CN101330002A - Fabrication method of patterned sapphire substrate for nitride epitaxial growth - Google Patents

Abstract

A method for making a patterned sapphire substrate for nitride epitaxial growth, comprising the following steps: depositing a layer of silicon dioxide film on the sapphire substrate for nitride epitaxial growth; Patterned mask; use hydrofluoric acid + ammonium fluoride + H ₂ O mixed solution to etch the photolithographic pattern onto the silicon dioxide film; use the patterned silicon dioxide film as a mask, use a mixture of sulfuric acid and phosphoric acid Liquid wet etching of the sapphire substrate, etch the pattern on the sapphire substrate; use dilute hydrofluoric acid solution to wet etch to remove the residual silicon dioxide film, and clean the sapphire substrate to complete the graphic sapphire substrate preparation. The manufacturing method has the advantages of low cost, protecting the sapphire substrate from dry etching damage, and the like. The patterned sapphire substrate can be used for epitaxial growth of nitride with low dislocation density and high crystal quality.

Description

Fabrication method of patterned sapphire substrate for nitride epitaxial growth

technical field

The invention belongs to the technical field of semiconductors, in particular to a method for manufacturing a patterned sapphire substrate used for nitride epitaxial growth. The patterned sapphire substrate can be used for epitaxial growth of nitride with low dislocation density and high crystal quality.

Background technique

Nitride compound semiconductors represented by III-V gallium nitride (GaN), such as gallium nitride (GaN), aluminum nitride (AlN), indium nitride (InN), aluminum gallium nitride (AlGaN), nitride Gallium indium (InGaN), aluminum indium nitride (AlInN) or aluminum gallium indium nitride (AlGaInN) etc. are used in ultraviolet/blue/green light-emitting diodes, lasers, solar blind ultraviolet photodetectors, and high-frequency, high-temperature, high-power It has important and extensive applications in many fields such as electronic devices. At present, sapphire substrate is the most commonly used substrate for nitride heteroepitaxial growth. Due to the large lattice constant mismatch and thermal expansion coefficient difference between the sapphire substrate and the nitride epitaxial layer, metal organic chemical vapor deposition (MOCVD), hydride vapor phase epitaxy (HVPE) or molecular beam epitaxy (MBE), etc. There is a lot of stress and many crystal defects such as dislocations in the nitride epitaxial layer grown by epitaxial technology, so the crystal quality of the material is greatly affected, which in turn degrades the device performance. The use of patterned sapphire substrate technology can alleviate the stress caused by lattice mismatch in the heteroepitaxial growth of sapphire substrate and nitride epitaxial layer, so that it can be effectively relaxed, and the position in the epitaxially grown nitride material can be greatly reduced. Mistaken density, so that the crystal quality is greatly improved. However, most of the current preparation techniques for patterned sapphire substrates use traditional photolithography methods to prepare photolithographic patterns, and then use silicon dioxide (SiO ₂ ) or silicon nitride (SiN ₄ ) layers as masks, and then use reactive ions ( RIE) or inductively coupled plasma (ICP) and other equipment dry etching formed. Since dry etching equipment is involved in the process, the process is complicated and the cost is high, and the sapphire substrate is easily damaged and polluted by dry etching. In order to be more effectively applied to the epitaxial growth of nitrides with low dislocation density and high crystal quality, it is imperative to develop low-cost, easy-to-implement patterned sapphire substrate technology.

Contents of the invention

The purpose of the present invention is to provide a method for making a patterned sapphire substrate for nitride epitaxial growth. This method can effectively reduce the dislocation density in the nitride epitaxial layer, avoid the generation of cracks, and improve the quality of the epitaxial material. Crystal quality and uniformity, which in turn can improve the performance of optoelectronic devices. The preparation technology does not involve dry etching equipment such as reactive ion (RIE) or inductively coupled plasma (ICP), and has the advantages of low cost and easy realization of large-scale production.

