Low-temperature technology for the formation of interconnections and contacts using ion beams

The work is studing of the formation of low-resistance contacts in the molybdenum-silicon system by the ion mixing method. The relevance of the work is due to the need to reduce the size of very large scale integration elements while maintaining low interconnect resistance. Refractory metal silicides, especially molybdenum, are considered as promising materials for metallization due to their compatibility with CMOS technology. The studies were carried out on n-type silicon wafers with a deposited molybdenum layer 90 nm thick. It was found that reproducible formation of the MoSi2 phase occurs at doses of 1016–1017 cm–2. The contact resistance is ~8 Ohm. A decrease in resistance with increasing dose is explained by the formation of silicide under the influence of the ion beam and doping of the contact area. The surface roughness after annealing decreases with increasing dose. The mechanism of silicide formation includes cascade mixing of atoms during collisions and accelerated diffusion due to an increase in the density of vacancies and the concentration of interstitial atoms. When phosphorus ions are introduced at room temperature, an amorphous silicon layer is formed (dose 1016 cm–2), which leads to a sharp decrease in the specific transition resistance after annealing at 600°C. When introduced at 350 °C, amorphization does not occur, and the resistance decreases gradually with increasing annealing temperature. The results of the study demonstrate the efficiency of the ion mixing method for forming low-resistance molybdenum-silicon contacts at low temperatures.