Semiconductor structure and manufacturing method thereof

Abstract

The present application provides a semiconductor structure and a method for manufacturing the same, relating to the field of semiconductor technology. First, an aluminum nitride buffer layer is prepared based on a substrate, and then the substrate and the aluminum nitride buffer layer are annealed to form an aluminum nitride film on one side of the substrate, wherein the aluminum nitride film includes a plurality of first base islands, and two adjacent first base islands are spaced apart and partially expose the substrate, and then a second base island is grown based on the first base island using preset growth conditions, and finally an epitaxial layer is formed. The semiconductor structure and the method for manufacturing the same provided by the present application have the effect of improving the quality of epitaxial crystals and suppressing leakage of the GaN interface near the substrate.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a semiconductor structure and a method for manufacturing the same. Background Art

[0002] Compared with traditional silicon materials, GaN materials have the characteristics of high bandgap width, high electron saturation drift velocity, high breakdown electric field strength and high operating temperature, and have great advantages in the application of power electronic devices and radio frequency devices.

[0003] However, the dislocation density of GaN epitaxially grown on sapphire substrates is still high, and the quality of the epitaxial GaN crystals is poor, which limits the application of GaN electronic devices. In addition, oxygen impurities in the sapphire substrate may diffuse into the GaN epitaxial layer, causing interface leakage problems. In summary, the existing technology suffers from the problems of poor quality of epitaxial GaN crystals and interface leakage. Summary of the Invention

[0004] The purpose of the present application is to provide a semiconductor structure and a method for manufacturing the same, so as to solve the problems of poor quality of epitaxial GaN crystals and interface leakage in the prior art.

[0005] In order to achieve the above objectives, the technical solutions adopted in the embodiments of the present application are as follows:

[0006] In one aspect, an embodiment of the present application provides a method for fabricating a semiconductor structure, the method comprising:

[0007] preparing an aluminum nitride buffer layer based on a substrate;

[0008] Annealing the substrate and the aluminum nitride buffer layer to form an aluminum nitride film on one side of the substrate, wherein the aluminum nitride film includes a plurality of first base islands, and two adjacent first base islands are spaced apart and partially expose the substrate;

[0009] A second base island is grown based on the first base island using preset growth conditions, and an epitaxial layer is finally formed.

[0010] Optionally, the step of growing a second base island based on the first base island using preset growth conditions and finally forming an epitaxial layer includes:

[0011] Using preset three-dimensional growth conditions to form a partial epitaxial layer along one side of the substrate and the aluminum nitride buffer layer;

[0012] The remaining epitaxial layer is formed along one side of the substrate and the aluminum nitride buffer layer using preset two-dimensional growth conditions.

[0013] Optionally, the step of forming a partial epitaxial layer along one side of the substrate and the aluminum nitride buffer layer using preset three-dimensional growth conditions includes:

[0014] Under the conditions of ammonia gas, a reaction chamber pressure of 400-800 mbar, a temperature of 900° C.-980° C., and a Group V / III element ratio of 200-2000, forming an epitaxial layer along one side of the substrate and the aluminum nitride buffer layer;

[0015] The three-dimensional growth conditions are changed, and the epitaxial layer is continuously grown under the conditions of ammonia gas, a reaction chamber pressure of 300-500 mbar, a temperature of 950° C.-1020° C., and a Group V / III element ratio of 1000-3000.

[0016] Optionally, the step of forming the remaining epitaxial layer along one side of the substrate and the aluminum nitride buffer layer using preset two-dimensional growth conditions includes:

[0017] The remaining epitaxial layer is formed under the conditions of ammonia gas, a reaction chamber pressure of 300-50 mbar, a temperature of 1000-1070° C., and a V / III group element ratio of 1000-4000.

[0018] Optionally, the step of annealing the substrate and the aluminum nitride buffer layer to form an aluminum nitride thin film on one side of the substrate includes:

[0019] The substrate and the aluminum nitride buffer layer are annealed to form an aluminum nitride thin film with a thickness of 8 to 17 nm on one side of the substrate.

[0020] Optionally, the step of annealing the substrate and the aluminum nitride buffer layer to form an aluminum nitride thin film on one side of the substrate includes:

[0021] The substrate and the aluminum nitride buffer layer are annealed to form an aluminum nitride film with a thickness of 10 to 14 nm on one side of the substrate.

