Growth method of epitaxial layer on substrate and semiconductor structure

Abstract

The invention relates to a growth method of an epitaxial layer on a substrate and a semiconductor structure. The growth method of the epitaxial layer on the substrate comprises the following steps: providing the substrate, wherein the substrate comprises a front surface and a back surface which are oppositely distributed; forming a back sealing structure covering the back surface of the substrate; forming an intrinsic layer covering the front surface of the substrate; and forming an epitaxial layer covering the surface, deviating from the substrate, of the intrinsic layer by adopting an epitaxial growth process. According to the invention, the self-doping effect in the growth process of the epitaxial layer is reduced or even inhibited, the concentration of doped ions in the epitaxial layer is ensured, the uniformity of the resistivity of the epitaxial layer is improved, and the growth quality of the epitaxial layer is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing, and in particular to a method for growing an epitaxial layer on a substrate and a semiconductor structure. Background Art

[0002] As competition in the consumer market intensifies, the requirements for the performance and quality of power devices continue to increase. At the same time, reducing the power consumption and cost of semiconductor structures has always been the unremitting pursuit of all semiconductor industries. The low-resistance substrate epitaxial process refers to the process of forming an epitaxial layer on a low-resistance substrate. The low-resistance substrate epitaxial process is an important part of the semiconductor industry. It helps to reduce the external dependence of the semiconductor industry and can improve the technical capabilities and competitiveness of the semiconductor industry. With the rapid development of the semiconductor industry, the market demand for semiconductor industries such as mobile phones, tablets, televisions, lighting and communications is increasing. By developing low-resistance substrate epitaxial products, companies can occupy a larger market share and improve their competitive advantage.

[0003] The self-doping effect refers to the phenomenon that in the high-temperature epitaxial process, impurities in the highly doped substrate diffuse back into the gas phase boundary layer and diffuse from the boundary layer into the epitaxial layer. Since the resistivity of the low-resistance substrate is low and the low-resistance substrate has a higher doping concentration, the self-doping effect of the low-resistance substrate is more serious. At the same time, due to the influence of the self-doping effect, the resistivity uniformity of the epitaxial layer formed by epitaxial growth on the low-resistance substrate is poor. Poor resistivity uniformity will affect the quality of the epitaxial layer, thereby reducing the performance and manufacturing yield of the semiconductor structure including the low-resistance substrate and the epitaxial layer.

[0004] Therefore, how to reduce the self-doping effect during the implementation of the epitaxial process on the substrate, thereby improving the growth quality of the epitaxial layer, improving the performance of the semiconductor structure, and increasing the manufacturing yield of the semiconductor structure is a technical problem that needs to be solved urgently. Summary of the invention

[0005] The present invention provides a method for growing an epitaxial layer on a substrate and a semiconductor structure, which are used to reduce the self-doping effect during the implementation of an epitaxial process on the substrate, thereby improving the growth quality of the epitaxial layer, improving the performance of the semiconductor structure, and increasing the manufacturing yield of the semiconductor structure.

[0006] According to some embodiments, the present invention provides a method for growing an epitaxial layer on a substrate, comprising the following steps:

[0007] Providing a substrate, the substrate comprising a front side and a back side that are oppositely distributed;

[0008] forming a back sealing structure covering the back side of the substrate;

[0009] forming an intrinsic layer covering the front surface of the substrate;

[0010] An epitaxial layer covering the surface of the intrinsic layer facing away from the substrate is formed by an epitaxial growth process.

[0011] In some embodiments, the substrate has doping ions therein, and the resistivity of the substrate is lower than 1Ω·cm.

[0012] In some embodiments, the specific steps of forming a back seal structure covering the back side of the substrate include:

[0013] forming a first back-sealing layer covering the back side of the substrate;

[0014] A second back sealing layer is formed to cover the surface of the first back sealing layer facing away from the substrate, wherein the material of the second back sealing layer is different from that of the first back sealing layer.

