Abstract: This article introduces the process flow of processing sapphire (Al2O3) crystal substrates with domestic equipment and domestic raw materials, and focuses on the principle and effects of the polishing solution used to polish sapphire crystal substrates.
Keywords: white gem (Al2O3) crystal substrate physical grinding, chemical polishing, polishing solution
1 Introduction The sapphire (Al2O3) crystal substrate is the basic material for the production of blue light emitters and blue lasers. The quality of his substrate surface directly affects the performance and yield of the device. Therefore, (Al2O3) crystal substrate processing technology, like other semiconductor wafers, has experienced continuous development and improvement and has become a new bright spot in crystal substrate processing. With the introduction of crystal substrate processing equipment in China, the processing technology of (Al2O3) crystal substrates has also been introduced. However, its cost is high and controlled by people. Whether it is possible to process qualified Al2O3 crystal substrates with domestic equipment and materials has become a new issue.
This article will introduce the selection, process characteristics, process flow, core technology and principles of (Al2O3) crystal substrate processing equipment, the actual use effect and promotion application prospect of polishing liquid and Al2O3 crystal substrate processing technology.
2 Equipment selection Equipment selection is very critical. Its own technical indicators, manufacturing quality and operating conditions have a great influence on the quality of crystal processing. For grinding, the smoothness of the equipment operation is crucial, which directly affects the quality of the processed substrate. For polishing, the speed is slow, the rate is low, and it is easy to corrode. The chemical rate of the processed wafer is greater than the mechanical rate. The speed is fast, the mechanical effect is too strong, it is easy to fall off, the surface damage layer is very large, and the quality is not good. Relative revolutions between 100 and 120 rpm are suitable. After investigation and experiments, the UNPOL-1501, UNPOL-1502, UNPOL-801 and UNPOL-802 precision grinding and polishing machines developed and produced by Shenyang Kejing Equipment Manufacturing Co., Ltd. meet the requirements of various crystal substrate processing and are applicable The processing technology of the sapphire crystal substrate. It is an ideal processing equipment for a better small production line.
3 Technological characteristics Due to the high hardness and the structure of the Al2O3 crystal substrate, as well as the influence of the process attached to the imported processing equipment, it is basically a physical grinding-based processing technology, and various abrasives are imported. Starting from the larger grain diamond abrasive, after repeated grinding, the particle size of the diamond is reduced every time until the fine diamond powder suitable for the process is reached, and the white sapphire crystal substrate is processed into a substrate that meets the process requirements. The wafer comes, so-called physical polishing process. It is very time-consuming, and the cost of the equipment and abrasive materials required is also expensive.
Using domestic equipment and domestic abrasives, the processing technology of white gem (Al2O3) crystal substrates adopts physical grinding and chemical polishing processing methods, all of which are localized, thereby reducing processing costs. Its characteristics are: the first half of the process is a physical grinding process (respectively rough grinding and fine grinding), and the second half of the process is a chemical polishing process (respectively rough polishing and fine polishing).
4 The technological process is based on the structure, properties and hardness of the sapphire (Al2O3), the domestic equipment and abrasive materials, and the characteristics of the sapphire crystal substrate polishing liquid developed on this basis, and the processing technology of the sapphire crystal substrate The process is as follows:
Picking → Sticking → Rough Grinding 1 → Rough Grinding 2 → Rough Grinding 3
↓
Qualified film ↠fine polishing ↠rough polishing ↠fine grinding 2 ↠fine grinding 1
The above process depends on the condition of the sapphire (Al2O3) crystal substrate itself, which can reduce the number of grinding steps and the processing time is approximately 8 hours. Grinding for 5 hours, each polishing process is about 1 hour. It can reduce the time during rough grinding. During fine grinding, the time can be increased appropriately. Polishing for 3 hours, including: rough polishing process for 2 hours and fine polishing process for 1 hour.
5 Core technology and principle The core of this process is the use of chemical mechanical polishing. On the basis of finely ground sapphire (Al2O3) crystal substrates, chemical mechanical polishing is performed to replace the rear physical polishing method of the introduced process. The polishing process uses a combination of rough polishing and fine polishing to remove the mechanical damage layer of the abrasive on the surface of the white sapphire (Al2O3) crystal substrate during fine grinding, and further improve the flatness and smoothness of the surface of the white sapphire crystal substrate. Qualified substrate wafers required on the process line.
