CN105226152A - Graphical sapphire substrate and light-emitting diode - Google Patents

Abstract

The invention discloses a patterned sapphire substrate, its manufacturing method and a light-emitting diode using the substrate, wherein the patterned sapphire substrate has opposite first and second surfaces, and the first surface of the substrate Arranged by a plurality of patterns spaced apart from each other, it is characterized in that: the pattern has a top surface, a bottom surface, a plurality of side surfaces, and at least one recessed area sandwiched between the adjacent side surfaces and the top surface, The depth and width of the recessed area gradually decrease from the top to the bottom of the pattern. The recessed area on the patterned surface of the patterned sapphire substrate increases the area for reflecting light, thereby improving the light extraction efficiency of the patterned sapphire substrate.

Description

Patterned sapphire substrate and light emitting diode

technical field

The invention belongs to the field of semiconductors, and in particular relates to a patterned sapphire substrate, a manufacturing method thereof and a light-emitting diode using the patterned sapphire substrate.

Background technique

PSS (Patterned Sapphire Substrate, patterned sapphire substrate) is to use photolithography, etching and other processes on the sapphire substrate to form a sapphire substrate with a patterned surface. On the one hand, the patterned substrate can effectively reduce the dislocation density of the epitaxial structure layer, improve the crystal quality and uniformity of the epitaxial material, and then improve the internal quantum luminous efficiency of the light-emitting diode. On the other hand, because the pattern structure increases the light scattering , changing the optical circuit of the light-emitting diode, thereby improving the probability of light emission.

The width of the bottom of the PSS pattern has a certain influence on the light extraction efficiency of the substrate: the larger the bottom width, the larger the surface area of the pattern, the larger the reflective area, and the higher the light extraction efficiency. At the same time, the spacing of adjacent patterns has a certain influence on the growth of the subsequent epitaxial layer: if the spacing is too small, the internal defects of the formed epitaxial layer will increase, which is not conducive to the light extraction of semiconductor elements; if the spacing is too large, it will cause The number of substrate patterns arranged on the substrate surface of the same size is less, which reduces the light extraction efficiency of the substrate. Therefore, how to obtain a substrate pattern with an appropriate density and a large bottom width is one of the key technologies for improving the light extraction efficiency of semiconductor devices.

Contents of the invention

The invention provides a patterned sapphire substrate and a light-emitting diode using the substrate. By increasing the reflective area of the patterned surface of the patterned substrate, the reflection of light by the substrate can be improved, thereby improving the light extraction efficiency of the light-emitting diode.

The technical solution of the present invention is: a patterned sapphire substrate, which has opposite first surface and second surface, the first surface of the substrate is arranged by a plurality of mutually spaced patterns, and the pattern has a plurality of The sides and at least one recessed region interposed between the adjacent sides, the depth and width of the recessed region gradually decrease from the top to the bottom of the pattern.

Preferably, the pattern further includes a top surface and a bottom surface, and the recessed area is interposed between the adjacent side surfaces and the top surface.

Preferably, the recessed area is formed by connecting two inclined surfaces. More preferably, the projection of the recessed area on the bottom surface of the pattern is triangular.

Preferably, the two inclined surfaces are arranged axially symmetrically.

Preferably, the range of the included angle between the two inclined surfaces is 90° to 150°.

Preferably, the top surface of the pattern is a polygon with protrusions.

Preferably, the sides are composed of a first side and a second side with different inclinations and located at the upper part and the lower part of the pattern respectively.

Preferably, the inclination of the first side is smaller than the inclination of the second side.

Preferably, the second side is arc-shaped.

The width of the bottom of the patterns of the substrate ranges from 4 μm to 20 μm.

The above-mentioned patterned sapphire substrate can be prepared by the following method: S1. Provide a sapphire flat plate substrate with opposite first surface and second surface, and form a mask layer on the first surface, which has periodically arranged mask Film pattern; S2, using wet etching to form a plurality of periodically arranged and spaced patterns on the first surface of the sapphire flat substrate, the patterns have a plurality of sides and at least one is sandwiched between the adjacent sides The depth and width of the depressions gradually decrease from the top to the bottom of the pattern.

