Co-sputtering phenomenon in plasma immersion ion implantation of samples for semiconductor applications

Co-sputtering in the plasma immersion ion implantation (PIII) of the different materials and structures used in silicon integrated circuit technology was investigated. Layer structures like SiO2 (grown)/Si, SiO2 (deposited)/Si, SiO2/Al/Si, polysilicon/SiO2/Si, and photoresist (patterned)/Si were implanted with nitrogen ions at −10 kV pulse voltage. Dose of the implantation was varied from 1014 to 1017 ions/cm2. In order to control the dose, frequency of the pulses was varied from 1 Hz to 1 kHz corresponding to lower and higher dose, respectively. The change in the film thickness of different samples was measured with ellipsometry and reflectivity based systems. Severe sputtering of the surface was observed at higher doses of the order of 1017 ions/cm2. Topographical structures of selectively implanted samples were observed using a scanning electron microscope (SEM). A marked change in the structure of Si and SiO2/Si was observed in case of samples implanted at highest dose. Sputtering generated micro-roughness was also observed using a surface profiler system.