Method for reducing defects in nitride single crystals, nitride single crystals, and semiconductor devices

Abstract

The application discloses a method for reducing defects of nitride single crystals, nitride single crystals and semiconductor devices. The method comprises the following steps: growing a first nitride layer on a substrate based on a first epitaxial growth device to obtain a first template structure; transferring the first template structure into a second epitaxial growth device; performing interface processing on a second template structure with impurities formed after the transferring to remove the impurities and obtain a new interface with pits; the pits are composed of the same material as the first nitride layer; and continuing to grow target nitride based on the new interface in the second epitaxial growth device to obtain a nitride single crystal layer without cavity defects. The application effectively removes the particulate impurities attached to the template structure during the device transfer and temperature rising process, forms a new interface with the same pit material, and grows the target nitride based on the new interface to reduce the dislocation density and stress, eliminate the cavity defects, and significantly improve the crystal quality of the nitride single crystal.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor growth technology and relates to a method for reducing defects in nitride single crystals, nitride single crystals, and semiconductor devices. Background Technology

[0002] GaN is an important wide-bandgap semiconductor material, widely used in the fabrication of high-brightness Micro-LEDs, semiconductor lasers, and high-power electronic devices. However, the high-quality growth of GaN single crystals and the improvement of growth efficiency have always been a trade-off. For example, metal-organic chemical vapor deposition (MOCVD) can produce GaN single crystals with good quality, but the growth efficiency is low; hydride vapor phase epitaxy (HVPE) has the advantage of fast growth rate, but the grown single crystals have more defects, and the growth quality needs to be improved. Summary of the Invention

[0003] The main objective of this invention is to provide a method for reducing defects in nitride single crystals, nitride single crystals, and semiconductor devices. This method can remove particulate impurities generated on the surface of the template structure due to transfer or heating during the transfer of the template structure between devices, and obtain a high-quality, void-free nitride single crystal layer based on the new interface, thereby improving the growth quality of nitride single crystals while ensuring growth efficiency.

[0004] To achieve the aforementioned objectives, the technical solution adopted by this invention includes: The first aspect of this invention provides a method for reducing defects in nitride single crystals, comprising: A first nitride layer is grown on a substrate using a first epitaxial growth device to obtain a first template structure; The first template structure is transferred to the second epitaxial growth device. In the second epitaxial growth device, the second template structure with impurities formed after the transfer is subjected to interface treatment to remove the impurities and obtain a new interface with pits distributed thereon. The pits are composed of the same material as the first nitride layer. The first epitaxial growth device and the second epitaxial growth device are different devices. The target nitride is then grown in the second epitaxial growth apparatus based on the new interface to obtain a nitride single crystal layer without voids.

[0005] By performing interface treatment on the second template structure containing impurities in the second epitaxial growth equipment, the impurities attached during the transfer and heating process are removed, and a new interface with homogeneous pits is formed. This new interface provides high-quality nucleation sites for subsequent growth without the introduction of impurities, thereby achieving the effects of reducing dislocations and stress, eliminating void defects, and improving crystal quality.

[0006] In one specific embodiment, the second template structure containing impurities formed after transfer is subjected to interface treatment in the aforementioned second epitaxial growth apparatus to remove the impurities and obtain a new interface with distributed pits, including: In the second epitaxial growth apparatus, a second nitride layer is grown on the second template structure. Through stress accumulation, the second template structure undergoes self-separation within the first nitride layer to separate the nitride structure portion containing impurities, thereby obtaining the new interface. Alternatively, an etching process can be used in the second epitaxial growth apparatus to etch the surface of the second template structure to remove surface impurities and obtain the new interface.

[0007] In one specific embodiment, stress accumulation causes the second template structure to self-separate within the first nitride layer, including: Tensile stress is generated within the second template structure due to the lattice mismatch and the difference in thermal expansion coefficients between the substrate and the nitride. This tensile stress accumulates continuously during the growth of the second nitride layer. When the growth thickness of the second nitride layer causes the accumulated tensile stress to exceed the elastic distortion threshold of the nitride, a self-separation interface is generated. The upper structure corresponding to the separation of the self-separation interface is the nitride structure portion, which includes: a nitride template layer with impurities and the upper second nitride layer. The lower structure corresponding to the separation of the self-separation interface includes a new interface with distributed pits.

[0008] In one specific embodiment, the thickness of the first nitride layer is 100 μm to 300 μm, and the thickness of the second nitride layer is 300 μm to 500 μm.

[0009] In one specific embodiment, the distance between the self-separating interface inside the first nitride layer and the substrate is 50 μm to 100 μm.

[0010] In one specific embodiment, after the second template structure separates itself, the second template structure is driven to rotate at high speed, and centrifugal force is used to throw the nitride structure part away from the top of the new interface to expose the new interface; or, the nitride structure part is removed from the top of the new interface by mechanical clamping to expose the new interface; wherein, during the throwing or removal process and after the throwing or removal, the nitride structure part is located in the second epitaxial growth device, and the second epitaxial growth device is always in operation and the temperature is within the preset growth temperature range of the target nitride.

[0011] This invention completes separation and removal while the second epitaxial growth equipment is in operation, without the need to open the lid or stop the machine. This avoids secondary contamination caused by opening the lid or temperature changes, ensuring the continuity and purity of the growth process. In other words, self-separation occurs during the sample growth period in a stable state of the second epitaxial growth equipment, eliminating the possibility of impurities arising from sample changes or temperature fluctuations.

[0012] Furthermore, the nitride structure portion is thrown off the new interface using centrifugal force, including: increasing the rotation speed of the sample tray carrying the second template structure in the second epitaxial growth equipment to 10 to 50 times the preset growth speed; after the nitride structure portion has been thrown off, restoring the second template structure to the preset growth speed, and continuing to grow the target nitride based on the new interface within the preset growth temperature range in the second epitaxial growth equipment to obtain a nitride single crystal layer without void defects.

