Method for lateral epitaxial growth of gallium nitride layer and gallium nitride structure

Abstract

The invention discloses a method for lateral epitaxial growth of a gallium nitride layer and a gallium nitride structure, and the method comprises the following steps: providing a substrate structure which comprises a substrate and a graphene layer which are stacked; etching the graphene layer to form a first window and a first graphene mask structure which are arranged at an interval; the bottom of the first window is in contact with the upper surface of the substrate, and an oxide mask structure is arranged at the bottom; etching the first graphene mask structure to form a second window to obtain a second graphene mask structure; the bottom of the second window is in contact with the upper surface of the substrate, and the second window is located around the second graphene mask structure; and growing a gallium nitride layer on the substrate at the boundary of the second graphene mask structure in a nucleation manner. According to the invention, GaN is subjected to nucleation growth in the nano-scale second window, dislocation of the substrate is blocked by the oxide mask structure and the second graphene mask structure, and a large amount of dislocation is prevented from extending to the gallium nitride layer, so that the dislocation density is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for lateral epitaxial growth of a gallium nitride layer and a gallium nitride structure. Background Art

[0002] Currently, GaN and its compounds have been widely studied for optoelectronic applications, such as light-emitting diodes (LEDs), laser diodes, and high-frequency electronics. However, because GaN is mainly obtained by heteroepitaxial growth, the heterogeneous substrate makes it impossible to further reduce the dislocation density of GaN, which limits the crystal quality of GaN. These dislocations will affect the performance of the final device. In order to overcome these challenges, researchers have tried various technical improvements and material innovations.

[0003] Lateral epitaxy technology is used as an effective solution. Generally, a dielectric film (such as SiO2) is used as a mask and prepared through photolithography and other related processes. The film first grows into a nucleation layer from the window area and does not grow in the mask area. Then, by controlling the growth conditions, lateral epitaxial growth is achieved, the nucleation layer merges, and the mask area is covered to form a film. In the process of lateral epitaxial growth of nitride, the dislocations of the substrate will be blocked by the mask and cannot extend to the gallium nitride epitaxial layer. In the process of lateral merging of the nucleation layer, the dislocations with opposite Burgers vectors will merge with each other and terminate. Therefore, lateral epitaxial growth of nitride can significantly reduce the dislocation density.

[0004] As an emerging two-dimensional material, graphene has attracted attention due to its excellent conductivity, chemical stability and unique influence on the epitaxial growth process. The application of graphene mask technology in the semiconductor field has shown its potential in improving material quality and controlling growth morphology. And because GaN has a strong lateral growth ability, using graphene as a mask for lateral epitaxial growth of GaN has become a method that can effectively reduce the dislocation density of GaN; however, the current scheme still has the problem of high dislocation density, and the quality of the grown GaN is not high. Summary of the invention

[0005] The present invention provides a method for lateral epitaxial growth of a gallium nitride layer and a gallium nitride structure, which can enable gallium nitride to nucleate and grow in a nanometer-scale second window, avoid a large number of dislocations extending to the gallium nitride layer, and reduce the dislocation density to the greatest extent.

[0006] In order to solve the above technical problem, the first aspect of the present invention provides a method for lateral epitaxial growth of a gallium nitride layer, comprising the following steps:

[0007] Providing a substrate structure, the substrate structure comprising a stacked substrate and a graphene layer;

[0008] Etching the graphene layer to form a first graphene mask structure disposed between the first windows disposed at intervals; wherein the bottom of the first window contacts the upper surface of the substrate, and an oxide mask structure is disposed at the bottom of the first window;

[0009] Etching the first graphene mask structure to form a plurality of second windows spaced apart from each other, thereby obtaining a second graphene mask structure; wherein the bottom of the second window contacts the upper surface of the substrate, and the second window is located around the second graphene mask structure;

[0010] A gallium nitride layer is nucleated and grown on the substrate at a boundary of the second graphene mask structure.

[0011] The present invention first etches the graphene layer stacked on the substrate to form an oxide at the bottom of the first window as an oxide mask structure; then etches the retained graphene layer to form a nanoscale second window (referred to as a nanoscale window) at the edge of the graphene layer, and gallium nitride nucleates and grows in the extremely narrow nanoscale window, with a small contact area with the substrate. Dislocations of the substrate are blocked by the oxide mask structure and the second graphene mask structure, thereby preventing a large number of dislocations from extending to the gallium nitride layer grown on the oxide mask structure and the second graphene mask structure, thereby greatly reducing the dislocation density of the gallium nitride layer.

[0012] Furthermore, the etching of the graphene layer to form a first graphene mask structure disposed between the first windows disposed at intervals includes:

[0013] forming a photoresist layer on the surface of the graphene layer;

[0014] Performing photolithography on the photoresist layer to form a plurality of mask patterns arranged at intervals;

[0015] The graphene layer not covered by the mask pattern is etched to expose the substrate by using an oxygen plasma etching process, so as to form the first graphene mask structure and the oxide mask structure.

[0016] In the present invention, the graphene layer is etched by oxygen plasma to form an oxide mask structure on the substrate when the substrate is exposed. GaN is difficult to nucleate on the substrate with the oxide mask structure. The oxide mask structure will become a mask to block dislocations under the substrate, that is, the oxide mask structure is obtained by oxygen plasma etching.

