Gallium oxide semiconductor structure and preparation method thereof
By pre-laying atomic layers of predetermined elements and growing a composite barrier layer on the substrate during the gallium oxide epitaxial growth process, the problems of substrate impurity diffusion and lattice mismatch were solved, and a gallium oxide epitaxial layer with low background carrier concentration was achieved, thereby improving device performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-19
- Publication Date
- 2026-04-03
AI Technical Summary
During gallium oxide epitaxial growth, substrate impurity diffusion, defects caused by lattice mismatch, and difficulty in controlling background carrier concentration can all affect device performance.
By pre-laying an atomic layer containing preset elements on a substrate and growing a composite barrier layer, the substrate surface is modified, dangling bonds are filled, impurity diffusion is restricted, and the background carrier concentration is reduced by blocking impurities from diffusing into the epitaxial layer through the composite barrier layer.
It effectively alleviates the defects caused by substrate impurity diffusion and lattice mismatch, reduces background carrier concentration, improves the crystal quality and resistivity of the epitaxial layer, and enhances the device's breakdown voltage and carrier mobility.
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Figure CN121793641A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and in particular to a gallium oxide semiconductor structure and its preparation method. Background Technology
[0002] Gallium oxide (Ga2O3), as an ultrawide bandgap semiconductor material (bandgap ~4.8 eV), has significant potential in high-voltage power devices and deep ultraviolet detection. However, the high background carrier concentration in its epitaxial layer severely restricts device performance, becoming a bottleneck for industrialization. In the substrate processing flow of related technologies, impurities such as silicon (Si) are easily introduced into the substrate surface. During the high-temperature growth of MOCVD (Metal-Organic Chemical Vapor Deposition), these impurities rapidly diffuse to the epitaxial layer, forming shallow donor centers. Furthermore, MOCVD uses metal-organic sources, with carbon (C) and hydrogen (H) as typical donor impurities, resulting in high concentrations. The native oxide layer and defects on the substrate surface adsorb external impurities (such as residual SiO2 from grinding). These impurities migrate through interface defect channels during epitaxy, leading to an abnormally high carrier concentration in the interface region. The high background carrier concentration causes a decrease in the resistivity of the epitaxial layer, failing to meet the requirements of high-resistivity devices. It also affects the device's breakdown voltage performance; the coupling between defects and impurities reduces carrier mobility, further limiting device performance. In summary, there is a lack of effective solutions to the problems of substrate impurity diffusion, defects caused by lattice mismatch, and difficulty in controlling background carrier concentration during gallium oxide epitaxial growth. Summary of the Invention
[0003] The purpose of this invention is to provide a gallium oxide semiconductor structure and its preparation method, so as to alleviate the defects caused by substrate impurity diffusion and lattice mismatch during gallium oxide epitaxial growth, while reducing the background carrier concentration.
[0004] The present invention provides a method for fabricating a gallium oxide semiconductor structure, the method comprising: obtaining a pretreated substrate; pre-depositing an atomic layer containing a preset element on the pretreated substrate to obtain a first structure; wherein the preset element is: aluminum, gallium, or indium; growing a composite barrier layer on the first structure to obtain a second structure; and growing a gallium oxide epitaxial film on the second structure to obtain a gallium oxide semiconductor structure.
[0005] Furthermore, the step of pre-depositing an atomic layer containing a preset element on the pretreated substrate to obtain the first structure includes: placing the pretreated substrate into the reaction chamber of a designated reaction device, heating the pretreated substrate to a first preset temperature, and holding it at that temperature for a first preset time; controlling the chamber pressure of the reaction chamber of the designated reaction device to a first preset pressure; and introducing a reaction gas containing a preset element into the reaction chamber of the designated reaction device at a first preset flow rate to pre-deposit an atomic layer containing a preset element on the pretreated substrate to obtain the first structure.
[0006] Furthermore, the thickness of the atomic layer containing the preset element is 10 nm to 15 nm.
