1、 Development history of ion sputtering implantation technology
Ion sputtering implantation technology has been used as early as 1944. During World War II, new materials were made on U235 by isotope isolation method, and the uranium beam was generated from the ion source working on UF6. The 100 Ma uranium ion beam accumulates on the target at a rate of 170 micrograms per second, which is extremely expensive for commercial applications. In 1950, Bell Laboratories Used ion sputtering implantation technology to improve the material properties and doped semiconductors. At the same time, it was found that annealing technology can eliminate the damage of semiconductor wafers after ion implantation. However, from 1960 to 1970, due to the low doping requirements of semiconductor devices at that time, the diffusion doping method could fully meet the needs of semiconductor doping at that time, and the diffusion furnace was simple, low-cost, without high vacuum environment, and the implanter was complex, requiring high vacuum environment and high cost. Therefore, in this decade, the implanter did not get corresponding development The advantages of doping are not reflected. Until later, Mostek Corp of Bell Laboratories successfully used low-dose ion implantation to adjust the threshold voltage for the first time, which reflected the advantages of ion implanter to accurately control the dose but the diffusion method could not. In the early 1970s, Bill Appleton of solid
state department made an experimental study on ion beam materials. The project focused on the channel effect and physical properties of energy ions in solids, and soon this research was extended to ion implantation. Ion beam modification of semiconductors, metals, insulators, ceramics, etc. was carried out by enthusiastic collaborators from universities and industry, and the results soon surpassed those of Appleton member group. As a result, the center for surface modification and characterization (SMAC) was formed in 1980, and ion implantation equipment was expanded. The center now has four accelerators with unique characteristics of high current, high energy implantation and low energy ion beam deposition. In the 1980s, with the large-scale development of integrated circuits, the energy, dose range and elements needed to be implanted increased, which developed into medium beam ion implanter, large beam ion implanter, special high energy machine and special low energy machine. Since 1984, the technology of ion sputtering implantation has also developed rapidly. Parallel beams can be obtained, which can be tilted, repositioned or rotated in the beam.
2. Development trend of ion sputtering implantation technology
At present, the leading manufacturers of ion implanters mainly include applied materials from the United States, ashelet and Verion, and Sen, Nissan and Japanese vacuum in Japan. Generally speaking, equipment manufacturers produce three types of implanters: high current implanter, medium beam implanter and high energy implanter. High current injector provides high dose injection, large beam current and low cost. The working voltage ranges from 200ev to 120kev, and various elements can be implanted. Either the filament structure or the hot cathode is used to generate electrons and ions by indirect heating. Another method is to use RF source technology, which is to generate molecular excitation in magnetic field environment, and then produce higher extraction beam and colder static plasma. Traditional high current injection adopts batch process to reduce cost. This requires 13 discs to be placed on a solid aluminum plate and rotated at 1000-11200 rpm. Varian recently introduced a new technology to handle wafers, which minimizes the risk of wafers and does not idle them. Varian introduces shc-80 wafer, which is essentially a series of process types. This type is faster and cleaner than others on the market, requiring only a small part of the batch system to work. The machine allows the processing of 200 mm and 300 m wafers at low cost.
High energy injection brings more flexibility and improves the structure characteristics of submicron devices. Its advantages also include low heat load and high process flexibility in IC fabrication. The doping surface can be trimmed and optimized to meet the performance requirements of different devices, with channel flexibility, thermal load generation, junction capacitance and CMOS latch up sensitivity. High energy injection can ensure the formation of the micro layer below the surface without any disturbance. The technology used is similar to the general technology at 200keV, when the ion penetrates the substrate higher and there is no disturbance in the substrate background layer near the surface. The concentrated peak moves slowly towards the surface and forms a retrograde wall. Therefore, high energy injection brings more opportunities for IC production.
International semiconductor technology roadmap shows that ion implantation faces two major challenges: (1) forming low leakage shallow junction; (2) using low-cost MeV implantation instead of epitaxy, and using low-energy boron ion beam implantation technology to obtain high-quality shallow p-junction for molecular dynamics research. The latest technology for obtaining high quality shallow p-junction was completed by ion beam Engineering Laboratory of Kyoto University. Cluster ion implantation with hydrogen borate was used to form shallow junctions. Small boron beam and monomer injection were used to simulate the molecular dynamics. In the final stage, the damage of B10 cluster formation is expected to avoid the transient increase of diffusion of additional B atoms, and high quality shallow p-junction can be obtained.
3. Application fields of ion implantation technology
3.1 ion sputtering implantation technology applied to metal material modification
The application of ion sputtering implantation technology in metal material modification is to inject a certain amount of ion and energy into the surface of metal material through heat treatment or surface coating process. The chemical composition, physical structure and phase state of material surface layer are changed by ion implantation machine, so as to change the mechanical property, chemical property and physical property of material. Specifically, ion implantation can change the acoustic, optical and superconducting properties of materials, improve the working hardness, wear resistance, corrosion resistance and oxidation resistance of materials, and finally extend the working life of materials.
3.2 ion sputtering implantation technology applied to doping process
In semiconductor technology, ion sputtering implantation technology is advantaged by nature, with high precision dose uniformity and repeatability, which can obtain ideal doping concentration and integration degree, greatly improve the integration, speed, yield and life of the circuit, and reduce the cost and power consumption. This is different from CVD. In order to obtain ideal parameters, such as film thickness and density, CVD needs to adjust the equipment setting parameters such as temperature and gas flow rate, which is a complex process. In the 1970s, it may take only 6-8 injections to process simple n-type metal oxide semiconductors, while modern CMOS integrated circuits with embedded memory functions may need up to 35 injections.
3.3 application of ion sputtering implantation technology in SOI Technology
Due to the increasingly mature application of SOI technology in submicron ULSI low-voltage low-power circuit and anti radiation circuit, people have carried out extensive exploration on SOI preparation technology. In 1966, Watanabe and tooI first reported that o + It is possible to inject Si oxide on the surface of sIlf to insulate devices. In 1978, NTT reported that after developing a high-speed, low-power CMOS chain oscillator circuit with this technology, the o-beam was injected into the system + Technology has become a new technology of public attention. So the oxygen injection isolation technology, SIMOX, has become the most promising large-scale integrated circuit production technology among many SOI preparation technologies. In 1983, NTT successfully applied SIMOX technology to mass produce comsbsh integrated circuits; in 1986, NTT also developed radiation resistant devices. After that, Eaton company produced a series of nv-200 super current oxygen ion implanters. Later, Ibis company also developed ibis-1000 super current oxygen ion implantation machine. Since then, SIMOX technology has entered the era of mass production. In the late 1990s, when people studied the wide application of SIMOX materials, they also found some insuperable defects in SOI materials formed by oxygen injection, such as silicon island, defects, uneven thickness of top silicon layer and oxide layer, etc., which led to the research of smart cut technology which combines hydrogen injection and silicon wafer bonding technology.
In addition to semiconductor industry, ion sputtering implantation technology is also widely used in metal, ceramic, glass, composite, polymer, mineral and plant seed improvement.