[0017] Further, the parameters of the oxygen plasma etching process include: an oxygen flow rate of 150-250sccm (for example, 150sccm, 175sccm, 200sccm, 225sccm, 250sccm, etc.), an etching power of 300-500W (for example, 300W, 350W, 400W, 450W, 500W, etc.), and an etching time of 80-90s (for example, 80s, 82W, 84W, 86W, 88W, 90W, etc.); and / or

[0018] The width of the mask pattern is 1-3 μm (for example, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, etc.), and the width of the first window is 4-6 μm (for example, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, etc.); and / or

[0019] The thickness of the graphene layer is 4-8 nm (for example, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, etc.), and the thickness of the oxide mask structure is 3-5 nm (for example, 3 nm, 3.5 nm, 4 nm, 4.5 nm or 5 nm, etc.); and / or

[0020] The thickness of the photoresist layer is 1-2 μm (for example, it may be 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm or 2 μm, etc.).

[0021] Furthermore, the first graphene mask structure is etched to form a plurality of second windows spaced apart to obtain a second graphene mask structure, including:

[0022] The boundary of the first graphene mask structure is etched to expose the substrate by an ammonia etching process to obtain the second graphene mask structure. Ammonia etching of graphene will preferentially etch the boundary of graphene, so that the nanoscale substrate will be exposed at the boundary of the first graphene mask structure as a growth window for gallium nitride.

[0023] Furthermore, the width of the second window is 200-600 nm (for example, it may be 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, etc.).

[0024] The present invention firstly adopts an oxygen plasma process to etch the graphene layer to obtain an oxide mask structure; then, the oxide mask structure is used as a mask, and ammonia is used to etch the first graphene mask structure to obtain a nanometer-scale second window, so that GaN nucleates at the boundary of the graphene, and no advanced high-precision nano-scale lithography machine is required, so the cost is relatively low.

[0025] Furthermore, the ammonia etching process includes:

[0026] Under the conditions of a temperature of 700-800°C (for example, 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, etc.), an ammonia flow rate of 12000-20000sccm (for example, 12000sccm, 14000sccm, 16000sccm, 18000sccm, 20000sccm, etc.) and a nitrogen flow rate of 500-1000sccm, the boundary of the first graphene mask structure is etched for 10-30min (for example, 10min, 15min, 20min, 25min, 30min, etc.).

[0027] The size of the second window is regulated by adjusting the ammonia etching process parameters, so as to obtain a nanometer-scale second window.

[0028] Furthermore, the material of the substrate includes aluminum nitride or gallium nitride, and the corresponding oxides are aluminum oxide and gallium oxide, respectively. Ammonia etching will not have a destructive effect on the aluminum nitride or gallium nitride substrate, nor will it produce other substances that affect the growth of gallium nitride. Aluminum oxide and gallium oxide have strong stability and corrosion resistance at 700-800°C and ammonia and hydrogen atmospheres, and will not be etched or decomposed by ammonia.

[0029] Furthermore, the step of nucleating and growing a gallium nitride layer on the substrate at the boundary of the second graphene mask structure comprises:

[0030] (1) At a temperature of 800-900°C (for example, 800°C, 820°C, 840°C, 860°C, 880°C, 900°C, etc.), ammonia gas with a flow rate of 8000-14000sccm (for example, 8000sccm, 9000sccm, 10000sccm, 11000sccm, 12000sccm, 13000sccm, 14000sccm, etc.), trimethylgallium with a flow rate of 30-80sccm (for example, 30sccm, 40sccm, 50sccm, 60sccm, 70sccm, 80sccm, etc.) and a carrier gas are introduced, and the reaction is carried out for 10-30min (for example, 10min, 20sccm, 30sccm, etc.), and a nucleation layer is grown at the boundary of the second graphene mask structure.

[0031] Since the graphene in the second graphene mask structure lacks dangling bonds and the oxide in the oxide mask structure is not easy for gallium nitride to nucleate, gallium nitride nucleates at the extremely narrow nanoscale second window at the edge of the second graphene mask structure.

[0032] (2) At a temperature of 1000-1200°C (for example, 1000°C, 1050°C, 1100°C, 1150°C, 2000°C, etc.), ammonia with a flow rate of 5000-8000sccm, trimethylgallium with a flow rate of 30-90sccm (for example, 30sccm, 40sccm, 50sccm, 60sccm, 70sccm, 80sccm, 90sccm, etc.) and a carrier gas are introduced, and the reaction is carried out for 150-200min (for example, 150min, 160min, 170min, 180min, 190min, 200min, etc.), so that the nucleation layer is combined to form a gallium nitride layer with a thickness of 5-10μm.

[0033] The carrier gas includes nitrogen with a flow rate of 400-600 sccm and hydrogen with a flow rate of 40-60 sccm.

[0034] Furthermore, the method comprises:

[0035] Providing the substrate and a temporary substrate; growing the graphene layer on the temporary substrate; peeling the graphene layer from the temporary substrate, and transferring the graphene layer to the substrate by wet transfer; wherein the substrate and the temporary substrate are made of different materials; or

[0036] Providing the substrate; performing annealing on the substrate, and growing the graphene layer on the annealed substrate.

[0037] Furthermore, the temporary substrate is copper foil, and the method comprises:

[0038] Under the condition of a temperature of 1000-1100° C., hydrogen gas with a flow rate of 10-20 sccm and a gas flux of 10-20 sccm / min is introduced to anneal the substrate for 10-20 min;

[0039] Passing methane with a flow rate of 5-10 sccm and hydrogen with a flow rate of 80-100 sccm to grow the graphene layer on the copper foil;

[0040] The graphene layer is peeled off from the copper foil using polymethyl methacrylate (PMMA).

