was baked at a predetermined temperature; and

[0013] Reactive 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.

[0014] Specifically, at least during the baking and deposition reactions, the flow rate of primary hydrogen is greater than or equal to 55 slm, or the flow rate of auxiliary hydrogen is less than or equal to 18 slm.

[0015] In some implementations, at least during the baking and deposition reactions, the flow rate of primary hydrogen can be greater than or equal to 55 slm and the flow rate of auxiliary hydrogen can be less than or equal to 18 slm.

[0016] In some embodiments, where the main hydrogen flow rate is greater than or equal to 55 slm during at least the baking and deposition reactions described above, the main hydrogen flow rate can be between 55 slm and 65 slm, and the auxiliary hydrogen flow rate can be greater than or equal to 13 slm.

[0017] In some embodiments, where the auxiliary hydrogen flow rate is less than or equal to 18 slm during at least the baking and deposition reactions described above, the auxiliary hydrogen flow rate can be from 13 slm to 18 slm, and the main hydrogen flow rate can be less than or equal to 65 slm.

[0018] In some embodiments, at least during the baking and deposition reactions, the main hydrogen flow rate can be 55 slm to 65 slm and the auxiliary hydrogen flow rate can be 13 slm to 18 slm.

[0019] In some implementations, the main hydrogen flow rate can be 60 slm and the auxiliary hydrogen flow rate can be 15 slm, at least during the baking and deposition reactions.

[0020] In some embodiments, the predetermined temperature can be from 1130°C to 1150°C, and the baking duration can be from 80s to 100s.

[0021] In some embodiments, the deposition reaction temperature can be from 1110°C to 1118°C.

[0022] According to another aspect of this disclosure, an epitaxial wafer is also provided, which is prepared from a heavily doped substrate without a back seal using an epitaxial growth method according to any of the above embodiments, wherein the resistivity uniformity of the epitaxial layer of the epitaxial wafer can be less than 2.5%.

[0023] According to another aspect of this disclosure, an epitaxial wafer is also provided, which is prepared from a heavily doped substrate without a back seal using an epitaxial growth method according to some of the embodiments described above. 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 30 nm.

[0024] According to the above technical solution, by making the flow rate of the main hydrogen gas greater than or equal to 55 slm or the flow rate of the auxiliary hydrogen gas less than or equal to 18 slm at least in the baking and deposition stages, the escape of dopant released from the back side and edge of the substrate 1 to the front side of the substrate 1 can be effectively suppressed. This reduces gas phase self-doping and improves the resistivity uniformity of the epitaxial layer formed on the substrate. Attached Figure Description

[0025] The features and advantages of embodiments of the present disclosure will become more readily understood from the following description with reference to the accompanying drawings. The drawings are not drawn to scale and some features may be enlarged or reduced to show details of specific components. In the drawings:

[0026] Figure 1 is a schematic diagram showing the self-doping process of a heavily doped substrate in an epitaxial process, showing a base and a portion of the substrate it supports.

[0027] Figure 2 is a flowchart of an epitaxial growth method according to an embodiment of the present disclosure.

[0028] Figure 3 is a top view showing a schematic structure of the reaction chamber.

[0029] In the accompanying drawings, the same or corresponding technical features or components are represented by the same or corresponding reference numerals. Detailed Implementation

[0030] The present disclosure will now be described in detail with reference to the accompanying drawings and exemplary embodiments. It should be noted that the following detailed description of the present disclosure is for illustrative purposes only and is not intended to limit the scope of the disclosure.

[0031] 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 disclosure, only the apparatus structures and method steps closely related to the technical solutions of this disclosure are described and shown in the specification and drawings, while other details that are not closely related to the technical content of this disclosure and are known to those skilled in the art are omitted.

[0032] Typically, the epitaxial growth process can include a substrate loading stage, a stabilization stage, a heating stage, a baking stage, a deposition stage, and a cleaning and cooling stage.

[0033] Specifically, in the substrate loading stage, the substrate is placed on the base of the reaction chamber for subsequent epitaxial growth; 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 from the reaction chamber and 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 being introduced into the reaction chamber and the residual reaction gas and byproducts in the reaction chamber are removed by hydrogen, and the temperature of the reaction chamber is reduced in preparation for unloading the formed epitaxial wafer.