[0007] Furthermore, the step of growing a composite barrier layer on the first structure to obtain the second structure includes: adjusting the temperature of the substrate of the first structure to a second preset temperature and maintaining it; introducing multiple reactive gases into the reaction chamber of a designated reaction device for a first preset growth time to grow a first sub-barrier layer on the first structure to obtain the third structure; wherein each reactive gas is introduced into the reaction chamber according to its corresponding flow rate; the multiple reactive gases include: a first reactive gas containing aluminum, a second reactive gas containing gallium, a third reactive gas containing iron or magnesium, and oxygen; after reaching the first preset growth time, reducing the flow rate of the first reactive gas from a preset first initial flow rate to a preset second flow rate. The flow rate of the second reactant gas is increased from a preset second initial flow rate to a preset third inlet flow rate, while maintaining the current flow rates of the third reactant gas and oxygen. Growth continues for a second preset growth time to grow a second sub-barrier layer on the third structure, resulting in a fourth structure. After reaching the second preset growth time, the flow rate of the first reactant gas is decreased from the second inlet flow rate to a preset fourth inlet flow rate, and the flow rate of the second reactant gas is increased from the third inlet flow rate to a preset fifth inlet flow rate, while maintaining the current flow rates of the third reactant gas and oxygen. Growth continues for a third preset growth time to grow a third sub-barrier layer on the fourth structure, resulting in a second structure.
[0008] Furthermore, the step of growing a composite barrier layer on the first structure to obtain the second structure includes: adjusting the temperature of the substrate of the first structure to a second preset temperature and maintaining it; and introducing multiple reactive gases into the reaction chamber of a designated reaction device for a fifth preset growth time to grow the composite barrier layer on the first structure to obtain the second structure; wherein each reactive gas is introduced into the reaction chamber according to its corresponding flow rate; the multiple reactive gases include: a first reactive gas containing aluminum, a second reactive gas containing gallium, a third reactive gas containing iron or magnesium, and oxygen; during the growth of the composite barrier layer, the flow rate of the first reactive gas decreases linearly from a preset first initial flow rate at a preset decreasing rate, the flow rate of the second reactive gas increases linearly from a preset second initial flow rate at a preset increasing rate, and the current flow rates of the third reactive gas and the oxygen are always maintained.
[0009] Furthermore, the step of growing a gallium oxide epitaxial film on the second structure to obtain a gallium oxide semiconductor structure includes: adjusting the temperature of the substrate of the second structure to a third preset temperature and maintaining it; stopping the introduction of the first and third reactant gases, adjusting the current flow rate of the second reactant gas to a preset sixth flow rate, maintaining the current flow rate of oxygen, and continuing to grow for a fourth preset growth time to grow a gallium oxide epitaxial film on the second structure; stopping the introduction of the second reactant gas, maintaining the current flow rate of oxygen, and holding the temperature for a preset holding time to anneal the gallium oxide epitaxial film; and reducing the temperature of the substrate at a preset cooling rate until the temperature of the substrate drops to a preset room temperature to obtain a gallium oxide semiconductor structure.
[0010] Furthermore, the steps for obtaining the pretreated substrate include: obtaining the substrate to be treated; cleaning and drying the substrate to be treated to obtain the pretreated substrate.
[0011] Furthermore, the thickness of the composite barrier layer ranges from 200 nm to 250 nm.
[0012] Furthermore, the composite barrier layer includes aluminum and a specified element; wherein the specified element is either iron or magnesium.
[0013] The present invention provides a gallium oxide semiconductor structure, which is prepared by any of the gallium oxide semiconductor structure preparation methods described above; the gallium oxide semiconductor structure includes: a substrate, an atomic layer containing a predetermined element, a composite barrier layer and a gallium oxide epitaxial thin film stacked sequentially from bottom to top; wherein the predetermined element is: aluminum, gallium or indium.
[0014] The present invention provides a gallium oxide semiconductor structure and its fabrication method, comprising: obtaining a pretreated substrate; pre-depositing an atomic layer containing a predetermined element on the pretreated substrate to obtain a first structure; wherein the predetermined element is aluminum, gallium, or indium; growing a composite barrier layer on the first structure to obtain a second structure; and growing a gallium oxide epitaxial film on the second structure to obtain a gallium oxide semiconductor structure. This method, by pre-depositing an atomic layer containing a predetermined element, can modify the substrate surface, fill dangling bonds on the substrate surface, reduce interface defect density, and restrict the diffusion of impurities from the substrate surface to the gallium oxide epitaxial film. The composite barrier layer further blocks the upward diffusion of impurities. Therefore, by pre-depositing an atomic layer containing a predetermined element and the composite barrier layer, the defects caused by substrate impurity diffusion and lattice mismatch during gallium oxide epitaxial growth can be effectively alleviated, while simultaneously reducing the background carrier concentration. Attached Figure Description
[0015] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0016] Figure 1 A flowchart illustrating a method for fabricating a gallium oxide semiconductor structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a gallium oxide semiconductor structure provided in an embodiment of the present invention. Detailed Implementation
[0017] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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 are within the scope of protection of the present invention.
