CN100435279C - A method for fabricating a large-area self-supporting wide-bandgap semiconductor material - Google Patents

Abstract

The invention discloses a large-area, self-supporting wide bandgap semiconductor material manufacturing method based on a double-buffer flexible substrate. It mainly solves technical problems such as high defect density, a large number of cracks, too small thickness of epitaxial material and inability to peel off the wide bandgap semiconductor material produced by the prior art. The technical solution is: firstly fabricate an SOI structure on a silicon wafer; then use photolithography and epitaxial processes to fabricate an island-shaped buffer layer on the SOL of the SOI structure to form a double-buffered flexible substrate; then epitaxially Growth of semiconductor materials; finally, the double-buffered flexible substrate or SOI structure layer under the grown semiconductor materials is peeled off to finally form the required large-area, self-supporting wide-bandgap semiconductor material. The invention has the advantage of being able to release high stress caused by lattice mismatch and thermal mismatch between the epitaxial material and the silicon wafer material, and can be used for making silicon carbide SiC, gallium nitride GaN and other materials.

Description

A method for fabricating a large-area self-supporting wide-bandgap semiconductor material

technical field

The invention belongs to the technical field of microelectronics, relates to semiconductor materials and device manufacturing technology, specifically a large-area, self-supporting wide-bandgap semiconductor material manufacturing method, which can be used for thin film materials such as silicon carbide SiC and gallium nitride GaN production.

Background technique

In recent years, the third-generation wide-bandgap semiconductor materials represented by SiC and GaN have large bandgap width, high critical field strength, high thermal conductivity, high carrier saturation rate, and high concentration of two-dimensional electron gas at the heterojunction interface. Its excellent characteristics have attracted widespread attention from people. In theory, high electron mobility transistor HEMT, heterojunction bipolar transistor HBT, light-emitting diode LED, laser diode LD and other devices made of these materials will have excellent performance that cannot be compared with existing devices. It has conducted extensive and in-depth research and has achieved remarkable results.

However, a major obstacle facing the third-generation wide-bandgap semiconductor materials and related devices is that there is no natural single-crystal material, and it is difficult to artificially prepare high-quality, large-size single-crystal materials. At the same time, as the integration and power density of high-power devices based on third-generation wide-bandgap semiconductor materials and microwave power devices are getting higher and higher, the problem of heat dissipation is becoming more and more serious. , cooling capacity, insulation performance requirements are becoming more and more stringent.

Take GaN material as an example. In the late 1980s, Nakamura et al. proposed a two-step method to epitaxially grow GaN materials on sapphire substrates, see Nakamura S.GaN Growth Using GaN Buffer Lager.Jpn.J Appl Phys.30(10), L 1705～L 1707, 1991. The solution is to first grow a GaN buffer layer on the sapphire substrate to reduce the high defect density caused by lattice mismatch between sapphire and GaN, and then re-grow GaN material on the buffer layer. Although this solution can obtain GaN materials with better quality than the single-step process, the lattice mismatch between the (0001) growth plane of the GaN material and the (0001) crystal plane of the sapphire substrate is as high as about 13.8%. The defect density of the GaN material grown by the scheme is still as high as 10 ⁸ -10 ¹⁰ /cm ² or more.

In 1993, Detchprohm and Amano et al. further proposed a plan to grow GaN materials on ZnO substrates, see Detchprohm T, Amano H, Hiramatsu K, et al.J Cryst Growth.128, 384, 1993. The scheme is to first epitaxially layer a layer of ZnO material on the sapphire substrate as the substrate for the epitaxial growth of GaN material; GaN material. Although ZnO material and GaN material have similar crystal structures and lattice constants, due to the large lattice mismatch between ZnO material and sapphire material, the ZnO material grown by epitaxy itself has a high defect density, so in The defect density of GaN material grown on ZnO substrate is still high.

