Composite patterned substrate with trapezoidal window structure and preparation method thereof

Abstract

The invention discloses a composite patterned substrate with a trapezoidal window structure and a preparation method of the composite patterned substrate. The composite patterned substrate comprises a base and a composite pattern layer arranged on the surface of the base, the composite pattern layer is composed of a plurality of pattern units arranged periodically, and cavities penetrating through the composite pattern layer and exposing the surface of the base are arranged among the pattern units. The section, perpendicular to the surface of the substrate, of the cavity is of a trapezoidal structure, the bottom width of the cavity is larger than the opening width of the side away from the substrate, and the side wall of the cavity inclines relative to the surface of the substrate. The composite patterned substrate is beneficial to improving initial conditions of epitaxial growth, improving crystal quality and device performance, and is suitable for preparation of semiconductor devices such as light emitting diodes.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronic device manufacturing, and more specifically, to a composite patterned substrate with a trapezoidal window structure and its preparation method. Background Technology

[0002] In the manufacture of nitride light-emitting diodes (LEDs), patterning (PSS) technology is widely used to improve light extraction efficiency (LEE) and the quality of epitaxial crystals. Traditional PSS technology typically involves dry etching sapphire to form periodic conical or cylindrical structures.

[0003] However, the existing technology has the following main drawbacks: 1. Insufficient stress relief: The bottom area (i.e., the C-surface growth area) of traditional patterned structures is small, which leads to thermal stress concentration between the epitaxial layers. Microcracks are easily generated during the cooling process, affecting the reliability of high-power devices.

[0004] 2. Dislocation density constraint: Due to the limited area of ​​the top C-face window, the dislocation bending and annihilation efficiency during the lateral epitaxy process is low, which limits the further improvement of the internal quantum efficiency (IQE).

[0005] 3. Processing bottlenecks: In order to obtain better light extraction effect, a high aspect ratio pattern is required. However, directly etching sapphire is not only difficult and costly, but also easily leads to pattern collapse or uncontrollable morphology. Summary of the Invention

[0006] The main objective of this invention is to provide a composite patterned substrate with a trapezoidal window structure and its preparation method. Through a special composite structure design, the effective growth area of ​​the bottom C-plane is increased while constructing a high aspect ratio cavity that is conducive to light scattering, thereby solving the problems of stress concentration, limited crystal quality, and low light extraction efficiency in the prior art.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A composite patterned substrate with a trapezoidal window structure, comprising: Base; and A composite pattern layer is disposed on the surface of the substrate; The composite graphics layer comprises multiple periodically arranged graphics units; Each of the graphic units has a cavity that extends through the composite graphic layer and exposes the substrate surface; The cavity has a trapezoidal cross-sectional shape perpendicular to the substrate surface, and the width of the cavity at the bottom of the substrate surface is greater than the width of its opening on the side away from the substrate.

[0008] The sidewall of the cavity is inclined relative to the normal direction of the base surface, and the interior angle between the sidewall and the base surface is an acute angle.

[0009] The composite pattern layer includes a first material layer and a second material layer stacked sequentially along the direction away from the substrate; Wherein, the material of the first material layer is the same as the material of the substrate, and the material of the second material layer is different from the material of the substrate; The sidewall of the cavity is composed of a lower sidewall made of the first material layer and an upper sidewall made of the second material layer.

[0010] The substrate material is selected from sapphire, aluminum nitride, and gallium nitride. The material of the composite patterned layer is selected from silicon dioxide.

[0011] The above-mentioned method for fabricating a composite patterned substrate with a trapezoidal C-plane window includes the following steps: S1: A first mask pattern is formed on the substrate surface, the first mask pattern having a trapezoidal cross-sectional structure with an upper base width smaller than a lower base width; S2: Deposit a covering material layer on the substrate and the first mask pattern; S3: A second mask pattern is formed on the cover material layer, the second mask pattern defining the opening area; S4: Using the second mask pattern as a mask, etch the cover material layer to form a channel penetrating the cover material layer and expose at least a portion of the structure of the first mask pattern; S5: Remove the first mask pattern through the channel to form a cavity with a bottom width greater than the opening width inside the cover material layer, thereby obtaining the composite patterned substrate.

[0012] The material of the first mask pattern is photoresist; In step S1, by controlling the exposure focal length or the thermal reflow process after development, the photoresist is made to form a trapezoid with an upper base width smaller than the lower base width.