[0041] Furthermore, the method comprises:

[0042] At a temperature of 600-650° C., hydrogen gas with a flow rate of 10-15 sccm and argon gas with a flow rate of 30-35 sccm are introduced to anneal the substrate for 30-40 minutes;

[0043] Under the conditions of a temperature of 750-800° C. and an ion source power of 50-70 W, methane with a flow rate of 8-10 sccm, hydrogen with a flow rate of 2-3 sccm, and argon with a flow rate of 2-3 sccm are introduced for a reaction of 60-70 minutes to grow the graphene layer on the substrate.

[0044] A second aspect of the present invention provides a gallium nitride structure, comprising a substrate, an oxide mask structure, a second graphene mask structure and a gallium nitride layer, wherein the oxide mask structure and the second graphene mask structure are arranged on the substrate, the gallium nitride layer covers the oxide mask structure and the second graphene mask structure, and the gallium nitride layer is prepared by the method for lateral epitaxial growth of a gallium nitride layer according to the first aspect.

[0045] Beneficial effects of the present invention:

[0046] (1) The present invention first etches the graphene layer by oxygen plasma to form an oxide mask structure and a first graphene mask structure on the substrate; then etches the edge of the first graphene mask structure by ammonia gas to obtain a nanometer-scale window. GaN nucleates and grows in the extremely narrow nanometer-scale window, and the contact area with the substrate is small. The dislocations of the substrate are blocked by the oxide and graphene. By setting the two mask structures, a large number of dislocations are prevented from extending to the gallium nitride layer, thereby greatly reducing the dislocation density of the gallium nitride layer.

[0047] (2) In the existing schemes for growing gallium nitride on graphene, the size of the window is generally in the micrometer range. The accuracy of ordinary photolithography machines cannot reach the extremely small nanometer range, so it is necessary to use advanced high-precision nanometer-level photolithography machines, which are relatively expensive. However, the present invention uses ammonia to etch the boundary of the first graphene mask structure. By controlling the ammonia etching process parameters, a size-controllable nanometer-level window can be obtained. There is no need to use advanced high-precision nanometer-level photolithography machines to etch the graphene, so the production cost is relatively low.

[0048] (3) In the present invention, the size of the second graphene mask structure is relatively small. The two GaN strips nucleated and grown at the boundary of the second graphene structure are contacted and then merged on the second graphene structure. The dislocations with opposite Burgers vectors in the GaN strips will cancel each other out, thereby further reducing the dislocation density of the gallium nitride layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a process flow chart of lateral epitaxial growth of a gallium nitride layer provided by the present invention;

[0050] Figure 2 The structure of the lateral epitaxial growth gallium nitride layer provided by the present invention is schematically shown. Figure 1 ;

[0051] Figure 3 The structure of the lateral epitaxial growth gallium nitride layer provided by the present invention is schematically shown. Figure 2 ;

[0052] Figure 4 is a schematic structural diagram of a gallium nitride structure provided by the present invention;

[0053] Figure 5 is a SEM image of GaN grown for 10 min in Example 1;

[0054] Figure 6 is the SEM image of GaN grown for 30 min in Example 1;

[0055] Figure 7 is the TEM image of the GaN interface in Example 1;

[0056] Figure 8 yes Figure 6 The enlarged image of the white dotted box part;

[0057] Fig. 9 yes Figure 7 An enlarged view of the portion in the white dotted line frame, wherein the portion in the white solid line frame is the second graphene mask structure;

[0058] Fig.10 yes Fig. 9 Line scan of Area-1 and Area-2;

[0059] Explanation of the numbers in the figure: 1. substrate structure, 11. substrate, 12. graphene layer, 121. first graphene mask structure, 122. second window, 2. oxide mask structure, 3. second graphene mask structure, 4. gallium nitride layer, 41. nucleation layer, 5. photoresist layer, 51. mask pattern. DETAILED DESCRIPTION

[0060] The present invention is further described below in conjunction with specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0061] Please refer to Figure 1 and Figure 2 , Figure 1 is a process flow chart of lateral epitaxial growth of a gallium nitride layer provided by the present invention, Figure 2 1 is a schematic diagram of the structure of a lateral epitaxial growth gallium nitride layer provided by the present invention. The present invention provides a method for lateral epitaxial growth of a gallium nitride layer, comprising the following steps:

[0062] S1: Provide a substrate structure 1, the substrate structure 1 comprising a stacked substrate 11 and a graphene layer 12, Figure 2 As shown in (a).

[0063] The material of the substrate 11 includes aluminum nitride or gallium nitride, and the thickness of the substrate 11 is 3-5 nm, for example, 3 nm, 3.2 nm, 3.4 nm, 3.6 nm, 3.8 nm, 4 nm, 4.2 nm, 4.4 nm, 4.6 nm, 4.8 nm or 5 nm. The graphene layer 12 can be one layer or more than one layer.

[0064] S2: etching the graphene layer 12 to form a first graphene mask structure 121 disposed between the first windows spaced apart, such as Figure 2 as shown in (b).

[0065] The bottom of the first window contacts the upper surface of the substrate 11 , and an oxide mask structure 2 is disposed at the bottom of the first window.

[0066] S3: Etching the first graphene mask structure 121 to form a plurality of second windows 122 spaced apart from each other, thereby obtaining a second graphene mask structure 3, such as Figure 2 as shown in (c).

[0067] The bottom of the second window 122 contacts the upper surface of the substrate 11 , and the second window 122 is located around the second graphene mask structure 3 .

[0068] S4: growing a gallium nitride layer 4 on the substrate 11 at the boundary of the second graphene mask structure 3, such as Figure 2 as shown in (d).

