A patterned sapphire substrate

Abstract

The utility model discloses a kind of patterned sapphire substrates, including sapphire substrate layer, and a plurality of periodic arrangement's convex unit being arranged on the surface of the sapphire substrate layer, the convex unit has bottom and side surface;The section of convex unit is triangle or trapezoid, with left side wall and right side wall, the angle of left side wall and bottom is first angle right side wall and bottom angle is second angle, right X axis positive direction is defined with the origin point, left X axis negative direction is defined with the origin point, then along X axis positive direction, first angle linearly reduces, while second angle linearly increases;With the center of substrate layer surface as origin point, convex unit is symmetrically distributed on the left and right sides of origin point.Periodic arrangement is designed by designing conical convex of different inclination angle in substrate, improve the growth quality of gallium nitride epitaxial layer, improve light extraction efficiency, to further enhance the performance of semiconductor device.

Description

Technical Field

[0001] This utility model relates to the field of semiconductor technology, specifically to a patterned sapphire substrate. Background Technology

[0002] In the fabrication of semiconductor devices such as gallium nitride (GaN)-based light-emitting diodes (LEDs), sapphire substrates are widely used due to their excellent physical and chemical properties. However, because sapphire substrates are heterojunctions of gallium nitride, there is a significant lattice mismatch and thermal expansion coefficient mismatch between them and gallium nitride, resulting in a high dislocation density in the epitaxially grown gallium nitride thin film, which limits the internal quantum efficiency of LEDs. On the other hand, since the refractive index of gallium nitride is greater than that of air, the critical angle for total internal reflection of light emanating from gallium nitride is only 23°, resulting in very low light extraction efficiency. Patterned sapphire substrates are an effective means to improve this problem. By constructing specific patterned structures on the surface of the sapphire substrate, the lateral growth of the gallium nitride epitaxial layer can be promoted, the dislocation density can be reduced, and the propagation path of light at the interface between the substrate and the epitaxial layer can be changed, thereby improving the light extraction efficiency.

[0003] Traditional patterned sapphire substrates typically feature relatively simple pattern structures. For example, common conical patterns are usually vertically aligned, which limits the diversity of control over the epitaxial layer growth direction and light propagation direction, making it difficult to fully meet the demands for further performance enhancements in devices. Therefore, developing a sapphire substrate with an innovative pattern structure is of great significance. Utility Model Content

[0004] The purpose of this invention is to provide a patterned sapphire substrate, which improves the growth quality of gallium nitride epitaxial layers and increases light extraction efficiency by designing conical protrusions with different tilt angles and arranging them periodically, thereby enhancing the performance of semiconductor devices.

[0005] A patterned sapphire substrate includes a sapphire substrate layer and a plurality of periodically arranged protrusions on the surface of the sapphire substrate layer. Each protrusion has a bottom and a side. The cross-section of each protrusion is triangular or trapezoidal, with a left side wall and a right side wall. The angle between the left side wall and the bottom is a first angle, and the angle between the right side wall and the bottom is a second angle. Taking the center of the substrate surface as the origin, and defining the positive X-axis direction to the right of the origin and the negative X-axis direction to the left, the first angle decreases linearly along the positive X-axis, while the second angle increases linearly. With the origin as the center of symmetry, the protrusions along the negative X-axis are symmetrically distributed with respect to the protrusions along the positive X-axis.

[0006] In some preferred embodiments, the first included angle of the protruding unit along the positive X-axis ranges from 30° to 60°.

[0007] In some preferred embodiments, the protruding unit in the positive X-axis direction has a first included angle smaller than a second included angle.

[0008] In some preferred embodiments, the protruding units are of equal height.

[0009] In some preferred embodiments, the height of the protruding unit ranges from 1.8 to 1.9 μm, the bottom diameter ranges from 2.8 to 2.9 μm, and the period is 3 μm. The spacing between adjacent protruding units is 0.1 to 0.2 μm.

[0010] The tilt direction of the protrusion unit is along the crystal axis of the sapphire substrate or at a certain angle to the crystal axis. The tilt direction refers to the degree of deviation of the line connecting the midpoint of the top surface and the midpoint of the bottom surface on the cross-section of the protrusion unit from the X-axis; when the cross-section is triangular, it is the line connecting the midpoint of the vertex and the midpoint of the bottom surface. The tilt direction can be set according to actual needs; for example, it can be tilted along a certain crystal axis of the sapphire substrate body, or tilted at a certain angle to the crystal axis, to adapt to different semiconductor device manufacturing processes and performance requirements.