[0013] Step S2 specifically includes: S21: A first material layer is deposited on the substrate and the first mask pattern using a low-temperature deposition process, wherein the material of the first material layer is the same as that of the substrate; S22: Deposit a second material layer on the first material layer, wherein the material of the second material layer is different from that of the substrate; In step S4, the etching penetrates the second material layer and the first material layer located on top of the first mask pattern.

[0014] The height of the sidewall at the bottom of the cavity, which is composed of the first material layer, is controlled by adjusting the height of the first mask pattern and the deposition thickness of the first material layer.

[0015] In step S4, an inductively coupled plasma etching process is used to etch to the depth of the first mask pattern to the interior or expose the sidewalls of the first mask pattern, thereby forming a channel for the stripping liquid to enter in step S5.

[0016] The present invention also provides a light-emitting diode epitaxial wafer, comprising: The aforementioned composite patterned substrate; and An epitaxial growth layer is grown on the composite patterned substrate; The epitaxial growth layer begins on the substrate surface at the bottom of the cavity and grows upward along the cavity.

[0017] The beneficial effects of this invention include: 1. Reduced defect density: The enlarged C-face window at the bottom provides a wider lateral starting area for epitaxial growth, effectively promoting the lateral bending and annihilation of penetrating dislocations.

[0018] 2. Improved light extraction efficiency: The high aspect ratio cavity structure with inclined sidewalls significantly increases the photon scattering and reflection interface, making it easier for photons to escape from the device.

[0019] 3. Enhanced stress relief: The wide bottom contact area optimizes stress distribution, provides a larger lateral relaxation path, and reduces the risk of warpage and cracking during chip manufacturing. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the fabrication process and corresponding structural cross-section of a composite patterned substrate with a trapezoidal window structure provided in Embodiment 1 of the present invention.

[0021] Figure 2 This is a schematic diagram of the fabrication process and corresponding structural cross-section of a composite patterned substrate with a trapezoidal window structure provided in Embodiment 2 of the present invention.

[0022] Explanation of key component symbols: 100: Base; 200: Composite graphics layer; 201: First material layer; 202: Second material layer; 300: Cavity; 400: First mask pattern; 500: Second mask pattern. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0024] Example 1: Composite patterned substrate composed of a single layer of material This embodiment provides a composite patterned substrate made of a single dielectric material and its fabrication method. Please refer to [link / reference]. Figure 1 .

[0025] S1: Forming the first mask pattern 400: Sapphire (Al2O3) on the C-side is used as the substrate 100. Positive photoresist (EPI 612 from Yongguang Chemical) is spin-coated onto the surface of the substrate 100. Through photolithography (exposure, development) and subsequent thermal reflow processes, the periodically arranged first mask pattern 400 is formed on the substrate 100. Key control point: By controlling the exposure focal length deviation or the post-development baking temperature, the photoresist undergoes controlled collapse, resulting in a trapezoidal structure in the cross-section of the first mask pattern 400 where the upper base width is smaller than the lower base width.

[0026] S2: A silicon dioxide layer 203 is deposited on the surface of the substrate 100 and the first mask pattern 400 using a PECVD (plasma-enhanced chemical vapor deposition) process. In this embodiment, the composite pattern layer 200 is a single-layer structure. The silicon dioxide deposition thickness needs to be greater than the height of the first mask pattern 400 to ensure complete coverage.

[0027] S3: Forming the second mask pattern 500: Photoresist is spin-coated onto the silicon dioxide layer 203, and an opening region is defined by photolithography to form the second mask pattern 500. The opening region corresponds to the top position of the first mask pattern 400.

[0028] S4: The etching channel uses the second mask pattern 500 as a barrier layer, and employs ICP (Inductively Coupled Plasma) etching technology to dry etch the silicon dioxide layer 203. The etching gas used is a chlorine-containing gas (a combination of Cl2 and BCl3). Etching depth control: The etching must penetrate the silicon dioxide layer 203 and expose the interior or sidewalls of the first mask pattern 400, thereby forming a physical channel connecting the outside to the first mask pattern 400.

[0029] S5: Remove the sacrificial layer to form cavity 300. Immerse the sample in the resist remover. The resist remover enters the interior through the channel formed in step S4, dissolving and peeling off the first mask pattern 400. Final structure: After the first mask pattern 400 is removed, a cavity 300 is formed in the original position inside the silicon dioxide layer 203, and the remaining silicon dioxide layer 203 forms the composite pattern layer 200. Since the first mask pattern 400 has a trapezoidal cross-section that is narrow at the top and wide at the bottom, the replicated cavity 300 is also trapezoidal, and the bottom width of the cavity 300 on the surface of the substrate 100 is significantly larger than the opening width at the top. Trapezoidal parameters: top base width 0.1~0.2μm, height 0.25~0.4μm, bottom base width 0.15~0.3μm.

