Preparation method of GaN patterned substrate and GaN patterned substrate
By using photoelectrochemical etching technology to form patterns on GaN substrates, the problems of uneven etching and impurity residue in GaN layers in existing technologies have been solved. Vertical etching and automatic separation of GaN layers have been achieved, thus improving growth quality.
Patent Information
- Application Number
- CN202511353214.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-19
- Publication Date
- 2025-12-16
AI Technical Summary
Existing technologies make it difficult to effectively control the etching of GaN layers when preparing GaN patterned substrates, leading to warping or cracking. Furthermore, the etching process can easily affect the growth quality, especially since laser etching and plasma etching suffer from inhomogeneity and impurity residue.
By employing photoelectrochemical etching technology, through-holes are formed on the sapphire layer and filled with conductors. Combined with photoresist and photoelectrochemical electrolyte treatment, selective etching of the GaN layer is achieved, ensuring that the sapphire layer is not etched and maintaining the perpendicularity of the etched surface.
It achieves complete etching of the GaN layer without damaging the sapphire layer, with good verticality of the etched surface, which is beneficial for GaN liquid-phase nucleation and automatic separation, thus improving growth quality.
Smart Images
Figure CN121152272A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor design technology, and in particular to a method for preparing a GaN patterned substrate and the GaN patterned substrate itself. Background Technology
[0002] GaN (gallium nitride) substrates grown using the liquid-phase flux method are grown in a gas-liquid-solid three-phase system, with a GaN / sapphire seed crystal. However, as the size of the grown GaN increases, such as to 2 inches, 4 inches, or even 6 inches, GaN warping can easily occur due to lattice mismatch between GaN and sapphire, and in severe cases, it can crack. If the GaN in the seed crystal is patterned from the beginning, reducing the contact area between the GaN in the seed crystal and the GaN in the liquid-phase method, then automatic separation of the GaN and sapphire layers can be achieved during the cooling process.
[0003] However, this requires that the GaN layer be completely etched away in the etched area, exposing the sapphire layer, and ideally, the sapphire layer should not be etched at all. The goal is to ensure lateral growth in the etched area. If GaN layer remains or sapphire is etched away, experiments show that a large amount of GaN polycrystalline material will be present, severely affecting the growth quality.
[0004] If laser etching is used, the etching degree is difficult to control, as shown in the attached diagram in the instruction manual. Figure 5 The problem is that the laser etching is insufficient, and GaN remains in the etched areas. Figure 6 The laser etching was too excessive, and the sapphire layer was also etched away. Figure 7 This is ideal, as the GaN layer first heals the etched areas through lateral lattice growth before continuing to grow. Furthermore, the GaN edges left by laser etching also show signs of high-temperature laser burning and discoloration, affecting growth quality.
[0005] For direct plasma etching (ICP), the process typically involves coating a seed GaN layer with photoresist, followed by photolithography, and finally ICP. However, due to the large thickness of the GaN layer, generally between 5-15µm, the etching time is very long. During plasma etching, carbonization at the edges of the photoresist can easily occur, causing the side surfaces of the etched portion, which should be vertical, to become sloping surfaces instead. Figure 8 Furthermore, under the influence of plasma, photoresist exposed to plasma for extended periods forms a dense layer on the GaN surface, which is difficult to remove with organic solvents, concentrated acids, or plasma strippers, and the resulting impurities severely affect the experiment.
[0006] In order to enable the GaN layer on the seed crystal to form a pattern, finding a technical solution that can solve the above-mentioned technical problems has become an important research topic for those skilled in the art. Summary of the Invention
[0007] This invention discloses a method for preparing a GaN patterned substrate and a GaN patterned substrate to address the technical deficiencies existing in the prior art.
[0008] The present invention provides a method for preparing a GaN patterned substrate, comprising the following steps:
[0009] S1. Prepare a GaN substrate, wherein the GaN substrate includes a sapphire layer and a GaN layer formed on the surface of the sapphire layer;
[0010] S2. Laser etching is performed on the sapphire layer to form a plurality of first vias arranged in a matrix on the sapphire layer, and the first vias extend to the GaN layer;
[0011] S3. Vacuum vapor deposition is performed on the first through hole to fill the first through hole with a conductive material;
[0012] S4. A conductive thin film layer is deposited on the surface of the sapphire layer away from the GaN layer;
[0013] S5. Photoresist is coated on the surface of the GaN layer away from the sapphire layer to form a photoresist layer. Then, photolithography is performed on the photoresist layer to form a second via corresponding to the position of the first via. The second via extends to the GaN layer.