[0011] In some preferred embodiments, the protruding units are divided into several groups, with identical protruding units within the same group and equal first included angles. Adjacent groups have different first included angles. For example, in the first group closest to the origin, the included angle is α1, while the angle of the adjacent group is β1, and α1 ≠ β1. This setting of different tilt angles α1 and β1 can guide the GaN epitaxial layer to grow laterally in multiple directions, increasing the diversity of growth directions and helping to further reduce dislocation density.

[0012] Beneficial effects: The raised unit is an inclined conical or trapezoidal structure, and the setting of different inclination angles changes the reflection and refraction path of light at the interface between the substrate and the epitaxial layer, increases the scattering of light in the substrate, and increases the probability of light escaping from inside the active layer, thereby effectively improving the light extraction efficiency and enhancing the luminous brightness of semiconductor devices.

[0013] On the other hand, it enhances process adaptability: by flexibly adjusting the tilt angle, size and tilt direction of the tilted protrusion unit, it can better adapt to different semiconductor device manufacturing processes, providing more controllable means to optimize device performance. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the patterned sapphire substrate of this utility model, showing the periodic arrangement of protrusions on the surface of the sapphire substrate. The difference in tilt angle of the tilted protrusions in different periods can be clearly seen.

[0015] Figure 2This is a cross-sectional schematic diagram of the raised unit along the positive X-axis of the patterned sapphire substrate of this utility model, showing the first included angle, the second included angle, and the height H of the raised unit.

[0016] Figure 3 This is another structural schematic diagram of the patterned sapphire substrate of this utility model, where the cross-section of the protruding unit is trapezoidal.

[0017] Figure 4 yes Figure 3 A cross-sectional view of one of the protruding units along the positive X-axis.

[0018] Reference numerals: 10, raised unit; 20, substrate layer; 1, bottom; 2, left side wall; 3, right side wall; 4, first included angle; 5, second included angle. Detailed Implementation

[0019] To better understand the technical solution of this utility model, the embodiments of this utility model will be described in detail below with reference to the accompanying drawings.

[0020] It should be understood that the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0021] Although some asymmetric structural designs exist in existing technologies, they still have shortcomings in terms of controlling the gradual change of the protrusion angle and realizing the functions, making it difficult to accurately regulate the physical properties.

[0022] Figure 1 The diagram illustrates a patterned sapphire substrate. The overall structure includes a sapphire substrate layer 20. Multiple periodically arranged protrusions 10 are disposed on the surface of the sapphire substrate layer 20. Each protrusion 10 is an inclined conical or trapezoidal structure, having a bottom 1 and side surfaces. The height of each protrusion (represented by H in the diagram) is equal. The cross-section of each protrusion 10 is triangular or trapezoidal, having a left side wall 2 and a right side wall 3. The angle between the left side wall 2 and the bottom 1 is a first angle 4, and the angle between the right side wall 3 and the bottom 1 is a second angle 5. Figure 2 As shown. Taking the center of the substrate 20 surface as the origin, defining the positive X-axis direction to the right of the origin and the negative X-axis direction to the left, then along the positive X-axis direction, the first included angle 4 of the protrusion unit 10 decreases linearly, while the second included angle 5 increases linearly. Simultaneously, with the origin as the center of symmetry, the protrusion units 10 in the positive X-axis direction and the protrusion units 10 in the negative X-axis direction are symmetrically distributed. That is, the protrusion units 10 in the negative X-axis direction are mirror-symmetrical to the protrusion units 10 in the positive X-axis direction. Furthermore, the first included angle 4 of the protrusion unit 10 in the positive X-axis direction ranges from 30° to 60°.

[0023] The tilt direction of the protrusion unit 10 can be set according to actual needs. For example, it can be tilted along a certain crystal axis of the sapphire substrate, or tilted at a certain angle to the crystal axis, to adapt to different semiconductor device manufacturing processes and performance requirements. The tilt direction refers to the degree of deviation between the line connecting the midpoint of the top surface and the midpoint of the bottom surface 1 on the cross-section of the protrusion unit 10 and the X-axis. When the cross-section is triangular, it is the line connecting the vertex and the midpoint of the bottom surface 1. Figure 2 The dashed line indicates the tilt direction of the raised unit 10.

[0024] The height of the raised unit 10 is 1.8–1.9 μm, the bottom diameter is 2.8–2.9 μm, and the period is 3 μm. The spacing between adjacent raised units 10 is 0.1–0.2 μm.