[0030] Example 2: A double-layer patterned substrate with composite sidewalls This embodiment provides a composite material whose bottom depth can be adjusted by using a homogeneous material to raise it. Please refer to... Figure 2 .

[0031] S1: Form the first mask pattern 400 Similar to Example 1, a first photoresist mask pattern 400 with a trapezoidal cross-section is prepared on a sapphire substrate 100.

[0032] S2: Stepped deposition of composite patterned layers 200 This step (S2) is specifically divided into two sub-steps: S21 (Homogeneous layer deposition): A first material layer 201 is deposited on the surface of the substrate 100 and the first mask pattern 400 using a low-temperature ALD (Atomic Layer Deposition) or sputtering process. Key feature: The material of the first material layer 201 is selected from the same material as the substrate 100 (Al2O3 in this example). S22 (Heterogeneous layer deposition): Subsequently, a second material layer 202 is deposited on top of the first material layer 201. Key feature: The material of the second material layer 202 is different from that of the substrate 100 (SiO2 in this example). At this point, the first material layer 201 and the second material layer 202 together constitute the composite patterned layer 200.

[0033] S3-S4: Etching and Exposure A second mask pattern 500 is prepared on the second material layer 202. During dry etching, the etching depth sequentially penetrates the second material layer 202 and the first material layer 201 located on top of the first mask pattern 400 until the first mask pattern 400 is exposed.

[0034] S5: Form a composite sidewall cavity of 300 mm The first mask pattern 400 is removed using a resist remover. Structural features: The resulting cavity 300 has a layered sidewall structure. The lower sidewall is composed of the first material layer 201 (sapphire) deposited on the original mask sidewall in step S21. The upper sidewall is composed of the second material layer 202 (silicon dioxide). By adjusting the height of the first mask pattern 400 and the deposition thickness of the first material layer 201, the height of the "dam" made of sapphire material at the bottom of the cavity 300 can be precisely controlled, thereby optimizing the lateral epitaxial growth pattern in the initial stage of subsequent epitaxial growth.

[0035] Example 3: LED epitaxial wafer Epitaxial growth of GaN-based LED structures was performed on the composite patterned substrate prepared in Example 1 or Example 2. The epitaxial process included: 1. Place it into the MOCVD reaction chamber.

[0036] 2. Growth of nucleation layer and buffer layer. Epitaxial growth begins on the substrate surface at the bottom of the cavity (in Example 2, it also includes the lower sidewall surface composed of the first material layer).

[0037] 3. Since the bottom width of the cavity is greater than the opening width, the epitaxial layer first grows fully laterally inside the cavity, and then grows upward along the sidewall of the cavity until it heals at the top opening.

[0038] 4. Continue growing the N-type GaN layer, the multi-quantum-well light-emitting layer, and the P-type GaN layer. The cavity structure in this embodiment provides ample space for dislocation slip and annihilation, significantly reducing the dislocation density penetrating to the epitaxial surface; at the same time, the trapezoidal cavity serves as a highly efficient light scattering center, greatly improving the light extraction efficiency of the device.

[0039] Performance testing and comparative analysis: In order to verify the performance improvement effect of the composite patterned substrate with trapezoidal window structure proposed in this invention on the device, the applicant prepared an LED epitaxial wafer based on the structure of Example 1 of this invention (experimental group) and an LED epitaxial wafer based on a traditional conical PSS substrate (control group, Standard PSS).

[0040] The two sets of epitaxial wafers were fabricated into LED chips with a size of 15mil × 30mil using the same chip manufacturing process. At room temperature, with an injection current density of 50A / cm², the light output power (LOP) of the system was measured using an integrating sphere. The test results are shown in Table 1.

[0041] Table 1: Brightness Comparison Data Between Embodiments of the Invention and Standard PSS Chips Test sample Chip size Current density Luminance (LOP) Standard PSS (control group) 15mil × 30mil <![CDATA[50A / cm 2 ]]> 282.3 mW This invention's PSS (experimental group) 15mil × 30mil <![CDATA[50A / cm 2 ]]> 285.6 mW As shown in Table 1, under the same chip size and test current, the LED chip using the composite patterned substrate of this invention achieves a brightness of 285.6mW, which is an effective improvement compared to the standard PSS sample (282.3mW).

