CN104465926B - 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 each of the first protrusions There is no C plane (ie (0001) plane) in the connection area between them. There may be no C-plane on the growth surface of the patterned sapphire substrate, thereby reducing the threading dislocation density of the gallium nitride epitaxial material on the sapphire substrate.

Description

Patterned sapphire substrate and light emitting diode

technical field

The invention relates to a patterned sapphire substrate, its manufacturing method and a light-emitting diode using the patterned sapphire substrate.

Background technique

PSS (Patterned Sapphire Substrate) is a sapphire substrate with a patterned surface formed on a sapphire substrate by photolithography, etching and other processes. 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. Scattering changes the optical circuit of the light-emitting diode, thereby increasing the probability of light emission.

In the existing patterned substrates, there is generally a large-area C-plane (that is, the (0001) plane of sapphire). Threading dislocations formed on the C-plane easily extend to the quantum wells of the LED, resulting in non-radiative recombination. Chinese patent document CN102244170B discloses a quasi-photonic crystal pattern sapphire substrate, which attempts to reduce the proportion of the exposed C surface in the sapphire substrate pattern structure in the entire sapphire substrate area, but because its pattern structure consists of a series of photonic crystals structure, there must be a gap 205 between each photonic crystal structure, that is, there is a C-plane.

Contents of the invention

The present invention proposes a patterned sapphire substrate, its manufacturing method and a light-emitting diode using the patterned sapphire substrate, wherein the growth surface of the patterned sapphire substrate may not have a C-plane, thereby reducing the sapphire substrate. Threading dislocation density of GaN epitaxial materials.

According to a first aspect of the present invention, a patterned sapphire substrate has opposite first and second surfaces, wherein the first surface has a series of regularly arranged first protrusions with a first size d1, each of the first protrusions There is no C-plane (that is, (0001) plane) in the connection area between the protrusions.

In some specific embodiments, a triangle is formed between the three adjacent first protrusions, and each triangle has a second protrusion with a second size d2 inside, where d1>d2, and the first The protruding part and the second protruding part are connected directly or with a curved surface so that there is no C-plane in the connecting area.

Preferably, the first protrusion has no C-face.

Preferably, the second protrusion has no C-face.

Preferably, the first surface has no C-plane at all.

Preferably, the four adjacent first protrusions form a rhombus, wherein there are two second protrusions between the long diagonals, and a third dimension d3 between the short diagonals The third protrusion, where d3<d2. Preferably, there is a depression between the two second protrusions, the lowest part of which is the highest point of the third protrusion.

Preferably, the second protrusion is a cone mainly composed of three or more inclined surfaces, and each main inclined surface corresponds to the three first protrusions. Preferably, the included angle between the inclined surface of the second protrusion and the C-plane of the sapphire substrate is 10°-40°. In some embodiments, there is a V-shaped groove between the two nearest first protrusions, which is located between two adjacent second protrusions, and the two sides of the V-shaped groove are respectively It is formed by the inclined surfaces of the two second protrusions.

Preferably, the ratio of the height h1 of the first protrusion to the height h2 of the second protrusion is 2-50.

Preferably, the first protrusion accounts for 50%-90% of the total area of the first surface.

Preferably, the top of the first protrusion is a cone and its projection on the C plane is circular or polygonal.

According to a second aspect of the present invention, a method for fabricating a patterned sapphire substrate includes the steps of: 1) providing a sapphire substrate having opposite first and second surfaces, and forming a patterned mask on the first surface layer; 2) using dry etching to form a series of protruding structures on the first surface, and the connecting areas between the protruding structures are etched into small convex surfaces; 3) performing wet etching on the first surface of the sapphire substrate , so as to form a patterned surface, the surface has a series of regularly arranged first protrusions of the first size d1, and there is no C-plane (ie (0001) plane) in the connection area between each of the first protrusions.

Preferably, the patterned mask layer formed in step 1) is composed of a series of columnar photoresists, oxides or metals.

Preferably, the diameter of the pattern formed in the step 1) is 0.5um-6um, and the gap between each pattern is 0.5um-6um.

Preferably, the small convex surface formed in step 2) connecting each protruding structure is a curved surface.

Preferably, the height of the small convex surface connecting each protruding structure formed in the step 2) is 0.05um~0.5um.