[0018] Currently, the epitaxial growth of gallium oxide single-crystal thin films faces numerous technical challenges. For example, high background carrier concentration leads to a decrease in epitaxial layer resistivity, making it difficult to meet the requirements of high-resistivity devices; high concentrations of impurities at the interface form "conductive channels," affecting the device's breakdown voltage performance; and the coupling of defects and impurities forms complexes, reducing carrier mobility and limiting device switching speed and detection sensitivity. One solution offered by related technologies is to utilize the doping compensation effect by introducing acceptor doping, such as magnesium (Mg) doping, to reduce donor impurities introduced into unintentionally doped gallium oxide epitaxial layers. However, the doping uniformity of this method is difficult to control, and the distribution of doped atoms in the epitaxial layer is easily affected by growth temperature, gas flow disturbances, etc., leading to concentration fluctuations in the in-plane or depth directions. For example, at high temperatures, Mg may diffuse along defects to form enriched regions, causing local over-compensation and resulting in uneven carrier concentration. Furthermore, doping easily introduces new point defects, leading to a decrease in mobility. Another solution offered by related technologies is to optimize epitaxial growth parameters, controlling the growth temperature, growth pressure, and the ratio of oxygen atoms to gallium atoms to slow down impurity diffusion or the formation of intrinsic defects. However, this method presents a contradiction between optimizing epitaxial growth parameters and maintaining crystal quality, particularly in suppressing oxygen vacancies (V0.05). o Intrinsic defects such as impurities (e.g., Si) necessitate increasing the oxygen source ratio. However, excessively high oxygen partial pressure can lead to over-oxidation of the epitaxial layer surface, resulting in an amorphous oxide layer or a rough morphology. Simultaneously, while lowering the growth temperature can suppress impurity diffusion, it reduces atomic mobility, leading to a decrease in the crystal quality of the epitaxial layer. Optimizing growth parameters can slow down the impurity diffusion rate, but it cannot fundamentally block the high-temperature migration of impurities such as Si from the substrate.
[0019] In summary, there is a lack of effective solutions to the problems of substrate impurity diffusion, defects caused by lattice mismatch, and difficulty in controlling background carrier concentration during gallium oxide epitaxial growth. Based on this, the present invention provides a gallium oxide semiconductor structure and its preparation method, which can be applied to scenarios requiring the growth of gallium oxide epitaxial layers.
[0020] To facilitate understanding of this embodiment, a method for preparing a gallium oxide semiconductor structure disclosed in this embodiment will first be described, such as... Figure 1 As shown, the method includes the following steps: Step S102: Obtain the pretreated substrate; The aforementioned substrate can be any heterogeneous substrate, such as sapphire (Al2O3) substrate, SiC substrate, or GaN substrate, or a Ga2O3 homogeneous substrate. Taking sapphire (Al2O3) substrate as an example, the bevel angle of the sapphire (Al2O3) substrate can range from 0.2° to 6°. The aforementioned pretreatment method can be selected according to actual needs, such as cleaning or drying. In actual implementation, when it is necessary to prepare gallium oxide semiconductor structures, it is usually necessary to obtain a pretreated substrate first. The pretreated substrate is usually a clean and dry substrate.
[0021] Step S104: A first structure is obtained by pre-depositing an atomic layer containing a preset element on the pre-treated substrate; wherein the preset element is: aluminum, gallium, or indium. In actual implementation, after obtaining the pretreated substrate, an atomic layer containing preset elements, such as an aluminum atomic layer, a gallium atomic layer, or an indium atomic layer, can be pre-deposited on the upper surface of the pretreated substrate to obtain the first structure. The process parameters, thickness, etc. of the pre-deposited atomic layer containing preset elements can be set according to actual needs.
[0022] Step S106: A composite barrier layer is grown on the first structure to obtain the second structure; After obtaining the first structure, a composite barrier layer can be grown on the upper surface of the first structure to obtain the second structure. The process parameters, thickness, etc. of growing the composite barrier layer can be set according to actual needs. For example, the composite barrier layer usually contains aluminum elements with varying concentration gradients, which can be used to block impurities from diffusing upwards and effectively alleviate lattice mismatch and thermal mismatch between the substrate and the epitaxial layer, reducing the stress influence during the growth process.
