A patterned composite substrate and a method of making the same

Abstract

The application discloses a kind of patterning composite substrate and its preparation method, in the preparation method of the application, the edge is chamfered, and the etching rate of matching edge is slower, and the etching rate of matching center area is higher, solve the production problem caused by edge effect, and finally microstructure meeting process requirements can be obtained on the whole substrate, i.e. it can guarantee the crystallization quality of edge area GaN material growth, reduce the output of final qualified finished product core grain.The composite substrate of the application is formed with microstructure, and the high-quality growth of GaN material is facilitated.

Description

Technical Field

[0001] This invention relates to the field of semiconductors, and more specifically to a patterned composite substrate and its preparation method. Background Technology

[0002] Patterned silica composite substrates can improve the crystal quality and light extraction efficiency of GaN-based LED devices. On one hand, in epitaxial growth, to ensure that dislocations in the GaN material grown at the patterned window bend along the sides of the pattern and then converge at the top, a key issue is to minimize the growth of GaN material on the sides of the periodic pattern on the patterned substrate. Traditional patterned sapphire substrates (PSS) struggle to prevent GaN material from growing on the sides of its periodic patterns. However, patterned silica composite substrates have a significant advantage in this regard. Since silica itself is not suitable for GaN growth, it easily prevents GaN material from growing on the sides of the pattern, thus promoting dislocation bending along the sides and convergence at the top, further improving the crystal quality of the GaN material.

[0003] However, edge effects exist in semiconductor manufacturing processes. In composite substrates, there are pattern-ineffective regions at the edges (sapphire is not exposed, only a silicon dioxide film is present). Because silicon dioxide is unsuitable for GaN growth, high-quality GaN material cannot be formed in these ineffective regions. After the electrode fabrication process, the LED chips formed from these ineffective regions exhibit substandard performance.

[0004] In summary, there is an urgent need for a patterned composite substrate and its fabrication method to solve the problem of high-quality GaN growth in existing technologies. Summary of the Invention

[0005] The purpose of this invention is to provide a patterned composite substrate and its preparation method to solve the problem of high-quality GaN growth. The specific technical solution is as follows:

[0006] A method for preparing a patterned composite substrate includes the following steps:

[0007] Step S1: Deposit a silicon dioxide film on the substrate;

[0008] Step S2: Chamfer the silica film layer;

[0009] Step S3: Coat a photoresist film onto the silicon dioxide film layer;

[0010] Step S4: After exposure, development and etching are performed sequentially, a microstructure is formed on the surface of the substrate;

[0011] Step S5: Clean the workpiece obtained in step S4 to obtain a patterned composite substrate.

[0012] In the preferred embodiment of the above technical solution, the thickness of the silicon dioxide film layer in step S1 is 1.95-2.05 micrometers.

[0013] In the preferred embodiment of the above technical solution, in step S2, an R-type diamond grinding wheel is used to chamfer the edge area of ​​the silicon dioxide film, and the grinding wheel speed is set to 3000-4000 revolutions.

[0014] In the preferred embodiment of the above technical solution, in step S2, the length L of the chamfer after processing is 80-150um, and the angle θ of the chamfer is 30°-60°.

[0015] In the preferred embodiment of the above technical solution, step S3 includes:

[0016] Step S3.1: Clean the silica film layer;

[0017] Step S3.2: Coat the upper surface of the silicon dioxide film with a photoresist film, and before coating the photoresist, spray the photoresist solvent on the edge area of ​​the silicon dioxide film so that the thickness of the photoresist film in the edge area is less than the thickness of the photoresist film in the center area.

[0018] In the preferred embodiment of the above technical solution, in step S3.2, the difference between the photoresist film thickness in the central region and the photoresist film thickness in the edge region is 0.03-0.05 micrometers.

[0019] In the preferred embodiment of the above technical solution, step S4 includes:

[0020] Step S4.1, Exposure: Set the exposure time for the edge area to T1 milliseconds and the exposure time for the center area to T2 milliseconds, where T1 > T2;

[0021] Step S4.2, Development: The exposed workpiece is developed to form multiple sets of photoresist pillars on the surface of the silicon dioxide film.