[0013] In one specific embodiment, the etching process includes: etching the surface of the second template structure using a mixed gas containing HCl, H2 and NH3; After etching is completed, the atmosphere is switched to the growth atmosphere of the target nitride, and the target nitride is grown on the new interface.

[0014] Furthermore, the above etching process specifically includes: first introducing H2 and NH3 into the second epitaxial growth equipment to establish a stable H2 and NH3 gas flow, and then introducing HCl.

[0015] Furthermore, the flow rate of HCl is 20 sccm to 50 sccm, the flow rate of H2 is 2000 sccm to 5000 sccm, and the flow rate of NH3 is 50 sccm to 200 sccm.

[0016] Furthermore, the etching temperature is 850℃~950℃, and the time is 1min~5min.

[0017] In one specific embodiment, after etching is completed, the HCl supply is stopped, so that the etched second template structure is kept in a mixed atmosphere of H2 and NH3. Then, the growth atmosphere and growth temperature of the target nitride are switched. The growth atmosphere of the target nitride includes H2, NH3, N2 and GaCl3, and the growth temperature of the target nitride is 1000℃~1200℃.

[0018] In some embodiments, the first growth process corresponding to the first epitaxial growth equipment is different from the second growth process corresponding to the second epitaxial growth equipment. The growth efficiency of the second growth process is higher than that of the first growth process, and the single crystal growth quality of the first growth process is higher than that of the second growth process. It should be noted that if the process is transferred between two devices with the same process, problems such as the introduction of impurities may also be encountered. Therefore, in other embodiments, the first epitaxial growth equipment and the second epitaxial growth equipment can also use the same growth process. This invention does not limit the specific application scenario.

[0019] In some embodiments, the first epitaxial growth equipment is an MOCVD equipment, and the second epitaxial growth equipment is an HVPE equipment. This invention combines the advantages of high-quality MOCVD growth and high-efficiency HVPE growth, first using MOCVD to prepare a high-quality template, and then using HVPE to rapidly grow a thick film, thus balancing quality and efficiency.

[0020] In one specific embodiment, the above method further includes at least one of the following: The aforementioned substrate includes one of the following materials: sapphire, silicon, and silicon carbide; The first nitride layer mentioned above is made of the same material as the target nitride mentioned above, including one of the following materials: gallium nitride, aluminum nitride; The first nitride layer is made of a different material than the target nitride. The first nitride layer is gallium nitride or aluminum nitride, and the target nitride layer is aluminum nitride or gallium nitride.

[0021] Specifically, the impurities in the second template structure include one or more of the following: dust particles introduced during the transfer and conveying of the first template structure to the second epitaxial growth equipment, splashed particles caused by mechanical vibration, reactor parasitic particles introduced during the heating process after transfer to the second epitaxial growth equipment, chloride source salt particles from the backflow of the reaction chamber, and splashed particles from thermal vibration.

[0022] Specifically, the pits on the new interface are unevenly distributed.

[0023] In one specific embodiment, the distribution of at least one of the area, depth, and spacing of the pits in the new interface is uneven.

[0024] In one specific embodiment, the size of the pit is 50μm to 300μm, the depth of the pit is 1μm to 5μm, and the spacing between the pits is 500μm to 2000μm.

[0025] In one specific embodiment, the surface of the first template structure is a flat extended surface, while the surface of the second template structure is uneven.

[0026] In one specific embodiment, the surface roughness of the first template structure is 0.2nm~0.5nm, the surface roughness of the second template structure is 0.5nm~2nm, and the surface roughness of the new interface is 2nm~5nm.

[0027] A second aspect of this invention provides a nitride single crystal structure, comprising: Substrate; A template nitride layer located on the aforementioned substrate; A nitride single crystal layer is located on top of the template nitride layer, wherein the nitride single crystal layer and the template nitride layer are homogeneous or heterogeneous materials. The aforementioned nitride single-crystal structure was obtained by the method described above for reducing defects in nitride single crystals.

[0028] A third aspect of the present invention provides a semiconductor device, wherein the substrate of the semiconductor device is the aforementioned nitride single crystal structure; or, The substrate of the aforementioned semiconductor device is formed from a nitride single-crystal layer peeled off from the aforementioned nitride single-crystal structure; or, The epitaxial layer of the aforementioned semiconductor device is formed in situ grown on the aforementioned nitride single crystal structure; or, The epitaxial layer of the aforementioned semiconductor device is formed by epitaxy on the stripped nitride single crystal layer.

[0029] In some embodiments, the semiconductor device described above includes optoelectronic devices or electronic devices.

[0030] Compared with the prior art, the beneficial effects of the technical solution provided by the embodiments of the present invention include: During the transfer of the first template structure from the first epitaxial growth equipment to the second epitaxial growth equipment and / or during the heating process of the second epitaxial growth equipment, particulate impurities are introduced onto the upper surface of the first template structure, forming a second template structure with impurities. By performing interface treatment on the second template structure in the second epitaxial growth equipment to remove impurities in situ, a new interface with homogeneous pits is obtained. This not only removes particulate impurities introduced during the transfer and heating processes, thus eliminating heterogeneous materials and avoiding subsequent growth defects caused by particulate matter, but also provides better nucleation sites based on the distributed pits. These pits are composed of homogeneous materials, have low nucleation energies, and are easy to induce 3D growth modes, effectively reducing the dislocation density and stress of the target nitride, eliminating void defects, and improving single crystal quality. Since both the impurity removal process and the growth process of the target nitride occur within the second epitaxial growth equipment, and the reaction chamber environment is stable and does not require sample replacement, secondary contamination is avoided. Ultimately, a high-quality nitride single crystal layer with a smooth surface and no void defects is obtained, significantly improving the yield and performance of the device. Attached Figure Description