The invention provides a method for making a patterned sapphire substrate for nitride epitaxial growth, which is characterized in that it comprises the following steps:

Step 1: Deposit a layer of silicon dioxide film on the sapphire substrate for nitride epitaxial growth;

Step 2: using conventional photolithography technology to prepare a photolithographic pattern mask;

Step 3: using a mixed solution of hydrofluoric acid + ammonium fluoride + H ₂ O to etch the photolithography pattern onto the silicon dioxide film;

Step 4: using the patterned silicon dioxide film as a mask, wet etching the sapphire substrate with a mixture of sulfuric acid and phosphoric acid, and etching the pattern onto the sapphire substrate;

Step 5: use dilute hydrofluoric acid solution to wet etch to remove the remaining silicon dioxide film, and clean the sapphire substrate to complete the preparation of the patterned sapphire substrate.

The sapphire substrate described herein is any one of (0001) or c-plane, (1102) or r-plane, (1010) or m-plane, (1120) or a-plane sapphire substrate.

Wherein the silicon dioxide film has a thickness of 20 nanometers to 2 micrometers.

The photolithographic pattern is a periodic pattern array, and the photolithographic pattern units are formed by any one or combination of circles, squares, regular hexagons, rhombuses, triangles or irregular patterns.

Wherein the size and pitch of each unit in the photolithography pattern is 1 micron-10 micron.

The structure of the photolithographic pattern is any one of mesa shape or groove shape or a combination of both.

The wet etching temperature of the mixed solution of sulfuric acid and phosphoric acid is between 320° C. and 520° C., and the etching time is 30 seconds to 30 minutes.

The nitride used for nitride epitaxial growth is any one or more of gallium nitride, aluminum nitride, indium nitride, aluminum gallium nitride, gallium indium nitride, aluminum indium nitride or aluminum gallium indium nitride combination of species.

The method used for nitride epitaxial growth is any one or combination of metal organic compound chemical vapor deposition method, hydride vapor phase epitaxy method or molecular beam epitaxy method.

The manufacturing method of the patterned sapphire substrate used for nitride epitaxial growth has the advantages of low cost, protecting the sapphire substrate from dry etching damage, and the like. The patterned sapphire substrate can be used for epitaxial growth of nitride with low dislocation density and high crystal quality.

Description of drawings

In order to further illustrate content of the present invention, the present invention is described in detail below in conjunction with the example of implementation, wherein:

Fig. 1 is a schematic cross-sectional view of a sapphire substrate for nitride epitaxial growth after photolithographic patterning; among the figures, 1 is a sapphire substrate, 2 is a silicon dioxide film, and 3 is a photoresist layer;

Figure 2 is a schematic cross-sectional view of a silicon dioxide film etched by a mixture of hydrofluoric acid (HF) + ammonium fluoride (NH ₄ F) + H ₂ O using the photoresist layer as a mask; 1 in the figure is a sapphire lining Bottom, 2 is a silicon dioxide layer, 3 is a photoresist layer;

Figure 3 is a schematic cross-sectional view of using a patterned silicon dioxide film as a mask, wet etching sapphire with a mixture of sulfuric acid and phosphoric acid, and transferring the pattern to the sapphire substrate; 1 in the figure is the sapphire substrate, 2 is the second Silicon oxide film;

Fig. 4 is a schematic cross-sectional view after dilute hydrofluoric acid (HF) wet etching removes the residual silicon dioxide film, cleans the substrate, and prepares a patterned sapphire substrate; 1 in the figure is the sapphire substrate.

specific embodiment

Please refer to Fig. 1-shown in Fig. 4, a kind of fabrication method of the pattern sapphire substrate that is used for nitride epitaxial growth of the present invention, comprises the following steps:

Step 1: Deposit a layer of silicon dioxide film 2 on the sapphire substrate 1 used for nitride epitaxial growth; wherein the sapphire substrate 1 is (0001) or c plane, (1102) or r plane, ( 1010) or any one of the m-plane, (1120) or a-plane sapphire substrate 1; wherein the thickness of the silicon dioxide film 2 is 20 nanometers-2 microns; the nitride used for nitride epitaxial growth is nitride Any one or combination of gallium, aluminum nitride, indium nitride, aluminum gallium nitride, gallium indium nitride, aluminum indium nitride or aluminum gallium indium nitride; the method for nitride epitaxial growth It is any one or combination of metal-organic chemical vapor deposition method, hydride vapor phase epitaxy method or molecular beam epitaxy method;