Preferably, the mask pattern formed in the step S1 has at least one outwardly extending depression, and the depression corresponds to the crystal lattice direction of the sapphire substrate.

Preferably, the mask pattern formed in the step S1 has a plurality of protrusions extending outward, and the protrusions correspond to the lattice directions of the sapphire substrate.

Preferably, the protrusions and the depressions are arranged alternately, and the number of the protrusions and the depressions is three.

Preferably, an included angle is formed between the adjacent protrusions, and the included angle ranges from 90° to 150°.

Preferably, the distance between the edge and the center of the mask pattern formed in the step S1 is 0.25 μm-10 μm, the height of the mask pattern is 1 μm-10 μm, and the pitch of the mask pattern is 0.1 μm-10 μm.

Preferably, the material of the mask layer formed in the step S1 is photoresist, oxide or metal.

Preferably, in the step S2, wet etching uses a mixture of concentrated sulfuric acid and phosphoric acid to etch the first surface of the sapphire substrate to form a patterned sapphire substrate, the etching time is 500s~3500s, and the etching temperature is 150°C~ 300°C.

The present invention also provides a light-emitting diode, comprising any one of the aforementioned patterned sapphire substrates and a light-emitting epitaxial layer formed on the patterned sapphire substrate.

Preferably, there is an AlN layer formed by PVD on the surface of the patterned sapphire substrate, and the light-emitting epitaxial layer is formed on the AlN layer.

Preferably, the thickness of the AlN layer is 10 angstroms to 200 angstroms.

Another aspect of the present invention provides a method for manufacturing the aforementioned light-emitting diode, including the following steps: S1, providing a sapphire flat substrate with opposite first and second surfaces, forming a mask layer on the first surface, It has a periodically arranged mask pattern; S2, using wet etching to form a plurality of periodically arranged mutually spaced patterns on the first surface of the sapphire flat substrate, the patterns have a plurality of side surfaces and at least one clip A recessed area placed between the adjacent side faces, the depth and width of the recessed area gradually decrease from the top of the pattern to the bottom; S3, forming an AlN on the surface of the patterned sapphire substrate by PVD method layer; S4, epitaxially growing a light-emitting epitaxial layer on the AlN layer, which at least includes an N-type semiconductor, a light-emitting layer and a P-type semiconductor layer.

Preferably, the pattern in the step S2 further includes a top surface and a bottom surface, and the recessed area is interposed between the adjacent side surfaces and the top surface.

Preferably, the mask pattern formed in the step S1 has at least one outwardly extending depression, and the depression corresponds to the crystal lattice direction of the sapphire substrate.

Preferably, the mask pattern formed in the step S1 also has a plurality of outwardly extending protrusions corresponding to the lattice directions of the sapphire substrate.

Preferably, the thickness of the AlN layer in the step S3 is 10 angstroms to 200 angstroms.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the description, and are used together with the embodiments of the present invention to explain the present invention, and do not constitute a limitation to the present invention. In addition, the drawing data are descriptive summaries and are not drawn to scale.

Figure 1 is a schematic top view of the sapphire lattice structure.

2 to 3 are SEM side views of patterns of patterned sapphire substrates in the prior art.

4 to 6 show SEM images of a patterned sapphire substrate implemented according to the present invention. 4 is an overall perspective view of a patterned sapphire substrate, FIG. 5 is a schematic side view of a single pattern of a patterned sapphire substrate, and FIG. 6 is a schematic top view of a single pattern of a patterned sapphire substrate.

FIG. 7 is a schematic flow chart for fabricating a patterned sapphire substrate according to the present invention.

FIG. 8 is a pattern of a mask layer for fabricating a patterned sapphire substrate according to the present invention.

FIG. 9 is an enlarged view of the pattern of the mask layer shown in FIG. 8 .

FIG. 10 is a schematic flow chart for manufacturing a light-emitting diode according to the present invention.

Fig. 11 is a schematic structural diagram of a light emitting diode implemented according to the present invention.

