CN105244316A - Mask-assisted method for preparing porous GaN layer - Google Patents

Abstract

The invention relates to a mask-assisted method for preparing a porous GaN layer—that is, a method for preparing a porous GaN layer by etching a mask after making a mask on a gallium nitride (GaN) substrate by photolithography—by photolithography on a GaN substrate Carve a stripe mask pattern, use radio frequency magnetron sputtering method to plate SiO2 thin film on the substrate with mask pattern, wash with acetone to remove photoresist, and remove together with SiO2 on the glue to obtain SiO2 stripe mask. Then use HVPE equipment to carry out GaN epitaxial growth for a short period of time. During the growth, two processes are used successively. The first is a process with strong vertical growth capability, and the second is a process with strong lateral growth capability. The growth time of the two processes is Strict control is required so that the SiO2 mask is not completely covered by GaN, and then the SiO2 is corroded by hydrofluoric acid (HF) to obtain a porous GaN layer, and the prepared porous GaN layer is used as a weak layer to continue the GaN crystal growth process. The technical effect The prepared porous GaN layer is uniform, can realize assisted GaN self-stripping, and the manufacturing method is simple and controllable.

Description

A mask-assisted method for preparing porous GaN layer

technical field

The invention relates to a method for preparing a porous GaN layer, in particular to a mask-assisted method for preparing a porous GaN layer.

Background technique

Gallium Nitride (GaN) is a semiconductor material with a direct bandgap and a wide bandgap. Photoelectric fields such as ultraviolet detectors and microelectronics fields such as high-temperature, high-power, and high-frequency devices have broad application prospects. The growth of GaN is currently mainly obtained by vapor phase epitaxy using sapphire or other single crystal materials as substrates. Since self-supporting GaN has its unique advantages in device manufacturing, it requires the separation technology of substrate and epitaxial layer. Existing stripping technologies include Corrosion stripping, laser stripping, hydrogen injection stripping and self-stripping, etc., in which the epitaxial layer will also be eroded during the corrosion stripping process. After laser stripping, the stripping interface is rough and the integrity cannot be guaranteed. Hydrogen injection stripping will be limited by the implantation depth, so the current The most commonly used is the self-stripping technique. The key to the self-stripping technology lies in the fabrication of the weak layer. Using the porous GaN layer as the weak layer during the peeling can not only relieve the stress during growth, but also make the gap between the substrate and the epitaxial layer realizable due to the existence of thermal mismatch during the cooling process. separate. Therefore, in the current preparation of self-supporting GaN crystals, the fabrication of porous GaN has become a key technology to assist GaN self-exfoliation.

Contents of the invention

In view of the fact that the self-stripping technology of GaN growth has become a research hotspot in the semiconductor industry at present, the present invention uses SiO2 mask etching to assist in the fabrication of porous GaN layers, which are used as weak layers to assist the GaN self-stripping process. The specific technical solution is, a mask-assisted The method for preparing a porous GaN layer is characterized in that: the process steps are,

(1) Preparation of SiO2 stripe mask on GaN substrate

a) Using HVPE equipment, grow a layer of GaN film with a thickness of about 5 μm on the 2inchc surface sapphire as the substrate,

b) Photolithographic strip mask, uniformly coat a layer of photoresist on the GaN substrate with a coater, then bake the glue on a heating platform at about 70°C for 10 minutes, and then use a strip mask on the photolithography machine Exposure, the exposure time is between 20 and 30s. After the exposure is over, use KOH aqueous solution or other developer with a ratio of 1:50 to develop. The development time is controlled at about 1min. Finally, dry the glue at 70°C, that is Strip photolithography masks are available,

c) Turn on the magnetron sputtering apparatus, and plate a SiO2 film with a thickness of 100-200 nm on the GaN substrate with a mask pattern by adjusting the sputtering power and sputtering time,

d) Take out the coated film, and then ultrasonically clean it in acetone to remove the photoresist and SiO2 on the glue, and then rinse it with deionized water to obtain a SiO2 strip mask on the GaN substrate.

(2) Prepare a porous GaN layer by using a GaN substrate with a mask pattern

a) Put the GaN mask substrate prepared in (1) into the HVPE equipment, and heat up to 1020°C,

b) Under the condition of N2 as the carrier gas, first adopt a process with strong vertical growth capability, and control the growth time so that the growth height of GaN does not exceed the height of the mask,

c) Change the loading process, adopt a process with strong lateral growth ability, and ensure that the lateral epitaxial growth of GaN does not completely cover the SiO2 mask, that is, there is a gap at the top,

d) After the GaN epitaxial growth is completed, take out the sample and put it into a 1:10 concentration of HF acid aqueous solution. The HF acid penetrates into the SiO2 mask layer from the top gap, and finally removes the SiO2 in the GaN epitaxial layer to obtain a porous structure.