[0022] Step S4.3: Etching. The developed workpiece is then etched.

[0023] In the preferred embodiment of the above technical solution, in step S4.1, T1 is 1.05-1.30 times T2.

[0024] In the preferred embodiment of the above technical solution, in step S4.3, the workpiece is transferred to the ICP etching chamber for etching, the upper RF power of the ICP is set to 1000-1500W, the lower RF power is set to 450-750W, the boron trichloride gas flow rate is 60-140SCCM, and the reaction time is 15-30 minutes, forming multiple sets of uniformly distributed microstructures on the surface of the substrate.

[0025] A patterned composite substrate includes a substrate and multiple sets of microstructures uniformly distributed on the upper surface of the substrate; the microstructures are in the shape of cones, with the base of the cones disposed on the upper surface of the substrate.

[0026] The application of the technical solution of the present invention has the following beneficial effects:

[0027] (1) The method for preparing the patterned composite substrate of the present invention has chamfered the edges to match the slower etching rate of the edges with the higher etching rate of the central region, thus solving the production problem caused by the edge effect. Finally, the microstructure that meets the process requirements can be obtained on the entire substrate, which can ensure the crystal quality of GaN material growth in the edge region and reduce the output of the final qualified finished product core.

[0028] (2) Compared with the prior art, the improvements of this invention are: First, after depositing a thick silicon oxide film on the upper surface of the sapphire substrate, the substrate edge is chamfered, so that the substrate covered by silicon oxide has a new R-shaped chamfer; Second, in the photolithography stage, the photoresist film is adjusted to make its edge thinner. In the exposure process, the exposure energy is set in different regions for the substrate edge and the substrate center. The purpose is to reduce the volume of the photoresist pillars at the substrate edge (the explanation here is: the volume of the photoresist pillars is controlled by controlling the exposure time. For example, the longer the exposure time, the smaller the hardened area formed on the substrate surface). Through the above methods, the photoresist pillars at the edge are made smaller to match the slower etching rate at the edge, while the photoresist pillars in the central region are larger to match the higher etching rate in the central region. Finally, a microstructure that meets the process requirements can be obtained on the entire substrate. The preparation method of the present invention, by means of the two improvements mentioned above, can avoid the problem of incomplete etching of silicon oxide at the edge due to the low etching rate at the substrate edge, thereby ensuring the crystallization quality of GaN material growth in the edge region and reducing the output of qualified finished product cores.

[0029] (3) The patterned composite substrate of the present invention facilitates the growth of high-quality GaN materials and has a simple structure processing.

[0030] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0031] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0032] In the attached diagram:

[0033] Figure 1This is a flowchart of the preparation method in this embodiment;

[0034] Figure 2 This is a schematic diagram of the chamfering in the preparation method of this embodiment;

[0035] Figure 3 This is a top view of the patterned composite substrate in this embodiment;

[0036] Wherein, 1, substrate; 2, silicon dioxide film; 2.a, chamfer; 3, photoresist film; 3.a, photoresist pillar; 4, microstructure; Q, boundary between edge region and center region; Q1, edge region; Q2, center region. Detailed Implementation

[0037] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered by the claims.

[0038] Example:

[0039] This embodiment discloses a patterned composite substrate and its preparation method. First, the patterned composite substrate in this embodiment will be described.

[0040] The patterned composite substrate in this embodiment includes a substrate 1 and multiple sets of microstructures 4, such as... Figure 1 (e) and Figure 3 As shown;

[0041] The substrate 1 is a sapphire substrate 1 (preferably cylindrical), and multiple sets of microstructures 4 are formed on its upper surface. The multiple sets of microstructures 4 are uniformly distributed on the upper surface of the substrate 1. The shape of the microstructures 4 is preferably a cone, with the base of the cone disposed on the upper surface of the substrate 1. Preferably, the center distance between the bases of two adjacent sets of microstructures 4 is 3-4 micrometers (preferably 3 micrometers in this embodiment). In addition, the microstructures 4 in this embodiment are not limited to cones, and the shape of the microstructures 4 can also refer to the shapes in the prior art.