[0031] Figure 1 This is a flowchart of a method for reducing defects in nitride single crystals provided in a typical embodiment of the present invention; Figure 2 This is a flowchart of a method for reducing defects in nitride single crystals provided in a typical embodiment of the present invention; Figure 3 This is a schematic diagram of the first template structure provided in a typical embodiment of the present invention; Figure 4 This is a schematic diagram of the second template structure with surface-attached impurities provided in a typical embodiment of the present invention; Figure 5a This is a top view of a typical embodiment of the present invention, in which the interface of a second template structure with impurities formed after transfer is processed to obtain a new interface with distributed pits. Figure 5b This is a cross-sectional view of a second template structure with impurities formed after transfer, obtained by interface processing, to obtain a new interface with distributed pits in a typical embodiment of the present invention. Figure 6 This is a schematic diagram of a typical embodiment of the present invention in which a second nitride continues to grow on the second template structure; Figure 7 This is a schematic diagram of (a) the upper structure and (b) the lower structure obtained after the second template structure undergoes self-separation within the first nitride layer based on stress accumulation in a typical embodiment of the present invention. Figure 8 This is a schematic diagram of the structure of a nitride single crystal layer grown on a new interface in a typical embodiment of the present invention; Figure 9 This is a flowchart of a method for reducing defects in nitride single crystals provided in another typical embodiment of the present invention; Figure 10 This is a timing diagram of etching process parameter control in another typical embodiment of the present invention; Figure 11 This is a surface morphology diagram of a nitride single crystal layer obtained in a typical embodiment of the present invention; Figure 12 This is a morphology image of a nitride single crystal layer obtained under an optical microscope in a typical embodiment of the present invention. Detailed Implementation

[0032] In view of the shortcomings of the prior art, the inventors of this case, through long-term research and extensive practice, have proposed the technical solution of this invention. To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. The values ​​within the numerical range described in the embodiments of this invention should be understood to include boundary values.

[0033] Unless otherwise defined, all technical / scientific terms used in this invention have the same meaning as commonly understood by those skilled in the art. The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0034] To improve nitride growth efficiency while maintaining growth quality, a high-quality template structure can be grown using MOCVD equipment, followed by high-efficiency single-crystal nitride growth in an HVPE equipment, thus leveraging the advantages of both methods. However, the inventors discovered the following technical problems with this combination method during research and development: During the transfer of the sample template from the MOCVD equipment to the HVPE equipment for single-crystal nitride growth, particles fall off due to mechanical vibration; insufficient vacuum in the transfer chamber causes particles from the environment to adhere to the sample surface; and during the heating process in the HVPE equipment to the target temperature, changes in the thermal field distribution (which can also be described as thermal vibration) cause some particles to adhere to the sample surface. These issues result in significant defects on the sample surface before transfer to the HVPE equipment for growth, leading to numerous voids and other defects in the subsequently grown nitride crystals, thus affecting the single-crystal quality.

[0035] In view of this, embodiments of the present invention provide a method for reducing defects in nitride single crystals. (Refer to...) Figure 1As shown, the above method includes the following steps: S110, S120 and S130.

[0036] In step S110, a first nitride layer is grown on the substrate using the first epitaxial growth equipment to obtain a first template structure.

[0037] Reference Figure 3 As shown, a first nitride layer 202 is grown on a substrate 201 using a first epitaxial growth device to obtain a first template structure.

[0038] In step S120, the first template structure is transferred to the second epitaxial growth device. In the second epitaxial growth device, the second template structure with impurities formed after the transfer is subjected to interface treatment to remove the impurities and obtain a new interface with pits.

[0039] The aforementioned pits are composed of homogeneous material from the first nitride layer; wherein the first epitaxial growth equipment and the second epitaxial growth equipment are different equipment.

[0040] In some embodiments, the first growth process corresponding to the first epitaxial growth equipment is different from the second growth process corresponding to the second epitaxial growth equipment. The growth efficiency of the second growth process is higher than that of the first growth process, and the single crystal growth quality of the first growth process is higher than that of the second growth process. For example, the first epitaxial growth equipment is a metal-organic chemical vapor deposition (MOCVD) equipment, and the second epitaxial growth equipment is a hydride vapor phase epitaxy (HVPE) equipment. By combining the high growth quality advantage of MOCVD to first grow the first template structure, a template with high nucleation quality can be provided for subsequent rapid growth based on HVPE. Combined with the high growth efficiency of HVPE, i.e., first using MOCVD to prepare a high-quality template, and then using HVPE to rapidly grow a thick film, both quality and efficiency are taken into account. However, during the research and development, it was discovered that particulate impurities would adhere to the surface of the first template structure during the transfer process and the heating process in the HVPE equipment. Therefore, impurities were generated on the surface of the transferred template structure obtained in the second epitaxial growth equipment, which differed from the first template structure grown from MOCVD. The template structure with impurities after transfer is described as the second template structure, as referred to [reference needed]. Figure 4As shown, impurities 301 are distributed randomly and unevenly on the upper surface of the second template structure. These impurities 301 are embedded in the upper surface of the first nitride layer 202 and have protrusions relative to the upper surface. Due to the embedding of impurities, many void-like defects and high dislocation density are generated during the conventional HVPE growth stage. Therefore, by setting step S120 to perform interface treatment on the second template structure, a new interface with distributed pits 302 is obtained. The new interface provides better nucleation sites based on the distributed pits, promoting high-quality growth of subsequent single crystals. (Refer to...) Figure 5a , Figure 5b As shown, the pits on the new interface are unevenly distributed.

[0041] In one specific embodiment, the distribution of at least one of the area, depth, and spacing of the pits in the new interface is uneven.

[0042] As an example, the size of the pits is 50μm to 300μm, the depth of the pits is 1μm to 5μm, and the spacing between the pits is 500μm to 2000μm.

