Epitaxial structures and semiconductor devices

Abstract

This invention provides an epitaxial structure and a semiconductor device employing the epitaxial structure. The epitaxial structure includes, for example, a semiconductor substrate, a buffer layer, and a heteroepitaxial stack. The buffer layer is disposed on the semiconductor substrate and includes alternating high-aluminum-content regions and low-aluminum-content regions in a first direction. The high-aluminum-content regions are first dopant concentration regions, and the low-aluminum-content regions are second dopant concentration regions, such that the first and second dopant concentration regions are alternating in the first direction. The heteroepitaxial stack is disposed on the side of the buffer layer opposite to the semiconductor substrate and is used to provide a conductive channel by constructing a two-dimensional electron gas. The heteroepitaxial stack includes a gallium nitride channel layer and a barrier layer. The epitaxial structure of this invention can possess better stress control and high resistance, and correspondingly, the semiconductor device can have device performance such as low leakage current and high voltage withstand capability.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor and electronic device technology, and in particular to an epitaxial structure and a semiconductor device. Background Technology

[0002] Gallium nitride (GaN) power devices are semiconductor devices with a two-dimensional electron gas, exhibiting characteristics such as high breakdown voltage and high electron mobility. Typically, the epitaxial structure of a GaN power device includes a semiconductor substrate, such as a silicon substrate, and sequentially epitaxially grown on the silicon substrate: an aluminum nitride (AlN) nucleation layer, an aluminum gallium nitride (AlGaN) buffer layer, a GaN channel layer, and a barrier layer (e.g., an AlGaN layer). For this epitaxial structure, because the constituent materials of each layer are different, and the coefficients of thermal expansion of the constituent materials of each layer are also different, it will exhibit warping changes due to stress changes during epitaxial growth. If the warping is excessive, the epitaxial structure is at risk of cracking, which will affect the device's breakdown voltage performance. Therefore, how to provide an epitaxial structure with better stress control to avoid excessive warping and cracking is a pressing technical problem that needs to be solved. Summary of the Invention

[0003] In view of this, embodiments of the present invention provide an epitaxial structure and a semiconductor device that have better stress control and can effectively avoid excessive warping and cracking.

[0004] On one hand, an epitaxial structure provided by an embodiment of the present invention includes, for example, a semiconductor substrate, a buffer layer, and a heteroepitaxial stack; the buffer layer is disposed on the semiconductor substrate and includes alternating high-aluminum-content regions and low-aluminum-content regions in a first direction, wherein the high-aluminum-content regions are first dopant concentration regions and the low-aluminum-content regions are second dopant concentration regions, thereby the first dopant concentration regions and the second dopant concentration regions are alternating in the first direction; the first direction is from a first surface of the buffer layer facing the semiconductor substrate to a second surface of the buffer layer facing away from the semiconductor substrate. The direction; wherein, when both the first dopant concentration region and the second dopant concentration region contain iron dopant, the first dopant concentration region is a low iron concentration region and the second dopant concentration region is a high iron concentration region; when both the first dopant concentration region and the second dopant concentration region contain carbon dopant, the first dopant concentration region is a high carbon concentration region and the second dopant concentration region is a low carbon concentration region; and, the heteroepitaxial stack is disposed on the side of the buffer layer away from the semiconductor substrate and is used to provide a conductive channel by constructing a two-dimensional electron gas, the heteroepitaxial stack includes a gallium nitride channel layer and a barrier layer.

[0005] On the other hand, an embodiment of the present invention provides a semiconductor device, for example including: a first electrode, a gate electrode, a second electrode, and the epitaxial structure described in the foregoing embodiment; wherein, the gate electrode is disposed on the side of the heteroepitaxial stack away from the semiconductor substrate, the first electrode and the second electrode are disposed on the side of the heteroepitaxial stack away from the semiconductor substrate and are respectively located on opposite sides of the gate electrode, and the first electrode and the second electrode respectively form ohmic contacts with the heteroepitaxial stack.

