Temperature and substrate dependence of Ar sputtering of CoSi₂ thin films

Abstract

The temperature dependence of 300 eV argon ion sputtering of CoSi 2 thin films has been investigated in the range 50-600°C. Compared with the low-temperature values, the high-temperature etch rate of CoSi2 on Si decreases by a factor of 3, while the sputtering yield ratio of Si to Co increases by a factor of 3.5. This leads to effective motion of the silicide layer into the Si substrate at temperatures above 400°C. During sputtering of CoSi2 on SiO2, the thickness of the silicide layer decreases almost linearly with bombardment time until all the silicide is removed. Similar behavior is observed in low-temperature sputtering of CoSi2 on Si. However, at elevated temperatures (400°C<T≤600°C), the etch rate of the silicide decreases significantly after an initial fast sputtering period. For CoSi2 on Si, experimental results show that while Si atoms are sputtered from the surface, Co atoms are released and diffuse to the silicide/Si interface where they react with the underlying Si substrate to form new CoSi2.