[0043] The impurities in the second template structure mentioned above include, but are not limited to, one or more of the following: dust particles introduced during the transfer and conveying of the first template structure to the second epitaxial growth equipment, splashed particles caused by mechanical vibration, reactor parasitic particles introduced during the heating process after the transfer to the second epitaxial growth equipment, chloride source salt particles from the backflow of the reaction chamber, and splashed particles from thermal vibration.

[0044] In other embodiments, if the template is transferred between two devices with the same process (e.g., two devices with different levels of fineness), the problem of impurity introduction may also be encountered. Therefore, in other embodiments, the first epitaxial growth device and the second epitaxial growth device may also have the same growth process. This invention does not limit the specific application scenario.

[0045] In step S130, the target nitride is grown in the second epitaxial growth apparatus based on the new interface to obtain a nitride single crystal layer without void defects.

[0046] By performing interface treatment on the second template structure in the second epitaxial growth equipment to remove impurities in situ, a new interface with homogeneous pits is obtained. This not only removes particulate impurities introduced by processes such as transfer and heating, thus eliminating heterogeneous materials and avoiding subsequent growth defects caused by particulate matter, but also provides better nucleation sites based on the distributed pits. These pits are composed of homogeneous materials, have low nucleation energy, and are easy to induce 3D growth mode, effectively reducing the dislocation density and stress of the target nitride, eliminating void defects, and improving the quality of single crystals.

[0047] The above step S120 can be implemented in various ways, and will be described below according to different implementation methods.

[0048] First technical route.

[0049] Please see Figure 2 As shown, the method for reducing defects in nitride single crystals provided by the first technical route specifically includes the following steps: S110, S210, S220, S230 and S130, that is, step S120 specifically includes the following refined steps for interface treatment based on stress accumulation: S210~S230.

[0050] In step S110, a first nitride layer 202 is grown on the substrate 201 using the first epitaxial growth equipment to obtain a first template structure, as shown below. Figure 3 As shown.

[0051] Specifically, substrate 201 serves as the supporting base for the entire structure, and the material selection for substrate 201 must consider its lattice matching with the subsequently grown nitride material. For example, substrate 201 can be made of sapphire, silicon, or silicon carbide; typically, a sapphire wafer can be chosen as the sapphire substrate in practice. Specifically, the thickness of the substrate is usually on the order of several hundred micrometers, for example, around 450 μm, to provide sufficient mechanical strength. Specifically, the material of the first nitride layer 202 can be the same as the subsequent target nitride material, such as gallium nitride or aluminum nitride; or it can be different from the target nitride material, for example, the first nitride layer 202 is made of gallium nitride while the target nitride is aluminum nitride, or vice versa. This heterogeneous structure only requires ensuring that the lattice mismatch between the two is small.

[0052] In a preferred embodiment, the first epitaxial growth apparatus employs a metal-organic chemical vapor deposition (MOCVD) apparatus. For example, the surface roughness of the first nitride layer 202 grown by the MOCVD process can be controlled within 0.2 nm to 0.5 nm, exhibiting a smooth epitaxial surface. This high-quality surface condition provides a good foundation for subsequent transfer and growth. Specifically, the thickness of the first nitride layer 202 is typically 100 μm to 300 μm. If the thickness is too thin, it is difficult to alleviate the lattice mismatch between the heterogeneous substrate such as sapphire and the nitride layer, affecting the subsequent growth quality; if the thickness is too thick, considering the relatively slow growth rate of the MOCVD process (approximately 10 μm / hour), it will significantly increase production costs and time costs.

[0053] It should be noted that the process conditions for growing the first nitride layer by MOCVD are all known in the art. For example, the growth temperature of gallium nitride by MOCVD is usually 1020℃~1120℃, the growth pressure is usually 76 Torr~760 Torr, hydrogen or a mixture of hydrogen and nitrogen is usually used as the carrier gas, the flow rate of the nitrogen source (usually NH3) is 2000 sccm~5000 sccm, and the flow rate of the gallium source (usually trimethylgallium™Ga) is 30 μmol / min~60 μmol / min.

[0054] Taking a substrate 201 made of sapphire and a first nitride layer 202 made of gallium nitride as an example, during the growth of the first template structure in the first epitaxial growth apparatus, since the lattice constant and thermal expansion coefficient of gallium nitride are smaller than those of sapphire, tensile stress is introduced, causing the subsequently grown epitaxial layer to bend in a concave direction. During the MOCVD cooling and sampling stages, the cooling process causes the completed first template structure to bend in a convex direction.

[0055] In step S210, the first template structure is transferred to the second epitaxial growth apparatus to form a second template structure with impurity 301, as shown below. Figure 4 As shown.

[0056] As mentioned above, the template structure with impurity 301 after transfer is described as the second template structure. It can be understood that the second template structure has the same main structure as the first template structure, both of which include a substrate 201 and a first nitride layer 202 above the substrate.

[0057] In step S220, a second nitride layer continues to grow on the second template structure in the second epitaxial growth apparatus. Through stress accumulation, the second template structure undergoes self-separation within the first nitride layer to separate the nitride structure portion containing impurities, thereby obtaining a new interface.

[0058] Specifically, in a second epitaxial growth apparatus (such as an HVPE apparatus), a second nitride layer 203 is further grown on the first nitride 202, such as... Figure 6As shown in the figure, during the growth process, a specific stress field is formed inside the second template structure by utilizing the difference in physical properties between the substrate and the nitride material. Based on the lattice mismatch and the difference in thermal expansion coefficients between the substrate and the nitride (the lattice constants and thermal expansion coefficients of sapphire and several nitride materials are shown in Table 1), tensile stress is generated within the second template structure. For example, during the growth of a second gallium nitride layer on a second template structure containing impurities obtained after the first gallium nitride layer has been grown on sapphire and transferred, the thermal expansion coefficient of the sapphire substrate is greater than that of the nitride material layer (the combination of the first and second nitride layers), causing the nitride material layer to be subjected to tensile stress, resulting in the overall sample bending in a concave direction. During the growth stage, this tensile stress continuously accumulates inside the second template structure as the second nitride layer continues to grow. When the growth thickness of the second nitride layer causes the accumulated tensile stress to exceed the elastic distortion threshold of the nitride material, the second template structure will fracture under stress, thus generating a self-separation interface.