[0069] The present invention first etches the graphene layer 12 stacked on the substrate 11 to form an oxide at the bottom of the first window as the oxide mask structure 2; then etches the retained graphene layer to form a nanoscale second window 122 at the edge of the graphene layer, and gallium nitride nucleates and grows in the extremely narrow second window 122, with a small contact area with the substrate 11. The dislocations of the substrate 11 are blocked by the oxide mask structure 2 and the second graphene mask structure 3, thereby preventing a large number of dislocations from extending to the gallium nitride layer, thereby greatly reducing the dislocation density of the gallium nitride layer.

[0070] In a specific embodiment, the width of the first window is 4-6 μm, for example, 4 μm, 4.5 μm, 5 μm, 5.5 μm or 6 μm.

[0071] In a specific embodiment, the thickness of the graphene layer is 4-8 nm.

[0072] In a specific embodiment, the thickness of the oxide mask structure is 3-5 nm.

[0073] As a specific example of this embodiment, a graphene layer may be prepared by a chemical vapor deposition (CVD) process, and the above S1 includes:

[0074] S11a: providing a substrate and a temporary base, and growing a graphene layer on the temporary base.

[0075] The material of the substrate is different from that of the temporary substrate. For example, the temporary substrate is a copper foil, which is placed in a quartz tube furnace, and hydrogen gas with a flow rate of 10-20 sccm and a gas flux of 10-20 sccm / min is introduced at a temperature of 1000-1100°C to anneal the substrate for 10-20 minutes; then, methane with a flow rate of 5-10 sccm and hydrogen with a flow rate of 80-100 sccm are introduced to grow a graphene layer on the copper foil.

[0076] S12a: Peeling the graphene layer off the temporary substrate and transferring the graphene layer to a substrate by wet transfer.

[0077] After cooling the quartz tube furnace, the copper foil is taken out, the graphene layer is peeled off from the copper foil using polymethyl methacrylate, and then the graphene layer is transferred to the substrate using a wet transfer method.

[0078] In another embodiment, a graphene layer is grown on a substrate by a plasma enhanced chemical vapor deposition (PECVD) process, and the above S1 includes the following steps:

[0079] S11b: providing a substrate.

[0080] S12b: performing annealing treatment on the substrate, and growing a graphene layer on the annealed substrate.

[0081] The substrate can be placed in a high-temperature furnace, and at a temperature of 600-650°C, hydrogen with a flow rate of 10-15sccm and argon with a flow rate of 30-35sccm are introduced to anneal the substrate for 30-40min; then, at a temperature of 750-800°C and an ion source power of 50-70W, methane with a flow rate of 8-10sccm, hydrogen with a flow rate of 2-3sccm and argon with a flow rate of 2-3sccm are introduced to react for 60-70min to grow a graphene layer on the substrate.

[0082] In a specific implementation, the above S2 includes the following steps:

[0083] S21: forming a photoresist layer 5 on the surface of the graphene layer 12, Figure 3 (a) and (b) of .

[0084] The photoresist is uniformly coated on the surface of the graphene layer 12 to form a photoresist layer 5 , and the thickness of the photoresist layer 5 is 1-2 μm.

[0085] S22: Photolithography is performed on the photoresist layer 5 to form a plurality of mask patterns 51 arranged at intervals. Figure 3 (c).

[0086] The exposed photoresist layer 5 can form a grating stripe pattern structure (ie, a mask pattern). The width of the mask pattern 51 is 1-3 μm, for example, 1 μm, 1.5 μm, 2 μm, 2.5 μm or 3 μm.

[0087] S23: using an oxygen plasma etching process to etch the graphene layer 12 not covered by the mask pattern 51 to expose the substrate 11, thereby forming a first graphene mask structure 121 and an oxide mask structure 2. Figure 3 (d).

[0088] The graphene layer 12 is etched by oxygen plasma to expose the substrate 11 , and an oxide mask structure 2 is formed on the substrate 11 . It is difficult for GaN to nucleate on the substrate 11 with the oxide mask structure 2 , and the oxide mask structure 2 becomes a mask to block dislocations under the substrate 11 .

[0089] As a specific example of this embodiment, the parameters of the oxygen plasma etching process include: an oxygen flow rate of 150-250sccm (for example, it can be 150sccm, 175sccm, 200sccm, 225sccm or 250sccm, etc.), an etching power of 300-500W (for example, it can be 300W, 350W, 400W, 450W or 500W, etc.) and an etching time of 80-90s (for example, it can be 80s, 82W, 84W, 86W, 88W or 90W, etc.).

[0090] In a specific embodiment, the above S3 includes: using an ammonia etching process to etch the boundary of the first graphene mask structure 121 to expose the substrate 11, thereby obtaining a second graphene mask structure 3. Figure 3 (e).

[0091] Etching the first graphene mask structure 121 with ammonia gas will preferentially etch the boundary of the first graphene mask structure 121 , thus exposing the nanoscale substrate at the boundary of the first graphene mask structure 121 as a growth window (ie, the second window) for gallium nitride.

[0092] As a specific example of this embodiment, the ammonia etching process includes: at a temperature of 700-800° C. (for example, 700° C., 710° C., 720° C., 730° C., 740° C., 750° C., 760° C., 770° C., 780° C., 790° C., or 800° C., etc.), a flow rate of ammonia of 12000-20000 sccm (for example, 12000 sccm, 13000 sccm, 14000 sccm, 15000 sccm, 16000 sccm, 17000 sccm, 18000 sccm, 19000 sccm, or 20000 sccm). m, etc.) and a nitrogen flow rate of 500-1000sccm (for example, 500sccm, 550sccm, 600sccm, 650sccm, 700sccm, 750sccm, 800sccm, 850sccm, 900sccm, 950sccm or 1000sccm, etc.), the boundary of the first graphene mask structure 121 is etched for 10-30min (for example, 10min, 15min, 20min, 25min or 30min, etc.), and the size of the second window can be adjusted by adjusting the ammonia etching process parameters.

