1. Background, necessity and significance of the project
Due to the high price of foreign SOI materials and the blockade and embargo imposed on China, it is difficult for domestic research institutes and manufacturers to develop and produce SOI integrated circuits. It is impossible to rely on imports to realize the development of China's high-tech electronics, information technology and national defense modernization in the early 21st century. If we can realize the localization of SOI materials, we can mass produce various series of SOI radiation resistant, lock-free, high-speed, low-power integrated circuits and various high-performance high-temperature sensors that are urgently needed by the military. We can equip our country's electronic control systems for satellites, rockets, missiles and spaceships, so as to improve the service life, control accuracy and safety and reliability of these weapons and equipment, We should improve China's national defense strength. At the same time, it provides technical and industrial support for the large-scale promotion and application of SOI devices in high-tech civil fields such as mobile communication, computer, automobile, aerospace, nuclear energy and oil refining.
At present, although the quality of commercial SOI silicon wafers that can be prepared in the United States is not perfect, its price is expensive. If it is possible to take the lead in realizing the industrialization of SOI materials, it will further promote the development of electronic information materials in China and bring huge economic and social benefits.
2. Application and technology development of SOI
SOI material is the most important silicon integrated circuit material in the 21st century. Due to the special structure of SOI material, the device made of SOI material has very low parasitic capacitance and low working voltage, which can reduce the influence of short channel effect and hot electron effect. At the same time, it has the advantages of no latch up, low leakage current, low power consumption, fast speed and high driving ability, strong high temperature resistance and radiation resistance, high integration and simple process. It can be used to manufacture low-voltage, low-power devices and high-temperature devices (operating temperature up to 300 ℃, e.g High temperature pressure sensor ）。 In CMOS / SOI circuits, the photocurrent produced by irradiation is about three orders of magnitude smaller than that of bulk silicon CMOS circuits, and the ability to resist transient irradiation and neutron irradiation is much higher than that of bulk silicon CMOS circuits.
SOI devices are mainly used in low-voltage, low-power and high-temperature devices for computers, automobiles, aviation and petroleum refining, as well as radiation resistant circuits for satellites and missiles in military microelectronic aerospace. SOI materials, especially thin-film SOI structural materials, effectively overcome the shortcomings of bulk silicon materials and give full play to the potential of silicon integration technology. It has a very wide application prospect in high performance ULSI, high voltage, high temperature, radiation resistance, low voltage and low power consumption and three-dimensional integrated circuits. SOI material is an ideal material for manufacturing ultra-high speed signal processing and strong anti nuclear radiation ability computer and control components needed in national defense and economic construction. SOI technology has become the national defense microelectronics cutting-edge technology. There are many kinds of technologies to prepare SOI materials, such as lateral growth of silicon epitaxy, recrystallization of polycrystalline silicon or amorphous silicon on silicon dioxide, silicon wafer bonding and etch
back technology, SIMOX (separation by implanted) technology Oxygen (oxygen) and smart cut (smart cut, that is, the silicon wafer with oxide layer is synthesized by bonding method, and the upper layer is stripped and polished after the hydrogen atom layer is heated). SIMOX and smart cut are more suitable for mass production.
Smart cut is a new technology developed to overcome the difficulty of silicon wafer thinning in besoi technology. It has a bright future and has become one of the research hotspots of SOI technology. There are some difficulties in the preparation of SOI materials by smart cut technology: in the process of hydrogen injection stripping, high dose of injected hydrogen is in a discrete condensed state, which does not form a large area of continuous layer, which makes it difficult to peel off. After stripping, the surface of the top silicon layer must be further treated before manufacturing devices; due to the flatness and impurities of the surface layer, the physical properties of the bonding interface are also discussed Imperfect performance also affects the reliability of circuits on top silicon.
SIMOX technology is the mainstream manufacturing technology of SOI materials. Commercial SOI materials have been sold by ibis, spril and Soitec in France. With the development of thin film fully depleted submicron integrated circuits, SIMOX technology is developing towards the direction of low injection dose and low injection energy. The purpose of SIMOX technology is to manufacture SOI materials of ultra-thin silicon film, reduce injection time, reduce contamination, improve crystal integrity of top silicon film and reduce cost. SIMOX technology shows its unique advantages in this respect.
Compared with other countries, there is still a considerable gap in the comprehensive performance index of SIMOX materials in China. The main performance is that the resistivity uniformity, dislocation density and metal contamination of the top silicon layer are inferior to the advanced level of foreign countries, which can not meet the requirements of integrated circuits at present. Backward manufacturing equipment, lack of special oxygen injection machine with strong beam current (> 1mA) and ultra-high temperature annealing equipment (> 1300 ℃) are the main reasons for the huge gap in manufacturing technology of SIMOX materials in China. At present, most of the SOI materials that domestic research and production units can get are obtained from foreign countries through informal channels. The quantity is very small and the quality can not be guaranteed, which can not meet the needs.