[0022] Optionally, the step of annealing the substrate and the aluminum nitride buffer layer to form an aluminum nitride thin film on one side of the substrate includes:

[0023] The aluminum nitride film is formed on one side of the substrate by annealing at a temperature of 800-1100° C., a reaction chamber pressure of 50-1000 mbar, and an ammonia gas protection condition for an annealing time of 0-1000 seconds.

[0024] Optionally, the step of preparing an aluminum nitride buffer layer on a substrate includes:

[0025] An AlN buffer layer or an AlGaN buffer layer is prepared based on a substrate.

[0026] Optionally, the step of preparing an aluminum nitride buffer layer on a substrate includes:

[0027] An AlGaN buffer layer is prepared based on a substrate, wherein the Ga composition in the buffer layer is (10% to 50%).

[0028] On the other hand, an embodiment of the present application further provides a semiconductor structure, comprising:

[0029] substrate;

[0030] an aluminum nitride film connected to the substrate, wherein the aluminum nitride film comprises a plurality of first base islands, with two adjacent first base islands spaced apart and partially exposing the substrate;

[0031] An epitaxial layer connected to the substrate and the aluminum nitride film, wherein the epitaxial layer includes a three-dimensional island structure corresponding to the first base island.

[0032] Compared with the prior art, this application has the following beneficial effects:

[0033] The present application provides a semiconductor structure and a method for manufacturing the same. First, an aluminum nitride buffer layer is prepared based on a substrate. Then, the substrate and the aluminum nitride buffer layer are annealed to form an aluminum nitride film on one side of the substrate. The aluminum nitride film includes a plurality of first base islands, and two adjacent first base islands are spaced apart and partially expose the substrate. Then, a second base island is grown based on the first base island using preset growth conditions, and finally an epitaxial layer is formed. Since the substrate is exposed between the first base islands, selective nucleation is promoted in the early stages of GaN growth, so that when the epitaxial layer grows, a second base island with a higher density is formed, which promotes the bending of dislocations in the GaN epitaxial layer. Moreover, since the second base islands are close to each other, they are easy to interact with each other, so the dislocation density can be effectively reduced quickly, thereby achieving the preparation of a GaN epitaxial layer with a smaller dislocation density in a very thin case, greatly improving the crystal quality of the GaN epitaxial layer. In addition, the present application uses an aluminum nitride buffer layer, which has a blocking effect on oxygen impurities in the substrate, suppressing leakage at the GaN interface near the substrate, thereby enabling the production of a semi-insulating epitaxial layer.

[0034] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 A schematic flow chart of a method for fabricating a semiconductor structure according to an embodiment of the present application.

[0037] Figure 2 A cross-sectional view of a sputtered buffer layer on a flat sapphire substrate provided in an embodiment of the present application.

[0038] Figure 3 This is a cross-sectional view of the aluminum nitride buffer layer after annealing provided in an embodiment of the present application.

[0039] Figure 4 This is a cross-sectional view of the substrate, buffer layer, and epitaxial layer provided in an embodiment of the present application under a microscope.

[0040] Figure 5 This is an AFM scan of the surface of the buffer layer after annealing provided in an embodiment of the present application.

[0041] Figure 6 This is a cross-sectional diagram of the oxygen element distribution provided in the embodiment of the present application.

[0042] Figure 7 Schematic diagram of the dislocation and second base island of the epitaxial layer provided in an embodiment of the present application.

[0043] In the picture:

[0044] 110 - substrate; 120 - aluminum nitride buffer layer; 121 - first base island; 130 - epitaxial layer. DETAILED DESCRIPTION

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0046] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.

[0047] The following describes some embodiments of the present application in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features therein may be combined with each other.

[0048] As mentioned in the background, GaN-based electronic devices currently primarily utilize silicon and silicon carbide substrates. This is primarily due to the difficulty in producing high-resistance GaN due to the severe diffusion of O (oxygen) impurities on sapphire substrates. Furthermore, homogeneous GaN substrates are too expensive and large-scale production is not yet commercially viable. While GaN on silicon and silicon carbide substrates have been commercialized, the poor crystal quality of GaN on silicon substrates can lead to severe current collapse and significantly reduce the device's breakdown voltage. While GaN on silicon carbide substrates offers good crystal quality and can be used in higher voltage applications, the high cost of silicon carbide substrates limits the application of GaN electronic devices based on these substrates.