The symbols in the figure indicate: 10. Patterned sapphire substrate; 20. Patterned sapphire substrate; 21. Pattern of the substrate; 210. Top surface; 2101. Protruding structure on the top surface; 211. Bottom surface; 212. Side; 2121. First side; 2122. Second side; 213. Depression; 2130. Inclined surface; 30. Mask pattern; raised.

detailed description

The specific implementation of the present invention will be described in detail below in conjunction with the embodiments and the accompanying drawings.

PSS is generally prepared by dry etching or wet etching. Dry etching mainly uses plasma (ICP) to bombard the surface of the substrate to prepare patterns. It has the characteristics of isotropy and the shape of the prepared pattern is controllable, but it is prone to physical damage, and the surface reflectivity is poor, which is not conducive to Further improve the light-emitting efficiency of the LED. Wet etching mainly uses chemical solution to corrode the substrate to prepare patterns. It has the advantages of low equipment cost, simple operation process, and high reflectivity of the substrate surface, and is suitable for large-scale industrial production.

FIG. 1 shows a schematic top view of a sapphire lattice structure, specifically a hexagonal lattice structure, where A-plane, C-plane and R-plane are commonly used cutting planes. Due to the small lattice constant mismatch between the C-plane of sapphire and the III-V and II-VI deposited films, the C-plane is usually used for epitaxial growth. When wet etching the sapphire substrate, due to the characteristics of the sapphire lattice structure, the etching solution can only etch along the direction of the sapphire lattice, usually forming a triangular pyramid pattern. Figures 2 to 3 show a patterned sapphire substrate 10 obtained by wet etching in the prior art. The process is generally to form a cylindrical mask pattern on the C surface of the sapphire substrate, and then perform wet etching . In the aforementioned etching process, etching solution, etching time, and etching temperature are three main parameters. When the etching solution and etching temperature are constant, the longer the etching time, the wider the bottom width of the substrate pattern obtained. Large, but the spacing of adjacent substrate patterns will be reduced.

The following embodiment discloses a patterned sapphire substrate, which increases the width of the bottom of the pattern and increases the number of reflection surfaces for reflecting light on the surface of the pattern while keeping the spacing of the substrate pattern unchanged.

Referring to FIGS. 4-6 , a patterned sapphire substrate 20 has opposite first and second surfaces, wherein the first surface is formed by a series of mutually spaced patterns 21 . The height of the pattern 21 is 0.8 μm-3 μm, the pitch of the periodic arrangement is 0.1 μm-10 μm, and three adjacent patterns 21 are arranged in a triangle. The pattern 21 has a top surface 210, a bottom surface 211, a plurality of side surfaces 212, and a recessed region 213 sandwiched between adjacent side surfaces 212 and the top surface 210. The depth and width of the recessed region 213 gradually decrease from the top of the pattern 21 to the bottom. .

In this embodiment, the pattern top surface 210 is a polygonal plane with three protruding structures 2101 , parallel to the first surface of the substrate 20 , and all of them are the C-plane of the substrate. Specifically, the top surface 210 of the pattern corresponds to the side surface 212 to form a raised structure 2101 , and the place corresponding to the depressed area 213 forms a depressed structure 2102 between adjacent protrusions. The side 212 is composed of a first side 2121 and a second side 2122 with different inclinations located on the upper and lower parts of the pattern 21 respectively. The bottom surface 211 of the pattern 21 has three corners α, and the connecting line of the corners α is arc-shaped, so that the three second side surfaces 2122 are arc-shaped, the corner α ranges from 105° to 115°, and the bottom width d ranges from 4 μm to 20 μm. The depressed area 213 is formed by connecting two inclined surfaces 2130. More preferably, its projection on the bottom surface 211 of the pattern is triangular, and the two inclined surfaces 2130 are arranged axisymmetrically. In the embodiment, the size of the two inclined surfaces 2130 can also be set as required. The recessed areas 213 are mainly used to increase the area of the surface of the pattern 21 to reflect light, and the number of them can be designed to be 1-3 as required. In this embodiment, 3 recessed areas 213 are provided.