[0023] In step S108, a gallium oxide epitaxial film is grown on the second structure to obtain a gallium oxide semiconductor structure.
[0024] After obtaining the second structure, a gallium oxide epitaxial film can be grown on its upper surface. The process parameters and thickness of the gallium oxide epitaxial film can be set according to actual needs, ultimately resulting in a gallium oxide semiconductor structure containing the gallium oxide epitaxial film. The above-described method for fabricating a gallium oxide semiconductor structure involves obtaining a pretreated substrate; pre-depositing an atomic layer containing a predetermined element on the pretreated substrate to obtain a first structure; wherein the predetermined element is aluminum, gallium, or indium; growing a composite barrier layer on the first structure to obtain a second structure; and growing a gallium oxide epitaxial film on the second structure to obtain a gallium oxide semiconductor structure. This method, by pre-depositing an atomic layer containing a predetermined element, can modify the substrate surface, fill dangling bonds on the substrate surface, reduce the interface defect density, and restrict the diffusion of impurities from the substrate surface to the gallium oxide epitaxial film. The composite barrier layer further blocks the upward diffusion of impurities. Therefore, by pre-depositing an atomic layer containing a predetermined element and the composite barrier layer, the defects caused by substrate impurity diffusion and lattice mismatch during gallium oxide epitaxial growth can be effectively alleviated, while simultaneously reducing the background carrier concentration.
[0025] This invention also provides another method for fabricating a gallium oxide semiconductor structure, which is based on the method described in the above embodiments and includes the following steps: Step 1: Obtain the substrate to be processed; Step 2: Clean and dry the substrate to be processed to obtain the pretreated substrate; In practice, the substrate to be processed obtained above can be placed in containers containing acetone, ethanol and deionized water in sequence, and ultrasonically cleaned for 5 minutes each to clean the surface of the substrate. The cleaned substrate can be dried with high-purity nitrogen (N2) to obtain a clean and dry pretreated substrate.
[0026] Step 3: Place the pretreated substrate into the reaction chamber of the designated reaction equipment, and heat the pretreated substrate to a first preset temperature and keep it at that temperature for a first preset time. The aforementioned designated reaction equipment can be equipment for epitaxial growth methods such as magnetron sputtering, molecular beam epitaxy, hydride vapor phase epitaxy, and metal-organic chemical vapor phase epitaxy. The aforementioned first preset temperature and first preset time can be set according to actual needs. For example, after placing the pretreated substrate into the reaction chamber of the designated reaction equipment, the pretreated substrate can be heated to 1050°C and held at that temperature for 15-30 minutes.
[0027] Step 4: Control the chamber pressure of the reaction chamber of the designated reaction equipment to the first preset pressure; Step 5: According to the first preset flow rate, a reaction gas containing a preset element is introduced into the reaction chamber of the designated reaction device to pre-deposit an atomic layer containing the preset element on the pretreated substrate to obtain the first structure; wherein, the preset element is: aluminum, gallium, or indium. The thickness of the atomic layer containing the preset element is 10 nm to 15 nm. The first preset pressure and the first preset flow rate can be set according to actual needs; for example, the reaction chamber pressure of the specified reaction equipment can be controlled at 40 torr to 60 torr. Taking trimethylaluminum (TMAl) as the reaction gas containing the preset element, TMAl is used as the Al source. TMAl is introduced onto the Al2O3 substrate surface for pre-deposition. The flow rate of TMAl is 650 sccm to 750 sccm, and the thickness of the pre-deposited Al atomic layer is 10 nm to 15 nm.
[0028] Step 6: Grow a composite barrier layer on the first structure to obtain the second structure; The thickness of the composite barrier layer ranges from 200 nm to 250 nm. The composite barrier layer includes aluminum and a specified element; wherein the specified element is either iron or magnesium, and this specified element acts as a shallow acceptor dopant. The composite barrier layer can be composed of (Al...) x M y Ga 1-x-y )2O3 represents, where M is iron (Fe) or magnesium (Mg). The content range of aluminum is... x It can be 0.2~0.7; specifying the content range of the element. y It can be 0.05~0.1.