[0025] In some preferred embodiments, the protruding units 10 are divided into several groups, with identical protruding units 10 within the same group. The protruding units 10 in adjacent groups have different tilt directions, i.e., different first included angles 4 and 5. For example, in the first group closest to the origin, the first included angle 4 is α1, while the angle in the adjacent group is β1, and α1 ≠ β1. This setting of different tilt angles α1 and β1 can guide the GaN epitaxial layer to grow laterally in multiple directions, increasing the diversity of growth directions and further reducing dislocation density.

[0026] In some preferred embodiments, the cross-section of the protruding unit 10 is trapezoidal, such as... Figure 3 and Figure 4 As shown, Figure 4 yes Figure 3 A cross-sectional view of one of the protruding units 10 along the positive X-axis. Along the positive X-axis, the first included angle 4 of the protruding unit 10 decreases linearly, while the second included angle 5 increases linearly.

[0027] The patterned sapphire substrate described above can be fabricated using the following method: Select a sapphire substrate of suitable size, clean its surface to remove impurities and contaminants. Then, uniformly coat a layer of photoresist onto the surface of the sapphire substrate, with the thickness of the photoresist adjusted according to the requirements of subsequent photolithography processes.

[0028] Using photolithography, photoresist is exposed and developed according to the designed pattern of tilted protrusion units 10 and their periodic arrangement at different tilt angles. During the photolithography process, the accuracy of the photolithographic pattern is ensured by precisely controlling parameters of the photolithography equipment, such as exposure time, exposure dose, and alignment accuracy between the photomask and the substrate. The tilt angle (i.e., the size of the first included angle 4 or the second included angle 5) can be controlled by adjusting parameters such as the design of the photomask and the rotation angle of the substrate during the photolithography process. For example, using a programmable photolithography device, the substrate can be rotated according to a preset tilt angle value during different photolithography cycles, thereby forming tilted protrusion patterns with different tilt angles on the photoresist.

[0029] Finally, dry etching techniques such as inductively coupled plasma (ICP) etching are used, with the photoresist pattern serving as a mask, to etch the sapphire substrate. During the etching process, parameters such as the type and flow rate of the etching gas, etching power, and etching time are precisely controlled to ensure the dimensional accuracy and surface quality of the etched tilted conical pattern units. Electron beam lithography or nanoimprint lithography can also be used to achieve patterned sapphire substrates.

[0030] The above description is merely a preferred embodiment of the present utility model and does not constitute any limitation on the technical scope of the present utility model. Therefore, any minor modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present utility model shall still fall within the protection scope of the present utility model.

Claims

1. A patterned sapphire substrate, characterized in that, The system includes a sapphire substrate and a plurality of periodically arranged protruding units disposed on the surface of the sapphire substrate. Each protruding unit has a bottom and a side. The cross-section of each protruding unit is triangular or trapezoidal, with a left side wall and a right side wall. The angle between the left side wall and the bottom is a first angle, and the angle between the right side wall and the bottom is a second angle. With the center of the substrate surface as the origin, the positive X-axis direction is defined to the right of the origin, and the negative X-axis direction is defined to the left of the origin. Along the positive X-axis direction, the first angle decreases linearly, while the second angle increases linearly. With the center of the substrate surface as the center of symmetry, the protruding units along the negative X-axis direction are symmetrically distributed with the protruding units along the positive X-axis direction.

2. The patterned sapphire substrate according to claim 1, characterized in that, The protruding unit along the positive X-axis has a first included angle ranging from 30° to 60°.

3. The patterned sapphire substrate according to claim 1, characterized in that, The protruding unit along the positive X-axis has a first included angle smaller than the second included angle.

4. The patterned sapphire substrate according to claim 1, characterized in that, The heights of the protruding units are equal.

5. The patterned sapphire substrate according to claim 1, characterized in that, The height of the protruding unit ranges from 1.8 to 1.9 μm, the bottom diameter ranges from 2.8 to 2.9 μm, and the period is 3 μm.

6. The patterned sapphire substrate according to claim 1, characterized in that, The spacing between adjacent protrusions is 0.1 to 0.2 μm.

7. The patterned sapphire substrate according to claim 1, characterized in that, The tilt direction of the protrusion unit is along the crystal axis of the sapphire substrate or at a certain angle to the crystal axis.

8. The patterned sapphire substrate according to claim 1, characterized in that, The protruding units are divided into several groups, and the first included angle is the same within the same group.

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