[0049] Although the lattice mismatch between sapphire substrate and GaN is smaller than that between silicon substrate and GaN, the dislocation density of GaN epitaxial growth on traditional sapphire substrate is still close to 10 9 cm -2 Although the use of patterned sapphire (PSS) substrate can effectively reduce its dislocation density, the high price of PSS substrate and the poor flatness of the grown GaN epitaxial surface limit the application of GaN-based electronic devices.

[0050] In view of this, the present application provides a method for manufacturing a semiconductor structure. By forming a first base island on a substrate, a second base island can be grown based on the first base island when growing an epitaxial layer, which effectively promotes the bending of dislocations in the epitaxial layer. The second base islands are close to each other and are prone to interaction, thereby effectively reducing the dislocation density and improving the quality of the epitaxial layer.

[0051] The following is an exemplary description of the semiconductor structure manufacturing method provided in this application:

[0052] As an implementation, see Figure 1 , the semiconductor structure manufacturing method includes:

[0053] S102, preparing an aluminum nitride buffer layer based on a substrate.

[0054] S104 , annealing the substrate and the aluminum nitride buffer layer to form an aluminum nitride film on one side of the substrate, wherein the aluminum nitride film includes a plurality of first base islands, and two adjacent first base islands are spaced apart and partially expose the substrate.

[0055] S106 , growing a second base island based on the first base island using preset growth conditions, and finally forming an epitaxial layer.

[0056] Among them, the substrate described in the present application can be any substrate, and by forming the first base island, the effect of improving the crystal quality of the epitaxial layer can be achieved. For example, the substrate is a sapphire substrate or a silicon carbide substrate, preferably a flat sapphire substrate.

[0057] It should be noted that in traditional processes, in order to ensure the quality of epitaxial growth, silicon substrates or silicon carbide substrates are generally selected instead of sapphire substrates. The reasons are that, on the one hand, the serious diffusion of O (oxygen) impurities on the sapphire substrate makes it difficult to prepare high-resistance GaN; on the other hand, the dislocation density of the epitaxial layer grown on sapphire is relatively large, which leads to poor quality.

[0058] The semiconductor structure fabrication method provided by this application, on the one hand, uses an aluminum nitride buffer layer to block the diffusion of O (oxygen) impurities and suppress leakage at the GaN interface near the substrate. On the other hand, by forming a second base island in the epitaxial layer, the dislocation density can be reduced, thereby improving the crystal quality. On this basis, the semiconductor structure fabrication method enables the fabrication of GaN epitaxial layers with good crystal quality even on sapphire substrates.

[0059] It should be noted that this application does not limit the preparation process of the buffer layer. For example, the process used to prepare the buffer layer can be sputtering, MOCVD (Metal-organic Chemical Vapor Deposition), evaporation, etc. For ease of explanation, this application uses the sputtering process as an example.

[0060] Among them, when sputtering the buffer layer on the substrate, the thickness of the buffer layer is relatively thin, generally 6 to 15 nm. Optionally, after sputtering the buffer layer, the exposure rate of sapphire is less than 10%. Of course, in order to ensure the sputtering quality, the buffer layer after sputtering can completely cover the substrate, which is not limited here.

[0061] like Figure 2 FIG. 1 is a schematic diagram of the structure of a sputtered buffer layer on a flat sapphire substrate. It can be seen that the buffer layer after sputtering will also form a plane. Figure 2 In FIG. 1 , the aluminum nitride buffer layer 120 includes a plurality of boxes, each box representing a crystal column of the aluminum nitride buffer layer 120 .

[0062] Optionally, the aluminum nitride buffer layer 120 provided in the present application can be an AlN buffer layer or an AlGaN buffer layer. The AlN buffer layer and the AlGaN buffer layer have the effect of blocking the diffusion of oxygen impurities. Therefore, the oxygen impurities in sapphire are not easily diffused into the epitaxial layer 130, solving the problem of interface leakage.

[0063] After making the buffer layer, in order to make the first base island structure, the present application adopts annealing. During the annealing process, the buffer layer will decompose and re-deposit, and then decompose at some positions to expose the sapphire substrate at the bottom, thereby forming multiple discontinuous first base islands 121 on the buffer layer. The structure after annealing is as follows: Figure 3 shown.