In 1999, Hersee et al proposed the scheme of using nanometer heterogeneous epitaxy, see Zubia D, Hersee S D.J Appl Phys Lett.49, 140, 1996. In this scheme, Si nano-column arrays are fabricated on Si substrates first, and then GaN materials are directly epitaxy on them. Due to the nano-size effect, Si nanopillars can release the stress caused by the lattice mismatch between GaN and the substrate to a certain extent, but the thickness of the GaN material still cannot be large because of the poor norm of the Si substrate.

Taking SiC material as an example, because SiC material is difficult to form a melt under normal pressure, it will directly sublimate when the temperature reaches 2400 degrees, so it is difficult to use the traditional melting method to prepare. In 1983, Nishino et al. proposed a plan to grow 3C-SiC on Si substrates, see Nishino S, Powell J A, Will H A. Appl Phys Lett. 42, 460, 1983. Using this scheme, a SiC film with better quality cubic phase 3C structure was grown on Si by CVD technology at high temperature. However, since the lattice mismatch between SiC and the Si substrate is as high as 20%, and the thermal mismatch is also up to 8%, the residual stress in the SiC film is large, and it is difficult to grow SiC materials with large thickness. It can be seen that to solve the growth problem of high-quality wide-bandgap semiconductor materials, we must find new technical approaches.

content of the invention

The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a method for producing high-quality, large-size, self-supporting wide-bandgap semiconductor materials. To solve the problem of high stress caused by lattice mismatch and thermal mismatch caused by the lack of suitable substrates in the current third-generation wide-bandgap semiconductor material heteroepitaxial growth technology, it is used for the growth of various wide-bandgap semiconductor materials.

The technical solution for realizing the object of the present invention is: on the silicon chip, make the silicon structure on the insulating layer, that is, the SOI structure, then make the island-shaped array buffer layer on the SOI, and finally epitaxially grow the required components on the island-shaped buffer layer. Large-area, self-supporting wide-bandgap semiconductor materials.

Its specific production process is as follows:

(1) Select the crystal orientation and size of the silicon wafer according to the application of the self-supporting epitaxial layer;

(2) Use conventional oxygen injection isolation SIMOX, silicon wafer bonding BESOI, and intelligent peeling UNIBOND to make buried oxide layer BOX and surface silicon SOL on the selected silicon wafer to form an SOI structure;

(3) Make an island-shaped buffer layer on the surface silicon SOL of the SOI structure by photolithography and epitaxial technology to form a double buffer flexible substrate;

(4) Utilize conventional epitaxial process to grow semiconductor material on described double-buffered flexible substrate;

(5) The double-buffer flexible substrate or SOI structure layer under the semiconductor material is peeled off by a conventional stripping process to form a large-area, self-supporting wide-bandgap semiconductor material.

In the manufacturing method of the above-mentioned semiconductor material, the process of making the island-shaped buffer layer by photolithography process is as follows:

The first step is to make a mask according to the designed single island size and spacing;

The second step is to place the fabricated mask on the SOL coated with photoresist for photolithography and development;

The third step is to etch the SOL with an etching solution to ensure the height of each island, and then use an organic solvent to remove the photoresist and clean the surface to form an island-shaped buffer layer on the SOL.

In the manufacturing method of the above-mentioned semiconductor material, wherein the process of making the island-shaped buffer layer by using the epitaxial process is: selecting a material close to the wide-bandgap semiconductor material to be grown as the epitaxial material for making the island-shaped buffer layer on the SOL, by Control the temperature and pressure during epitaxy to make the epitaxy in the island growth mode, adjust the growth time to control the size and spacing of a single island, and form an island buffer layer on the SOL.

Because the present invention adopts the double-buffer flexible substrate structure based on SOI structure and island-shaped buffer layer, it can release the high stress caused by lattice mismatch and thermal mismatch between the epitaxial material and the silicon wafer material, and overcomes the problem based on silicon Substrate epitaxy technology has technical problems such as high defect density, a large number of cracks, and the thickness of the epitaxial material is too small to be peeled off. High-quality self-supporting wide-bandgap semiconductor materials can be produced. At the same time, since the size of the wide-bandgap semiconductor material produced by the present invention mainly depends on the size of the silicon wafer used, the production of large-scale epitaxial materials can be realized. At present, the size of silicon wafers has reached 8 to 12 inches, which is much larger than the 2 to 4 inches commonly used substrates of existing wide bandgap semiconductor materials.