[0006] The above embodiments of the present invention can have the following beneficial effects: Since an increase in aluminum content leads to the generation of tensile stress and high resistance, and a decrease in aluminum content leads to the generation of compressive stress, an increase in iron concentration leads to the generation of tensile stress and high resistance, and an increase in carbon concentration leads to the generation of compressive stress and high resistance; therefore, the buffer layer is configured with alternating high-aluminum-content regions and low-aluminum-content regions, and the high-aluminum-content regions of the buffer layer are doped with iron and / or carbon to become low-iron-concentration regions and / or high-carbon-concentration regions, and the low-aluminum-content regions are doped with iron and / or carbon to become high-iron-concentration regions and / or low-carbon-concentration regions, so that the iron concentration changes in the alternating low-iron-concentration and high-iron-concentration regions, and / or the carbon concentration changes in the alternating high-carbon-concentration and low-carbon-concentration regions, follow the aluminum content changes in the alternating high-aluminum-content and low-aluminum-content regions; the high-aluminum-content regions correspond to the low-iron-concentration and / or high-carbon-concentration regions, and the low-aluminum-content regions correspond to the high-iron-concentration and / or low-carbon-concentration regions, to achieve stress balance. This allows for better stress control in both high-aluminum and low-aluminum-content regions, effectively avoiding the risk of breakage due to excessive warping of the epitaxial structure during epitaxial growth. Furthermore, the better stress control facilitates the creation of a thicker buffer layer to effectively prevent the propagation of defects from the semiconductor substrate (such as dislocations and microcracks) to the heteroepitaxial stack, thereby improving crystal quality, resulting in lower leakage current, higher breakdown voltage, and ultimately enhanced device performance. In addition, the use of iron and / or carbon dopants can increase the resistance of the buffer layer. Therefore, the embodiments of the present invention can achieve epitaxial structures with better stress control and higher resistance. Moreover, semiconductor devices using the described epitaxial structure can exhibit device performance characteristics such as lower leakage current and higher breakdown voltage. Attached Figure Description

[0007] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0008] Figure 1 This is a schematic diagram of the layer structure of an epitaxial structure provided in an embodiment of the present invention.

[0009] Figures 2A-2D This is a schematic diagram illustrating various variations in aluminum content and iron concentration in the buffer layer according to an embodiment of the present invention.

[0010] Figures 3A-3D This is a schematic diagram illustrating various variations in aluminum content and carbon concentration in the buffer layer according to an embodiment of the present invention.

[0011] Figures 4A-4D This is a schematic diagram illustrating the variations in aluminum content, iron, and carbon concentration in the buffer layer according to an embodiment of the present invention.

[0012] Figure 5 This is a schematic diagram of another layer structure of an epitaxial structure provided in an embodiment of the present invention.

[0013] Figure 6 This is a schematic diagram of the structure of a semiconductor device provided in an embodiment of the present invention.

[0014] Figure 7 This is a schematic diagram of another semiconductor device provided in an embodiment of the present invention.

[0015] [Explanation of Key Figure Markings]

[0016] 10-Epipolar structure; 11-Semiconductor substrate; 12-Nucleation layer; 13-Buffer layer; 13B-First surface; 13T-Second surface; 14-Gallium nitride high-resistivity layer; 15-Heterogeneous epitaxial stack; B1-First direction; S-First electrode; D-Second electrode; G-Gate electrode. Detailed Implementation

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0018] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0020] It should also be noted that the division of multiple embodiments in this invention is only for the convenience of description and should not constitute a special limitation. Features in various embodiments can be combined and referenced in each other without contradiction.

[0021] See Figure 1 An epitaxial structure 10 provided in this embodiment of the invention includes, for example, a semiconductor substrate 11, a buffer layer 13, and a heteroepitaxial stack 15. The semiconductor substrate 11 is, for example, a silicon substrate, a silicon carbide substrate, a sapphire substrate, or other suitable material substrate. The buffer layer 13 is disposed on the semiconductor substrate 11, having a first surface 13B and a second surface 13T opposite to the first surface 13B in a first direction B1. The heteroepitaxial stack 15 is disposed on the side of the buffer layer 13 facing away from the semiconductor substrate 11 and is used to provide a conductive channel by constructing a two-dimensional electron gas 2DEG. The heteroepitaxial stack 15 includes a gallium nitride channel layer 151 and a barrier layer 153. The barrier layer 153 can be an AlGaN layer, an InGaN layer, an AlGaInN layer, an AlN layer, or an InAlN layer. It is worth noting that the heteroepitaxial stack 15 of this embodiment is not limited to... Figure 1 The two-layer structure shown can also be applied to other suitable epitaxial stacks that include gallium nitride channel layers and barrier layers in the prior art and are suitable for constructing two-dimensional electron gases to provide conductive channels.

[0022] Furthermore, please also refer to Figure 1 and Figures 2A-2DThe buffer layer 13 includes alternating high-aluminum-content regions A and low-aluminum-content regions C along a first direction B1. High-aluminum-content region A is a low-iron (Fe) concentration region, and low-aluminum-content region C is a high-iron concentration region, thus the low-iron concentration regions and the high-iron concentration regions are arranged alternately along the first direction B1. The first direction B1 is the direction from the first surface 13B of the buffer layer 13 facing the semiconductor substrate 11 to the second surface 13T of the buffer layer 13 away from the semiconductor substrate 11. In other words, in this embodiment, iron is used as a dopant, thus the low-iron concentration region is a specific implementation of the first dopant concentration region, and the high-iron concentration region is a specific implementation of the second dopant concentration region. Furthermore, it should be noted that in this embodiment, the aluminum content of the high-aluminum-content region A is higher than the aluminum content of the low-aluminum-content region C, and correspondingly, the iron concentration in the low-iron concentration region is lower than the iron concentration in the high-iron concentration region.

