Treatment homogeneity and conformal analysis of plasma based ion implanted 3D target

Abstract

A prismoid-shaped target was treated by plasma based ion implantation (PBII) with nitrogen plasma, in order to study the lateral homogeneity in the near region of square corner after treatment. Auger electron spectroscopy was used to execute sputter depth profiling to obtain nitrogen depth distribution and retained dose on the silicon wafer. It showed that, in addition to process parameters of PBII such as pulse voltage, pulse width and radio frequency power, treatment homogeneity is strongly dependent on the shape and dimensions of the workpiece being treated. The ion retained dose and its gradient of distribution are a strong function of the factors mentioned above. Due to enhanced sputtering effect induced by the oblique ion impact, lower retained dose and shallower implantation depth were observed in the vicinity of the edge contained by square corner. The gradient of retained dose distribution exhibits a higher value with higher pulse voltage, lower plasma density, longer pulse width and smaller target size. Aided by the results of numerical simulation, sheath expanding tendency and ion impact mode under various conditions were discussed. Through conformal condition analysis of plasma sheath and the resulting characteristic of ion impingement, a better understanding of the treatment homogeneity can be achieved.