Compared with the pattern 11 of the existing patterned sapphire substrate 10 shown in FIG. 3 , in this embodiment, the pattern 21 of the substrate 20 increases the area of reflected light by setting three recessed regions 213 on its surface, In addition, the rotation angle α of the bottom surface 211 of the pattern is increased by about 10° compared with the corresponding rotation angle of the substrate pattern 11 in the prior art, so that the width d of the bottom of the pattern 21 increases accordingly, so as to increase the area of the surface of the pattern 21 to reflect light. Therefore, the effect of improving the light extraction efficiency of the patterned sapphire substrate is achieved.

The method for fabricating the above-mentioned patterned sapphire substrate will be briefly described below in conjunction with accompanying drawings 7-9.

Referring to Fig. 7, the method for making a patterned sapphire substrate specifically includes the following steps: S1, providing a sapphire flat substrate, having opposite first surfaces and second surfaces, forming a mask layer on the first surface, the The mask layer has a mask pattern arranged periodically, wherein the first surface is the C surface of the sapphire substrate, and the mask layer is arranged on the C surface of the sapphire substrate; S2, using wet etching to form a plurality of The periodically spaced patterns 21 are shown in FIG. 4 , and its structure refers to the detailed description above. Wherein, the wet etching adopts the mixed solution of concentrated sulfuric acid and phosphoric acid to etch the first surface of the sapphire substrate to form the patterned sapphire substrate 20, the volume ratio of concentrated sulfuric acid and phosphoric acid is 1:1~10:1, and the etching time is 500s~3500s, etching temperature is 150℃~300℃.

In the above method, the mask pattern formed in step S1 is the key to forming the pattern shown in FIG. 4 . Referring to FIGS. 8 and 9 , the mask pattern 30 has at least one outwardly extending recess 31 corresponding to the crystal lattice directions ( a1 , a2 , a3 ) of the sapphire substrate. Preferably, the mask pattern 30 also has a plurality of outwardly extending protrusions 32 corresponding to the lattice directions of the sapphire substrate. In this embodiment, the depressions 31 and protrusions 32 are arranged alternately, which is consistent with the number of crystal lattice directions of sapphire, and the number of protrusions 31 and depressions 32 is 3. The number can also be set to 1 or 2.

The number of the recessed regions 213 of the sapphire substrate surface pattern 21 shown in FIG. The angle θ between adjacent protrusions 32 corresponds to the size. The angle θ between adjacent protrusions 32 can be the same or different, and the range is 90°~150°. The distance between the edge and the center of the mask pattern 30 ranges from 0.25 μm to 10 μm, specifically, the distance R1 between the edge and the center of the depression 31 ranges from 0.25 μm to 2.5 μm, and the distance R2 between the edge and the center of the protrusion 32 ranges from 0.75 μm to 10 μm The height of the mask pattern 30 ranges from 1 μm to 10 μm, the distance between adjacent mask patterns 30 ranges from 0.5 μm to 10 μm, and three adjacent mask patterns 30 are arranged in a triangle; the material of the mask layer is photoresist , oxides or metals.

In this embodiment, the pattern 30 of the mask layer is roughly in the shape of a "windmill", which has at least one depression 31 extending outward and corresponding to the crystal lattice direction of the sapphire substrate, and a plurality of depressions 31 extending outward and corresponding to the sapphire substrate. The protrusions 32 between the crystal lattice directions of the bottom, so, in the wet etching process of step S2, the etching rate of the etching chemical etching solution is faster along the recess 31, and the etching rate is faster along the protrusion 32. Slower, so that the pattern 21 of the patterned sapphire substrate 20 formed after the etching has three light-reflecting recessed regions 213, and the bottom width d of the pattern 21 increases to improve the reflective area of the pattern 21 and improve the patterned sapphire pattern. The light extraction efficiency of the substrate 20.

Fig. 10 has shown a kind of flow chart of making light-emitting diode according to the present invention, comprises step S1～S4, wherein step S1～S2 forms patterned sapphire substrate, and step S3 is to adopt PVD method on the patterned sapphire substrate 20 Forming an AlN layer, step S4 is to epitaxially grow a light-emitting epitaxial layer on the AlN layer. Each step is briefly described below, and steps S1 to S2 can be referred to the foregoing description.