[0014] S6. Immerse the GaN substrate in a photoelectrochemical electrolyte, connect the conductive thin film layer to the positive terminal of the power supply, connect the photoelectrochemical electrolyte to the negative terminal of the power supply and the comparison electrode, and point the light source directly at the position of the second through hole. After the GaN layer is photoelectrochemically etched, the position of the GaN layer corresponding to the second through hole is etched to expose the conductor.
[0015] S7. Clean up the remaining photoresist layer to obtain a GaN patterned substrate.
[0016] Optionally, in step S1, the thickness of the GaN layer is 5-15 μm.
[0017] Optionally, step S2, the step of laser etching the sapphire layer, specifically includes:
[0018] The sapphire layer is laser-etched using an infrared laser.
[0019] Optionally, in step S2, the plurality of first through holes are arranged in a regular hexagonal, regular quadrilateral, or circular matrix, and the first through holes are square holes or circular holes.
[0020] Optionally, in step S3, the conductor is a conductive metal, wherein the conductive metal is one of molybdenum, tungsten, platinum, and gold.
[0021] Optionally, step S4 specifically includes:
[0022] A conductive thin film layer is formed on the surface of the sapphire layer away from the GaN layer by vacuum evaporation or physical vapor deposition.
[0023] Optionally, the conductive thin film layer is one of a molybdenum conductive thin film layer, a tungsten conductive thin film layer, a platinum conductive thin film layer, and a gold conductive thin film layer.
[0024] Optionally, in step S6, the photoelectrochemical electrolyte includes one or more of sulfuric acid, hydrogen peroxide, oxalic acid, and phosphoric acid;
[0025] Alternatively, in step S6, the photoelectrochemical electrolyte may include one or more of potassium hydroxide, ammonia, and sodium hydroxide.
[0026] Optionally, in step S6, the light source is ultraviolet light with a wavelength of 365mm-400mm and the light source voltage is 10-20V.
[0027] The present invention provides a GaN patterned substrate, which is prepared by the above-described method for preparing a GaN patterned substrate.
[0028] Compared with the prior art, the present invention has the following beneficial effects:
[0029] In the method for preparing the GaN patterned substrate of the present invention, the GaN substrate is mainly patterned by photoelectrochemical etching. This method can completely etch the GaN layer without etching the sapphire layer, and can make the inner side of the etching pit have good verticality, which is beneficial to GaN liquid phase nucleation and automatic separation. Attached Figure Description
[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0031] Figure 1 This invention provides a fabrication path diagram for a method of fabricating a GaN patterned substrate.
[0032] Figure 2This is a schematic diagram of the pattern formed by multiple first vias after the sapphire layer is laser-etched in a method for preparing a GaN patterned substrate provided by the present invention.
[0033] Figure 3 This invention provides a schematic diagram of a three-dimensional structure of a GaN layer in a patterned GaN substrate.
[0034] Figure 4 A flowchart illustrating a method for fabricating a GaN patterned substrate provided by this invention;
[0035] Figure 5 This is a schematic diagram of the GaN patterned substrate with insufficient laser etching mentioned in the background art;
[0036] Figure 6 This is a schematic diagram of the structure of a GaN patterned substrate that has been excessively laser-etched, as mentioned in the background art.
[0037] Figure 7 This is a schematic diagram of a suitable GaN patterned substrate etched by laser, as mentioned in the background art.
[0038] Figure 8 This is a schematic diagram of a GaN patterned substrate etched by the ionization process (ICP) mentioned in the background art.
[0039] Illustration: Sapphire layer 100; first via 101; GaN layer 200; conductor 300; conductive thin film layer 301; photoresist layer 400; second via 401. Detailed Implementation
[0040] To enable those skilled in the art to better understand the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0041] Please see Figures 1 to 4 The present invention provides a method for fabricating a GaN patterned substrate, comprising the following steps:
[0042] S1, such as Figure 1 As shown in (a), a GaN substrate is prepared, which is obtained by metal-organic chemical vapor deposition (MOCVD). The GaN substrate includes a sapphire layer 100 and a GaN layer 200 formed on the surface of the sapphire layer 100.