[0029] This step six can be achieved through the following steps 60 to 63: Step 60: Adjust the temperature of the substrate of the first structure to the second preset temperature and maintain it; Step 61: According to the first preset growth time, multiple reaction gases are introduced into the reaction chamber of the designated reaction equipment to grow a first sub-barrier layer on the first structure to obtain a third structure; wherein, each reaction gas is introduced into the reaction chamber according to its corresponding flow rate; the multiple reaction gases include: a first reaction gas containing aluminum, a second reaction gas containing gallium, a third reaction gas containing iron or magnesium, and oxygen. The aforementioned second preset temperature and first preset growth time can both be set according to actual needs. In one embodiment, the first reaction gas containing aluminum can be trimethylaluminum (TMAl), which serves as the Al source; the second reaction gas containing gallium can be trimethylgallium (TMGa) or triethylgallium (TEGa), which serves as the Ga source. For ease of explanation, subsequent embodiments will use triethylgallium (TEGa) as an example. If the third reaction gas contains iron, it can be ferrocene (Fe(C5H5)2), which serves as the Fe source. When growing the first sub-barrier layer, the temperature of the substrate of the first structure can be adjusted to 1000°C and maintained. The flow rate of trimethylaluminum (TMAl) is 650 sccm ~ 800 sccm; the flow rate of triethylgallium (TEGa) is 400 sccm ~ 550 sccm; and the flow rate of ferrocene (Fe(C5H5)2) is 400 sccm ~ 550 sccm. The flow rate of (C5H5)2 is maintained at 20 sccm ~ 30 sccm; oxygen is used as the oxygen source, with a flow rate of 2500 sccm ~ 3000 sccm; the first preset growth time is 15 ~ 20 minutes.
[0030] Step 62: After reaching the first preset growth time, the flow rate of the first reaction gas is reduced from the preset first initial flow rate to the preset second inlet flow rate, and the flow rate of the second reaction gas is increased from the preset second initial flow rate to the preset third inlet flow rate. The current flow rate of the third reaction gas and the current flow rate of oxygen are maintained, and the second preset growth time is continued to grow the second sub-barrier layer on the third structure to obtain the fourth structure. The first initial flow rate mentioned above can be understood as the initial flow rate when the first reactant gas is introduced. This first initial flow rate can be set according to actual needs, for example, it can be 650 sccm ~ 800 sccm. The second initial flow rate mentioned above can be understood as the initial flow rate when the second reactant gas is introduced. This second initial flow rate can be set according to actual needs, for example, it can be 400 sccm ~ 550 sccm. The second flow rate, the third flow rate, and the second preset growth time mentioned above can be set according to actual needs. For ease of explanation, we will continue to use the embodiment in the above steps as an example. The substrate temperature can be maintained at 1000℃. After the first preset growth time is reached, the flow rate of the first reactant gas can be reduced from 650 sccm ~ 800 sccm to 450 sccm ~ 600 sccm, and the flow rate of the second reactant gas can be increased from 400 sccm ~ 550 sccm to 650 sccm ~ 800 sccm. Oxygen (O2) is used as the oxygen source, and the O2 flow rate is 2500 sccm ~ 3000 sccm. Ferrocene (Fe (C5H5)2 was used as the Fe source, and the flow rate was maintained at 20 sccm ~ 30 sccm; the second preset growth time was 15 ~ 20 minutes.
[0031] Step 63: After reaching the second preset growth time, reduce the flow rate of the first reaction gas from the second inlet flow rate to the preset fourth inlet flow rate, increase the flow rate of the second reaction gas from the third inlet flow rate to the preset fifth inlet flow rate, maintain the current flow rate of the third reaction gas and the current flow rate of oxygen, and continue to grow for the third preset growth time to grow the third sub-barrier layer on the fourth structure to obtain the second structure.
[0032] The fourth and fifth inlet flow rates and the third preset growth time can all be set according to actual needs. For ease of explanation, the example in the above steps can be used as an example. The substrate temperature can be maintained at 1000℃. After the second preset growth time is reached, the flow rate of the first reaction gas can be reduced from 450 sccm ~ 600 sccm to 250 sccm ~ 400 sccm, and the flow rate of the second reaction gas can be increased from 650 sccm ~ 800 sccm to 850 sccm ~ 1000 sccm. Oxygen (O2) is used as the oxygen source, and the O2 flow rate is 2500 sccm ~ 3000 sccm. Ferrocene (Fe(C5H5)2) is used as the Fe source, and the flow rate is maintained at 20 sccm ~ 30 sccm. The third preset growth time is 20 ~ 30 minutes. The composite barrier layer obtained through steps 60 to 63 includes a first sub-barrier layer, a second sub-barrier layer, and a third sub-barrier layer. That is, the composite barrier layer is actually a multilayer structure.