[0064] Annealing is performed in an MOCVD reaction chamber, and the annealing conditions satisfy 0s ≤ annealing time ≤ 1000s. The annealing temperature can be consistent with the growth temperature or different, and the annealing temperature range is 800°C-1100°C. The reaction chamber pressure range is 50-1000mbar, and ammonia protection is used. In one implementation, the preferred annealing time is 30-300s, and the reaction chamber pressure range is preferably 300-800mbar. In addition, the ammonia protection allows the buffer layer on the sapphire surface to decompose in some areas and then redeposit in other locations, forming a discontinuous undulating surface and exposing a certain area of ​​sapphire.

[0065] For example, when the buffer layer is an AlN buffer layer, during the annealing process, Al atoms will migrate. It is understandable that when the Al atoms in a certain area migrate to other areas, the bottom substrate 110 will be exposed; and when the Al atoms in other areas migrate to a certain area, the first base island 121 will be formed. Figure 2 It can be seen that when all Al atoms in a crystal column migrate to other crystal columns, the crystal column disappears, exposing the substrate 110. When the buffer layer is an AlGaN buffer layer, during the annealing process, Al atoms will migrate and Ga atoms will migrate and desorb, thereby forming multiple first base islands 121.

[0066] It should be noted that in order to make the spacing between the first base islands 121 more obvious and facilitate the subsequent production of the epitaxial layer 130, in this application, when the buffer layer is an AlGaN buffer layer, the Ga component in the buffer layer is (10% to 50%). Under this component, since Ga atoms will desorb, that is, Ga atoms partially detach from the buffer layer, the spacing between the first base islands 121 is more obvious.

[0067] It should also be noted that, since the generation of the first base islands 121 is random during the annealing process, the shape and size of each first base island 121 are inconsistent. For example, some first base islands 121 are larger, some first base islands 121 are smaller, some first base islands 121 have relatively flat tops, and some first base islands 121 have relatively sharp tops. Of course, the shape of the first base islands 121 can also be discontinuous and connected, which is not limited here. Figure 3 As shown, Figure 3The first base islands 121 include a plurality of first base islands 121. From left to right, the top of the first first base island 121 is relatively flat, while the top of the second first base island 121 is relatively sharp. Of course, in actual situations, the topography of the first base islands 121 may be more complex. Figure 4 As shown, Figure 4 FIG shows a cross-sectional view of the buffer layer after annealing under a microscope. Figure 5 FIG. 3 shows an AFM scan of the surface of the buffer layer after annealing. In the figure, the black portion is the exposed substrate 110 .

[0068] Among them, the exposure rate of the sapphire substrate after annealing (calculated by area) ranges from 2% to 50%, for example, the sapphire exposure rate is 20%. If the sapphire substrate exposure rate is too large, GaN will nucleate on the sapphire substrate, thereby greatly increasing the dislocations in the early stage of nucleation. In addition, the reduction of the AlN buffer layer will also lead to an increase in the diffusion of O into GaN, which in turn leads to serious interface leakage; on the contrary, if the sapphire substrate exposure rate is too small, GaN will not be selectively nucleated in the early stage of growth, and will directly grow in two dimensions, resulting in poor crystal quality. It should be noted that the sapphire substrate exposure rate described in this application refers to the ratio of the area of ​​the sapphire substrate not covered by the buffer layer to the total surface area of ​​the sapphire substrate.

[0069] In addition, the highest height of the first base island 121 is substantially the same, and the height of the first base island 121 is greater than the height of the aluminum nitride buffer layer 120. It can be understood that, in combination with Figure 2 It can be seen that when Al atoms migrate, if all Al atoms in the same region migrate to the same crystal column, the height of the crystal column will increase accordingly. Therefore, the maximum height of the first base island 121 after annealing will be higher than the height of the aluminum nitride buffer layer 120 before annealing. Of course, in other embodiments, the height of the first base island 121 may also be less than or equal to the height of the aluminum nitride buffer layer 120, and this is not limited here.

[0070] Optionally, the height of the first base island 121 is 2 nm greater than the height of the aluminum nitride buffer layer 120 . For example, when the height of the aluminum nitride buffer layer 120 is 6-15 nm, the height of the aluminum nitride film formed after annealing is 8-17 nm.