[0034] Heavy-doped substrates without a back seal, such as LTO films, are prone to self-doping during epitaxial growth. Referring to Figure 1, self-doping is divided into two categories: solid-phase self-doping (shown as hollow arrow E1 in Figure 1) and gas-phase self-doping (shown as hollow arrow E2 in Figure 1). Solid-phase self-doping refers to the phenomenon where dopant F in the substrate 200 placed on the substrate 100 at high temperatures during the epitaxial process diffuses upwards from the substrate 200 to the epitaxial layer 201. Gas-phase self-doping refers to the phenomenon where dopant F in the substrate 200 is released from the back side and edges of the substrate 200 into the reaction chamber 300 at high temperatures during the epitaxial process and re-grows in the epitaxial layer 201 with the reaction gas (shown as hollow arrow E3 in Figure 1).

[0035] Vapor phase self-doping results in lower resistivity at the edges of the grown epitaxial layer compared to the center. Even when the substrate doping concentration is too high, affecting the resistivity of the entire epitaxial layer, the edges remain the areas with the most severe resistivity degradation. This leads to poor resistivity uniformity across the entire epitaxial layer, thus impacting the quality of the epitaxial wafer.

[0036] In view of this, according to embodiments of the present disclosure, an epitaxial growth method for heavily doped substrates without a back seal is proposed. The epitaxial growth method will now be described in detail with reference to FIGS. 2 and 3.

[0037] As shown in Figure 2, the epitaxial growth method includes:

[0038] Step S1: Place the heavily doped substrate on the base of the reaction chamber;

[0039] Step S2: Introduce main hydrogen gas into the reaction chamber through the first inlet and introduce auxiliary hydrogen gas into the area of ​​the reaction chamber located below the base through the second inlet;

[0040] Step S3: Bake the reaction chamber at a predetermined temperature; and

[0041] Step S4: Reactive 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.

[0042] Specifically, at least during the baking and deposition reactions, i.e., in steps S3 and S4, the flow rate of the main hydrogen is greater than or equal to 55 standard liters per minute (slm), or the flow rate of the auxiliary hydrogen is less than or equal to 18 slm.

[0043] Referring to Figure 3, the reaction chamber 10 typically includes two gas inlets: a first gas inlet 11 and a second gas inlet 12. In Figure 3, the direction of the first gas inlet 11 is shown exemplarily as orthogonal to the direction of the second gas inlet 12. The first gas inlet 11, also commonly referred to as the main gas inlet, is used to supply gas to the main region of the reaction chamber 10, i.e., primarily to the area above the heavily doped substrate 1 placed on the base 20. This gas includes hydrogen (i.e., commonly referred to as main hydrogen (Main H2)), reactant gases, etc. The second gas inlet 12, also commonly referred to as the secondary gas inlet, primarily supplies gas to the region of the reaction chamber 10 located below the base 20. This gas includes hydrogen (i.e., commonly referred to as auxiliary hydrogen (Slit H2)). The flow rates of the gas entering through the first gas inlet 11 and the second gas inlet 12 can be controlled, for example, by valves.

[0044] The introduction of main hydrogen and auxiliary hydrogen into reaction chamber 10 continues after step S4, for example, until the cleaning and cooling stages 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 stages, and as a carrier gas for the reaction, for example in step S4.

[0045] In steps S3 and 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.

[0046] This is because the baking and deposition stages have higher temperatures compared to other stages of the epitaxial growth process, for example, above 1120°C. Furthermore, the epitaxial layer growth is complete by the end of the deposition stage. Therefore, during the baking and deposition stages, dopants in substrate 1 are more likely to be released from their back side and edges, resulting in vapor-phase self-doping and affecting the resistivity uniformity of the epitaxial layer formed on substrate 1. The inventors discovered that during the baking and deposition stages, when the main hydrogen flow rate is greater than or equal to 55 slm, or when the auxiliary hydrogen flow rate is less than or equal to 18 slm, the dopants released from the back side and edges of substrate 1 cannot escape to the front side of substrate 1, but instead are released through the holes penetrating substrate 20 below substrate 20. This reduces vapor-phase self-doping, thereby improving the resistivity uniformity of the epitaxial layer formed on substrate 1.