Various high-performance semiconductor devices can be constructed based on the wide-bandgap semiconductor material produced by the present invention. For high-power microwave power devices, the heat dissipation capability of these devices is better than that of traditional sapphire and silicon substrate devices, and the device's The gate length is larger than that of commonly used SiC substrate devices. For optoelectronic devices, because more devices can be integrated on a piece of epitaxial material, the yield of devices is greatly improved and the cost of a single device is reduced.

Description of drawings

Fig. 1 is the making process figure of the present invention

Fig. 2 is a diagram of the manufacturing process of the hexagonal 6H structure SiC material based on the double buffer layer flexible substrate of the present invention, the double buffer layer flexible substrate is composed of (100) crystal plane SOI and Si island buffer layer.

Fig. 3 is a diagram of the manufacturing process of the cubic phase 3C structure GaN material based on the double buffer layer flexible substrate of the present invention, the double buffer layer flexible substrate is composed of (111) crystal plane SOI and AlN island buffer layer.

Detailed ways

The process and embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

With reference to Fig. 1, the manufacturing process of the present invention is as follows:

In the first step, a silicon wafer of a certain size is selected according to the application of the self-supporting epitaxial layer.

The selection of the crystal plane of the silicon wafer: choose silicon wafers with different crystal planes according to the crystal orientation of the epitaxial material, for example, the silicon wafer with the (100) crystal plane can be selected for the 6H structure SiC with the hexagonal phase; and the silicon wafer with the 3C structure for the cubic phase SiC can choose (111) crystal plane silicon wafer.

The selection of the size of the silicon wafer: select the size of the silicon wafer according to the epitaxy technology and application of the epitaxial material. For example, for the metal organic chemical vapor deposition MOCVD epitaxy technology used for GaN, the size of the silicon wafer depends on the size of the MOCVD reaction chamber. In addition, for experimental epitaxial materials, small-sized silicon wafers can be used in order to reduce the cost of a single test; for production epitaxial materials, large-sized silicon wafers can be selected in order to reduce the cost of a single device. In short, the choice of silicon wafer size must take into account both the size of the reaction chamber and the use of materials.

In the second step, BOX and SOL are fabricated on the silicon wafer to form an SOI structure.

The process of the SOI structure: According to actual conditions, conventional SOI processes such as oxygen injection isolation SIMOX, silicon wafer bonding BESOI, and intelligent stripping UNIBOND can be selected.

The thickness of each layer of the SOI: the thickness of the SOL is less than 200 nanometers, and the thickness of the BOX is between 10 and 200 nanometers.

In the third step, an island-shaped buffer layer is fabricated on the above-mentioned SOI structure to form a double-buffered flexible substrate structure.

The manufacturing process of the island-shaped buffer layer: different processes such as lithography, epitaxy, and nano-self-organized growth can be selected according to the epitaxial material and equipment conditions. For example, the MOCVD epitaxial process can be used for GaN materials, and the photolithography process can be used for SiC materials. , Nano self-organization process can be selected for ZnO material.

The process of making the island-shaped buffer layer by photolithography is as follows:

1. Make a mask according to the designed single island size and spacing;

2. Use the adhesive machine to evenly adhere the photoresist to the silicon wafer;

3. Put the silicon wafer coated with photoresist into a constant temperature drying oven for baking;

4. Press the prepared mask and the silicon wafer tightly, and expose it under the ultraviolet high-pressure mercury lamp;

5. First put the exposed silicon wafer into the developing solution for development. Then put the silicon wafer into the cleaning solution for rinsing to get the desired pattern;

6. First, put the developed silicon wafer into the oven. Then, bake it from the back with an infrared lamp;

7. Use HF acid and _HNO3 acid solution to etch the silicon wafer to ensure the height of each island and form an island-shaped buffer layer on the SOL.