The technical effect of the invention is that the prepared porous GaN layer is uniform, can realize auxiliary GaN self-stripping, and the manufacturing method is simple and controllable.

Description of drawings

Fig. 1 is a process flow diagram of the present invention.

detailed description

A method for mask-assisted preparation of a porous GaN layer, the process steps are:

(1) Preparation of SiO2 stripe mask on GaN substrate

a) Using HVPE equipment, grow a layer of GaN film with a thickness of about 5 μm on the 2inchc surface sapphire as the substrate,

b) Photolithographic strip mask, uniformly coat a layer of photoresist on the GaN substrate with a coating machine, then bake the glue on a heating platform at about 70°C for 10 minutes, and then use a strip mask plate on the photolithography machine Exposure, the exposure time is 25s. After the exposure is over, use KOH aqueous solution or other developer with a ratio of 1:50 to develop. The development time is controlled at about 1min. Finally, dry the glue at 70°C to obtain strip light engraved mask,

c) open the magnetron sputtering apparatus, on the GaN substrate with mask pattern by adjusting the sputtering power and sputtering time to plate a SiO2 film with a thickness of 200nm,

d) Take out the coated film, and then ultrasonically clean it in acetone to remove the photoresist and SiO2 on the glue, and then rinse it with deionized water to obtain a SiO2 strip mask on the GaN substrate.

(2) Prepare a porous GaN layer by using a GaN substrate with a mask pattern

a) Put the GaN mask substrate prepared in (1) into the HVPE equipment, and heat up to 1020°C,

b) Under the condition of N2 as the carrier gas, first adopt a process with strong vertical growth capability, and control the growth time so that the growth height of GaN does not exceed the height of the mask,

c) Change the loading process, adopt a process with a strong lateral growth capability, and ensure that the lateral epitaxial growth of GaN does not completely cover the SiO2 mask, that is, there is a gap at the top,

d) After the GaN epitaxial growth is completed, take out the sample and put it into a 1:10 concentration of HF acid aqueous solution. The HF acid penetrates into the SiO2 mask layer from the top gap, and finally removes the SiO2 in the GaN epitaxial layer to obtain a porous structure.

Put the finished porous GaN sample into the HVPE equipment, and continue the subsequent GaN thick film epitaxial growth, using the porous layer as a weak layer to assist GaN self-stripping.

Claims (1)

1. A mask-assisted method for preparing a porous GaN layer, characterized in that: the process steps are, (1) Preparation of SiO2 stripe mask on GaN substrate a) Using HVPE equipment, grow a layer of GaN film with a thickness of about 5 μm on the 2inchc surface sapphire as the substrate, b) Photolithographic strip mask, uniformly coat a layer of photoresist on the GaN substrate with a coating machine, then bake the glue on a heating platform at about 70°C for 10 minutes, and then use a strip mask plate on the photolithography machine Exposure, the exposure time is between 20 and 30s. After the exposure is over, use KOH aqueous solution or other developer with a ratio of 1:50 to develop. The development time is controlled at about 1min. Finally, dry the glue at 70°C, that is Strip photolithography masks are available, c) Turn on the magnetron sputtering apparatus, and plate a SiO2 film with a thickness of 100-200 nm on the GaN substrate with a mask pattern by adjusting the sputtering power and sputtering time, d) Take out the coated film, and then ultrasonically clean it in acetone to remove the photoresist and SiO2 on the glue, and then rinse it with deionized water to obtain a SiO2 strip mask on the GaN substrate. (2) Prepare a porous GaN layer by using a GaN substrate with a mask pattern a) Put the GaN mask substrate prepared in (1) into the HVPE equipment, and heat up to 1020°C, b) Under the condition of N2 as the carrier gas, first adopt a process with strong vertical growth capability, and control the growth time so that the growth height of GaN does not exceed the height of the mask, c) Change the loading process, adopt a process with a strong lateral growth capability, and ensure that the lateral epitaxial growth of GaN does not completely cover the SiO2 mask, that is, there is a gap at the top, d) After the GaN epitaxial growth is completed, take out the sample and put it into a 1:10 concentration of HF acid aqueous solution. The HF acid penetrates into the SiO2 mask layer from the top gap, and finally removes the SiO2 in the GaN epitaxial layer to obtain a porous structure.