[0047] Moreover, it is understandable that in other process stages of this epitaxial growth method besides the baking and deposition stages, the flow rate of the main hydrogen gas can be greater than or equal to 55 slm, or the flow rate of the auxiliary hydrogen gas can be less than or equal to 18 slm.

[0048] In other words, in one or more process stages of the epitaxial growth method other than the baking stage and the deposition stage, for example, throughout the entire epitaxial process, more specifically, from the beginning of the introduction of main hydrogen and auxiliary hydrogen into the reaction chamber 10 until the introduction of main hydrogen and auxiliary hydrogen into the reaction chamber 10 is stopped, the flow rate of the main hydrogen is greater than or equal to 55 slm, or the flow rate of the auxiliary hydrogen is less than or equal to 18 slm.

[0049] Understandably, the reasons for determining the range of main hydrogen flow rate and auxiliary hydrogen flow rate are similar to those discussed previously, and will not be repeated here.

[0050] By introducing the main hydrogen and auxiliary hydrogen at the above-mentioned flow rates into the reaction chamber in other process stages of this epitaxial growth method, except for the baking and deposition stages, the release of dopants to the front side of the substrate can be effectively suppressed in process stages where dopants may be released from the back side and edges of the substrate, i.e., process stages where the temperature is high and dopants in the substrate are released from the back side and edges of the substrate. This can more effectively reduce gas phase self-doping and thus more effectively improve the resistivity uniformity of the epitaxial layer formed on the substrate.

[0051] In some implementations, at least during the baking and deposition reactions, the flow rate of primary hydrogen can be greater than or equal to 55 slm and the flow rate of auxiliary hydrogen can be less than or equal to 18 slm.

[0052] When the main hydrogen flow rate is greater than or equal to 55 slm, and when the auxiliary hydrogen flow rate is less than or equal to 18 slm, the escape of dopant released from the back side and edges of the substrate to the front side of the substrate can be suppressed. Furthermore, when both the main and auxiliary hydrogen flow rates meet the above conditions simultaneously, the escape of dopant released from the back side and edges of the substrate to the front side is suppressed more effectively than when only one of the conditions is met. Therefore, gas-phase self-doping can be reduced more effectively, and thus the resistivity uniformity of the epitaxial layer formed on the substrate can be improved more effectively.

[0053] In some embodiments, where the main hydrogen flow rate is greater than or equal to 55 slm during at least the baking and deposition reactions described above, the main hydrogen flow rate can be between 55 slm and 65 slm, and the auxiliary hydrogen flow rate is greater than or equal to 13 slm.

[0054] This is because when the main hydrogen flow rate 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 previously. Furthermore, if the main hydrogen flow rate is greater than 65 slm or the auxiliary hydrogen flow rate is less than 13 slm, the surface flatness of the formed epitaxial wafer will deteriorate. In other words, by keeping the flow rates of the main and auxiliary hydrogen within the aforementioned ranges, not only can the resistivity uniformity of the epitaxial layer be improved, but the surface flatness of the epitaxial wafer can also be ensured.

[0055] In some embodiments, where the auxiliary hydrogen flow rate is less than or equal to 18 slm during at least the baking and deposition reactions described above, the auxiliary hydrogen flow rate can be from 13 slm to 18 slm, and the main hydrogen flow rate is less than or equal to 65 slm.

[0056] This is because when the auxiliary hydrogen flow rate 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 previously. Furthermore, if the auxiliary hydrogen flow rate is less than 13 slm or the main hydrogen flow rate is greater than 65 slm, the surface flatness of the formed epitaxial wafer will deteriorate. In other words, by keeping the flow rates of both the main and auxiliary hydrogen within the aforementioned ranges, not only can the resistivity uniformity of the epitaxial layer be improved, but the surface flatness of the epitaxial wafer can also be ensured.