Step 2: Utilize the conventional photolithography technique to prepare the mask 3 of the photolithographic pattern; wherein the photolithographic pattern is a periodic pattern array, and the units of the photolithographic pattern are formed from circles, squares, regular hexagons, rhombuses, triangles or not Any one or a combination of regular patterns; the size and spacing of each unit in the photolithographic pattern is 1 micron to 10 microns; the structure of the photolithographic pattern is either mesa-shaped or groove-shaped one or a combination of two;

Step 3: using a mixed solution of hydrofluoric acid + ammonium fluoride + H ₂ O to etch the photolithography pattern onto the silicon dioxide film 2;

Step 4: Using the patterned silicon dioxide film 2 as a mask, wet-etching the sapphire substrate 1 with a mixture of sulfuric acid and phosphoric acid, and etching the pattern onto the sapphire substrate 1; the mixture of sulfuric acid and phosphoric acid is wet-etched The etching temperature is between 320°C and 520°C, and the etching time is between 30 seconds and 30 minutes;

Step 5: use dilute hydrofluoric acid solution to wet etch away the remaining silicon dioxide film 2, and clean the sapphire substrate 1 to complete the preparation of the patterned sapphire substrate 1.

The technical characteristics and remarkable progress of the present invention will be further elaborated below through two specific examples.

Example 1

Please refer to FIG. 1-FIG. 4 again. This embodiment is a method for fabricating a patterned c-plane sapphire substrate 1 for nitride epitaxial growth. The c-plane sapphire substrate 1 is currently one of the most commonly used substrate materials for epitaxial growth of nitride.

First, a 0.3-micron silicon dioxide film 2 is deposited on a 2-inch c-plane sapphire substrate 1 using plasma-enhanced chemical vapor deposition (PECVD), and a photoresist is coated on the silicon dioxide film 2 using conventional photolithography techniques. Layer 3, a circular array is formed by exposure and development. The size and spacing of the circular array unit structure are 3 microns, and the structural section after photolithography is shown in Figure 1;

Next, using the photoresist layer 3 as a pattern mask, using hydrofluoric acid (HF) + ammonium fluoride (NH ₄ F) + H ₂ O mixed solution, the photolithography pattern is etched onto the silicon dioxide film 2, which The structural section is shown in Figure 2;

Then use the silicon dioxide film 2 as a pattern mask, and wet-etch the c-plane sapphire substrate 1 at 400° C. with a mixture of sulfuric acid and phosphoric acid. The etching time is 10 minutes. The structural section is shown in Figure 3; the sulfuric acid The volume ratio of the phosphoric acid mixed solution is 3:1.

Finally, dilute hydrofluoric acid (HF) is used to remove the remaining silicon dioxide film 2 by wet etching, and then a patterned c-plane sapphire substrate 1 can be produced. The structural section is shown in FIG. 4 .

The graphic unit of the sapphire substrate 1 is a mesa structure, the height of the mesa is 1.3 microns, and the side surface is a nearly regular triangle structure due to the anisotropy of wet etching, consisting of {11-20}, {-2110} and {1-210 } crystal plane, and the surface is a circular shape of a photolithography mask. The c-plane sapphire substrate 1 with periodic pattern array can be used for epitaxial growth of nitride with low dislocation density and high crystal quality.

Example 2

This embodiment is a method for fabricating a patterned r-plane sapphire substrate 1 for nitride epitaxial growth. The r-plane sapphire substrate 1 can be used for epitaxial growth of non-polar nitride. Non-polar nitrides can avoid the built-in electric field caused by the strain effect in the vertical growth direction, thereby enhancing the radiative recombination probability of carriers and improving the performance of optoelectronic devices.

Using a process similar to that of Example 1, on the r-plane sapphire substrate 1, a silicon dioxide film 2 was deposited by plasma enhanced chemical vapor deposition (PECVD), conventional photolithographic technology photolithographic patterns, hydrofluoric acid (HF ) + ammonium fluoride (NH ₄ F) + H ₂ O mixed solution to etch the silicon dioxide film 2, sulfuric acid and phosphoric acid mixed solution to etch the r-plane sapphire substrate 1 at 400 ° C, the etching time is 6 minutes, and finally use dilute Hydrofluoric acid (HF) wets and removes the remaining silicon dioxide film 2 to form a patterned r-plane sapphire substrate 1 .

