ANOMALOUS BEHAVIOR OF SHALLOW BF3 PLASMA IMMERSION ION-IMPLANTATION

Plasma immersion ion implantation (PIII) with BF3 and SiF4 plasmas is used to fabricate shallow P+/N junctions in Si. Exposure to the plasma and accelerated ions can lead to simultaneous etching and deposition on the substrate during implantation. A simple mathematical model for this process is presented and applied to the case of shallow implantat ion of BF3. Etching rates of SiO2 are seen to vary with power and pres sure of the process gas. Etching rates of Si, SiO2, and CoSi2 are stud ied by spectrophotometry and Rutherford backscattering spectrometry. T he roughness of Si substrates and SiO2 and CoSi2 films before and afte r PIII is monitored by atomic force microscopy.