[0057] In some embodiments, at least during the baking and deposition reactions, the main hydrogen flow rate can be 55 slm to 65 slm and the auxiliary hydrogen flow rate can be 13 slm to 18 slm.

[0058] In this configuration, since the main hydrogen flow rate is greater than or equal to 55 slm and the auxiliary hydrogen flow rate is less than or equal to 18 slm, compared to the case where only one of the main or auxiliary hydrogen meets the aforementioned conditions, the escape of dopant released from the back and edges of the substrate to the front side of the substrate can be more effectively suppressed, thereby improving the resistivity uniformity of the epitaxial layer formed on the substrate more effectively. Furthermore, since the main hydrogen flow rate is less than or equal to 65 slm and the auxiliary hydrogen flow rate is greater than or equal to 13 slm, the surface of the formed epitaxial wafer can have good flatness.

[0059] In some embodiments, the temperature of the deposition reaction in step S4 can be from 1110°C to 1118°C.

[0060] This is because when the deposition temperature is below 1110℃, the resistivity uniformity of the resulting epitaxial wafer deteriorates, while when the deposition temperature is above 1118℃, the surface flatness of the epitaxial layer formed on the substrate deteriorates. A deposition temperature between 1110℃ and 1118℃ improves the resistivity uniformity of the epitaxial layer formed on the substrate and also ensures good surface flatness of the epitaxial wafer.

[0061] Furthermore, self-doping also affects the target resistivity of the epitaxial layers formed on various substrates obtained from different locations on the crystal rod.

[0062] The dopant concentration inside a crystal ingot can vary along both its longitudinal and radial directions. Therefore, the dopant concentration can also differ for substrates obtained at different locations on the ingot. Consequently, when self-doping occurs, the target resistivity of the epitaxial layer formed on substrates obtained from different locations on the ingot will differ, leading to significant differences in the resistance of the final product obtained from the ingot.

[0063] In some embodiments, the predetermined baking temperature in step S3 can be 1130°C to 1150°C, and the baking duration can be 80s to 100s.

[0064] This is because if the predetermined baking temperature is below 1130°C, the dopant release from the substrate is slow, making it difficult for the dopant on the outermost layer of the substrate (including the back surface, front surface, and edge surface) to be released prematurely during the baking stage. If the predetermined baking temperature is above 1150°C, haze defects are easily induced. Furthermore, if the baking duration is less than 80 seconds, it is also difficult to accelerate the dopant release from the substrate, hindering the premature release of dopant on the outermost layer of the substrate during the baking stage. If the baking duration is greater than 100 seconds, haze defects are also easily induced.

[0065] When the predetermined baking temperature is 1130°C to 1150°C and the baking duration is 80 to 100 seconds, the tendency of dopant to be released from the substrate is accelerated, causing the dopant on the outermost layer of the substrate to be released earlier during the baking stage and fully volatilized before the deposition stage in step S4. This reduces self-doping during the deposition stage, thereby reducing the impact of dopant concentration differences on the resistivity of the epitaxial layers formed on different substrates obtained from different positions on the ingot. This reduces the difference in the target resistivity values ​​of the formed epitaxial layers, and thus reduces the difference in resistance between the final products obtained from the ingot. Furthermore, when the predetermined baking temperature is 1130°C to 1150°C and the baking duration is 80 to 100 seconds, the risk of halogenation can be avoided.

[0066] Epitaxial wafers can be prepared using the epitaxial growth method described above. In embodiments of this 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%.

[0067] In some embodiments, the resistivity uniformity of the epitaxial layer of the epitaxial wafer can be less than 2.5%, and the site flatness quality requirements (SFQR) of the epitaxial wafer after polishing can be less than or equal to 30 nm.

[0068] Resistivity uniformity here refers to the consistency of resistivity across different locations in the epitaxial layer. It can be measured using various methods, including four-probe testing and Hall effect measurement. In this paper, resistivity uniformity can be obtained, for example, as follows: First, excluding the region 5 mm from the edge of the epitaxial layer, samples are taken at one point at the center, four points at half the radius, and four points at the edge of the epitaxial layer. Then, the ratio of the difference between the maximum and minimum resistivity values ​​at each sampled point to the sum of the maximum and minimum resistivity values ​​is calculated.