Preferably, in the step 3), the first surface of the sapphire substrate is etched with a mixture of sulfuric acid and phosphoric acid to form the patterned surface.

According to a third aspect of the present invention, a light-emitting diode includes any one of the aforementioned patterned sapphire substrates and a light-emitting epitaxial stack formed on the patterned sapphire substrate.

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

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

According to a fourth aspect of the present invention, a method for manufacturing a light-emitting diode includes the steps of: 1) providing a sapphire substrate having opposite first and second surfaces, and forming a patterned mask on the first surface; 2) A series of protruding structures are formed on the first surface by dry etching, and the connection areas between the protruding structures are etched into small convex surfaces; 3) Wet etching is performed on the first surface of the sapphire substrate to form a pattern The surface has a series of regularly arranged first protrusions of the first size d1, and the first protrusions are connected by a curved surface so that the connecting area has no C plane (that is, the (0001) plane) ; 4) forming an AlN layer on the patterned surface by PVD; 5) epitaxially growing a light-emitting epitaxial stack on the AlN layer, which at least includes an n-type semiconductor layer, a light-emitting layer and a p-type semiconductor layer.

Preferably, the small convex surface formed in step 2) connecting each protruding structure is a curved surface.

Preferably, in the step 3), the first surface of the sapphire substrate is etched with a mixture of sulfuric acid and phosphoric acid to form the patterned surface.

The patterned sapphire substrate of the present invention can have no c-plane in its surface pattern structure, which can effectively eliminate the threading dislocations formed on the c-plane and improve the crystal quality of the epitaxial structure. The c surface is conducive to more light emitting from the light-emitting diode, which greatly improves the light extraction rate of the LED.

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.

FIG. 1 is a SEM image of a patterned sapphire substrate implemented according to the present invention.

Fig. 2 is a top view of a patterned sapphire substrate implemented according to the present invention.

Fig. 3 is a cross-sectional view taken along line A-A in Fig. 2 .

Fig. 4 is a cross-sectional view taken along line B-B in Fig. 2 .

FIG. 5 shows a variation of the structure shown in FIG. 4 .

FIG. 6 is a flow chart of fabricating a patterned sapphire substrate according to the present invention.

7 to 8 are the fabrication process of a patterned sapphire substrate according to the present invention.

FIG. 9 is a flow chart of manufacturing a light emitting diode according to the present invention.

Fig. 10 is a structural diagram of a light emitting diode implemented according to the present invention.

The symbols in the figure are as follows:

100: sapphire substrate; 110: AlN layer; 120: buffer layer; 130: n-type semiconductor layer; 140: light-emitting layer; 150: p-type semiconductor layer; 200: patterned mask layer; 210: protrusion structure; 220: small convex surface; P ₁ : the first protrusion; P ₂ : the second protrusion; P ₃ : the third protrusion; H ₁ : the first depression; H ₂ : the second depression; S ₁ ~ S ₃ : the third The inclined surface of the two protrusions.

detailed description

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

Accompanying drawing 1～4 has shown a preferred embodiment of the present invention, and wherein Fig. 3 is the sectional view cut along line A-A in Fig. 2, and Fig. 4 is the sectional view cut along line B-B in Fig. 2.

Please refer to accompanying drawings 1 and 2, a patterned sapphire substrate, the upper surface of which is composed of a pattern structure, and there is no C-plane at all. The pattern structure includes a series of regularly arranged first protrusions P ₁ of the first size d1, wherein three adjacent first protrusions P ₁ -1 _, P ₁ -2 and P ₁ -4 form a triangle or Similar to a triangle, it has a second protrusion P ₂ with a second size d2 inside, and four adjacent first protrusions P ₁ -1 _, P ₁ -2, P ₁ -3 and P ₁ -4 form a A rhombus with a second protrusion between the long diagonals and a third protrusion P3 of a _third dimension d3 between the short diagonals, where d3<d2<d1.

Please refer to Figures 2 and 3, the projection of the first protrusion P ₁ on the C-plane of the sapphire substrate is circular or similar, accounting for 50% to 90% of the total area of the upper surface of the sapphire, and its diameter d1 is preferably 0.5 to 90%. 6um, and the height h1 is preferably 0.5um~2um, which is selected according to the actual design. The _first protrusion P1 is divided into a top and a bottom, wherein the top is a cone formed by a plurality of inclined surfaces, the bottom has a closed inclined surface, and the angle between the inclined surface of the top and the c-plane is 20-40°, The angle between the inclined surface of the bottom and the c-plane is 40-70°.