[0059] It should be noted that the elastic distortion threshold here refers to the maximum stress that the material can withstand within its elastic deformation range. Exceeding this threshold, the material will undergo plastic deformation or fracture. This invention cleverly utilizes this physical mechanism to ensure that the separation interface is precisely located inside the first nitride layer, rather than at the interface between the substrate and the nitride material layer.

[0060] Table 1. Lattice constants and coefficients of thermal expansion of sapphire and nitride materials For example, in an MOCVD (Multi-Layer Ceramic Deposition) device, GaN is grown on a sapphire substrate to form a first template structure. During GaN growth, initially, the lattice constant and coefficient of thermal expansion of gallium nitride are smaller than those of sapphire, introducing tensile stress that causes the subsequently grown epitaxial layer to bend in a concave direction. After cooling, the opposite occurs, and the grown sample exhibits a convex bending direction. In an HVPE (High-Voltage Variation) device, after the HVPE device has stabilized at the growth temperature, for example, 1000°C, GaN layers of 300-500 micrometers are grown on the first template structure. At this point, the sample is again subjected to tensile stress and begins to bend in a concave direction. During the growth of gallium nitride in the HVPE device, the concave tensile stress continuously accumulates.

[0061] It should be noted that the process conditions for growing the second nitride layer using HVPE are known in the art and are not limited here. For example, the growth temperature for gallium nitride growth using HVPE is typically 1020℃~1120℃, the pressure in the growth chamber is typically 76 Torr~760 Torr, and hydrogen or a mixture of hydrogen and nitrogen is typically used as the carrier gas.

[0062] Typically, the distance between the self-separation interface inside the first nitride layer 202 and the substrate 201 is between 50 μm and 100 μm. This ensures that the new interface after separation has sufficient thickness to support subsequent growth, and also ensures that the upper structure above the separation interface can be completely peeled off.

[0063] Reference Figure 7 As shown in (a) and (b), the upper structure corresponding to the separation of the self-separating interface is the nitride structure portion, comprising: a nitride template layer with impurities (i.e., the first portion 202a of the first nitride layer) and an upper second nitride layer 203; the lower structure corresponding to the separation of the self-separating interface includes a new interface with distributed pits 302, formed by... Figure 7 As can be seen in (a) and (b), the second template structure breaks and separates from the first nitride layer. The upper structure contains the first part 202a of the first nitride layer, and the lower structure contains the second part 202b of the first nitride layer. The new interface with the pits 302 is the surface of the second part 202b.

[0064] Since the separation occurs within the first nitride layer 202, the new interface is naturally composed of homogeneous material from the pure first nitride layer. The separation process removes impurity particles attached to the original surface, thus exposing a clean crystal surface. Simultaneously, the accompanying micro-fractures during separation create unevenly distributed pits on the new interface, also composed of homogeneous material from the first nitride layer. This means the new interface is not a perfectly flat mirror surface but possesses a specific microstructure. Preferably, the pits on the new interface are unevenly distributed, with at least one of their area, depth, or spacing being uneven. For example, the pit size can be between 50 μm and 300 μm, the depth between 1 μm and 5 μm, and the spacing between the pits between 500 μm and 2000 μm. This unevenly distributed pit structure provides abundant nucleation sites for subsequent crystal growth. Compared to a flat surface, the nucleation energy at these pits is lower, which is beneficial for inducing subsequent growth into a three-dimensional (3D) growth mode, thereby effectively reducing dislocation density and growth stress. The surface roughness of the new interface after interface treatment is usually between 2nm and 5nm, which is slightly higher than that of the initial first template structure. However, this moderate roughness is the key to improving the subsequent growth quality.

[0065] In step S230, the separated nitride structure is removed to expose a new interface for subsequent growth.

[0066] As a typical implementation method, the separated nitride structure can be removed by centrifugal force. Specifically, this involves driving the second template structure to rotate at high speed, using centrifugal force to throw the nitride structure off the new interface. It should be noted that this process is completed in situ inside the second epitaxial growth apparatus. In practice, the rotational speed of the sample tray carrying the second template structure can be rapidly increased to 10 to 50 times the preset growth speed. For example, if the preset growth speed is 100 rpm, it can be increased to 1000 to 5000 rpm. Under the immense centrifugal force, the nitride structure is thrown off the new interface and falls into the collection area at the bottom of the reaction chamber.

[0067] It is particularly important to emphasize that the aforementioned self-separation and removal processes are all completed while the second epitaxial growth equipment is running and the temperature is within the preset growth temperature range of the target nitride. This means that the entire process does not require opening the equipment (second epitaxial growth equipment) chamber, sample removal, cooling, cleaning, or reheating. This feature has a significant defensive advantage: it completely eliminates secondary impurity contamination (such as dust adhesion, thermal vibration splashing particles, etc.) introduced by opening the lid for sample change or drastic temperature fluctuations. With the nitride structure already separated, simply restoring the second template structure to the preset growth speed allows for continued growth of the target nitride based on the new interface in the second epitaxial growth equipment, resulting in a nitride single crystal layer without voids or defects. This integrated growth-self-separation-removal-continued growth process greatly simplifies the production flow, improves production efficiency, and significantly enhances crystal growth quality.