[0069] <Preliminary Study on Epitaxial Growth Methods>

[0070] Epitaxial wafers according to Examples A1 to A3 and Comparative Examples A1 to A5 were prepared using the epitaxial growth method described above. Except for the flow rates of the main hydrogen and auxiliary hydrogen, these epitaxial wafers were prepared under the same process conditions. Specifically, in the stabilization phase, the heating lamp power was 40 kW, and the heating time was 10 s; in the heating phase, the reaction chamber was heated to 1120 °C; in the baking phase, the temperature was maintained at 1120 °C, and the baking time was 30 s; in the deposition phase, the temperature was maintained at 1120 °C, and the TCS flow rate was 8 slm; in the cleaning phase, the temperature was maintained at 1120 °C, and the cleaning time was 10 s; in the cooling phase, the heating lamp power was 5 kW, and the cooling time was 10 s, and no auxiliary gases such as hydrogen chloride (HCl) were introduced throughout the entire process.

[0071] Table 1

[0072] Table 1 shows the flow rates of main hydrogen and auxiliary hydrogen introduced into the reaction chamber during the baking and deposition stages when preparing epitaxial wafers 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 wafer and the corresponding flatness of the epitaxial wafer, expressed in SFQR.

[0073] In Examples A1 and A3, the flow rate of the main hydrogen gas was greater than 55 slm, and in Examples A2 and A3, the flow rate of the auxiliary hydrogen gas was less than 18 slm, and the resistivity uniformity of the epitaxial layer was less than 8.5%. In Comparative Example A1, the flow rate of the main hydrogen gas was less than 55 slm and the flow rate of the auxiliary hydrogen gas was greater than 18 slm, and the resistivity uniformity of the epitaxial layer was 14.17%, 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] Furthermore, 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, resulting in a resistivity uniformity of 6.14% for the epitaxial layer. 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, resulting in resistivity uniformities of 7.64% and 8.23% for the epitaxial layer, 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 improved more effectively.

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

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

[0077] In Example A3, the main hydrogen flow rate is in the range of 55 slm to 65 slm and the auxiliary hydrogen flow rate 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 main hydrogen flow rate is in the range of 55 slm to 65 slm, but the auxiliary hydrogen flow rate is greater than 18 slm, the SFQR of the epitaxial wafer is equal to 30 nm, and the resistivity uniformity of the epitaxial layer is greater than 6.14%. In Example A2, the auxiliary hydrogen flow rate is in the range of 13 slm to 18 slm, but the main hydrogen flow rate is less than 55 slm, the SFQR of the epitaxial wafer is less than 30 nm, and 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 55 slm to 65 slm and the flow rate of the auxiliary hydrogen gas is in the range of 13 slm to 18 slm, 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 improved more effectively.

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

[0079] Table 2

[0080] Table 2 shows the deposition temperature during the preparation of epitaxial wafers 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 wafers and the corresponding flatness of the epitaxial wafers, expressed in terms of SFQR.

[0081] In Example B1, the deposition temperature was in the range of 1110°C to 1118°C, the resistivity uniformity of the epitaxial layer was 5.26%, and the SFQR of the epitaxial wafer was 29 nm. In Comparative Example B1, the deposition temperature was less than 1110°C, the SFQR of the epitaxial wafer was 27 nm, but the resistivity uniformity of the epitaxial layer was 7.51%, which was worse than 5.26%. In Comparative Example B2, the deposition temperature was greater than 1118°C, the resistivity uniformity of the epitaxial layer was 4.78%, but the SFQR of the epitaxial wafer was 38 nm, which was worse than 27 nm. 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 the surface of the epitaxial wafer can also have good flatness.

[0082] With the same flow rates of main hydrogen and auxiliary hydrogen, epitaxial wafers according to Example C1 and Comparative Examples C1 and C2 were prepared under the same process conditions as those described above for Examples A1 to A3, except for the baking temperature.