[0023] In this embodiment, since an increase in aluminum content leads to tensile stress and high resistance, a decrease in aluminum content leads to compressive stress, and an increase in iron concentration leads to tensile stress and high resistance, the buffer layer 13 is configured with alternating high-aluminum-content regions A and low-aluminum-content regions C. Iron is used to dope the high-aluminum-content regions A and C of the buffer layer 13 into low-iron-concentration and high-iron-concentration regions, respectively. This ensures that the iron concentration changes in the alternating low-iron-concentration and high-iron-concentration regions follow the aluminum content changes in the alternating high-aluminum-content regions A and C. For example... Figures 2A-2D As shown, region A with high aluminum content corresponds to region with low iron concentration, and region C with low aluminum content corresponds to region with high iron concentration, thus achieving stress balance. This allows for better stress control in both regions, effectively preventing the risk of breakage due to excessive warping of the epitaxial structure 10 during epitaxial growth. Furthermore, the better stress control facilitates the implementation of a thicker buffer layer 13 to effectively prevent defects (such as dislocations and microcracks) from the semiconductor substrate 11 from propagating to the heteroepitaxial stack 15, thereby improving crystal quality, resulting in lower leakage current, higher breakdown voltage, and ultimately enhanced device performance. Additionally, the use of iron dopant increases the resistance of the buffer layer 13. Therefore, this embodiment achieves an epitaxial structure 10 with better stress control and higher resistance, with the buffer layer 13 being a high-resistivity buffer layer.

[0024] Furthermore, it is worth mentioning that the material of the buffer layer 13 can be an AlGaN layer, or other ternary nitride semiconductor materials or more ternary nitride semiconductor materials. In short, in some embodiments, the material of the buffer layer 13 can be represented as: Alx M 1-x N and x represent molar fractions, Al represents aluminum, M represents gallium and / or indium, and N represents nitrogen. Furthermore, for the buffer layer 13, if the aluminum content is too high, the epitaxial growth rate will be too slow; conversely, if the aluminum content is too low, it may lead to a large device leakage current. Therefore, in this embodiment of the invention, the aluminum content of the high-aluminum-content region A and the low-aluminum-content region C in the buffer layer 13 is preferably configured to satisfy 0.3 ≤ x ≤ 0.75.

[0025] In some embodiments, please also refer to Figure 1 and Figure 2A The buffer layer 13 further includes aluminum content gradient regions B and D connecting adjacent high-aluminum-content region A and low-aluminum-content region C in the first direction B1, and the aluminum content gradient regions B and D are iron concentration gradient regions; wherein, the aluminum content of the aluminum content gradient regions B and D is between the aluminum content of the high-aluminum-content region A and the aluminum content of the low-aluminum-content region C, and the iron concentration of the iron concentration gradient regions is between the iron concentration of the low-iron-concentration region and the iron concentration of the high-iron-concentration region. It is worth noting that the lattice constant of the buffer layer 13 along its a-axis changes with the aluminum content. Therefore, by setting the aluminum content gradient regions B and D between the high-aluminum-content region A and the low-aluminum-content region C, it helps to gradually change the lattice constant of the buffer layer 13, thereby improving crystal quality. Furthermore, configuring the aluminum content gradient regions B and D as iron concentration gradient regions by using iron dopant helps to gradually change the resistance value of the buffer layer 13. Additionally, from... Figure 2A It can be seen that the aluminum content gradient trends in aluminum content gradient regions B and D are opposite to the iron concentration gradient trends in the iron concentration gradient regions; for example, the aluminum content in aluminum content gradient region B gradually decreases, while the iron concentration in the corresponding iron concentration gradient region gradually increases; or, the aluminum content in aluminum content gradient region D gradually increases, while the iron concentration in the corresponding iron concentration gradient region gradually decreases.

[0026] As stated above, Figure 2A It is shown that each high-aluminum content region A and its adjacent low-aluminum content region C are provided with an aluminum content gradient region B or D, and correspondingly, each low-iron concentration region and its adjacent high-iron concentration region are provided with the aforementioned iron concentration gradient region; however, the embodiments of the present invention are not limited thereto, for example... Figure 2B or Figure 2C As shown, an aluminum content gradient region B or D can be provided between a portion of the high aluminum content region A and the adjacent low aluminum content region C, and correspondingly, an iron concentration gradient region can be provided between a portion of the low iron concentration region and the adjacent high iron concentration region.

[0027] In some embodiments, the iron concentration in the low iron concentration region, the high iron concentration region, and the iron concentration gradient region is greater than or equal to 1E17 / cm³.3 And less than 1E20 / cm 3 It is worth mentioning here that if the iron concentration is too low, for example less than 1E17 / cm³, 3 If the iron concentration is too high, for example, reaching 1E20 / cm³, the increase in resistance of the buffer layer 13 will be insignificant. 3 If the level is 10 or above, it will excessively affect the crystal quality.