S3. Form an AlN layer on the surface of the patterned sapphire substrate 20 formed by the method in steps S1-S2 by PVD method; the thickness of this layer is 10-200 angstroms.

S4. Using epitaxial growth, sequentially grow a buffer layer, an N-type semiconductor layer, a light-emitting layer, and a P-type semiconductor layer, wherein the buffer layer is a material based on group III nitride, preferably gallium nitride, and aluminum nitride material can also be used Or aluminum gallium nitride material; the N-type semiconductor layer is preferably gallium nitride, and aluminum gallium nitride material can also be used, and the silicon doping concentration is preferably 1×10 ¹⁹ cm ^-3 ; the light emitting layer preferably has at least one quantum well structure, Preferably, it has 5-50 pairs of quantum wells; the P-layer semiconductor layer is preferably gallium nitride, doped with magnesium, and the doping concentration is 1×10 ¹⁹ ~5×10 ²¹ cm ^-3 , preferably P-type The semiconductor layer is a multilayer structure, including a P-type electron blocking layer, a P-type conductive layer and a P-type contact layer, wherein the P-type electron blocking layer is adjacent to the light-emitting layer, and is used to prevent electrons from entering the P-type layer and recombining holes. AlGaN material, the thickness can be 50nm~200nm.

Fig. 11 shows the light-emitting diode formed by the manufacturing method shown in Fig. 10, and its structure includes: patterned sapphire substrate 20, AlN layer 40, buffer layer 50, N-type semiconductor layer 60, light-emitting layer 70 and P-type semiconductor layer 80 . In this light-emitting diode, the surface of each pattern 21 of the patterned sapphire substrate 20 adopted is provided with three recessed areas 213, and the width of the bottom thereof is increased to increase the area of reflected light on the surface of the pattern 21, thereby improving the patterned sapphire The light extraction efficiency of the substrate 20.

It should be understood that the above specific implementation is a preferred embodiment of the present invention, the scope of the present invention is not limited to this embodiment, and any changes made according to the present invention are within the protection scope of the present invention.

Claims (12)

1. A patterned sapphire substrate, having opposite first surfaces and second surfaces, the first surface of the substrate is arranged by a plurality of mutually spaced patterns, and it is characterized in that: the patterns have a plurality of sides and at least A recessed area interposed between the adjacent sides, the depth and width of the recessed area gradually decrease from the top to the bottom of the pattern. 2 . The patterned sapphire substrate according to claim 1 , wherein the pattern further comprises a top surface and a bottom surface, and the concave region is interposed between the adjacent side surfaces and the top surface. 3. The patterned sapphire substrate according to claim 2, characterized in that: the recessed area is formed by connecting two inclined surfaces. 4. The patterned sapphire substrate according to claim 3, characterized in that: the projection of the recessed area on the bottom surface of the pattern is triangular. 5 . The patterned sapphire substrate according to claim 3 , wherein the two inclined surfaces are symmetrically arranged. 6 . 6. The patterned sapphire substrate according to claim 3, characterized in that: the angle between the two inclined surfaces ranges from 90° to 150°. 7 . The patterned sapphire substrate according to claim 1 , wherein the side surfaces are composed of a first side surface and a second side surface with different inclinations and respectively located above and below the pattern. 8 . 8. The patterned sapphire substrate according to claim 7, wherein the inclination of the first side is smaller than the inclination of the second side. 9. The patterned sapphire substrate according to claim 7, wherein the second side is arc-shaped. 10. The patterned sapphire substrate according to claim 1, characterized in that: the width of the bottom of the pattern of the substrate is in the range of 4 μm to 20 μm. 11. A light-emitting diode, comprising a patterned sapphire substrate and a light-emitting epitaxial layer formed on the patterned sapphire substrate, characterized in that: the patterned sapphire substrate adopts the pattern according to any one of claims 1 to 10 sapphire substrate. 12. The light-emitting diode according to claim 11, characterized in that: the surface of the patterned sapphire substrate has an AlN layer formed by PVD method, and the light-emitting epitaxial layer is formed on the AlN layer .