[0042] This performance improvement is mainly attributed to the following two points: 1. Enhanced light extraction: The unique trapezoidal cavity structure and inclined sidewall design of this invention create a more complex light scattering interface than the traditional solid structure, increasing the probability of total reflection and scattering of photons at the substrate interface, thereby improving the light extraction efficiency.

[0043] 2. Improved crystal quality: The enlarged trapezoidal window at the bottom optimizes the healing process of lateral epitaxial growth, effectively blocking and reducing the dislocation density extending upward from the substrate, and improving internal quantum efficiency.

Claims

1. A composite patterned substrate with a trapezoidal window structure, characterized in that, include: A substrate (100); and a composite pattern layer (200) disposed on the surface of the substrate (100); The composite graphic layer (200) includes a plurality of periodically arranged graphic units; each graphic unit has a cavity (300) that extends through the composite graphic layer (200) and exposes the surface of the substrate (100); the cavity (300) has a trapezoidal cross-sectional shape perpendicular to the surface of the substrate (100), and the bottom width of the cavity (300) on the surface of the substrate (100) is greater than the opening width on the side of the cavity (300) away from the substrate (100).

2. The composite patterned substrate according to claim 1, characterized in that, The sidewall of the cavity (300) is inclined relative to the normal direction of the surface of the substrate (100), and the interior angle between the sidewall and the surface of the substrate (100) is an acute angle.

3. The composite patterned substrate according to claim 1, characterized in that, The composite graphic layer (200) includes a first material layer (201) and a second material layer (202) stacked sequentially along the direction away from the substrate (100); wherein the material of the first material layer (201) is the same as that of the substrate (100), and the material of the second material layer (202) is different from that of the substrate (100); the sidewall of the cavity (300) is composed of a lower sidewall formed by the first material layer (201) and an upper sidewall formed by the second material layer (202).

4. The composite patterned substrate according to claim 1, characterized in that, The substrate (100) is made of a material selected from sapphire, aluminum nitride, and gallium nitride; the composite patterned layer (200) is made of a material selected from silicon dioxide.

5. A method for preparing a composite patterned substrate with a trapezoidal window structure as described in any one of claims 1-4, characterized in that, Includes the following steps: S1: A first mask pattern (400) is formed on the surface of a substrate (100), the first mask pattern (400) having a trapezoidal cross-sectional structure with an upper base width smaller than a lower base width; S2: A cover material layer is deposited on the substrate (100) and the first mask pattern; S3: A second mask pattern (500) is formed on the cover material layer, the second mask pattern defining an opening region; S4: Using the second mask pattern (500) as a mask, the cover material layer is etched to form a channel penetrating the cover material layer and expose at least a portion of the structure of the first mask pattern (400); S5: The first mask pattern (400) is removed through the channel to form a cavity (300) with a bottom width greater than the opening width inside the cover material layer, thereby obtaining the composite patterned substrate.

6. The preparation method according to claim 5, characterized in that, The material of the first mask pattern (400) is photoresist; in step S1, by controlling the exposure focal length or the hot reflow process after development, the photoresist is made to form a trapezoid with an upper base width smaller than the lower base width.

7. The preparation method according to claim 5, characterized in that, Step S2 specifically includes: S21: using a low-temperature deposition process, depositing a first material layer (201) on the substrate (100) and the first mask pattern, wherein the material of the first material layer (201) is the same as that of the substrate (100); S22: depositing a second material layer (202) on the first material layer (201), wherein the material of the second material layer (202) is different from that of the substrate (100); wherein, the etching in step S4 penetrates the second material layer (202) and the first material layer (201) located on top of the first mask pattern (400).

8. The preparation method according to claim 7, characterized in that, The height of the sidewall formed by the first material layer (201) at the bottom of the cavity (300) is controlled by adjusting the height of the first mask pattern and the deposition thickness of the first material layer (201).

9. The preparation method according to claim 5, characterized in that, In step S4, an inductively coupled plasma etching (ICP) process is used to etch to the interior of the first mask pattern or expose the sidewalls of the first mask pattern, thereby forming a channel for the stripping fluid to enter in step S5.

10. A light-emitting diode epitaxial wafer, characterized in that, include: The composite patterned substrate according to any one of claims 1-4; And an epitaxial growth layer grown on the composite patterned substrate; the epitaxial growth layer starts at the surface of the substrate (100) at the bottom of the cavity (300) and grows upward along the cavity (300).

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