[0028] In some embodiments, please also refer to Figure 1 and Figure 2D The aluminum content of each high-aluminum-content region A abruptly changes to the aluminum content of its adjacent low-aluminum-content region C, and the iron concentration of each high-aluminum-content region A abruptly changes to the iron concentration of its adjacent low-aluminum-content region C. This simplifies the epitaxial growth process control of the buffer layer 13. However, the embodiments of the present invention are not limited thereto; for example… Figure 2B or Figure 2C As shown, the aluminum content in a high-aluminum region A can abruptly change to the aluminum content in the adjacent low-aluminum region C, and correspondingly, the iron concentration in a low-iron-concentration region abruptly changes to the iron concentration in the adjacent high-iron-concentration region; while an aluminum content gradient region B or D is provided between another high-aluminum-content region A and the adjacent low-aluminum-content region C, and correspondingly, an iron concentration gradient region is provided between another low-iron-concentration region and the adjacent high-iron-concentration region, in order to improve crystal quality.

[0029] In some embodiments, please also refer to Figure 1 and Figures 3A-3D The buffer layer 13 includes a high-aluminum content region A and a low-aluminum content region C alternately arranged in the first direction B1. The high-aluminum content region A is a high-carbon (Fe) concentration region, and the low-aluminum content region C is a low-carbon concentration region, thus the high-carbon concentration region and the low-carbon concentration region are alternately arranged in the first direction B1. In other words, in this embodiment, carbon is used as a dopant, thus the high-carbon concentration region is another specific implementation of the first dopant concentration region, and the low-carbon concentration region is another specific implementation of the second dopant concentration region. Furthermore, it should be noted that in this embodiment of the invention, the aluminum content of the high-aluminum content region A is higher than that of the low-aluminum content region C, and correspondingly, the carbon concentration of the high-carbon concentration region is higher than that of the low-carbon concentration region.

[0030] In this embodiment, since an increase in aluminum content leads to tensile stress and high resistance, a decrease in aluminum content leads to compressive stress, and an increase in carbon concentration also leads to compressive stress and high resistance, the buffer layer 13 is configured with alternating high-aluminum-content regions A and low-aluminum-content regions C. Furthermore, carbon dopant is used to dope the high-aluminum-content regions A and C of the buffer layer 13 into high-carbon-concentration regions and low-carbon-concentration regions, respectively. This ensures that the carbon concentration changes in the alternating high-carbon-concentration and low-carbon-concentration regions follow the aluminum content changes in the alternating high-aluminum-content regions A and C. For example... Figures 3A-3D As shown, region A with high aluminum content corresponds to region with high carbon concentration, and region C with low aluminum content corresponds to region with low carbon concentration, thus achieving stress balance. This allows for better stress control in both regions, effectively preventing the risk of breakage due to excessive warping of the epitaxial structure 10 during epitaxial growth. Furthermore, the better stress control facilitates the implementation of a thicker buffer layer 13 to effectively prevent defects (such as dislocations and microcracks) from the semiconductor substrate 11 from propagating to the heteroepitaxial stack 15, thereby improving crystal quality, resulting in lower leakage current, higher breakdown voltage, and ultimately enhanced device performance. Additionally, the use of carbon dopant increases the resistance of the buffer layer 13. Therefore, this embodiment can achieve another epitaxial structure 10 with better stress control and higher resistance, with the buffer layer 13 being a high-resistance buffer layer.

[0031] Furthermore, it is worth mentioning that the material of the buffer layer 13 can be an AlGaN layer, or other ternary nitride semiconductor materials or more ternary nitride semiconductor materials. In short, in some embodiments, the material of the buffer layer 13 can be represented as: Al x M 1-x N and x represent molar fractions, Al represents aluminum, M represents gallium and / or indium, and N represents nitrogen. Furthermore, for the buffer layer 13, if the aluminum content is too high, the epitaxial growth rate will be too slow; conversely, if the aluminum content is too low, it may lead to a large device leakage current. Therefore, in this embodiment of the invention, the aluminum content of the high-aluminum-content region A and the low-aluminum-content region C in the buffer layer 13 is preferably configured to satisfy 0.3 ≤ x ≤ 0.75.

[0032] In some embodiments, please also refer to Figure 1 and Figure 3AThe buffer layer 13 further includes aluminum content gradient regions B and D connecting adjacent high-aluminum-content region A and low-aluminum-content region C in the first direction B1, and the aluminum content gradient regions B and D are carbon concentration gradient regions; wherein, the aluminum content of the aluminum content gradient regions B and D is between the aluminum content of the high-aluminum-content region A and the aluminum content of the low-aluminum-content region C, and the carbon concentration of the carbon concentration gradient regions is between the carbon concentration of the high-carbon-concentration region and the carbon concentration of the low-carbon-concentration region. It is worth noting that the a-axis lattice constant of the buffer layer 13 changes with the aluminum content; therefore, by setting the aluminum content gradient regions B and D between the high-aluminum-content region A and the low-aluminum-content region C, it helps to gradually change the lattice constant of the buffer layer 13, thereby improving crystal quality. Furthermore, configuring the aluminum content gradient regions B and D as carbon concentration gradient regions by doping with carbon helps to gradually change the resistance value of the buffer layer 13. Additionally, from... Figure 3A It can be seen that the aluminum content gradient trends in aluminum content gradient regions B and D are the same as the carbon concentration gradient trends in the carbon concentration gradient regions; for example, the aluminum content in aluminum content gradient region B gradually decreases, and the carbon concentration in the carbon concentration gradient region gradually decreases accordingly; or, the aluminum content in aluminum content gradient region D gradually increases, and the carbon concentration in the carbon concentration gradient region gradually increases accordingly.