[0015] In some embodiments, the material of the first back-sealing layer is silicon dioxide, and the material of the second back-sealing layer is polysilicon; or

[0016] The material of the first back sealing layer is polysilicon, and the material of the second back sealing layer is silicon dioxide.

[0017] In some embodiments, before forming the intrinsic layer covering the front surface of the substrate, the following steps are further included:

[0018] Placing the substrate with the back seal structure formed thereon into a reaction chamber;

[0019] The reaction chamber is purged with a first gas.

[0020] In some embodiments, the specific steps of forming the intrinsic layer covering the front side of the substrate include:

[0021] The intrinsic layer is epitaxially grown on the front side of the substrate at a preset temperature.

[0022] In some embodiments, the preset temperature is a temperature higher than 1000°C.

[0023] In some embodiments, the epitaxial layer has the doping ions; and the specific step of epitaxially growing the intrinsic layer on the front side of the substrate at a preset temperature further includes:

[0024] The thickness of the intrinsic layer is adjusted according to the difference between the doping concentration of the doping ions in the epitaxial layer and the doping concentration of the doping ions in the substrate.

[0025] In some embodiments, before forming the epitaxial layer covering the surface of the intrinsic layer away from the substrate by using an epitaxial growth process, the following steps are also included:

[0026] The reaction chamber is purged with a second gas.

[0027] According to some other embodiments, the present invention further provides a semiconductor structure, including:

[0028] A substrate, the substrate comprising a front side and a back side that are oppositely distributed;

[0029] The epitaxial layer is formed by using the method for growing an epitaxial layer on a substrate as described above.

[0030] The present invention provides a method for growing an epitaxial layer on a substrate and a semiconductor structure. By first forming a back-sealing structure on the back of the substrate and forming an intrinsic layer on the front of the substrate, and then growing the epitaxial layer on the surface of the intrinsic layer away from the substrate, it is possible to simultaneously suppress the escape of impurities such as doped ions in the substrate from the back and the front of the substrate, reduce the impurity content entering the gas phase during the epitaxial growth of the epitaxial layer, reduce or even suppress the self-doping effect during the growth of the epitaxial layer, ensure the concentration of doped ions in the epitaxial layer, and improve the uniformity of the resistivity of the epitaxial layer, thereby improving the quality of epitaxial layer growth and further improving the performance and manufacturing yield of the semiconductor structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a flow chart of a method for growing an epitaxial layer on a substrate in a specific embodiment of the present invention;

[0032] Figure 2 is a cross-sectional schematic diagram after a back-sealing structure is formed on the back side of a substrate in a specific embodiment of the present invention;

[0033] Figure 3 is a schematic cross-sectional view after an intrinsic layer is formed on the front side of a substrate in a specific embodiment of the present invention;

[0034] Figure 4 It is a schematic cross-sectional view after an epitaxial layer is formed on the surface of the intrinsic layer facing away from the substrate in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0035] The specific implementation manner of the method for growing an epitaxial layer on a substrate and a semiconductor structure provided by the present invention will be described in detail below with reference to the accompanying drawings.

[0036] This specific embodiment provides a method for growing an epitaxial layer on a substrate. Figure 1 FIG. 1 is a flow chart of a method for growing an epitaxial layer on a substrate in a specific embodiment of the present invention. Figure 1 As shown, the method for growing an epitaxial layer on a substrate comprises the following steps:

[0037] Step S11, providing a substrate, wherein the substrate includes a front side and a back side that are relatively distributed;

[0038] Step S12, forming a back seal structure covering the back side of the substrate;

[0039] Step S13, forming an intrinsic layer covering the front surface of the substrate;

[0040] Step S14: forming an epitaxial layer covering the surface of the intrinsic layer facing away from the substrate by using an epitaxial growth process.