[0093] Further, the width of the second window is 200-600 nm, for example, it can be 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm or 600 nm.

[0094] Since the material of the substrate 11 includes aluminum nitride or gallium nitride, and the corresponding oxides are aluminum oxide and gallium oxide respectively, ammonia etching will not have a destructive effect on the substrate 11 of aluminum nitride or gallium nitride material, nor will it produce other substances that affect the growth of gallium nitride; in addition, aluminum oxide and gallium oxide have strong stability and corrosion resistance at 700-800°C in an ammonia and hydrogen atmosphere, and will not be etched or decomposed by ammonia.

[0095] As a specific example of this embodiment, the above S4 includes:

[0096] S41: Under the condition of a temperature of 800-900° C. (for example, 800° C., 820° C., 840° C., 860° C., 880° C. or 900° C., etc.), ammonia gas with a flow rate of 8000-14000 sccm (for example, 8000 sccm, 9000 sccm, 10000 sccm, 11000 sccm, 12000 sccm, 13000 sccm or 14000 sccm, etc.), trimethylgallium with a flow rate of 30-80 sccm (for example, 30 sccm, 40 sccm, 50 sccm, 60 sccm, 70 sccm or 80 sccm, etc.) and a carrier gas are introduced, and the reaction is carried out for 10-30 min (for example, 10 min, 20 sccm or 30 sccm, etc.), and a nucleation layer 41 is grown at the boundary of the second graphene mask structure 3, as shown in FIG. Figure 3 (f).

[0097] The graphene of the second graphene mask structure 3 lacks dangling bonds, and the oxide of the oxide mask structure 2 is not easy for gallium nitride to nucleate. Therefore, gallium nitride nucleates at the extremely narrow nanoscale second window at the edge of the second graphene mask structure 3 .

[0098] S42: At a temperature of 1000-1200°C (for example, 1000°C, 1050°C, 1100°C, 1150°C or 2000°C), ammonia gas with a flow rate of 5000-8000sccm (for example, 5000sccm, 5500sccm, 6000sccm, 6500sccm, 7000sccm, 7500sccm or 8000sccm) and ammonia gas with a flow rate of 30-90sccm (for example, 30sccm, 40sccm, 50sccm) are introduced. ccm, 60sccm, 70sccm, 80sccm or 90sccm, etc.) and a carrier gas are reacted for 150-200min (for example, 150min, 160min, 170min, 180min, 190min or 200min, etc.) so that the nucleation layer 41 is merged to form a gallium nitride layer with a thickness of 5-10μm (for example, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 9μm, 9.5μm or 10μm).

[0099] The carrier gas includes nitrogen with a flow rate of 400-600sccm and hydrogen with a flow rate of 40-60sccm; for example, the flow rate of nitrogen is 400sccm, 430sccm, 460sccm, 490sccm, 520sccm, 550sccm, 575sccm or 600sccm, and the flow rate of hydrogen is 40sccm, 42sccm, 44sccm, 46sccm, 48sccm, 50sccm, 52sccm, 54sccm, 56sccm, 58sccm or 60sccm.

[0100] The present invention also provides a gallium nitride structure, such as Figure 4 As shown, the gallium nitride structure includes a substrate 11, an oxide mask structure 2, a second graphene mask structure 3 and a gallium nitride layer 4. The oxide mask structure 2 and the second graphene mask structure 3 are arranged on the substrate 11, and the gallium nitride layer 4 covers the oxide mask structure 2 and the second graphene mask structure 3. The gallium nitride layer 4 is prepared by the method of lateral epitaxial growth of the gallium nitride layer in the above embodiment.

[0101] Specific examples and comparative examples are provided below.

[0102] Example 1

[0103] This embodiment relates to a method for lateral epitaxial growth of a gallium nitride layer, comprising the following steps:

[0104] (1) The AlN substrate was placed in a high-temperature furnace, and annealed for 30 min at 600°C with H2 at a flow rate of 10 sccm and Ar at a flow rate of 30 sccm. In an environment of 800°C, the ion source power was set to 60 W, and CH4 at a flow rate of 10 sccm, H2 at a flow rate of 2 sccm, and Ar at a flow rate of 2 sccm were introduced for 60 min to grow multiple layers of graphene on the substrate. The thickness of the graphene layer was 6 nm, and the AlN substrate was taken out after cooling.

[0105] (2) uniformly coating the surface of the graphene layer with photoresist to form a photoresist layer with a thickness of 1 μm; exposing the photoresist layer to form a plurality of mask patterns arranged at intervals; etching the surface of the graphene layer not covered by the mask pattern using oxygen plasma to expose the substrate, thereby forming a first graphene mask structure and an oxide mask structure located at the bottom of the first window.

[0106] The oxygen flow rate is 200 sccm, the etching power is 400 W, the etching time is 80 s, the width of the first window is 5 μm, the width of the mask pattern is 2 μm, and the thickness of the oxide mask structure is 5 nm.

[0107] Oxygen plasma etches into the substrate and generates aluminum oxide on the substrate. It is difficult for GaN to nucleate on a substrate with aluminum oxide. Aluminum oxide will become a new mask to block dislocations under the substrate.

[0108] (3) At a temperature of 800° C., ammonia gas with a flow rate of 12000 sccm and nitrogen gas with a flow rate of 500 sccm are introduced to etch the boundary of the first graphene mask structure. After etching for 20 minutes, a new substrate is exposed to form a second graphene mask structure and a second window located at the edge of the second graphene mask structure. The width of the second window is 200 nm.