[0071] Preferably, the height of the aluminum nitride buffer layer 120 is 8-12 nm, and the height of the aluminum nitride film formed after annealing is 10-14 nm.

[0072] After research, it was found that the quality of the epitaxial layer 130 is optimal when the height of the aluminum nitride buffer layer 120 is 10 nm and the height of the aluminum nitride film formed after annealing is 12 nm.

[0073] In addition, the use of an aluminum nitride buffer layer 120 such as AlN or AlGaN can achieve a barrier effect on oxygen impurities in the substrate 110. Taking the AlN buffer layer and the GaN epitaxial layer as an example, Figure 6 As shown, since the sapphire substrate 110 is an α-Al2O3 single crystal, and under the high temperature conditions of GaN growth (generally exceeding 1000°C), the O in Al2O3 will diffuse into the GaN material of the epitaxial layer 130 due to the high temperature etching effect or high temperature diffusion. Since the traditional GaN buffer layer and GaN substrate do not block O, and the AlN buffer layer is used, the Al-O bond energy is much greater than the Ga-O bond energy, so the concentration of O in AlN will be very high, and it will block the diffusion of O in AlN into GaN (the bonding of Al-O is much greater than that of Ga-O, which is equivalent to the barrier that O in AlN needs to overcome the difference in Al-O and Ga-O bond energies in order to diffuse into GaN). Therefore, the oxygen concentration in the GaN grown on the AlN buffer layer will be much lower than the O concentration in AlN, and compared with the GaN epitaxial layer 130 on the traditional GaN buffer layer, its O concentration will be several orders of magnitude lower.

[0074] After forming the aluminum nitride thin film having the first base island 121 on the substrate 110 , an epitaxial layer 130 may be formed along one side of the substrate 110 and the aluminum nitride buffer layer 120 using certain growth conditions.

[0075] The epitaxial layer 130 described in the present application may be a GaN epitaxial layer 130 . When growing the epitaxial layer 130 , S106 includes:

[0076] S1061 , forming a partial epitaxial layer along one side of the substrate and the aluminum nitride buffer layer 120 using preset three-dimensional growth conditions;

[0077] S1062 , using preset two-dimensional growth conditions, forming the remaining epitaxial layer along one side of the substrate and the aluminum nitride buffer layer.

[0078] That is, in this application, a portion of the epitaxial layer is first grown using 3D growth conditions, and then the remaining epitaxial layer is grown using 2D growth conditions. As an implementation method, the growth conditions can be switched based on time. For example, after 1000 seconds of growth using 3D growth conditions, the epitaxial layer can be grown using 2D growth conditions.

[0079] Among them, three-dimensional growth is conducive to the turning of dislocations and the interaction of dislocations, while two-dimensional growth is conducive to making the surface grow flat as quickly as possible. It should be noted that although three-dimensional growth is conducive to the turning of dislocations, long-term three-dimensional growth will lead to an uneven GaN surface. Moreover, since dislocations have already had strong interactions in the early stage, the effect of three-dimensional growth in reducing dislocation density in the later stage is not as obvious as before. Therefore, after a certain period of three-dimensional growth, two-dimensional growth is required to make the surface grow flat as quickly as possible. Because GaN-based devices require not only high crystal quality but also steep heterojunction interfaces, a flat surface will greatly help improve other electrical properties of subsequent devices, such as improving carrier mobility and reducing interface scattering.

[0080] It should be noted that in the early stage of growing the epitaxial layer, the present application will grow a second base island based on the first base island in the buffer layer. As the growth continues, the second base islands merge with each other and eventually form an epitaxial layer, which includes a three-dimensional island structure at the bottom.

[0081] Among them, the three-dimensional island structure described in the present application refers to a discontinuous structure in which the portion of the epitaxial layer 130 connected to the aluminum nitride buffer layer 120 corresponds to the first base island structure of the aluminum nitride buffer layer 120, that is, if a certain area in the buffer layer is a groove, then a corresponding position in the epitaxial layer 130 is a protrusion; conversely, if a certain position in the buffer layer is a protrusion, then a corresponding position in the epitaxial layer 130 is a groove.