[0068] As an alternative implementation, after separation, the nitride structure can be removed from the top of the new interface using mechanical clamping. For example, a robotic arm installed inside the HVPE equipment can grasp the upper structure and move it to one side of the chamber during or after separation. This method also achieves the removal of the nitride structure in a closed environment and is suitable for scenarios where the nitride structure is large, centrifugal force is difficult to effectively remove, or where it is necessary to completely retain and recycle the removed nitride structure. It should be understood that whether it is centrifugal force removal or mechanical clamping removal, the core is in-situ removal, that is, completing the physical separation of impurities while the equipment is running and without damaging the growth environment. It should be noted that in both of the above removal methods, the removed nitride structure can be recycled. The second removal method, compared to the first, can more completely retain the removed nitride structure.

[0069] In step S130, the target nitride is grown in the second epitaxial growth apparatus based on the new interface to obtain a nitride single crystal layer without void defects.

[0070] Specifically, in the second epitaxial growth apparatus, the target nitride is grown on the second portion 202b of the remaining first nitride layer based on the new interface to obtain a void-free nitride single crystal layer 204, as shown below. Figure 8 As shown.

[0071] Specifically, since the impurity-containing upper structure has been removed in the previous step, exposing a pure new interface with nucleation advantages, the crystal will begin epitaxial growth from this new interface when the target nitride continues to grow in the second epitaxial growth apparatus. At this point, the growth environment is relatively stable, and there is no impurity interference at the interface. The grown nitride single crystal layer will not contain impurity particles, thus avoiding the formation of void defects. The resulting nitride single crystal layer exhibits low dislocation density, uniform stress distribution, and a smooth surface, significantly improving the electrical and optical properties of the material.

[0072] It should be noted that, for example, the target nitride can be gallium nitride or aluminum nitride, etc. The specific process conditions for growing nitrides using HVPE are known in the art, and the growth thickness of the target nitride can be determined according to specific needs and is not limited here. The following is only a simple example, taking gallium nitride as the target nitride. When growing gallium nitride using the HVPE process, the carrier gas is usually nitrogen or a mixture of hydrogen and nitrogen. When a mixture of hydrogen and nitrogen is used as the carrier gas, the volume ratio of nitrogen in the mixture is usually above 40%, the growth temperature is usually between 1020℃ and 1100℃, the growth pressure is usually 760 Torr (atmospheric pressure) or 76 Torr to 760 Torr, the V / III ratio is usually 50 to 150, the flow rate of NH3 is 2000 sccm to 5000 sccm, and the flow rate of HCl is 30 μmol / min to 60 μmol / min.

[0073] The surface morphology of a nitride single crystal layer obtained by growth in an embodiment of the present invention is as follows: Figure 11 As shown, its optical microscope image is as follows Figure 12 As shown, its surface is smooth and free of pores or defects.

[0074] Second technical route.

[0075] Please see Figure 9 As shown, the method for reducing defects in nitride single crystals provided by the second technical route specifically includes the following steps: S110, S310, S320 and S130. Steps S110 and S130 are consistent with the first technical route. The difference between the second technical route and the first technical route is that step S120 in the second technical route specifically includes the following refined steps for interface treatment based on in-situ etching process: S310~S320.

[0076] In step S110, a first nitride layer is grown on the substrate using the first epitaxial growth equipment to obtain a first template structure. The structure and formation process of the first template structure have been described above and will not be repeated here.

[0077] In step S310, the first template structure is transferred to the second epitaxial growth device to form a second template structure with impurities.

[0078] The structural relationship between the first and second template structures, as well as the causes of impurities, have been described above and will not be repeated here.

[0079] In step S320, an etching process is used in the second epitaxial growth apparatus to etch the surface of the second template structure to remove surface impurities and obtain a new interface.

[0080] Specifically, after transferring the first template structure to the second epitaxial growth equipment (such as an HVPE equipment), the growth of the target nitride does not begin directly. Instead, an etching process is performed first. In the second epitaxial growth equipment, the surface of the second template structure is etched to remove surface impurities and obtain a new interface. This process utilizes the selective removal principle of chemical reactions, enabling precise control of the removal depth and complete stripping away the surface layer with attached impurities.

[0081] The etching process in this invention relies on a specific gas combination and process parameter control. Specifically, a mixed gas containing HCl, H2, and NH3 is used to etch the surface of the second template structure. These three gases work synergistically within the reaction chamber to achieve a highly efficient and controllable etching effect. HCl (hydrogen chloride) acts as the primary etchant, reacting with nitride materials (such as GaN) to generate gaseous byproducts (such as GaCl3), thereby removing the material. H2 (hydrogen) serves as the carrier gas, primarily transporting the reactant gases, regulating the etching rate, and improving etching uniformity. The introduction of NH3 (ammonia) is particularly important. Since etching typically occurs at high temperatures, without nitrogen source protection, nitride materials are prone to thermal decomposition, leading to surface roughening and even crystal structure collapse. The presence of NH3 provides a sufficient nitrogen source, maintaining surface chemical balance and preventing excessive decomposition of nitrides, thus making the etching process smoother and more controllable.

[0082] To further optimize the etching effect, avoid excessive reaction leading to surface morphology deterioration, and improve the nucleation effect of the new interface, such as... Figure 10 As shown, the present invention has strictly designed the sequence of etching gas introduction, specifically including: First, H2 and NH3 are introduced into the second epitaxial growth device to establish a stable H2 and NH3 gas flow (corresponding to...). Figure 10The annealing process (in the process described above) is followed by the introduction of HCl. NH3 provides nitrogen source protection, preventing severe thermal decomposition of GaN at high temperatures due to nitrogen deficiency, thus maintaining the chemical reaction balance on the surface. This makes etching smoother and more controllable. This sequential control of protection before etching ensures that the sample is in a nitrogen-protected atmosphere before the etchant contacts the sample surface, effectively avoiding localized thermal decomposition in the initial stage, and also effectively alleviating the thermal stress on the grown sample. Figure 10 The process parameter control timing diagram shown clearly illustrates the relationship between gas flow rate and time. Regarding specific process parameter windows, this technical route has determined the optimal parameter range through extensive experimental verification. Specifically, the HCl inlet flow rate is 20 sccm to 50 sccm. If the HCl flow rate is too low (e.g., below 20 sccm), the etching rate will be too slow, requiring too much time to remove impurities, affecting production efficiency and potentially causing uneven etching. If the HCl flow rate is too high (e.g., above 50 sccm), the etching reaction will be too vigorous, easily leading to the formation of deep pits or steps on the surface, damaging the interface smoothness. The preferred H2 inlet flow rate is 2000 sccm to 5000 sccm, and the preferred NH3 inlet flow rate is 50 sccm to 200 sccm. This flow rate ratio ensures the stability of the main gas flow field and the sufficiency of the nitrogen source supply.