[0083] Table 3

[0084] Table 3 shows the baking temperature and baking time for preparing corresponding epitaxial wafers according to Example C1 and Comparative Examples C1 and C2 for various silicon substrates obtained from different positions of the crystal rod, the target resistivity values ​​of the epitaxial layers of the epitaxial wafers prepared from silicon substrates obtained from the head, middle and tail of the crystal rod, respectively, and the corresponding Haze.

[0085] In Example C1, the baking temperature was in the range of 1130°C to 1150°C and the baking time was in the range of 80s to 100s. The resistivity target values ​​of the epitaxial wafers corresponding to the head, middle, and tail portions of the crystal ingot tended to be consistent, and the haze was 0.25 ppm. In Comparative Example C1, the baking temperature was less than 1130°C and the baking time was less than 80s. The haze was 0.21 ppm, but there was a significant difference from the resistivity target values ​​of the epitaxial wafers corresponding to the head, middle, and tail portions of the crystal ingot. In Comparative Example C2, the baking temperature was greater than 1150°C and the baking time was greater than 100s. The resistivity target values ​​of the epitaxial wafers corresponding to the head, middle, and tail portions of the crystal ingot tended to be consistent, but the haze was 0.43 ppm, which was significantly worse than 0.25 ppm. Therefore, when the predetermined baking temperature is 1130°C to 1150°C and the baking duration is 80s to 100s, it is possible not only to reduce the difference between the target resistivity values ​​of the epitaxial layers formed on the various substrates obtained from different positions of the crystal rod, but also to avoid the risk of halogenation.

[0086] In this disclosure, the terms "first," "second," etc., are used merely for descriptive purposes and should not be considered restrictive. Furthermore, although this disclosure has been described with reference to exemplary embodiments, it should be understood that this disclosure is not limited to the specific embodiments described and shown herein. Various changes to the exemplary embodiments can be made by those skilled in the art without departing from the scope defined by the claims of this disclosure.

[0087] The features mentioned and / or shown in the foregoing description of exemplary embodiments of this disclosure may be combined in the same or similar manner with one or more other embodiments, combined with features in other embodiments, or substituted for corresponding features in other embodiments. Such combinations or substitutions should also be considered as including within the scope of protection of this disclosure.

Claims

1. An epitaxial growth method for a heavily doped substrate without a back seal, comprising: The heavily doped substrate is placed on the base of the reaction chamber; Main hydrogen gas is introduced into the reaction chamber through the first air inlet, and auxiliary hydrogen gas is introduced into the region of the reaction chamber located below the base through the second air inlet; The reaction chamber is baked at a predetermined temperature; as well as Reactive 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. Specifically, at least during the baking and deposition reactions, the flow rate of the primary 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, wherein, At least during the baking and deposition reactions, the flow rate of the primary 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, wherein, In the case where, at least during the baking and deposition reactions, the flow rate of the main hydrogen is greater than or equal to 55 slm, the flow rate of the main hydrogen is between 55 slm and 65 slm, and the flow rate of the auxiliary hydrogen is greater than or equal to 13 slm.

4. The epitaxial growth method according to claim 1, wherein, In the case where the auxiliary hydrogen flow rate is less than or equal to 18 slm during at least the baking and deposition reactions, the auxiliary hydrogen flow rate is between 13 slm and 18 slm, and the main hydrogen flow rate is less than or equal to 65 slm.

5. The epitaxial growth method according to claim 1, wherein, At least during the baking and deposition reactions, the flow rate of the primary 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, wherein, At least during the baking and deposition reactions, the flow rate of the primary 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, wherein, The predetermined temperature is 1130°C to 1150°C, and the baking duration is 80s to 100s.

8. The epitaxial growth method according to any one of claims 1 to 6, wherein, The deposition reaction was carried out at a temperature of 1110°C to 1118°C.

9. An epitaxial wafer prepared from a heavily doped substrate without a back seal using the epitaxial growth method according to any one of claims 1 to 8, wherein the resistivity uniformity of the epitaxial layer of the epitaxial wafer is less than 2.5%.

10. An epitaxial wafer prepared from a heavily doped substrate without a back seal using an epitaxial growth method according to any one of claims 3 to 6, wherein 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 30 nm.

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