[0033] This step six can also be achieved through the following steps 64 to 65: Step 64: Adjust the temperature of the substrate of the first structure to the second preset temperature and maintain it; Step 65: According to the fifth preset growth time, multiple reaction gases are introduced into the reaction chamber of the designated reaction equipment to grow a composite barrier layer on the first structure to obtain the second structure; wherein, each reaction gas is introduced into the reaction chamber according to its corresponding flow rate; the multiple reaction gases include: a first reaction gas containing aluminum, a second reaction gas containing gallium, a third reaction gas containing iron or magnesium, and oxygen; during the growth of the composite barrier layer, the flow rate of the first reaction gas decreases linearly from the preset first initial flow rate at a preset decreasing rate, the flow rate of the second reaction gas increases linearly from the preset second initial flow rate at a preset increasing rate, and the current flow rates of the third reaction gas and the oxygen are always maintained.
[0034] The aforementioned fifth preset growth time, preset decrease rate, and preset increase rate can all be set according to actual needs. For example, the fifth preset growth time can be 50-70 minutes. In one embodiment, the first reaction gas containing aluminum can be trimethylaluminum (TMAl), which serves as the Al source. The second reaction gas containing gallium can be triethylgallium (TEGa), which serves as the Ga source. If the third reaction gas contains iron, it can be ferrocene (Fe(C5H5)2), which serves as the Fe source. When growing the composite barrier layer, the substrate temperature of the first structure can be adjusted to 1000°C and maintained. The first initial flow rate of trimethylaluminum (TMAl) is 650 sccm ~ 800 sccm, and during the growth process, it can be linearly decreased according to the preset decrease rate. The second initial flow rate of triethylgallium (TEGa) is 400 sccm ~ 550 sccm, and during the growth process, it can be linearly increased according to the preset increase rate. The flow rate of (C5H5)2 is maintained at 20 sccm ~ 30 sccm; oxygen is used as the oxygen source, with a flow rate of 2500 sccm ~ 3000 sccm; the first preset growth time is 50 ~ 70 minutes. The composite barrier layer obtained through the above steps 64 to 65 is a single-layer structure.
[0035] As can be seen from the above embodiments, the Al element concentration in the composite barrier layer changes in a gradient. It can grow into a single-layer structure with a gradual change in Al composition from high to low during the epitaxial growth process, or it can be a multi-layer structure composed of a high Al composition layer, a medium Al composition layer, and a low Al composition layer.
[0036] Step 7: Adjust the temperature of the substrate of the second structure to the third preset temperature and maintain it; Step 8: Stop the flow of the first and third reaction gases, adjust the current flow rate of the second reaction gas to the preset sixth flow rate, maintain the current flow rate of oxygen, and continue the growth for the fourth preset growth time to grow a gallium oxide epitaxial film on the second structure. The aforementioned third preset temperature can be set according to actual needs, for example, it can be 950℃. For ease of explanation, we will continue to take the embodiment in the above steps as an example. The substrate temperature can be reduced from 1000℃ to 950℃, the Al source and Fe source can be turned off, that is, the first reaction gas and the third reaction gas can be stopped. The current flow rate of the second reaction gas can be increased to 1100 sccm ~ 1400 sccm, and the oxygen flow rate can be maintained at 2500 sccm ~ 3000 sccm. A gallium oxide epitaxial film can be grown on the upper surface of the second structure. The specific growth time can be set according to actual needs.
[0037] Step 9: Stop the flow of the second reaction gas, maintain the current oxygen flow rate, and maintain the temperature for the preset holding time to anneal the gallium oxide epitaxial film. The preset holding time can be set according to actual needs, such as 10 minutes; after the reaction in step eight above is completed, the Ga source can be turned off, that is, the second reaction gas can be stopped, the oxygen flow rate can be maintained at 2500 sccm ~ 3000 sccm, and the substrate temperature can be kept constant for 10 minutes to perform annealing treatment on the gallium oxide epitaxial film.
[0038] Step 10: Reduce the temperature of the substrate at a preset cooling rate until the temperature of the substrate drops to a preset room temperature to obtain a gallium oxide semiconductor structure.
[0039] The preset cooling rate can be set according to actual needs. For example, it can be 200 ℃ / h. After the gallium oxide epitaxial film is annealed, the temperature of the substrate can be reduced to the preset room temperature at the preset cooling rate to finally obtain the gallium oxide semiconductor structure.