[0033] As stated above, Figure 3A The diagram shows that each high-aluminum content region A and its adjacent low-aluminum content region C are connected by an aluminum content gradient region B or D, and correspondingly, each high-carbon concentration region and its adjacent low-carbon concentration region are connected by the aforementioned carbon concentration gradient region; however, the embodiments of the present invention are not limited thereto, for example... Figure 3B or Figure 3C As shown, an aluminum content gradient region B or D can also be provided between a portion of the high aluminum content region A and the adjacent low aluminum content region C, and correspondingly, a carbon concentration gradient region can be provided between a portion of the high carbon concentration region and the adjacent low carbon concentration region.

[0034] In some embodiments, the carbon concentration in the high carbon concentration region, the low carbon concentration region, and the carbon concentration gradient region is greater than or equal to 1E17 / cm³. 3 And less than 1E20 / cm 3 It is worth mentioning here that if the carbon concentration is too low, for example less than 1E17 / cm³, 3 If the carbon concentration is too high, for example, reaching 1E20 / cm, the increase in resistance of the buffer layer 13 will be insignificant. 3 If the level is 10 or above, it will excessively affect the crystal quality.

[0035] In some embodiments, please also refer to Figure 1 and Figure 3DThe aluminum content of each high-aluminum-content region A abruptly changes to the aluminum content of its adjacent low-aluminum-content region C, and the carbon concentration of each high-aluminum-content region A abruptly changes to the carbon concentration of its adjacent low-aluminum-content region C. This simplifies the epitaxial growth process control of the buffer layer 13. However, the embodiments of the present invention are not limited thereto; for example… Figure 3B or Figure 3C As shown, the aluminum content of a portion of the high-aluminum-content region A can abruptly change to the aluminum content of the adjacent low-aluminum-content region C, and correspondingly, the carbon concentration of a portion of the high-carbon-concentration region abruptly changes to the carbon concentration of the adjacent low-carbon-concentration region; while an aluminum content gradient region B or D is provided between another portion of the high-aluminum-content region A and the adjacent low-aluminum-content region C, and correspondingly, a carbon concentration gradient region is provided between another portion of the high-carbon-concentration region and the adjacent low-carbon-concentration region, in order to improve the crystal quality.

[0036] In some embodiments, please also refer to Figure 1 and Figures 4A-4D The buffer layer 13 includes a high-aluminum content region A and a low-aluminum content region C alternately arranged in a first direction B1. The high-aluminum content region A is simultaneously a low-concentration iron (Fe) region and a high-concentration carbon region, and the low-aluminum content region C is simultaneously a high-concentration iron region and a low-concentration carbon region. Thus, the low-concentration iron region and the high-concentration iron region are alternately arranged in the first direction B1, and the high-concentration carbon region and the low-concentration carbon region are alternately arranged in the first direction B1. In other words, in this embodiment, iron and carbon are both used as dopants, thus the low-concentration iron region and the high-concentration carbon region constitute another specific embodiment of the first dopant concentration region, and the high-concentration iron region and the low-concentration carbon region constitute another specific embodiment of the second dopant concentration region. Furthermore, it should be noted that in this embodiment, the aluminum content of the high-aluminum content region A is higher than the aluminum content of the low-aluminum content region C. Correspondingly, the iron concentration in the low-concentration iron region is lower than the iron concentration in the high-concentration iron region, and the carbon concentration in the high-concentration carbon region is higher than the carbon concentration in the low-concentration carbon region. Furthermore, co-doping with iron and carbon can not only achieve stress balance, but also reduce the memory effect caused by the dopant iron. For example, when iron is used as a dopant, its magnetic properties may cause a memory effect. However, carbon, as a non-magnetic element, can reduce the magnetic influence of iron by changing the electronic structure and band structure of the material, thereby reducing the memory effect.