The process of making the island-shaped buffer layer by using the epitaxial process is as follows:

First, select a material similar to the wide-bandgap semiconductor material to be grown as the epitaxial material for making the island-shaped buffer layer on the SOL, and then control the temperature and pressure of the epitaxy to make the epitaxy in the island-shaped growth mode, and then adjust the growth time to control a single The size and spacing of the islands are such that they form an island-like buffer layer on the SOL.

The fourth step is to epitaxially grow a wide bandgap semiconductor material on the double buffer flexible substrate structure.

The epitaxial growth technology: different epitaxial technologies are selected according to the type of material. For example: SiC material can use chemical vapor deposition CVD method; GaN material can use metal organic compound chemical vapor deposition MOCVD method. The process flow used in this step is the same as the conventional epitaxy process.

The fifth step is to peel off the double-buffered flexible substrate.

First, use HF acid and _HNO3 acid solution at a ratio of 1:10 to peel off the bulk silicon layer at the bottom of the SOI structure; then, use HF acid to peel off the BOX; finally, use HF acid and _HNO3 acid at a ratio of 1:10 The solution strips off the SOL and the island buffer layer.

A high-quality large-area, self-supporting wide-bandgap semiconductor material is obtained through the above process steps.

Example 1

The invention produces 6-inch self-supporting 80-micron SiC material with hexagonal phase 6H structure.

Substrate selection: commercially available 6-inch (100) crystal-faced Si wafer.

SOI manufacturing process: use oxygen injection to isolate SIMOX.

Fabrication of the island-shaped buffer layer: photolithography is used.

With reference to Fig. 2, the manufacturing process of present embodiment 1 is as follows:

1. An SOI structure is fabricated on a 6-inch (100) Si wafer, that is, a SOL layer with a thickness of 100 nanometers and a BOX layer with a thickness of 100 nanometers are fabricated using the SIMOX process.

2. Fabricate a Si island buffer layer on the SOI by photolithography to form a double buffer flexible substrate.

First design a single island with a size of 150 nanometers and a pitch of 200 nanometers, and make a mask for exposure based on these data;

Next, use a glue spinner to evenly adhere the polyvinyl alcohol cinnamate KPR photoresist to the Si wafer on the 6-inch (100) crystal plane;

Next, put the 6-inch (100) Si wafer with the photoresist coated in a constant temperature drying oven at 80°C for 12 minutes and then take it out;

Next, press the fabricated mask with a 6-inch (100) Si wafer, and expose it under an ultraviolet high-pressure mercury lamp;

Next, put the exposed silicon wafer into a methyl ethyl ketone solution for development, remove the unphotosensitive photoresist and keep the photosensitive part. Then put the Si sheet of 6 inches (100) crystal face into acetone and deionized water and take out after rinsing;

Next, put the rinsed 6-inch (100) silicon wafer into an oven, bake it at 150°C for 20 minutes, and then bake it with an infrared lamp from the back for 15 minutes;

Finally, use a ratio of 1:10, 49% HF acid and 70% _HNO3 acid solution to etch the silicon wafer at 25 ° C, and the etching depth is 70-80 nanometers to form an island-shaped buffer layer Double-buffered flexible substrate with SOI composition.

3. Using silane and methane as silicon source and carbon source respectively on the double-buffered flexible substrate, using CVD method, controlling the temperature to 1400°C, and epitaxially growing SiC material with a thickness of 80 microns on the double-buffered flexible substrate.

4. The double-buffered flexible substrate under the epitaxially grown SiC material is peeled off according to the following process:

First, the bulk silicon layer of SOI was stripped at 25°C using 49% HF acid at a ratio of 1:10 and 70% _HNO3 acid at a rate of 5.5 microns per second for 45 seconds, the bulk silicon layer is located under the BOX;

Then, use a concentration of 12% HF acid solution to corrode the BOX at 25° C., the corrosion rate is 32 Angstroms per second, and the time is 40 seconds;

Finally, using a ratio of 1:10, 49% HF acid and 70% _HNO3 acid solution at 25 ° C, the SOL and Si island buffer layer were stripped for 5 seconds, and finally formed 6-inch self-supporting 80-micron hexagonal phase 6H SiC material.