[0041] Figure 2 is a schematic cross-sectional view of a specific embodiment of the present invention after a back seal structure is formed on the back side of the substrate. Figure 2 As shown, the substrate 20 has doping ions therein, and the resistivity of the substrate 20 is lower than 1Ω·cm.

[0042] Specifically, the substrate 20 has a high concentration of the doping ions, so that the resistivity of the substrate 20 is lower than 1Ω·cm, so as to form the substrate 20 with low resistance.

[0043] In some embodiments, the specific steps of forming the back seal structure 21 covering the back side of the substrate 20 include:

[0044] forming a first back sealing layer 211 covering the back side of the substrate 20;

[0045] A second backing layer 212 is formed to cover the surface of the first backing layer 211 away from the substrate 20. The material of the second backing layer 212 is different from that of the first backing layer 211. Figure 2 shown.

[0046] Specifically, the back side of the substrate 20 has the first back sealing layer 211 and the second back sealing layer 212 made of different materials, and the second back sealing layer 212 covers the surface of the first back sealing layer 211 away from the substrate 20. On the one hand, by stacking the two back sealing layers, it is possible to further prevent the impurities such as the doped ions in the substrate 20 from diffusing into the gas phase during the epitaxial growth of the epitaxial layer and affecting the growth quality of the epitaxial layer; on the other hand, it is also possible to better protect the back side of the substrate 20 and prevent the reactants in the epitaxial process from entering the back side of the substrate 20, so as to avoid affecting the resistivity and other properties of the substrate 20.

[0047] In some embodiments, the material of the first back-sealing layer 211 is silicon dioxide, and the material of the second back-sealing layer 212 is polysilicon; or,

[0048] The material of the first back sealing layer 211 is polysilicon, and the material of the second back sealing layer 212 is silicon dioxide.

[0049] In one example, the first back-sealing layer 211 of silicon dioxide material directly covers the back side of the substrate 20, and the second back-sealing layer 212 of polysilicon material covers the surface of the first back-sealing layer 211 away from the substrate 20, so that the first back-sealing layer 211 can be used to seal the back side of the substrate 20, reduce the diffusion of impurities such as doped ions in the substrate 20 from the back side of the substrate 20 to the outside, and can also use the impurity absorption characteristics of polysilicon material to absorb impurities diffused from the substrate 20, and can also use the impurity absorption characteristics of polysilicon material to prevent impurities in the external environment from entering the substrate 20, thereby further suppressing the self-doping effect during the epitaxial growth of the epitaxial layer. Wherein, the first back-sealing layer 211 can be an LTO (low temperature oxide, low temperature silicon dioxide) layer.

[0050] In another example, the first back-sealing layer 211 of polysilicon material directly covers the back side of the substrate 20, and the second back-sealing layer 212 of silicon dioxide material covers the surface of the first back-sealing layer 211 away from the substrate 20, so that the impurities diffused from the substrate 20 can be first absorbed by the impurity absorption characteristics of the polysilicon material, and then the second back-sealing layer 212 of silicon dioxide material is used to seal the bottom surface of the first back-sealing layer 211 (that is, the surface of the first back-sealing layer 211 away from the substrate 20) to further suppress the self-doping effect. In addition, the first back-sealing layer 211 of polysilicon material is arranged between the substrate 20 and the second back-sealing layer 212 of silicon dioxide material, which can also reduce the leakage of the substrate 20, thereby further improving the electrical performance of the semiconductor structure.

[0051] Figure 3 2 is a schematic cross-sectional view of a specific embodiment of the present invention after an intrinsic layer is formed on the front side of the substrate. In some embodiments, before forming the intrinsic layer 30 covering the front side of the substrate 20, the following steps are also included:

[0052] Placing the substrate 20 formed with the back seal structure 21 into a reaction chamber;

[0053] The reaction chamber is purged with a first gas.

[0054] In some embodiments, the specific steps of forming the intrinsic layer 30 covering the front surface of the substrate 20 include:

[0055] The intrinsic layer 30 is epitaxially grown on the front surface of the substrate 20 at a preset temperature.