[0083] Specifically, temperature control is another key factor, with the preferred etching temperature being 850℃~950℃. If the etching temperature is below 850℃, the chemical reaction kinetics will be insufficient, resulting in a slow etching rate for nitrides such as GaN, making it difficult to effectively remove impurities. If the temperature is above 950℃, although the etching rate will be faster, it is very easy to trigger the intrinsic thermal decomposition of nitrides and may change the chemical state of impurities, making them even more difficult to remove.

[0084] Specifically, the etching time is controlled between 1 and 5 minutes. This time range is sufficient to remove the impurity layer attached to the surface (usually at a depth of micrometers) while avoiding excessive etching that would lead to excessive loss of substrate material.

[0085] Specifically, after etching is completed, the HCl supply is stopped, so that the etched second template structure is kept in a mixed atmosphere of H2 and NH3, thereby stabilizing the surface state. H2 and NH3 are participating gases in the growth of the target nitride, and the existing atmosphere can be smoothly switched to the growth atmosphere of the target nitride.

[0086] In step S130, the target nitride continues to grow based on the new interface in the second epitaxial growth apparatus to obtain a nitride single crystal layer without voids or defects. The growth process of the target nitride can be found above and will not be repeated here.

[0087] Specifically, after etching, the atmosphere is switched to the growth atmosphere of the target nitride, and the target nitride is grown at the new interface. Because the etching process removes surface-attached dust, particles, and parasitic reaction products, it exposes pure nitride material. Simultaneously, the etching process does not completely and uniformly thin the surface; there are microscopic differences in the etching rate between impurity attachment points and the pure surface. Therefore, after impurity removal, the new interface naturally forms a micromorphology with distributed pits. These pits are also composed of the same homogeneous material as the first nitride layer and are unevenly distributed, providing abundant nucleation sites for subsequent target nitride growth, which is beneficial for inducing a three-dimensional growth mode and reducing dislocation density.

[0088] The in-situ etching solution provided by this technical route has the core advantage of precise controllability of the process window. By adjusting the gas flow rate, temperature, and time, it can flexibly adapt to template structures with different levels of contamination, achieving precise control of impurities. Compared with the self-separation scheme used in the first technical route, the etching solution has lower requirements for equipment hardware (no need for high-speed rotating mechanisms or robotic arms) and is not limited by stress accumulation conditions, making it suitable for a wider range of material systems and growth process combinations. The entire process is also completed within a closed second epitaxial growth device, eliminating the need to open the cover and remove the wafer, effectively preventing the risk of secondary contamination, and ultimately obtaining a high-quality, void-free nitride single crystal layer.

[0089] Regardless of the interface treatment method used, the nitride single-crystal structures obtained by the two technical routes of this invention share the common characteristic of being free of void defects at the interface. Traditional nitride structures are prone to encapsulating particulate impurities at the interlayer interfaces, forming voids or dislocation clusters, which seriously affect device performance. During the transfer of the first template structure from the first epitaxial growth equipment to the second epitaxial growth equipment and / or during the heating process of the second epitaxial growth equipment, particulate impurities are introduced onto the upper surface of the first template structure, forming a second template structure with impurities. By performing interface treatment on the second template structure in the second epitaxial growth equipment to remove impurities in situ, a new interface with homogeneous pits is obtained. This not only removes particulate impurities introduced by the transfer and heating processes, thus removing heterogeneous materials and avoiding subsequent growth defects caused by particulates, but also provides better nucleation sites based on the distributed pits. These pits are composed of homogeneous materials, have low nucleation energies, and are easy to induce 3D growth modes, effectively reducing the dislocation density and stress of the target nitride, eliminating void defects, and improving single-crystal quality. Since both the impurity removal process and the growth process of the target nitride occur within the second epitaxial growth equipment, and the reaction chamber environment is stable and does not require sample replacement, secondary contamination is avoided. Ultimately, a high-quality nitride single crystal layer with a smooth surface and no void defects is obtained, which significantly improves the yield and performance of the device.

[0090] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for reducing defects in nitride single crystals, characterized in that, include: A first nitride layer is grown on a substrate using a first epitaxial growth device to obtain a first template structure; The first template structure is transferred to the second epitaxial growth device, where the second template structure with impurities formed after the transfer is subjected to interface treatment to remove the impurities and obtain a new interface with distributed pits; the pits are composed of homogeneous material of the first nitride layer; wherein the first epitaxial growth device and the second epitaxial growth device are different devices; The target nitride is grown in the second epitaxial growth apparatus based on the new interface to obtain a nitride single crystal layer without voids.

2. The method according to claim 1, characterized in that, In the second epitaxial growth apparatus, the second template structure containing impurities formed after transfer undergoes interface treatment to remove the impurities, resulting in a new interface with distributed pits, including: In the second epitaxial growth apparatus, a second nitride layer is continued to grow on the second template structure. Through stress accumulation, the second template structure undergoes self-separation within the first nitride layer to separate the nitride structure portion containing impurities, thereby obtaining the new interface. Alternatively, an etching process can be used in the second epitaxial growth apparatus to etch the surface of the second template structure to remove surface impurities and obtain the new interface.