The pattern unit of the sapphire substrate 1 is a mesa structure, and the height of the mesa of the pattern unit is about 0.6 micron. Due to the anisotropy of wet etching, its surface changes from a circle of a photolithography pattern to a half-moon shape. The patterned r-plane sapphire substrate 1 can be used for epitaxial growth of non-polar nitride with low dislocation density and high crystal quality.

The above embodiments describe the fabrication method of patterned c-plane and r-plane sapphire substrates for nitride epitaxial growth. Since no dry etching process such as RIE or ICP is involved, the prepared patterned sapphire substrate can be free from dry etching damage. At the same time, the wet etching technology does not involve expensive equipment, and has the advantages of low cost and easy large-scale production. The patterned sapphire substrate technology can alleviate the stress caused by lattice mismatch during the heteroepitaxial growth process between the sapphire substrate and the nitride, reduce the defect density of the nitride epitaxial layer, improve the crystal quality, and then improve the performance of the device.

Claims (9)

1, a kind of manufacture method that is used for the graphical sapphire substrate of nitride epitaxial growth is characterized in that, comprises the steps:

Step 1: be used for deposit layer of silicon dioxide film on the Sapphire Substrate of nitride epitaxial growth;

Step 2: utilize conventional photoetching technique to prepare the mask of litho pattern;

Step 3: utilize hydrofluoric acid+ammonium fluoride+H ₂The O mixed liquor etches into litho pattern on the silicon dioxide film;

Step 4: as mask, adopt the mixed liquor wet etching Sapphire Substrate of sulfuric acid and phosphoric acid with the figure silicon dioxide film, with pattern etching on Sapphire Substrate;

Step 5: utilize the dilute hydrofluoric acid solution wet etching to remove remaining silicon dioxide film, and Sapphire Substrate is cleaned up, finish the preparation of graphical sapphire substrate.

2, the manufacture method that is used for the graphical sapphire substrate of nitride epitaxial growth according to claim 1, it is characterized in that wherein said Sapphire Substrate is any in (0001) or c face, (1102) or r face, (1010) or m face, (1120) or a surface sapphire substrate.

3, the manufacture method that is used for the graphical sapphire substrate of nitride epitaxial growth according to claim 1 is characterized in that, wherein the thickness of silicon dioxide film is 20 nanometers-2 micron.

4, the manufacture method that is used for the graphical sapphire substrate of nitride epitaxial growth according to claim 1, it is characterized in that, wherein litho pattern is the periodic pattern array, and the unit of its litho pattern is by any or several the combining in circular, square, regular hexagon, rhombus, triangle or the irregular figure.

5, the manufacture method that is used for the graphical sapphire substrate of nitride epitaxial growth according to claim 1 is characterized in that, wherein the size of each unit and spacing are 1 micron-10 microns in the litho pattern.

6, the manufacture method that is used for the graphical sapphire substrate of nitride epitaxial growth according to claim 1 is characterized in that, wherein the structure of litho pattern is any or two kinds of combinations in mesa shaped or the groove shape.

7, the manufacture method that is used for the graphical sapphire substrate of nitride epitaxial growth according to claim 1 is characterized in that, wherein the temperature of the mixed liquor wet etching of sulfuric acid and phosphoric acid is between 320 ℃-520 ℃, and the time of etching is 30 seconds-30 minutes.

8, the manufacture method that is used for the graphical sapphire substrate of nitride epitaxial growth according to claim 1, it is characterized in that the nitride that wherein is used for nitride epitaxial growth is any or several combination of gallium nitride, aluminium nitride, indium nitride, aluminium gallium nitride alloy, indium gallium nitride, aluminum indium nitride or aluminum indium gallium nitride.

9, the manufacture method that is used for the graphical sapphire substrate of nitride epitaxial growth according to claim 1, it is characterized in that the method that wherein is used for nitride epitaxial growth is any or several combinations of the method for metal organic chemical vapor deposition method, hydride gas-phase epitaxy method or molecular beam epitaxy.

Images