[0043] S2, such as Figure 1As shown in (a)-(b), the sapphire layer 100 is laser etched to form a plurality of first vias 101 arranged in a matrix on the sapphire layer 100, and the first vias 101 extend to the GaN layer 200.
[0044] S3, such as Figure 1 As shown in (b)-(c), the first through hole 101 is vacuum vapor-deposited to fill the first through hole 101 with a conductor 300.
[0045] S4, such as Figure 1 As shown in (c)-(d), a conductive thin film layer 301 is deposited on the surface of the sapphire layer 100 away from the GaN layer 200;
[0046] S5, such as Figure 1 As shown in (d)-(f), photoresist is coated on the surface of the GaN layer 200 away from the sapphire layer 100 to form a photoresist layer 400. Then, the photoresist layer 400 is photolithographically processed to form a second via 401 on the photoresist layer 400 that corresponds one-to-one with the position of the first via 101. The second via 401 extends to the GaN layer 200.
[0047] S6, such as Figure 1 As shown in (f)-(g), the GaN substrate is immersed in a photoelectrochemical electrolyte, and the conductive thin film layer 301 is connected to the positive terminal of the power supply. The photoelectrochemical electrolyte is connected to the negative terminal of the power supply and the comparison electrode. The light source is positioned directly opposite the second through hole 401. After the GaN layer 200 is photoelectrochemically etched, the position of the GaN layer 200 corresponding to the second through hole 401 is etched to expose the conductor 300.
[0048] S7, such as Figure 1 As shown in (g)-(h), the remaining photoresist layer 400 is cleaned to obtain a GaN patterned substrate.
[0049] In the method for preparing the GaN patterned substrate of the present invention, the GaN substrate is mainly patterned by photoelectrochemical etching. This method can completely etch the GaN layer 200 but not the sapphire layer 100, and can make the inner side of the etching pit have good verticality, which is beneficial to GaN liquid phase nucleation and automatic separation.
[0050] Furthermore, in step S1 of this embodiment, the thickness of the GaN layer 200 is 5-15 μm.
[0051] It should be noted that in some specific embodiments, the thickness of the GaN layer 200 can be 5um, 7um, 15um, etc., and this embodiment does not limit it.
[0052] Furthermore, in step S2 of this embodiment, the step of laser etching the sapphire layer 100 specifically includes:
[0053] The sapphire layer 100 is laser-etched using an infrared laser.
[0054] It should be noted that, in this embodiment, infrared laser is preferred for laser etching of sapphire layer 100, while other lasers, such as ultraviolet laser, are used for etching GaN layer 200. Therefore, infrared laser is preferred in this step.
[0055] Furthermore, in step S2 above, the plurality of first through holes 101 are arranged in a regular hexagonal, regular quadrilateral or circular matrix, and the first through holes 101 are square holes or circular holes.
[0056] It should be noted that this embodiment does not limit the arrangement or specific shape of the first through hole 101, and designers can choose according to specific graphic requirements.
[0057] Furthermore, in step S3 of this embodiment, the conductor 300 is a conductive metal, wherein the conductive metal is one of molybdenum, tungsten, platinum, and gold.
[0058] It should be noted that the conductor 300 mentioned above needs to have properties such as conductivity, high temperature resistance, and chemical stability. Therefore, it is preferred that the conductor 300 is one of the conductive metals selected from molybdenum, tungsten, platinum, and gold. Designers can choose according to actual conditions, and this embodiment does not impose any restrictions on this.
[0059] Furthermore, step S4 in this embodiment specifically includes:
[0060] A conductive thin film layer 301 is formed on the surface of the sapphire layer 100 away from the GaN layer 200 by vacuum evaporation or physical vapor deposition.
[0061] It should be noted that the conductive thin film layer 301 mentioned above also needs to have properties such as conductivity, high temperature resistance, and chemical stability. Therefore, the conductive thin film layer 301 is preferably one of molybdenum conductive thin film layer 301, tungsten conductive thin film layer 301, platinum conductive thin film layer 301, and gold conductive thin film layer 301. Designers can choose according to actual conditions, and this embodiment does not limit this.
[0062] Furthermore, in step S6 of this embodiment, the photoelectrochemical electrolyte can specifically be an acidic solution or an alkaline solution.
[0063] When an acidic solution is used as the electrolyte, the photoelectrochemical electrolyte may include one or more of sulfuric acid, hydrogen peroxide, oxalic acid, and phosphoric acid.