The polishing solution is based on the chemical and physical properties of white gemstone (Al2O3) and the related chemical reaction principles. Several reagents were selected and successfully developed through reformulation and related chemical reactions. Divided into two dosage forms, used for rough polishing process and fine polishing process. The polishing liquid can also be made into concentrated mother liquor, which is easy to use and transport. When used, the concentrated mother liquor is diluted with high-purity water and used. It is non-toxic and tasteless.
In the processing technology of white sapphire (Al2O3) crystal substrates, the polishing principle should meet the following assumptions: First, a certain component in the polishing solution oxidizes Al2O3 to form an ionic form on the surface of AL2O3. Under alkaline conditions, there are Metaaluminate ion generation:
Al + + + + 3OHï¼ â†’ H2O + HAlO2 → H + AlO2ï¼
Under the action of mechanical conditions, these ions enter the polishing liquid, so that the Al2O3 crystal substrate is exposed to a new surface, so that a certain component of the polishing liquid and the Al2O3 crystal substrate surface can continue to undergo a chemical reaction. The metaaluminate ions entering the polishing liquid react with a certain metal ion in the polishing liquid to generate crystalline precipitates, which in turn participate in polishing. The above process is repeated to make the flatness and smoothness of the surface of the sapphire (Al2O3) crystal substrate meet the technological requirements.
6 Process effect Use this process to process the Al2O3 crystal substrate. The surface of the Al2O3 crystal substrate is bright and hydrophobic, without scratches, pits, cloudiness, arc pits, ripples and orange peel. Observed under a 400x microscope, the wafer substrate is good and meets the process requirements.
On domestic equipment, the use of domestic grinding and polishing materials to process white sapphire (Al2O3) crystal substrates is a requirement of some domestic manufacturers of white sapphire (Al2O3) crystal substrates. The process provides a feasible process flow required in this regard, and has obtained preliminary approval.
A company in Shenzhen that manufactures blue light-emitting diodes. After the die of the diode is fabricated on the Al2O3 wafer, the back of the AlL2O3 substrate should be thinned and polished. Using this process flow to conduct experiments, first grinding, then polishing, to achieve the purpose of thinning and polishing, in line with the final process requirements.
A semiconductor research institute in Tianjin processed the sapphire (Al2O3) crystal substrate, using the polishing and grinding equipment produced by Shenyang Kejing Equipment Manufacturing Co., Ltd., using the above-described process flow to produce a qualified (Al2O3) crystal substrate Process requirements.
7 Application background The processing technology and polishing liquid of Al2O3 crystal substrate is based on the replacement of imported equipment with domestic equipment, and the substitution of imported abrasives and polishing liquid with domestic abrasives and polishing liquid, which is the so-called all domestic Change. If this is achieved, the application prospects are optimistic and promising.
First of all, on the premise of ensuring the processing quality of the Al2O3 crystal substrate is unchanged, the use of domestic equipment to replace imported equipment, the price of the equipment itself has dropped several times or more, reducing processing costs and training costs. The maintenance of equipment and replacement of vulnerable parts are not only convenient, but also save a lot of expenses.
Secondly, the localization of abrasives and polishing liquids has replaced expensive imported abrasives and polishing liquids, and the price has also been reduced exponentially. The use of readily available domestic raw materials not only reduces costs, but also improves the economic benefits of processing manufacturers. .
The above two points are exactly what the processing technology of the white sapphire (Al2O3) crystal substrate described in this article is to use. Using domestic equipment and using domestic raw materials, the processed crystal substrate meets the process requirements and meets the domestic processing of sapphire crystal substrate Manufacturer's requirements.
Due to the localization of equipment, the localization of grinding raw materials and polishing liquid raw materials, the processing cost will be reduced exponentially, and the reduction in cost will produce higher economic benefits and increase the competitiveness of processing manufacturers. Therefore, the promotion of this process is optimistic.
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