3. SOI supply and demand
At present, SOI devices in China are in the stage of development, and the market demand is about 1000-2000 chips / year. In the next three to five years, with the wide use of SOI devices and circuits in national defense equipment, the demand for SOI materials will increase greatly. If SOI devices are produced on a large scale and widely used in communication, electronics, computer, aviation, automobile and other civil fields, the demand for SOI materials will rise rapidly in geometric order. Similar to other electronic products, since 1998, with the development of production scale and the decline of production cost, the price of SOI materials in the international market is basically in a slow downward trend. It is expected that this downward trend will be maintained in the next few years, but the decline rate will not be too large, especially in the domestic market.
4. Technical problems in SOI preparation technology
Although SIMOX technology has been commercialized in foreign countries, there are still three important problems to be solved: due to the high oxygen ion implantation, the residual oxygen concentration in the top silicon is high, resulting in the formation of high density dislocations, especially the through dislocations which are difficult to eliminate, and the quality of single crystal is poor; there are pinholes, pipes and silicon segregation products with silicon atoms as the main body in the buried layer of silicon dioxide; and there are still three important problems; Excessive annealing temperature The product yield and cost are affected. Generally speaking, high temperature annealing is an effective way to eliminate dislocations. In order to obtain high-quality materials, the annealing temperature is higher than 1300 ℃ and the annealing time is as long as 6 hours. If it is not very close to the melting point of silicon, the annealing temperature may be higher, and the method of increasing the annealing temperature uses the limit, which can not completely solve the problem.
In recent years, due to the successful research and the improvement of the performance of SOI thin films, with the thickness of silicon layer on the surface of SOI materials becoming thinner, SOI devices can reach a more superior fully depleted state. This SOI thin film material is more suitable for manufacturing high performance deep submicron ULSI circuits. Thin film fully depleted SOI devices have the advantages of high speed, low power consumption (1V power supply), good radiation resistance, high integration and low cost. Submicron ultra-thin SOI technology is an ideal choice for realizing high speed, high throughput and anti radiation circuit.
5. Technical process route of the project
Oxygen ion implantation into monocrystalline silicon wafer: the dose and energy of implantation should be controlled to reach the predetermined depth and concentration, and the electrical characteristics of surface silicon layer and silicon oxide layer should also be met. At the same time, the temperature of the silicon wafer is controlled to maintain the single crystal state of the top silicon layer. High temperature annealing: after thorough cleaning, a protective silicon oxide film is grown on the surface of silicon wafer. The annealing time and temperature of the silicon wafer are controlled. It is required that the metal contamination, damage and interface unevenness caused by the process should be controlled within the allowable range. Amorphous technology to improve product quality: combining silicon self injection amorphization and rapid thermal annealing technology, control process conditions, mainly solve the product quality problem of single crystal of surface silicon layer and integrity and uniformity of silicon oxide layer in SIMOX technology, and optimize injection and annealing process technology to reduce costs and improve productivity.
6. Environmental impact of the project
In the process of semiconductor material manufacturing, it is necessary to remove all kinds of impurities on the surface of silicon wafer, including surface layer, metal contamination, residual organic solvents and chemical reagents. The main purpose of high purity water (updi water) is to remove various chemical impurities on the surface of silicon wafer. In addition to the chemical impurities discharged in the process of cleaning silicon wafers, waste gas and waste liquid will be discharged from the cleaning and maintenance of special manufacturing equipment, especially the water making equipment. By products and all contaminated materials must be managed as hazardous materials and treated with special wastes (including solid waste residue, contaminated clothes, contaminated vacuum pump oil, waste liquid of water shower system, solid waste of dry-type adsorber, etc.). Appropriate precautions must be taken, such as wearing disposable coats, disposable gloves and masks. Contaminated materials such as work clothes and cleaning utensils that need to be reused must be specially treated to prevent employees from being affected by pollutants.
7. Social benefit evaluation of project implementation
The price of SOI materials in foreign countries is very high. Even if the embargo is lifted or the way to import them is found, the price is still unbearable for domestic users. For the country, it will cost a lot of precious foreign exchange. To realize the industrialization of SOI materials in China, its relatively low price will be welcomed by domestic users. On the one hand, it can meet the needs of domestic users, on the other hand, it can also reduce or even do not need to import, saving a lot of foreign exchange for the country. When domestic SOI materials enter the international market, they can also generate a large amount of foreign exchange for the country.
Up to now, there is no enterprise in China that has the ability of SOI material industrialization. If the large-scale production of SOI materials can be realized in China, and a new material industry system with independent intellectual property rights, digestion, absorption and innovation ability can be established, which will be a milestone of China's high-tech material manufacturing technology, and will certainly affect and drive the further development of domestic related science and technology fields. This article originates from Zetian sensing Please keep the source.