[0037] In this embodiment, since an increase in aluminum content leads to the generation of tensile stress and high resistance, while a decrease in aluminum content leads to the generation of compressive stress, an increase in iron concentration leads to the generation of tensile stress and high resistance, and an increase in carbon concentration leads to the generation of compressive stress and high resistance, the buffer layer 13 is configured with alternating high-aluminum-content regions A and C. The high-aluminum-content region A of the buffer layer 13 is doped with iron and carbon dopants to simultaneously be a low-iron-concentration region and a high-carbon-concentration region, and the low-aluminum-content region C is doped to simultaneously be a high-iron-concentration region and a low-carbon-concentration region. This ensures that changes in iron concentration in the alternating high-iron-concentration and low-iron-concentration regions, and changes in carbon concentration in the alternating high-carbon-concentration and low-carbon-concentration regions, follow changes in aluminum content in the alternating high-aluminum-content region A and low-aluminum-content region C. For example... Figures 4A-4D As shown, region A with high aluminum content corresponds to regions with low iron concentration and high carbon concentration, and region C with low aluminum content corresponds to regions with high iron concentration and low carbon concentration, thus achieving stress balance. This allows for better stress control in both regions A and C, effectively preventing the risk of breakage due to excessive warping of the epitaxial structure 10 during epitaxial growth. Furthermore, the better stress control facilitates the implementation of a thicker buffer layer 13 to effectively prevent defects (such as dislocations and microcracks) from the semiconductor substrate 11 from propagating to the heteroepitaxial stack 15, thereby improving crystal quality, resulting in lower leakage current, higher breakdown voltage, and ultimately enhanced device performance. In addition, the use of iron and carbon dopants increases the resistance of the buffer layer 13. Therefore, this embodiment can achieve an epitaxial structure 10 with better stress control and higher resistance, with the buffer layer 13 being a high-resistivity buffer layer.

[0038] Furthermore, it is worth mentioning that the material of the buffer layer 13 can be an AlGaN layer, or other ternary nitride semiconductor materials or more ternary nitride semiconductor materials. In short, in some embodiments, the material of the buffer layer 13 can be represented as: Al x M 1-x N and x represent molar fractions, Al represents aluminum, M represents gallium and / or indium, and N represents nitrogen. Furthermore, for the buffer layer 13, if the aluminum content is too high, the epitaxial growth rate will be too slow; conversely, if the aluminum content is too low, it may lead to a large device leakage current. Therefore, in this embodiment of the invention, the aluminum content of the high-aluminum-content region A and the low-aluminum-content region C in the buffer layer 13 is preferably configured to satisfy 0.3 ≤ x ≤ 0.75.

[0039] In some embodiments, please also refer to Figure 1 and Figure 4AThe buffer layer 13 further includes aluminum content gradient regions B and D connecting adjacent high-aluminum-content region A and low-aluminum-content region C in the first direction B1. These aluminum content gradient regions B and D are also iron concentration gradient regions and carbon concentration gradient regions. The aluminum content of the aluminum content gradient regions B and D is between that of the high-aluminum-content region A and the low-aluminum-content region C. The iron concentration of the iron concentration gradient regions is between that of the low-iron-concentration region and the high-iron-concentration region. The carbon concentration of the carbon concentration gradient regions is between that of the high-carbon-concentration region and the low-carbon-concentration region. It is worth noting that the a-axis lattice constant of the buffer layer 13 changes with the aluminum content. Therefore, by setting aluminum content gradient regions B and D between the high-aluminum-content region A and the low-aluminum-content region C, it helps to gradually change the lattice constant of the buffer layer 13, thereby improving crystal quality. Furthermore, by configuring the aluminum content gradient regions B and D as both iron and carbon concentration gradient regions using dopants iron and carbon, it contributes to the gradual change in the resistance value of the buffer layer 13. Additionally, from... Figure 4A It can be seen that the aluminum content gradient trends in aluminum content gradient regions B and D are opposite to the iron concentration gradient trends in the iron concentration gradient regions, and the same as the carbon concentration gradient trends in the carbon concentration gradient regions. For example, as the aluminum content in aluminum content gradient region B gradually decreases, the iron concentration in the corresponding iron concentration gradient region gradually increases, and the carbon concentration in the corresponding carbon concentration gradient region gradually decreases; or, as the aluminum content in aluminum content gradient region D gradually increases, the iron concentration in the corresponding iron concentration gradient region gradually decreases, and the carbon concentration in the corresponding carbon concentration gradient region gradually increases.

[0040] As stated above, Figure 4A The diagram shows that each high-aluminum content region A and its adjacent low-aluminum content region C are connected by an aluminum content gradient region B or D. Correspondingly, each low-iron concentration region and its adjacent high-iron concentration region are connected by the aforementioned iron concentration gradient region, and each high-carbon concentration region and its adjacent low-carbon concentration region are connected by the aforementioned carbon concentration gradient region. However, the embodiments of the present invention are not limited thereto; for example… Figure 4B or Figure 4C As shown, an aluminum content gradient region B or D may be provided between a high aluminum content region A and an adjacent low aluminum content region C. Correspondingly, an iron concentration gradient region may be provided between a low iron concentration region and an adjacent high iron concentration region, and a carbon concentration gradient region may be provided between a high carbon concentration region and an adjacent low carbon concentration region.