[0109] (4) Trimethylgallium was used as a gallium precursor, a mixture of nitrogen with a flow rate of 400 sccm and hydrogen with a flow rate of 40 sccm was used as a carrier gas, and ammonia was used as a nitrogen source; at a temperature of 900°C, ammonia with a flow rate of 12000 sccm and trimethylgallium with a flow rate of 40 sccm were introduced, and the reaction lasted for 30 minutes to grow a nucleation layer.

[0110] GaN grows into a nucleation layer at the boundary of the second graphene mask structure. The SEM image after 10 minutes of growth is shown in Figure 5 , we can see that the GaN core grows at the boundary of the second graphene mask structure, and after 30 minutes of growth, the GaN has merged into strips (see Figure 6 Since GaN nucleates in an extremely narrow window, the contact area with the substrate is small, and there are fewer dislocations extending from the substrate to the GaN layer. In addition, most of the dislocations in the substrate will be blocked by the second graphene mask structure and the oxide mask structure, such as Figure 7-Figure 9 As shown. Fig. 9 Line scans were performed on Area-1 and Area-2. The results are as follows: Fig.10 As shown, from Fig.10 It can be seen that there is a C element signal in Area-1 (i.e., area-1), indicating that there is graphene under the gallium nitride layer, and no C element signal is found in Area-2 (i.e., area-2), indicating that there is no graphene under the gallium nitride layer of Area-2.

[0111] (5) At a temperature of 1050° C., ammonia gas with a flow rate of 8000 sccm and TMGa with a flow rate of 30 sccm were introduced for 150 min to react for lateral growth, and the nucleation layers were merged to form a gallium nitride layer.

[0112] By continuing to grow the strip-shaped GaN, dislocations with opposite Burgers vectors will cancel each other out, thereby further reducing the dislocation density of the GaN layer, and eventually growing a GaN layer with a thickness of 5 μm.

[0113] Example 2

[0114] This embodiment relates to a method for lateral epitaxial growth of a gallium nitride layer, comprising the following steps:

[0115] (1) A copper foil is placed in a quartz tube furnace, and H2 is introduced at a temperature of 1000°C for 10 minutes. Then, CH4 with a flow rate of 5 sccm and H2 with a flow rate of 80 sccm are introduced to grow multi-layer graphene layers with a thickness of 5 nm. After cooling, the copper foil is taken out, and the graphene layer is peeled off from the copper foil using polymethyl methacrylate and transferred to an aluminum nitride substrate.

[0116] (2) uniformly coating the surface of the graphene layer with photoresist to form a photoresist layer with a thickness of 1 μm; exposing the photoresist layer to form a plurality of mask patterns arranged at intervals; etching the surface of the graphene layer not covered by the mask pattern using oxygen plasma to expose the substrate, thereby forming a first graphene mask structure and an oxide mask structure located at the bottom of the first window.

[0117] The oxygen flow rate is 200 sccm, the etching power is 400 W, the etching time is 70 s, the width of the first window is 5 μm, the width of the mask pattern is 2 μm, and the thickness of the oxide mask structure is 5 nm.

[0118] Oxygen plasma etches into the substrate and generates aluminum oxide on the substrate. It is difficult for GaN to nucleate on a substrate with aluminum oxide. Aluminum oxide will become a new mask to block dislocations under the substrate.

[0119] (3) At a temperature of 800° C., ammonia gas with a flow rate of 12000 sccm and nitrogen gas with a flow rate of 500 sccm are introduced to etch the boundary of the first graphene mask structure. After etching for 20 minutes, a new substrate is exposed to form a second graphene mask structure and a second window located at the edge of the second graphene mask structure. The width of the second window is 200 nm.

[0120] (4) Trimethylgallium was used as a gallium precursor, a mixture of nitrogen with a flow rate of 400 sccm and hydrogen with a flow rate of 40 sccm was used as a carrier gas, and ammonia was used as a nitrogen source; at a temperature of 900°C, ammonia with a flow rate of 12000 sccm and trimethylgallium with a flow rate of 40 sccm were introduced, and the reaction lasted for 30 minutes to grow a nucleation layer.

[0121] (5) At a temperature of 1050° C., ammonia gas with a flow rate of 8000 sccm and TMGa with a flow rate of 30 sccm were introduced for 150 min to react for lateral growth, and the nucleation layers were merged to form a gallium nitride layer.

[0122] By continuing to grow the strip-shaped GaN, dislocations with opposite Burgers vectors will cancel each other out, thereby further reducing the dislocation density of the GaN layer, and eventually growing a GaN layer with a thickness of 5 μm.

[0123] Example 3

[0124] This embodiment relates to a method for lateral epitaxial growth of a gallium nitride layer, comprising the following steps:

[0125] (1) The AlN substrate was placed in a high-temperature furnace, and annealed for 30 min at 600°C with H2 at a flow rate of 10 sccm and Ar at a flow rate of 30 sccm. In an environment of 800°C, the ion source power was set to 60 W, and CH4 at a flow rate of 10 sccm, H2 at a flow rate of 2 sccm, and Ar at a flow rate of 2 sccm were introduced for 60 min to grow multiple layers of graphene on the substrate. The thickness of the graphene layer was 6 nm, and the AlN substrate was taken out after cooling.

[0126] (2) uniformly coating the surface of the graphene layer with photoresist to form a photoresist layer with a thickness of 1 μm; exposing the photoresist layer to form a plurality of mask patterns arranged at intervals; etching the surface of the graphene layer not covered by the mask pattern using oxygen plasma to expose the substrate, thereby forming a first graphene mask structure and an oxide mask structure located at the bottom of the first window.