[0082] See also Figure 7 , Figure 7 The diagram shows the dislocation and second island structure of the epitaxial layer 130. In the diagram, the dotted lines represent the shapes of the second island structures at different growth times. It should be noted that the second island and the three-dimensional island of the epitaxial layer are different structures. The second island represents the structure of the epitaxial layer during its growth, while the three-dimensional island belongs to the structure formed after the epitaxial layer is grown. The three-dimensional growing dislocations (solid lines) are easy to tilt and turn. Due to the high density of the second islands, the adjacent second islands close quickly and the dislocations interact quickly. A large number of tilted dislocations merge or form loops, which greatly reduces the initial dislocations. In other words, in the early stage of growing the epitaxial layer, multiple second islands of the epitaxial layer will be formed on the basis of the first island of some buffer layers, that is, some first islands will not form second islands. As the epitaxial layer grows, the second islands will gradually merge and disappear, and finally form a large second island, which is the epitaxial layer. Moreover, after the epitaxial layer is formed, the lower region of the epitaxial layer, ie, the structure connected to the substrate and the buffer layer, is a non-flat structure, and its shape corresponds to the first base island of the buffer layer. This part of the structure is a three-dimensional island structure.

[0083] For example, Figure 7As shown, on the basis of the first base island of the buffer layer, the epitaxial layer will also form multiple second base islands, such as the second base island A and the second base island B, and the diagram also includes two dislocations a and b, wherein a represents the dislocation of the second base island A on the left, and b represents the dislocation of the second base island B on the right. Dislocation a and dislocation b are both oblique lines in the early stage. On this basis, as the growth time increases, the second base island A and the second base island B will continue to grow, and dislocation a and dislocation b will tilt, turn and merge. As the second base island A and the second base island B continue to grow, dislocation a and dislocation b will eventually disappear. Similarly, other dislocations will also merge, thereby greatly reducing the initial dislocations. Moreover, as the second base island A and the second base island B grow, the second base island A and the second base island B will merge. It can be understood that during the growth of the epitaxial layer, other second base islands will also merge, eventually forming a large second base island C, which represents the entire epitaxial layer.

[0084] As an implementation method, when the epitaxial layer 130 is produced using three-dimensional growth conditions, a single condition can be used to realize the three-dimensional growth process, for example, the epitaxial layer 130 is grown under the conditions of a reaction chamber pressure range of 300-800 mbar, a reaction chamber temperature range of 900°C-1020°C, ammonia gas, and a V / III group element ratio range of 200-3000.

[0085] As another implementation method, the three-dimensional growth conditions include strong three-dimensional growth conditions and weak three-dimensional growth conditions, wherein the strong three-dimensional growth conditions are conducive to dislocation deflection, and the weak three-dimensional growth conditions are conducive to the merging of the second base island of the epitaxial layer.

[0086] On this basis, S1061 includes:

[0087] Under the conditions of ammonia gas, a pressure of 400-800 mbar, a temperature of 900°C-980°C and a V / III group element ratio of 200-2000, an epitaxial layer 130 is formed along one side of the substrate 110 and the aluminum nitride buffer layer 120. The three-dimensional growth conditions are strong three-dimensional growth conditions.

[0088] The three-dimensional growth conditions are changed, and the epitaxial layer 130 is continued to be formed under the conditions of ammonia gas, pressure of 300-500 mbar, temperature of 950℃-1020℃ and group V / III element ratio of 1000-3000. The three-dimensional growth conditions are weak three-dimensional growth conditions.

[0089] It should be noted that the altered 3D growth conditions described herein can include continuous changes in temperature, ammonia flow rate, Group VIII ratio, and chamber pressure. For example, all parameters can be linearly varied until weak 3D growth conditions are achieved. Alternatively, the conditions can be altered first at low temperature, low Group VIII ratio, and high pressure to achieve strong 3D growth, followed by high temperature, high Group VIII ratio, and low pressure to achieve weak 3D growth. This means that the growth conditions can be varied abruptly rather than continuously, and this is not a limitation here.

[0090] Furthermore, S1062 includes:

[0091] The remaining epitaxial layer 130 is formed under the conditions of ammonia gas, a pressure of 300-50 mbar, a temperature of 1000-1070° C., and a Group V / III element ratio of 1000-4000.

[0092] The two-dimensional growth conditions may also be obtained by continuous changes, which is not limited here.