[0040] The aforementioned method for fabricating gallium oxide semiconductor structures specifically relates to the field of wide-bandgap semiconductor material fabrication technology, and involves a method that utilizes the synergistic effect of substrate pretreatment and barrier layer design, based on atomic layer pre-laying containing predetermined elements and (Al) x M y Ga 1-x-y The composite substrate structure with a 2O3 barrier layer is a method to suppress unintentional doping and reduce the background carrier concentration of gallium oxide epitaxial layers, which is applicable to the field of high-quality gallium oxide epitaxial growth.
[0041] This solution provides a method based on atomic layer pre-layout containing preset elements and (Al) x M y Ga 1-x-y The composite substrate with a 2O3 barrier layer and the method for epitaxial growth of gallium oxide involve pre-laying an atomic layer containing a predetermined element onto the substrate before gallium oxide epitaxial growth. This pre-laying modifies the substrate surface, fills dangling bonds, reduces interface defect density, and restricts the diffusion of impurities from the substrate surface to the epitaxial layer. Then, Al₂O₃ is grown on the pre-laid atomic layer containing the predetermined element. x M y Ga 1-x-y The Al₂O₃ layer acts as a barrier layer, further preventing impurities from diffusing into the epitaxial layer and effectively mitigating lattice and thermal mismatches between the substrate and the epitaxial layer, thus reducing the stress impact during growth. Utilizing the variation in Al element concentration gradient and trace amounts of M element, (Al₂O₃) x M y Ga 1-x-y The 2O3 layer can further reduce the lattice mismatch between the heterostructure substrate and the gallium oxide epitaxial layer, which is beneficial for reducing dislocation defects in the epitaxial layer and improving the crystal quality of the epitaxial layer. Element M, as a shallow acceptor dopant, compensates for shallow donor impurities in unintentionally doped gallium oxide, reducing the background carrier concentration. Through this compensation effect, the shallow donor concentration in the unintentionally doped epitaxial layer is reduced. This method is simple and effective; substrate pretreatment does not involve additional process equipment, effectively avoiding secondary contamination and simplifying the pretreatment process. It includes atomic layer pre-laying of preset elements and (Al) x M y Ga 1-x-y The growth of the 2O3 barrier layer can be integrated into existing MOCVD / MBE (Molecular Beam Epitaxy) combined equipment to achieve high-quality, low-background carrier concentration gallium oxide heteroepitaxy process.
[0042] High-quality gallium oxide epitaxial layers are crucial for manufacturing high-voltage power devices and solar-blind ultraviolet detectors, preventing defect-induced leakage and reliability degradation. Low background carrier concentration can significantly improve the resistivity of the epitaxial layer, weaken the "conductive channel" effect caused by high carrier concentration, reduce the coupling between impurities and intrinsic defects, reduce carrier scattering, and improve mobility.
[0043] This method uses pre-laid atomic layers containing preset elements and (Al) x M y Ga 1-x-y The composite substrate with a 2O3 barrier layer can alleviate lattice mismatch and thermal mismatch between the substrate and the epitaxial layer, and reduce the background carrier concentration of gallium oxide single crystal thin films. x M y Ga 1-x-yThe M element in the 2O3 barrier layer acts as a shallow acceptor, compensating for shallow donor impurities in the unintentionally doped epitaxial layer.
[0044] This invention provides a gallium oxide semiconductor structure, which is prepared by the method described in the above embodiments; such as Figure 2 The diagram shows a gallium oxide semiconductor structure, which includes: a substrate, an atomic layer containing a predetermined element, a composite barrier layer, and a gallium oxide epitaxial film stacked sequentially from bottom to top; wherein the predetermined element is: aluminum, gallium, or indium.
[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for fabricating a gallium oxide semiconductor structure, characterized in that, The method includes: Obtain the pretreated substrate; An atomic layer containing a preset element is pre-deposited on the pretreated substrate to obtain a first structure; wherein the preset element is: aluminum, gallium, or indium. A composite barrier layer is grown on the first structure to obtain the second structure; A gallium oxide epitaxial film is grown on the second structure to obtain a gallium oxide semiconductor structure.
2. The method according to claim 1, characterized in that, The step of pre-depositing an atomic layer containing a predetermined element on the pretreated substrate to obtain the first structure includes: The pretreated substrate is placed in the reaction chamber of a designated reaction device, and the pretreated substrate is heated to a first preset temperature and held at that temperature for a first preset time. The chamber pressure of the reaction chamber of the designated reaction device is controlled to a first preset pressure; A reaction gas containing the preset element is introduced into the reaction chamber of the designated reaction device at a first preset flow rate, so as to pre-deposit an atomic layer containing the preset element on the pretreated substrate to obtain a first structure.