[0127] The oxygen flow rate is 200 sccm, the etching power is 400 W, the etching time is 80 s, the width of the first window is 5 μm, the width of the mask pattern is 2 μm, and the thickness of the oxide mask structure is 5 nm.

[0128] Oxygen plasma etches into the substrate and generates aluminum oxide on the substrate. It is difficult for GaN to nucleate on a substrate with aluminum oxide. Aluminum oxide will become a new mask to block dislocations under the substrate.

[0129] (3) At a temperature of 800° C., ammonia gas with a flow rate of 14000 sccm and nitrogen gas with a flow rate of 500 sccm are introduced to etch the boundary of the first graphene mask structure. After etching for 20 minutes, a new substrate is exposed to form a second graphene mask structure and a second window located at the edge of the second graphene mask structure. The width of the second window is 300 nm.

[0130] (4) Using trimethylgallium as a gallium precursor, a mixture of nitrogen with a flow rate of 400 sccm and hydrogen with a flow rate of 40 sccm as a carrier gas, and ammonia as a nitrogen source; at a temperature of 850°C, ammonia with a flow rate of 13000 sccm and trimethylgallium with a flow rate of 45 sccm were introduced, and the reaction lasted for 30 minutes to grow a nucleation layer.

[0131] (5) At a temperature of 1030° C., ammonia gas with a flow rate of 7000 sccm and TMGa with a flow rate of 30 sccm were introduced for 150 min to react for lateral growth, and the nucleation layers were merged to form a gallium nitride layer.

[0132] By continuing to grow the strip-shaped GaN, dislocations with opposite Burgers vectors will cancel each other out, thereby further reducing the dislocation density of the GaN layer, and eventually growing a GaN layer with a thickness of 5 μm.

[0133] Comparative Example 1

[0134] This embodiment relates to a method for lateral epitaxial growth of a gallium nitride layer, comprising the following steps:

[0135] (1) The AlN substrate was placed in a high-temperature furnace, and annealed for 30 min at 600°C with H2 at a flow rate of 10 sccm and Ar at a flow rate of 30 sccm. In an environment of 800°C, the ion source power was set to 60 W, and CH4 at a flow rate of 10 sccm, H2 at a flow rate of 2 sccm, and Ar at a flow rate of 2 sccm were introduced for 60 min to grow multiple layers of graphene on the substrate. The thickness of the graphene layer was 6 nm, and the AlN substrate was taken out after cooling.

[0136] (2) uniformly coating the surface of the graphene layer with a photoresist to form a photoresist layer with a thickness of 1 μm; exposing the photoresist layer to form a plurality of mask patterns arranged at intervals; using oxygen plasma to etch the surface of the graphene layer not covered by the mask pattern until the substrate is exposed to form a first graphene mask structure and an oxide layer located at the bottom of the first window, and soaking the substrate in hydrochloric acid for 10 minutes to remove the oxide layer.

[0137] The oxygen flow rate is 200 sccm, the etching power is 400 W, the etching time is 80 s, the width of the first window is 3 μm, and the width of the mask pattern is 7 μm.

[0138] (3) Using trimethylgallium as a gallium precursor, a mixture of nitrogen with a flow rate of 400 sccm and hydrogen with a flow rate of 40 sccm as a carrier gas, and ammonia as a nitrogen source; at a temperature of 900°C, ammonia with a flow rate of 12000 sccm and trimethylgallium with a flow rate of 40 sccm were introduced, and the reaction lasted for 30 minutes to grow a nucleation layer.

[0139] (4) At a temperature of 1050° C., ammonia gas with a flow rate of 8000 sccm and TMGa with a flow rate of 30 sccm were introduced for 150 min to react for lateral growth, and the nucleation layers were merged to form a gallium nitride layer with a thickness of 5 μm.

[0140] The dislocation density of the gallium nitride layer prepared in each embodiment and comparative example was measured, and the data in Table 1 below were obtained:

[0141] Table 1

[0142] Group Dislocation density Example 1 <![CDATA[5×10 6 cm -1 ]]> Example 2 <![CDATA[9×10 6 cm -1 ]]> Example 3 <![CDATA[8×10 6 cm -1 ]]> Comparative Example 1 <![CDATA[5×10 7 cm -1 ]]>

[0143] By testing the dislocation density of the gallium nitride layers prepared in the embodiments and comparative examples, it can be found that the dislocation density of comparative example 1 is 5×10 7 cm -1 , while the dislocation density of the gallium nitride layer obtained in Example 1 of the present invention can reach 5×10 6 cm -1 , which is reduced by one order of magnitude. It can be seen that the method of the present invention can significantly reduce the dislocation density of the laterally epitaxially grown gallium nitride layer.

[0144] The present invention transfers or grows multilayer graphene on a substrate, forms a mask pattern by photolithography, etches graphene by oxygen plasma until the substrate is exposed to form a first graphene mask structure, and the etching of the substrate by oxygen plasma forms an oxide mask structure on the substrate; etches the first graphene mask structure by ammonia gas and exposes a new substrate to form a second graphene mask structure; then MOCVD is used to grow a nucleation layer, and since graphene lacks dangling bonds and the oxide mask structure exists on the substrate after oxygen plasma etching, it is not easy to grow GaN, so GaN does not nucleate on the second graphene mask structure and the oxide mask structure, but only nucleates on the substrate at the boundary of the second graphene mask structure, and then changes the growth parameters, performs lateral growth to merge GaN, and forms a gallium nitride layer; the gallium nitride layer prepared by the preparation method provided by the present invention has a low dislocation density.