[0041] In some embodiments, the iron concentration in the low iron concentration region, the high iron concentration region, and the iron concentration gradient region is greater than or equal to 1E17 / cm³. 3 And less than 1E20 / cm 3If the iron concentration is too low, for example less than 1E17 / cm³, 3 If the iron concentration is too high, for example, reaching 1E20 / cm³, the increase in resistance of the buffer layer 13 will be insignificant. 3 At concentrations of 1E17 / cm³ or higher, this will excessively affect crystal quality. Similarly, the carbon concentration in the high-carbon concentration region, the low-carbon concentration region, and the carbon concentration gradient region must be greater than or equal to 1E17 / cm³. 3 And less than 1E20 / cm 3 If the carbon concentration is too low, for example less than 1E17 / cm³, 3 If the carbon concentration is too high, for example, reaching 1E20 / cm, the increase in resistance of the buffer layer 13 will be insignificant. 3 If the level is 10 or above, it will excessively affect the crystal quality.

[0042] In some embodiments, please also refer to Figure 1 and Figure 4D The aluminum content of each high-aluminum-content region A abruptly changes to the aluminum content of its adjacent low-aluminum-content region C, and the iron concentration of each high-aluminum-content region A abruptly changes to the iron concentration of its adjacent low-aluminum-content region C, as well as the carbon concentration of each high-aluminum-content region A abruptly changes to the carbon concentration of its adjacent low-aluminum-content region C. This simplifies the epitaxial growth process control of the buffer layer 13. However, the embodiments of the present invention are not limited thereto; for example… Figure 4B or Figure 4C As shown, the aluminum content in a high-aluminum region A can abruptly change to the aluminum content in the adjacent low-aluminum region C. Correspondingly, the iron concentration in a low-iron concentration region abruptly changes to the iron concentration in the adjacent high-iron concentration region, and the carbon concentration in a high-carbon concentration region abruptly changes to the carbon concentration in the adjacent low-carbon concentration region. Meanwhile, an aluminum content gradient region B or D is provided between another high-aluminum region A and the adjacent low-aluminum region C. Correspondingly, an iron concentration gradient region is provided between another low-iron concentration region and the adjacent high-iron concentration region, and a carbon concentration gradient region is provided between another high-carbon concentration region and the adjacent low-carbon concentration region, in order to improve crystal quality.

[0043] In some embodiments, such as Figure 1 As shown, as an enhancement-type device, the epitaxial structure 10 may include, for example, a gallium nitride cap layer P-GaN, located on the side of the heteroepitaxial stack 15 facing away from the semiconductor substrate 11. It is understood, of course, that for depletion-type devices, the gallium nitride cap layer P-GaN is not required.

[0044] In some embodiments, see Figure 5The epitaxial structure 10 further includes, for example, a nucleation layer 12 and / or a GaN high-resistivity layer 14. The nucleation layer 12 is located between the semiconductor substrate 11 and the buffer layer 13, and is, for example, an AlN layer. The gallium nitride high-resistivity layer 14 is located between the buffer layer 13 and the heteroepitaxial stack 15, and is, for example, an iron-doped or carbon-doped GaN layer.

[0045] See Figure 6 The present invention also provides a semiconductor device, such as a lateral device, comprising: a first electrode S, a gate electrode G, a second electrode D, and... Figure 1 The epitaxial structure 10 is shown. The gate electrode G is disposed on the side of the heteroepitaxial stack 15 away from the semiconductor substrate 11, specifically on the side of the gallium nitride cap layer P-GaN away from the semiconductor substrate 11. The first electrode S and the second electrode D are disposed on the side of the heteroepitaxial stack 15 away from the semiconductor substrate 11 and are located on opposite sides of the gate electrode G. The first electrode S and the second electrode D form ohmic contacts with the heteroepitaxial stack 15, for example, the source and drain, respectively. It is worth noting that in some embodiments, the aforementioned semiconductor device may also employ... Figure 5 The epitaxial structure shown is described above; its specific structure will not be repeated here. The semiconductor device of this invention, due to the aforementioned epitaxial structure with superior stress control and high resistance, can achieve device performance such as low leakage current and high withstand voltage.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. An epitaxial structure, characterized in that, include: Semiconductor substrate; A buffer layer is disposed on the semiconductor substrate and includes alternating high-aluminum-content regions and low-aluminum-content regions in a first direction. The high-aluminum-content regions are first dopant concentration regions, and the low-aluminum-content regions are second dopant concentration regions, such that the first and second dopant concentration regions are alternating in the first direction. The first direction is from a first surface of the buffer layer facing the semiconductor substrate to a second surface of the buffer layer facing away from the semiconductor substrate. Wherein, when both the first and second dopant concentration regions contain iron dopant, the first dopant concentration region is a low-iron concentration region, and the second dopant concentration region is a high-iron concentration region; when both the first and second dopant concentration regions contain carbon dopant, the first dopant concentration region is a high-carbon concentration region, and the second dopant concentration region is a low-carbon concentration region. as well as A heteroepitaxial stack is disposed on the side of the buffer layer away from the semiconductor substrate and is used to provide a conductive channel by constructing a two-dimensional electron gas. The heteroepitaxial stack includes a gallium nitride channel layer and a barrier layer.