The second protrusion P ₂ is composed of three or more inclined surfaces S ₁ ~ S ₃ , each main inclined surface is just opposite to one first protrusion P ₁ , and the included angle between the inclined surface and the c-plane is 10° ~40°. The diameter d2 of the second protrusion P ₂ is generally smaller than or equal to the diameter d1 of the first protrusion P ₁ , which may be 0.1 um~3 um, and the height h2 may be 0.1 um~1.5 um. Please refer to FIGS. 1 and 3 , there is a small depression H _{2 between two adjacent second protrusions P 2 .}

Referring to FIGS. 1 and 4 , the highest point of the _third protrusion P3 located between adjacent _first protrusions P1 is the lowest point of the small depression _H2 .

In this embodiment, a series of regularly arranged first protrusions are designed on the upper surface of the patterned sapphire substrate, whose projection on the C plane is circular or polygonal, with a cone at the top, and three adjacent third protrusions A protrusion is formed into a triangle, and a second protrusion is designed inside it. The second protrusion is designed as a cone mainly composed of three or more inclined surfaces, and the main three inclined surfaces correspond to the three first protrusions respectively. part, thereby ensuring that there is no c-plane on the upper surface of the sapphire.

Figure 5 shows a variation of the above embodiment, in this embodiment, a v-shaped groove is formed between two adjacent _first protrusions P1, that is, there is no third protrusion P3 shown in Figure ₁ , which is located between two adjacent _second protrusions P2 at the same time, and the two sides of the V-shaped groove are formed by the inclined surfaces of the two second protrusions respectively.

The method for fabricating the above-mentioned patterned sapphire substrate will be briefly described below with reference to FIGS. 6-8 .

Please refer to accompanying drawing 6, the manufacturing method of patterned sapphire substrate, comprises step S01～S03, comprises forming photomask layer, adopts dry etching method to etch substrate surface and adopts wet etching substrate surface to form the pattern without c-plane surface.

Step S01: Provide a sapphire substrate having opposite first and second surfaces, and form a patterned mask layer 200 on the first surface, as shown in FIG. 7 . The details are as follows: First, a layer of photoresist is coated on a flat sapphire substrate, and the thickness of the photoresist can be 0.5um to 3um; then, the pattern is produced by using a yellow light process. This production method can include stepper exposure machine, For the contact exposure machine, projection exposure machine or embossing method, the diameter of the pattern size can be 0.5um-6um, and the gap between each pattern can be 0.5um-6um.

Step S02: dry etching the first surface of the sapphire substrate, forming a series of protruding structures 210 on the first surface, and the area between each protruding structure is etched into a small convex surface 220, as shown in FIG. 8 , preferably the The small convex surface 220 is a curved surface, and the height of the curved surface is preferably 0.05um~0.5um. The details are as follows: Send the sapphire substrate with photoresist pattern after the aforementioned treatment to the ICP machine for etching. The procedure mainly includes: upper electrode power, lower electrode power, cavity pressure, BCl ₃ gas flow rate, upper electrode and lower electrode The power can be 1:1~24:1, the cavity pressure can be 0.1~1 Pa, and the BCl ₃ gas flow can be 20~100% of the maximum value of the machine.

Step S03: Wet etching the first surface of the sapphire substrate to form a patterned surface, as shown in FIG. 1 . The details are as follows: put the above-mentioned sapphire substrate etched by ICP into a high-temperature sulfuric-phosphoric acid mixed solution for etching, wherein the temperature is 150-300 degrees, and the ratio of sulfuric acid to phosphoric acid can be 1:1-10:1.

Among the above steps, step 2) is a key step of this manufacturing method, which requires etching the connection area between each protrusion structure 210 into a small convex surface 220, so that there is no plane in the connection area between each protrusion structure 210, thereby ensuring Step 3) The pattern structure shown in Figure 1 can be obtained by wet etching.

Fig. 9 shows a flow chart of manufacturing a light-emitting diode according to the present invention, including steps S01-S05, wherein steps S01-S03 form a patterned sapphire substrate, and step S04 is to use PVD to form AlN on the patterned sapphire substrate layer, step S05 is to epitaxially grow a light-emitting epitaxial stack on the AlN layer. The following is a brief description of each step, and steps 01-03 can refer to the previous description.