[0145] The above-described embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or changes made by those skilled in the art based on the present invention are within the protection scope of the present invention. The protection scope of the present invention shall be subject to the claims.

Claims

1. A method for lateral epitaxial growth of a gallium nitride layer, characterized in that: The steps include: Providing a substrate structure, the substrate structure comprising a stacked substrate and a graphene layer; Etching the graphene layer to form a first graphene mask structure disposed between the first windows disposed at intervals; wherein the bottom of the first window contacts the upper surface of the substrate, and an oxide mask structure is disposed at the bottom of the first window; Etching the first graphene mask structure to form a plurality of second windows spaced apart from each other, thereby obtaining a second graphene mask structure; wherein the bottom of the second window contacts the upper surface of the substrate, and the second window is located around the second graphene mask structure; A gallium nitride layer is nucleated and grown on the substrate at a boundary of the second graphene mask structure.

2. The method for lateral epitaxial growth of a gallium nitride layer according to claim 1, characterized in that: The etching of the graphene layer to form a first graphene mask structure disposed between the first windows disposed at intervals comprises: forming a photoresist layer on the surface of the graphene layer; Performing photolithography on the photoresist layer to form a plurality of mask patterns arranged at intervals; The graphene layer not covered by the mask pattern is etched to expose the substrate by using an oxygen plasma etching process, so as to form the first graphene mask structure and the oxide mask structure.

3. The method for lateral epitaxial growth of a gallium nitride layer according to claim 2, characterized in that: The parameters of the oxygen plasma etching process include: oxygen flow rate of 150-250 sccm, etching power of 300-500 W and etching time of 80-90 s; and / or The width of the mask pattern is 1-3 μm, and the width of the first window is 4-6 μm; and / or The thickness of the graphene layer is 4-8 nm, and the thickness of the oxide mask structure is 3-5 nm; and / or The thickness of the photoresist layer is 1-2 μm.

4. The method for lateral epitaxial growth of a gallium nitride layer according to claim 1, characterized in that: The etching of the first graphene mask structure to form a plurality of second windows spaced apart from each other to obtain a second graphene mask structure comprises: An ammonia etching process is used to etch the boundary of the first graphene mask structure until the substrate is exposed, thereby obtaining the second graphene mask structure.

5. The method for lateral epitaxial growth of a gallium nitride layer according to claim 4, characterized in that: The ammonia etching process comprises: Under the conditions of a temperature of 700-800° C., a flow rate of ammonia of 12000-20000 sccm, and a flow rate of nitrogen of 500-1000 sccm, etching the boundary of the first graphene mask structure for 10-30 minutes; Wherein, the material of the substrate includes aluminum nitride or gallium nitride, and the width of the second window is 200-600nm.

6. The method for lateral epitaxial growth of a gallium nitride layer according to claim 1, characterized in that: The step of nucleating and growing a gallium nitride layer on a substrate located at a boundary of the second graphene mask structure comprises: Under the condition of temperature of 800-900° C., introducing ammonia gas with a flow rate of 8000-14000 sccm, trimethylgallium with a flow rate of 30-80 sccm and carrier gas, reacting for 10-30 minutes, and growing a nucleation layer at the boundary of the second graphene mask structure; Under the condition of temperature of 1000-1200° C., introducing ammonia gas with a flow rate of 5000-8000 sccm, trimethylgallium with a flow rate of 30-90 sccm and carrier gas, and reacting for 150-200 minutes, so that the nucleation layer is combined to form a gallium nitride layer with a thickness of 5-10 μm; The carrier gas includes nitrogen with a flow rate of 400-600 sccm and hydrogen with a flow rate of 40-60 sccm.

7. The method for lateral epitaxial growth of a gallium nitride layer according to claim 1, characterized in that: The method comprises: Providing the substrate and a temporary substrate; growing the graphene layer on the temporary substrate; peeling the graphene layer from the temporary substrate, and transferring the graphene layer to the substrate by wet transfer; wherein the substrate and the temporary substrate are made of different materials; or Providing the substrate; performing annealing on the substrate, and growing the graphene layer on the annealed substrate.

8. The method for lateral epitaxial growth of a gallium nitride layer according to claim 7, characterized in that: The temporary substrate is a copper foil, and the method comprises: Under the condition of a temperature of 1000-1100° C., hydrogen gas with a flow rate of 10-20 sccm and a gas flux of 10-20 sccm / min is introduced to anneal the substrate for 10-20 min; Passing methane with a flow rate of 5-10 sccm and hydrogen with a flow rate of 80-100 sccm to grow the graphene layer on the copper foil; The graphene layer is peeled off from the copper foil by using polymethyl methacrylate.

9. The method for lateral epitaxial growth of a gallium nitride layer according to claim 7, characterized in that: The method comprises: At a temperature of 600-650° C., hydrogen gas with a flow rate of 10-15 sccm and argon gas with a flow rate of 30-35 sccm are introduced to anneal the substrate for 30-40 minutes; Under the conditions of a temperature of 750-800° C. and an ion source power of 50-70 W, methane with a flow rate of 8-10 sccm, hydrogen with a flow rate of 2-3 sccm, and argon with a flow rate of 2-3 sccm are introduced for a reaction of 60-70 minutes to grow the graphene layer on the substrate.

10. A gallium nitride structure, characterized in that: The gallium nitride structure includes a substrate, an oxide mask structure, a second graphene mask structure and a gallium nitride layer, the oxide mask structure and the second graphene mask structure are arranged on the substrate, the gallium nitride layer covers the oxide mask structure and the second graphene mask structure, and the gallium nitride layer is prepared by the method for lateral epitaxial growth of a gallium nitride layer according to any one of claims 1 to 9.

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