[0064] When an alkaline solution is used as the electrolyte, the photoelectrochemical electrolyte includes one or more of potassium hydroxide, ammonia, and sodium hydroxide.
[0065] Furthermore, in step S6 of this embodiment, the light source is ultraviolet light with a wavelength of 365mm-400mm and the light source voltage is 10-20V.
[0066] It should be noted that in step S6, the ultraviolet light combined with the electrolyte can achieve photoelectrochemical etching of the GaN layer 200, thereby accurately controlling the etching depth of the GaN layer 200 and preventing the sapphire layer 100 from being etched.
[0067] The present invention provides a GaN patterned substrate, which is prepared by the above-described method for preparing a GaN patterned substrate.
[0068] It should be noted that in the GaN patterned substrate prepared by the above method, only the GaN layer 200 is etched, while the sapphire layer 100 is not etched. Furthermore, the verticality of the inner side of the etched pit is good, which is beneficial for GaN liquid phase nucleation and automatic separation.
[0069] The foregoing has provided a detailed description of the preparation method of a GaN patterned substrate and the GaN patterned substrate provided by the present invention. For those skilled in the art, based on the ideas of the embodiments of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.
Claims
1. A method for fabricating a GaN patterned substrate, characterized in that, Includes the following steps: S1. Prepare a GaN substrate, wherein the GaN substrate includes a sapphire layer and a GaN layer formed on the surface of the sapphire layer; S2. Laser etching is performed on the sapphire layer to form a plurality of first vias arranged in a matrix on the sapphire layer, and the first vias extend to the GaN layer; S3. Vacuum vapor deposition is performed on the first through hole to fill the first through hole with a conductive material; S4. A conductive thin film layer is deposited on the surface of the sapphire layer away from the GaN layer; S5. Photoresist is coated on the surface of the GaN layer away from the sapphire layer to form a photoresist layer. Then, photolithography is performed on the photoresist layer to form a second via corresponding to the position of the first via. The second via extends to the GaN layer. S6. Immerse the GaN substrate in a photoelectrochemical electrolyte, connect the conductive thin film layer to the positive terminal of the power supply, connect the photoelectrochemical electrolyte to the negative terminal of the power supply and the comparison electrode, and point the light source directly at the position of the second through hole. After the GaN layer is photoelectrochemically etched, the position of the GaN layer corresponding to the second through hole is etched to expose the conductor. S7. Clean up the remaining photoresist layer to obtain a GaN patterned substrate.
2. The method for fabricating a GaN patterned substrate according to claim 1, characterized in that, In step S1, the thickness of the GaN layer is 5-15 μm.
3. The method for fabricating a GaN patterned substrate according to claim 1, characterized in that, In step S2, the laser etching step of the sapphire layer specifically includes: The sapphire layer is laser-etched using an infrared laser.
4. The method for fabricating a GaN patterned substrate according to claim 3, characterized in that, In step S2, the plurality of first through holes are arranged in a regular hexagonal, regular quadrilateral, or circular matrix, and the first through holes are square holes or circular holes.
5. The method for fabricating a GaN patterned substrate according to claim 1, characterized in that, In step S3, the conductor is a conductive metal, wherein the conductive metal is one of molybdenum, tungsten, platinum, and gold.
6. The method for fabricating a GaN patterned substrate according to claim 1, characterized in that, Step S4 specifically includes: A conductive thin film layer is formed on the surface of the sapphire layer away from the GaN layer by vacuum evaporation or physical vapor deposition.
7. The method for fabricating a GaN patterned substrate according to claim 6, characterized in that, The conductive thin film layer is one of the following: molybdenum conductive thin film layer, tungsten conductive thin film layer, platinum conductive thin film layer, and gold conductive thin film layer.
8. The method for fabricating a GaN patterned substrate according to claim 1, characterized in that, In step S6, the photoelectrochemical electrolyte includes one or more of sulfuric acid, hydrogen peroxide, oxalic acid, and phosphoric acid. Alternatively, in step S6, the photoelectrochemical electrolyte may include one or more of potassium hydroxide, ammonia, and sodium hydroxide.
9. The method for fabricating a GaN patterned substrate according to claim 1, characterized in that, In step S6, the light source is ultraviolet light with a wavelength of 365mm-400mm and a voltage of 10-20V.
10. A GaN patterned substrate, characterized in that, The GaN patterned substrate is prepared by the method for preparing a GaN patterned substrate as described in any one of claims 1 to 9.