2. The epitaxial structure according to claim 1, characterized in that, The buffer layer comprises material Al. x M 1-x N and x are molar fractions, Al is aluminum, M is gallium and / or indium, and N is nitrogen; the aluminum content in the high aluminum content region and the low aluminum content region satisfies 0.3≤x≤0.

75.

3. The epitaxial structure according to claim 2, characterized in that, The buffer layer further includes an aluminum content gradient region connecting the adjacent high aluminum content region and the low aluminum content region in the first direction, and the aluminum content gradient region is a dopant concentration gradient region; the aluminum content of the aluminum content gradient region is between the aluminum content of the high aluminum content region and the aluminum content of the low aluminum content region, and the dopant concentration of the dopant concentration gradient region is between the dopant concentration of the first dopant concentration region and the dopant concentration of the second dopant concentration region.

4. The epitaxial structure according to claim 3, characterized in that, The dopant concentration gradient region is an iron concentration gradient region, and the iron concentration in the iron concentration gradient region is greater than or equal to 1E17 / cm³. 3 And less than 1E20 / cm 3 ; Furthermore, in the first direction, the aluminum content gradient trend in the aluminum content gradient region is opposite to the iron concentration gradient trend in the iron concentration gradient region.

5. The epitaxial structure according to claim 3, characterized in that, The dopant concentration gradient region is a carbon concentration gradient region, and the carbon concentration in the carbon concentration gradient region is greater than or equal to 1E17 / cm³. 3 And less than 1E20 / cm 3 ; Furthermore, in the first direction, the aluminum content gradient trend in the aluminum content gradient region is the same as the carbon concentration gradient trend in the carbon concentration gradient region.

6. The epitaxial structure according to claim 3, characterized in that, The aluminum content of at least one of the high-aluminum-content regions abruptly changes to the aluminum content of the adjacent low-aluminum-content region; the iron concentration of the at least one high-aluminum-content region abruptly changes to the iron concentration of the adjacent low-aluminum-content region, or the carbon concentration of the at least one high-aluminum-content region abruptly changes to the carbon concentration of the adjacent low-aluminum-content region.

7. The epitaxial structure according to claim 2, characterized in that, The aluminum content of each of the high aluminum content regions abruptly changes to the aluminum content of the adjacent low aluminum content region; the iron concentration of each of the high aluminum content regions abruptly changes to the iron concentration of the adjacent low aluminum content region, or the carbon concentration of each of the high aluminum content regions abruptly changes to the carbon concentration of the adjacent low aluminum content region.

8. The epitaxial structure according to claim 1, characterized in that, Both the first dopant concentration region and the second dopant concentration region contain dopant iron and dopant carbon. Therefore, the first dopant concentration region is simultaneously a low iron concentration region and a high carbon concentration region, and the second dopant concentration region is simultaneously a high iron concentration region and a low carbon concentration region. The iron concentration in the low iron concentration region and the high iron concentration region is greater than or equal to 1E17 / cm³. 3 And less than 1E20 / cm 3 The carbon concentration in the high-carbon concentration region and the low-carbon concentration region is greater than or equal to 1E17 / cm³. 3 And less than 1E20 / cm 3 .

9. The epitaxial structure according to claim 8, characterized in that, The buffer layer further includes an aluminum content gradient region connecting the adjacent high aluminum content region and the low aluminum content region in the first direction, and the aluminum content gradient region is a dopant concentration gradient region; the aluminum content gradient trend of the aluminum content gradient region is the same as the carbon concentration gradient trend of the dopant concentration gradient region, and opposite to the iron concentration gradient trend of the dopant concentration gradient region.

10. The epitaxial structure according to any one of claims 1 to 9, characterized in that, Also includes: A nucleation layer is located between the semiconductor substrate and the buffer layer; and / or A gallium nitride high-resistivity layer, located between the buffer layer and the heteroepitaxial stack, and being an iron-doped or carbon-doped gallium nitride layer; and / or A gallium nitride cap layer is located on the side of the heteroepitaxial stack opposite to the semiconductor substrate.

11. A semiconductor device, characterized in that, include: A first electrode, a gate electrode, a second electrode, and an epitaxial structure according to claims 1 to 10; wherein the gate electrode is disposed on the side of the heteroepitaxial stack opposite to the semiconductor substrate, the first electrode and the second electrode are disposed on the side of the heteroepitaxial stack opposite to the semiconductor substrate and are respectively located on opposite sides of the gate electrode, and the first electrode and the second electrode respectively form ohmic contacts with the heteroepitaxial stack.

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