3. The method according to claim 1, characterized in that, The thickness of the atomic layer containing the preset elements is 10 nm to 15 nm.
4. The method according to claim 2, characterized in that, The step of growing a composite barrier layer on the first structure to obtain the second structure includes: The temperature of the substrate of the first structure is adjusted to a second preset temperature and maintained. According to a first preset growth time, multiple reaction gases are introduced into the reaction chamber of the designated reaction device to grow a first sub-barrier layer on the first structure to obtain a third structure; wherein, each of the reaction gases is introduced into the reaction chamber according to its corresponding flow rate; the multiple reaction gases include: a first reaction gas containing aluminum, a second reaction gas containing gallium, a third reaction gas containing iron or magnesium, and oxygen; After the first preset growth time is reached, the flow rate of the first reaction gas is reduced from the preset first initial flow rate to the preset second inlet flow rate, and the flow rate of the second reaction gas is increased from the preset second initial flow rate to the preset third inlet flow rate. The current flow rate of the third reaction gas and the current flow rate of the oxygen are maintained, and the second preset growth time is continued to grow, so as to grow a second sub-barrier layer on the third structure to obtain a fourth structure. After the second preset growth time is reached, the flow rate of the first reactant gas is reduced from the second inlet flow rate to the preset fourth inlet flow rate, and the flow rate of the second reactant gas is increased from the third inlet flow rate to the preset fifth inlet flow rate. The current flow rate of the third reactant gas and the current flow rate of the oxygen are maintained, and the growth continues for the third preset growth time to grow a third sub-barrier layer on the fourth structure, thereby obtaining the second structure.
5. The method according to claim 2, characterized in that, The step of growing a composite barrier layer on the first structure to obtain the second structure includes: The temperature of the substrate of the first structure is adjusted to a second preset temperature and maintained. According to a fifth preset growth time, multiple reactive gases are introduced into the reaction chamber of the designated reaction device to grow a composite barrier layer on the first structure, thereby obtaining a second structure; wherein, each of the reactive gases is introduced into the reaction chamber according to its corresponding flow rate; the multiple reactive gases include: a first reactive gas containing aluminum, a second reactive gas containing gallium, a third reactive gas containing iron or magnesium, and oxygen; during the growth of the composite barrier layer, the flow rate of the first reactive gas decreases linearly at a preset decreasing rate starting from a preset first initial flow rate, the flow rate of the second reactive gas increases linearly at a preset increasing rate starting from a preset second initial flow rate, and the current flow rates of the third reactive gas and the oxygen are always maintained.
6. The method according to claim 4 or 5, characterized in that, The step of growing a gallium oxide epitaxial film on the second structure to obtain a gallium oxide semiconductor structure includes: The temperature of the substrate of the second structure is adjusted to a third preset temperature and maintained. Stop the flow of the first and third reactant gases, adjust the current flow rate of the second reactant gas to a preset sixth flow rate, maintain the current flow rate of the oxygen, and continue growth for a fourth preset growth time to grow a gallium oxide epitaxial film on the second structure. Stop the flow of the second reaction gas, maintain the current flow rate of the oxygen, and keep it at a preset temperature for a set time to anneal the gallium oxide epitaxial film. The temperature of the substrate is reduced at a preset cooling rate until the temperature of the substrate drops to a preset room temperature, thereby obtaining a gallium oxide semiconductor structure.
7. The method according to claim 1, characterized in that, The steps for obtaining the pretreated substrate include: Obtain the substrate to be processed; The substrate to be processed is cleaned and dried to obtain a pretreated substrate.
8. The method according to claim 1, characterized in that, The thickness of the composite barrier layer ranges from 200 nm to 250 nm.
9. The method according to claim 1, characterized in that, The composite barrier layer includes aluminum and a specified element; wherein the specified element is iron or magnesium.
10. A gallium oxide semiconductor structure, characterized in that, The gallium oxide semiconductor structure is prepared by the method for preparing the gallium oxide semiconductor structure according to any one of claims 1-9; the gallium oxide semiconductor structure includes: a substrate, an atomic layer containing a preset element, a composite barrier layer and a gallium oxide epitaxial film stacked sequentially from bottom to top; wherein the preset element is: aluminum, gallium or indium.