3. The method according to claim 2, characterized in that, The second template structure undergoes self-separation within the first nitride layer through stress accumulation, including: Tensile stress is generated within the second template structure due to the lattice mismatch and the difference in thermal expansion coefficients between the substrate and the nitride. This tensile stress accumulates continuously during the growth of the second nitride layer. When the growth thickness of the second nitride layer causes the accumulated tensile stress to exceed the elastic distortion threshold of the nitride, a self-separation interface is generated. The upper structure corresponding to the self-separation interface is the nitride structure portion, which includes: a nitride template layer with impurities and the upper second nitride layer. The lower structure corresponding to the self-separation interface includes a new interface with distributed pits. And / or, the thickness of the first nitride layer is 100 μm to 300 μm, and the thickness of the second nitride layer is 300 μm to 500 μm; And / or, the distance between the self-separating interface inside the first nitride layer and the substrate is 50 μm to 100 μm.

4. The method according to claim 2, characterized in that, After the second template structure separates itself, the second template structure is driven to rotate at high speed, and the nitride structure is thrown off from above the new interface by centrifugal force to expose the new interface. Alternatively, the nitride structure portion can be removed from above the new interface by mechanical clamping to expose the new interface; wherein, during and after the nitride structure portion is removed or flung away, it remains in the second epitaxial growth device and the second epitaxial growth device is always in operation and the temperature is within the preset growth temperature range of the target nitride. Preferably, the centrifugal force is used to detach the nitride structure portion from the new interface, which includes: increasing the rotational speed of the sample tray carrying the second template structure in the second epitaxial growth equipment to 10 to 50 times the preset growth rotational speed; after the nitride structure portion has been detached, restoring the second template structure to the preset growth rotational speed, and continuing to grow the target nitride based on the new interface within the preset growth temperature range in the second epitaxial growth equipment to obtain a nitride single crystal layer without voids or defects.

5. The method according to claim 2, characterized in that, The etching process includes: etching the surface of the second template structure using a mixed gas containing HCl, H2 and NH3; After etching is completed, the atmosphere is switched to the growth atmosphere of the target nitride, and the target nitride is grown at the new interface. Preferably, the etching process specifically includes: first introducing H2 and NH3 into the second epitaxial growth equipment to establish a stable H2 and NH3 gas flow, and then introducing HCl; Preferably, the flow rate of HCl is 20 sccm to 50 sccm, the flow rate of H2 is 2000 sccm to 5000 sccm, and the flow rate of NH3 is 50 sccm to 200 sccm. Preferably, the etching temperature is 850℃~950℃ and the etching time is 1min~5min; Preferably, after etching, the HCl supply is stopped, so that the etched second template structure is kept in a mixed atmosphere of H2 and NH3; then the growth atmosphere and growth temperature of the target nitride are switched, wherein the growth atmosphere of the target nitride includes H2, NH3, N2 and GaCl3, and the growth temperature of the target nitride is 1000℃~1200℃.

6. The method according to any one of claims 1-5, characterized in that, The first growth process corresponding to the first epitaxial growth equipment is different from the second growth process corresponding to the second epitaxial growth equipment. The growth efficiency of the second growth process is higher than that of the first growth process, and the single crystal growth quality of the first growth process is higher than that of the second growth process. Preferably, the first epitaxial growth equipment is an MOCVD equipment and the second epitaxial growth equipment is an HVPE equipment.

7. The method according to claim 6, characterized in that, It also includes at least one of the following: The substrate includes one of the following materials: sapphire, silicon, and silicon carbide; The first nitride layer is made of the same material as the target nitride, including one of the following materials: gallium nitride or aluminum nitride; The first nitride layer is made of a different material than the target nitride. The first nitride layer is gallium nitride or aluminum nitride, and the target nitride layer is aluminum nitride or gallium nitride.

8. The method according to any one of claims 1-5, characterized in that: The impurities in the second template structure include one or more of the following: dust particles introduced during the transfer and conveying of the first template structure to the second epitaxial growth equipment, splashed particles caused by mechanical vibration, reactor parasitic particles introduced during the heating process after the transfer to the second epitaxial growth equipment, chloride source salt particles from the backflow of the reaction chamber, and splashed particles from thermal vibration. Preferably, the pits on the new interface are unevenly distributed; Preferably, the distribution of at least one of the area, depth, and spacing of the pits in the new interface is uneven; Preferably, the size of the pit is 50μm to 300μm, the depth of the pit is 1μm to 5μm, and the spacing between the pits is 500μm to 2000μm; Preferably, the surface of the first template structure is a flat extended surface, and the surface of the second template structure is uneven. Preferably, the surface roughness of the first template structure is 0.2nm~0.5nm, the surface roughness of the second template structure is 0.5nm~2nm, and the surface roughness of the new interface is 2nm~5nm.

9. A nitride single crystal structure, characterized in that, include: Substrate; A template nitride layer located on the substrate; A nitride single crystal layer is located above the template nitride layer, wherein the nitride single crystal layer and the template nitride layer are homogeneous or heterogeneous materials; The nitride single crystal structure is obtained by the method for reducing defects in nitride single crystals as described in any one of claims 1-8.

10. A semiconductor device, characterized in that, The substrate of the semiconductor device is the nitride single crystal structure as described in claim 9; or, The substrate of the semiconductor device is formed from a nitride single-crystal layer peeled off from the nitride single-crystal structure of claim 9; or, The epitaxial layer of the semiconductor device is formed in situ grown on the nitride single crystal structure described in claim 9; or... The epitaxial layer of the semiconductor device is formed epitaxially on the stripped nitride single crystal layer; Preferably, the semiconductor device includes optoelectronic devices or electronic devices.

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