Example 2

The invention produces 4-inch self-supporting 100-micron cubic phase 3C GaN material.

Substrate selection: commercially available 4-inch (111) crystal plane Si wafer.

SOI manufacturing process: use oxygen injection to isolate SIMOX.

Island-shaped buffer layer production: using epitaxy.

With reference to Fig. 3, the manufacturing process of present embodiment 2 is as follows:

1. Using the SIMOX process to inject oxygen on the silicon wafer, make a SOL layer with a thickness of 30 nanometers, and a BOX layer with a thickness of 120 nanometers to form an SOI structure;

2. Use trimethylaluminum and high-purity ammonia gas as the source of aluminum and nitrogen on the SOL, and use the MOCVD method at a temperature of 450 ° C and a pressure of 40 torr to make an AlN island-shaped buffer layer by epitaxy. forming a double-buffered flexible substrate;

3. Using triethylgallium and high-purity ammonia gas as gallium and nitrogen sources on a double-buffered flexible substrate, using MOCVD method at a temperature of 950°C and a pressure of 40 Torr, on a double-buffered flexible substrate The GaN material is epitaxially grown to a thickness of 100 micrometers.

4. The SOI structure of the grown GaN material is peeled off according to the following process:

First, using 49% HF acid and 70% _HNO3 acid solution at a ratio of 1:10, the bulk silicon layer of SOI was stripped at 25°C, with an etching rate of 5.5 microns per second for For 45 seconds, the bulk silicon layer is located under the BOX layer;

Then, use a 12% HF acid solution to corrode the BOX at 25° C. at a corrosion rate of 32 angstroms per second for 40 seconds to peel off the BOX;

Finally, the SOL was stripped using a 1:10 ratio of 49% HF acid and 70% _HNO3 acid solution at 25°C for 3 seconds to form a 4-inch self-supporting 100-micron cube GaN material with phase 3C structure.

In addition, in addition to photolithography and epitaxy techniques, nanometer self-organization techniques can also be used to fabricate the island-shaped buffer layer of the present invention.

For those skilled in the art, after understanding the content and principles of the present invention, they can make various amendments and changes in form and details according to the methods of the present invention without departing from the principles and scope of the present invention. But these amendments and changes based on the present invention are still within the protection scope of the claims of the present invention.

Claims (3)

1. the manufacture method of a large area, self-supporting semiconductor material with wide forbidden band, carry out according to the following procedure:

The first step is according to the crystal orientation and the size of the application choice silicon chip of self-supporting epitaxial loayer;

Second step, utilize the isolation of notes oxygen SIMOX, wafer bonding BESOI, smart peeling UNIBOND on selected silicon chip, to make buried oxide layer BOX, surface silicon SOL, form soi structure;

The 3rd step, on the surface silicon SOL of soi structure, utilize photoetching, epitaxy technique to make the island resilient coating, form the double buffering flexible substrate that island resilient coating and SOI constitute;

In the 4th step, on described double buffering flexible substrate, utilize epitaxy technique growing semiconductor material;

The 5th step, utilize conventional stripping technology that double buffering flexible substrate or soi structure layer below the described semi-conducting material are peeled off, form the semiconductor material with wide forbidden band of large tracts of land, self-supporting.

2. the manufacture method of semi-conducting material according to claim 1 is characterized in that the process of utilizing photoetching process to make the island resilient coating is as follows:

The first step is made mask plate according to the single island size and the island spacing of design;

Second goes on foot, and the mask plate of making is placed carry out photoetching, development on the SOL that scribbles photoresist;

The 3rd step, use corrosive liquid that SOL is carried out etching earlier, to guarantee the height on each island, re-use organic solvent and remove photoresist and clean surface, on SOL, form the island resilient coating.

3. the manufacture method of semi-conducting material according to claim 1, it is characterized in that the process of utilizing epitaxy technique to make the island resilient coating is: select GaN or AlN material as making the epitaxial material that SOL goes up the island resilient coating, make extension be in the island growth pattern by temperature, the pressure of controlling outer time-delay, adjust growth time and control the size and the spacing on single island, on SOL, form the island resilient coating.

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