[0042] The method for preparing patterned composite substrate disclosed in this embodiment can solve the problem of poor GaN material growth quality at the edge of composite substrate 1, resulting in invalid LED chips and affecting the yield of substrate 1 in the later stage. The composite substrate 1 prepared by this method has normal microstructures 4 (triangular pyramids composed of sapphire platforms and silicon oxide protrusions) at its edge, and the sapphire plane is exposed between the microstructures 4, so that GaN material can be grown at any position of substrate 1.

[0043] The preparation method of the composite substrate 1 in this embodiment specifically includes the following steps S1 to S5, such as... Figures 1 to 3 As shown:

[0044] Step S1, as follows Figure 1 As shown in (a), a silicon dioxide film 2 with a thickness of 1.95-2.05 μm is deposited on the upper surface of the sapphire substrate 1 using a PECVD device, and more preferably the thickness of the silicon dioxide film 2 is 2.0 μm.

[0045] Step S2, as follows Figure 1 (b) and Figure 2 As shown, the substrate 1 obtained after step S1 is chamfered using a chamfering machine to chamfer the silicon dioxide film layer 2: an R-type diamond grinding wheel with a 45-degree opening is selected, the grinding wheel speed is set to 3000-4000 rpm (preferably 3500 rpm), the chamfer length L after processing is controlled between 80-150 μm (preferably 100 μm), and the chamfer angle θ of chamfer 2.a is 30-60° (preferably 45° in this embodiment);

[0046] Step S3, as follows Figure 1 As shown in (c), the photoresist is applied (positive photoresist is used in this embodiment), including steps S3.1 and S3.2:

[0047] Step S3.1: Clean the surface of the silica film layer 2 by spraying an organic surfactant onto the workpiece obtained in step S2 using a brushing machine.

[0048] Step S3.2: After cleaning, the workpiece undergoes surface pretreatment to make the surface of the silicon dioxide film 2 hydrophobic. The pretreated workpiece is then fed into a spin coater to coat the upper surface of the silicon dioxide film 2 with a photoresist film 3. Before coating the photoresist, a layer of photoresist is applied to the edge area of ​​the silicon dioxide film 2 (e.g., ...). Figure 3 (As shown in Q1) Photoresist solvent is sprayed, so that the thickness of the photoresist film 3 in the edge region is smaller than that in the center region (as shown in Q1). Figure 3 The thickness of the photoresist film 3 (as shown in Q2) is as follows: preferably, the difference between the thickness of the photoresist film 3 in the central region and the thickness of the photoresist film 3 in the edge region is 0.03-0.05 micrometers, and more preferably, the thickness in the central region is 2.08 μm and the thickness in the edge region is 2.03 μm.

[0049] Step S4: After sequentially exposing, developing, and etching the workpiece coated with photoresist, a microstructure 4 is formed on the surface of substrate 1, as detailed below:

[0050] Step S4.1 (Exposure): Set the exposure time of the edge area to T1ms (milliseconds) and the exposure time of the center area to T2ms, where T1 > T2. More preferably, T1 is 1.05-1.30 times T2. In this embodiment, T1 is preferably 180ms and T2 is preferably 160ms.

[0051] Step S4.2 (development), as follows Figure 1As shown in (d), the exposed workpiece is sent to a developing machine for development, and multiple sets of photoresist pillars 3.a are formed on the surface of the silicon dioxide film layer 2;

[0052] Step S4.3 (etching), as follows Figure 1 As shown in (e), the developed workpiece is transferred to the ICP etching chamber for etching. The upper RF power of the ICP is set to 1000-1500W (preferably 1200W), the lower RF power is set to 450-750W (preferably 600W), the boron trichloride gas flow rate is 60-140SCCM (preferably 120SCCM), and the reaction time is 15-30 minutes (preferably 20 minutes). After etching, multiple sets of uniformly distributed microstructures 4 are formed on the upper surface of the substrate 1.