[0056] In some embodiments, the preset temperature is a temperature higher than 1000°C.

[0057] Specifically, by growing the intrinsic layer 30 on the front side of the substrate 20, the intrinsic layer 30 is used to isolate the substrate 20 from the epitaxial layer subsequently grown by the epitaxial growth process, thereby reducing the diffusion of the impurities such as the doping ions in the substrate 20 from bottom to top (i.e., diffusion from the front side of the substrate 20 upward) into the epitaxial layer, thereby further improving the suppression effect of the self-doping effect during the growth of the epitaxial layer. Before growing the intrinsic layer 30, the reaction chamber used for epitaxial growth of the intrinsic layer 30 is purged with gas to improve the cleanliness of the reaction chamber, thereby further improving the growth quality of the intrinsic layer 30. Growing the intrinsic layer 30 by the epitaxial growth process at the preset temperature higher than 1000°C can improve the growth quality of the intrinsic layer 30, thereby further ensuring the quality of the epitaxial layer subsequently grown and the performance of the semiconductor structure.

[0058] In some embodiments, the epitaxial layer has the doping ions; and the specific step of epitaxially growing the intrinsic layer 30 on the front side of the substrate 20 at a preset temperature further includes:

[0059] The thickness T of the intrinsic layer 30 is adjusted according to the difference between the doping concentration of the doping ions in the epitaxial layer and the doping concentration of the doping ions in the substrate 20 .

[0060] Specifically, the epitaxial layer also has the doping ions, and the doping concentration of the doping ions in the epitaxial layer is less than the doping concentration of the doping ions in the substrate 20. The doping concentration of the doping ions in the epitaxial layer and the doping concentration of the doping ions in the substrate 20 are set according to the performance requirements of the semiconductor structure to be prepared. When the difference between the doping concentration of the doping ions in the epitaxial layer and the doping concentration of the doping ions in the substrate 20 increases, the thickness of the intrinsic layer 30 is increased; when the difference between the doping concentration of the doping ions in the epitaxial layer and the doping concentration of the doping ions in the substrate 20 decreases, the thickness of the intrinsic layer 30 is reduced. The thickness T of the intrinsic layer 30 is adjusted according to the difference between the doping concentration of the doping ions in the epitaxial layer and the doping concentration of the doping ions in the substrate 20, so as to further suppress the self-doping effect during the growth of the epitaxial layer and avoid the thickness or size of the semiconductor structure being too large.

[0061] In some embodiments, before forming the epitaxial layer covering the surface of the intrinsic layer 30 away from the substrate 20 by using the epitaxial growth process, the following steps are also included:

[0062] The reaction chamber is purged with a second gas.

[0063] Specifically, since a high-temperature epitaxial process is used to improve the quality of the intrinsic layer 30, and high temperature may aggravate the auto-doping effect, after the epitaxial growth of the intrinsic layer 30 and before the epitaxial growth of the epitaxial layer, the second gas is used to purge the reaction chamber to remove impurities in the reaction chamber, thereby further reducing the auto-doping effect during the subsequent epitaxial growth of the epitaxial layer. In one example, the composition of the first gas is the same as that of the second gas, for example, the first gas and the second gas are both nitrogen or an inert gas. The inert gas described in this specific embodiment refers to a gas composed of Group 0 elements in the periodic table.

[0064] Figure 4 2 is a schematic cross-sectional view of a specific embodiment of the present invention after an epitaxial layer is formed on a surface of the intrinsic layer away from the substrate. For example, after the intrinsic layer 30 is formed, an epitaxial growth process is used to form the epitaxial layer 40 on a surface of the intrinsic layer 30 away from the substrate 20, such as Figure 4 shown.