Step S04: Using PVD method, forming an AlN layer on the surface of the patterned sapphire substrate formed by the method of steps S01-S03, the thickness of the layer is 10-200 angstroms.

Step S05: Using epitaxial growth, sequentially grow the buffer layer 120, the n-type semiconductor layer 130, the light emitting layer 140 and the p-type semiconductor layer 150, wherein the buffer layer 120 is a material based on Group III nitride, preferably gallium nitride, or Aluminum nitride material or aluminum gallium nitride material can be used; the n-type semiconductor layer 130 is preferably gallium nitride, and aluminum gallium nitride material can also be used, and the preferred silicon doping concentration is 1×10 ¹⁹ cm ^-3 ; the light emitting layer 140 is preferably In order to have at least one quantum well structure, it is preferable to have 5 to 50 pairs of quantum wells; the p-layer semiconductor layer 150 is preferably gallium nitride, doped with magnesium, and the doping concentration is 1×10 ¹⁹ to 5×10 ²¹ cm ^-3 , the preferred p-type 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 140, and is used to block electrons from entering the p-type semiconductor layer. The type layer is recombined with holes, preferably using aluminum gallium nitride material, and the thickness can be 50-200nm.

Figure 10 shows a light-emitting diode formed by the manufacturing method shown in Figure 9, and its structure includes: a patterned sapphire substrate 100, an AlN layer 110, a buffer layer 120, an n-type semiconductor layer 1300, a light-emitting layer 140 and a p-type semiconductor layer 150 . In this light-emitting diode, there is no c-plane on the growth surface of the patterned sapphire substrate, which can effectively eliminate the threading dislocations formed on the c-plane and improve the crystal quality of the epitaxial structure; An AlN layer is formed first, which can be used as a seed layer, which is beneficial to the growth of subsequent light-emitting epitaxial stacks; in addition, there is no plane on the growth surface of the entire patterned sapphire substrate, increasing the area for light reflection and scattering, which is beneficial to more The light exits the light-emitting diode, which greatly improves the light extraction rate of the LED.

Claims (12)

1. A patterned sapphire substrate, having an opposite first surface and a second surface, wherein the first surface has a series of regularly arranged first protrusions of the first size d1, characterized in that: each of the first protrusions There is no C plane (that is, (0001) plane) in the connection area between them, and a triangle is formed between three adjacent first protrusions, and each triangle has a second protrusion with a second size d2 inside , the first protrusion and the second protrusion are connected directly or with a curved surface so that there is no C-plane in the connection area, and a rhombus is formed between four adjacent first protrusions, wherein, in the long pair There are two said second protrusions between the corners and one third protrusion of third dimension d3 between the short diagonals, where d3<d2<d1. 2. The patterned sapphire substrate according to claim 1, wherein the first protrusion has no C-plane. 3. The patterned sapphire substrate according to claim 1, wherein the second protrusion has no C-plane. 4. The patterned sapphire substrate according to claim 1, characterized in that: the first surface has no C-plane. 5 . The patterned sapphire substrate according to claim 1 , wherein there is a depression between the two second protrusions, and the lowest part thereof is the highest point of the third protrusion. 6. The patterned sapphire substrate according to claim 1, characterized in that: the second protrusion is a cone mainly composed of three inclined surfaces, and each main inclined surface corresponds to the three first inclined surfaces respectively. Protrusion. 7. The patterned sapphire substrate according to claim 6, characterized in that: the angle between the inclined surface of the second protrusion and the C-plane of the sapphire substrate is 10°-40°. 8 . The patterned sapphire substrate according to claim 1 , wherein the ratio of the height h1 of the first protrusion to the height h2 of the second protrusion is 2-50. 9. The patterned sapphire substrate according to claim 1, wherein the first protrusion accounts for 50%-90% of the total area of the first surface. 10. The patterned sapphire substrate according to claim 1, characterized in that: the top of the first protrusion is a cone and the projection on the C plane is a circle or a polygon. 11. A light-emitting diode, comprising a patterned sapphire substrate, a light-emitting epitaxial stack formed on the patterned sapphire substrate, characterized in that: the patterned sapphire substrate adopts the method described in any one of claims 1 to 10. patterned 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, and the light-emitting epitaxial stack is formed on the AlN layer superior.