[0053] Step S5: Perform surface cleaning on the workpiece obtained in step S4, specifically by chemical cleaning with a sulfuric acid-hydrogen peroxide mixture to obtain a clean patterned composite substrate, such as... Figure 1 (e) and Figure 3 As shown.

[0054] In this embodiment, a batch (500 pieces) comparative experiment was conducted to compare the yield of LED chip finished products produced by the preparation method of this embodiment with the preparation method of the prior art, as shown in Table 1.

[0055] Table 1

[0056] The product obtained by the preparation method in this embodiment 100％ 99.0％ Products prepared by existing techniques 100％ 98.0％

[0057] As shown in Table 1 above, the composite substrate prepared by the method in this embodiment can improve the yield of LED chip products.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a patterned composite substrate, characterized in that, Includes the following steps: Step S1: Deposit a silicon dioxide film (2) on the substrate (1); Step S2: Chamfer the silicon dioxide film (2); Step S3: Coat a photoresist film (3) on a silicon dioxide film layer (2), and before coating the photoresist, spray a photoresist solvent on the edge region (Q1) of the silicon dioxide film layer (2) so that the thickness of the photoresist film (3) in the edge region (Q1) is less than the thickness of the photoresist film (3) in the center region (Q2). Step S4: After sequential exposure, development, and etching, a microstructure (4) is formed on the surface of the substrate (1); During exposure: the exposure time of the edge region (Q1) is set to... The exposure time for the central region (Q2) is in milliseconds. millisecond, ; Step S5: Clean the workpiece obtained in step S4 to obtain a patterned composite substrate.

2. The method for preparing a patterned composite substrate according to claim 1, characterized in that, In step S1, the thickness of the silicon dioxide film (2) is 1.95-2.05 micrometers.

3. The method for preparing a patterned composite substrate according to claim 1, characterized in that, In step S2, select A diamond grinding wheel is used to chamfer the edge region (Q1) of the silica film (2).

4. The method for preparing a patterned composite substrate according to claim 1, characterized in that, In step S2, the length of the chamfer after processing The angle of the chamfer (2.a) is between 80-150µm. The range is 30°-60°.

5. The method for preparing a patterned composite substrate according to any one of claims 1-4, characterized in that, Step S3 further includes cleaning the silicon dioxide film (2) before applying the photoresist film (3) to the silicon dioxide film (2).

6. The method for preparing a patterned composite substrate according to claim 5, characterized in that, In step S3, the difference between the thickness of the photoresist film (3) in the central region (Q2) and the thickness of the photoresist film (3) in the edge region (Q1) is 0.03-0.05 micrometers.

7. The method for preparing a patterned composite substrate according to claim 5, characterized in that, Step S4 further includes: Development involves developing the exposed workpiece to form multiple sets of photoresist pillars (3.a) on the surface of the silicon dioxide film (2). Etching: The workpiece after development undergoes etching treatment.

8. The method for preparing a patterned composite substrate according to claim 7, characterized in that, for 1.05-1.30 times.

9. The method for preparing a patterned composite substrate according to claim 7, characterized in that, The workpiece is transferred to the ICP etching chamber for etching. The upper RF power of the ICP is set to 1000-1500W, the lower RF power is set to 450-750W, the boron trichloride gas flow rate is 60-140SCCM, and the reaction time is 15-30 minutes. Multiple sets of uniformly distributed microstructures (4) are formed on the surface of the substrate (1).

10. A patterned composite substrate prepared using the method of claim 7, characterized in that, It includes a substrate (1) and multiple sets of microstructures (4) uniformly distributed on the upper surface of the substrate (1); the microstructures (4) are cone-shaped, and the bottom surface of the cone is disposed on the upper surface of the substrate (1).

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