Thermal wave dopant profiling for phosphorous ion implantation

Abstract

Thermal wave (TW) thermal-probe is a common metrology tool to monitor implantation conditions. In most cases, TW signals have been used as a relative unit for ion implantation monitoring. Therefore, there is a requirement for a model to correlate the TW signal to ion implant parameters. In this study, a model is presented to address the issue of ion dopant profiling using the thermal wave technology. Study has been done on thermal wave signaling for Phosphorous ion implantation with different implant conditions (such as different implant energy from 70keV to 1800keV, different dose from 9x10 13 cm -2 to 1.1x10 14 cm -2 , different tilt angle from 2 o to 7 o , and different beam current from 0.04mA to 0.4mA) The result shows that 7 o and 2 o 320keV Phosphorous implants have similar implant profiles and TW signals as well. Therefore, TW signal is dependent on dopant profile instead of a function of implant angle, on the basis that same TW signals have the same SIMS profile. Then, the correlation between the TW signals and ion distribution has been studied. A model has been developed for thermal-wave depth profiling that provides expressions for ion range and concentration, where TW = K* Ai (x) ni (x) dx. The model is based on the concept of Thermal wave dampening due to lattice disorder by ion perturbation (Thermal wave is generated when the laser beam strikes the silicon substrate). Factor, Ai (x) is a function of ion range and ni is the ion concentration. The Ai (x) ni (x) dx, component of the TW model represents the dopant profile, while K (function of implant energy, beam current, dosage, and specie) is the damage factor that affects the magnitude of TW signal. In this paper, a simple method for dopant profiling has been demonstrated by using the model.