[0093] Based on the above implementation method, the present application also provides a semiconductor structure, which includes a substrate 110, an aluminum nitride compound film and an epitaxial layer 130, wherein the aluminum nitride compound film is connected to the substrate 110, wherein the aluminum nitride compound film includes a plurality of first base islands 121, and two adjacent first base islands 121 are spaced apart and partially expose the substrate 110; the epitaxial layer 130 is connected to the substrate 110 and the aluminum nitride compound film, wherein the epitaxial layer 130 includes a three-dimensional island structure corresponding to the first base island 121.

[0094] It can be understood that the aluminum nitride compound film of the present application can be a film made of AlN or AlGaN material, and the epitaxial layer 130 can be a GaN epitaxial layer 130. The semiconductor structure can be prepared by the above-mentioned semiconductor structure manufacturing method, so the semiconductor structure will not be described in detail.

[0095] In summary, the present application provides a semiconductor structure and a method for manufacturing the same. First, an aluminum nitride buffer layer is prepared based on a substrate, and then the substrate and the aluminum nitride buffer layer are annealed to form an aluminum nitride film on one side of the substrate, wherein the aluminum nitride film includes a plurality of first base islands, and two adjacent first base islands are spaced apart and part of the substrate is exposed. Then, a second base island is grown based on the first base island using preset growth conditions, and finally an epitaxial layer is formed. Since the substrate is exposed between the first base islands, selective nucleation in the early stage of GaN growth is promoted, so that when the epitaxial layer grows, a second base island with a higher density is formed, which promotes the bending of dislocations in the GaN epitaxial layer; and since the second base islands are close to each other, they are easy to interact with each other, so the dislocation density can be effectively reduced quickly, thereby realizing the preparation of a GaN epitaxial layer with a smaller dislocation density in a very thin case, greatly improving the crystal quality of the GaN epitaxial layer. In addition, the present application uses an aluminum nitride buffer layer, which has a blocking effect on oxygen impurities in the substrate, suppresses leakage of the GaN interface near the substrate, and thus can realize the production of a semi-insulating epitaxial layer.

[0096] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

[0097] It will be apparent to those skilled in the art that the present application is not limited to the details of the exemplary embodiments described above and that the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the present application is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A method for manufacturing a semiconductor structure, characterized in that: The method comprises: An aluminum nitride buffer layer is prepared based on a substrate; wherein the aluminum nitride buffer layer is an AlN buffer layer formed by a sputtering process; Annealing for 0 to 1000 seconds at an annealing temperature of 800° C. to 1100° C., a reaction chamber pressure of 50 to 1000 mbar, and ammonia protection is applied to form an aluminum nitride compound film with a thickness of 8 to 17 nm on one side of the substrate, wherein the aluminum nitride compound film includes a plurality of first base islands, and adjacent two first base islands are spaced apart and partially expose the substrate; Under the conditions of ammonia gas, a reaction chamber pressure of 400-800 mbar, a temperature of 900° C.-980° C., and a Group V / III element ratio of 200-2000, forming an epitaxial layer along one side of the substrate and the aluminum nitride buffer layer; Changing the three-dimensional growth conditions and continuing to grow the epitaxial layer under the conditions of ammonia gas flow, a reaction chamber pressure of 300-500 mbar, a temperature of 950° C.-1020° C., and a Group V / III element ratio of 1000-3000; The remaining epitaxial layer is formed along one side of the substrate and the aluminum nitride buffer layer using preset two-dimensional growth conditions.

2. The method for manufacturing a semiconductor structure according to claim 1, wherein: The step of forming the remaining epitaxial layer along one side of the substrate and the aluminum nitride buffer layer using a preset two-dimensional growth condition comprises: The remaining epitaxial layer is formed under the conditions of ammonia gas, a reaction chamber pressure of 300-50 mbar, a temperature of 1000-1070° C., and a V / III group element ratio of 1000-4000.

3. The method for manufacturing a semiconductor structure according to claim 1, wherein: An aluminum nitride film with a thickness of 10 to 14 nm is formed on one side of the substrate.

4. A semiconductor structure, characterized in that The semiconductor structure is manufactured by the method according to any one of claims 1 to 3, and the structure comprises: substrate; an aluminum nitride film connected to the substrate, wherein the aluminum nitride film comprises a plurality of first base islands, with two adjacent first base islands spaced apart and partially exposing the substrate; An epitaxial layer connected to the substrate and the aluminum nitride film, wherein the epitaxial layer includes a three-dimensional island structure corresponding to the first base island.

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