[0065] This specific embodiment also provides a semiconductor structure. The schematic diagram of the semiconductor structure provided in this specific embodiment can be seen in Figure 4 .like Figure 4 As shown, the semiconductor structure comprises:

[0066] A substrate 20, wherein the substrate 20 includes a front surface and a back surface that are relatively distributed;

[0067] The epitaxial layer 40 is grown by the method for growing an epitaxial layer on a substrate as described above (see Figure 1-Figure 4 )form.

[0068] The method for growing an epitaxial layer on a substrate and the semiconductor structure provided in this specific embodiment form a back-sealing structure on the back side of the substrate first, form an intrinsic layer on the front side of the substrate, and then grow the epitaxial layer on the surface of the intrinsic layer away from the substrate, thereby being able to simultaneously suppress the escape of impurities such as doped ions in the substrate from the back side and the front side of the substrate, reducing the impurity content entering the gas phase during the epitaxial growth of the epitaxial layer, reducing or even suppressing the self-doping effect during the growth of the epitaxial layer, ensuring the concentration of doped ions in the epitaxial layer, and improving the uniformity of the resistivity of the epitaxial layer, thereby improving the quality of epitaxial layer growth, and further improving the performance and manufacturing yield of the semiconductor structure.

[0069] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for growing an epitaxial layer on a substrate, characterized in that: The steps include: Providing a substrate, the substrate comprising a front side and a back side that are oppositely distributed; forming a back sealing structure covering the back side of the substrate; forming an intrinsic layer covering the front surface of the substrate; An epitaxial layer covering the surface of the intrinsic layer facing away from the substrate is formed by an epitaxial growth process.

2. The method for growing an epitaxial layer on a substrate according to claim 1, characterized in that: The substrate has doping ions in it, and the resistivity of the substrate is lower than 1Ω·cm.

3. The method for growing an epitaxial layer on a substrate according to claim 1, characterized in that: The specific steps of forming a back seal structure covering the back side of the substrate include: forming a first back-sealing layer covering the back side of the substrate; A second back sealing layer is formed to cover the surface of the first back sealing layer facing away from the substrate, wherein the material of the second back sealing layer is different from that of the first back sealing layer.

4. The method for growing an epitaxial layer on a substrate according to claim 3, characterized in that: The material of the first back-sealing layer is silicon dioxide, and the material of the second back-sealing layer is polysilicon; or, The material of the first back sealing layer is polysilicon, and the material of the second back sealing layer is silicon dioxide.

5. The method for growing an epitaxial layer on a substrate according to claim 2, characterized in that: Before forming the intrinsic layer covering the front surface of the substrate, the following steps are also included: Placing the substrate with the back seal structure formed thereon into a reaction chamber; The reaction chamber is purged with a first gas.

6. The method for growing an epitaxial layer on a substrate according to claim 5, characterized in that: The specific steps of forming the intrinsic layer covering the front side of the substrate include: The intrinsic layer is epitaxially grown on the front side of the substrate at a preset temperature.

7. The method for growing an epitaxial layer on a substrate according to claim 6, characterized in that: The preset temperature is a temperature higher than 1000°C.

8. The method for growing an epitaxial layer on a substrate according to claim 6, characterized in that: The epitaxial layer has the doping ions; and the specific step of epitaxially growing the intrinsic layer on the front side of the substrate at a preset temperature also includes: The thickness of the intrinsic layer is adjusted according to the difference between the doping concentration of the doping ions in the epitaxial layer and the doping concentration of the doping ions in the substrate.

9. The method for growing an epitaxial layer on a substrate according to claim 7, characterized in that: Before forming an epitaxial layer covering the surface of the intrinsic layer away from the substrate by using an epitaxial growth process, the following steps are also included: The reaction chamber is purged with a second gas.

10. A semiconductor structure, characterized in that: include: A substrate, the substrate comprising a front side and a back side that are oppositely distributed; The epitaxial layer is formed by the method for growing an epitaxial layer on a substrate as claimed in claim 1.

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