Plasma purification by ion cyclotron resonance for plasma sourceion implantation doping of semiconductors

摘要

Summary form only given. Using Plasma Source Ion Implantation(PSII) to create the shallow source and drain structures required fornext generation devices may be a necessity. A critical concern for theuse of PSII in doping these next generation semiconductor devices is toavoid implanting contaminant ions. For example, future devices arepredicted to require that heavy metal doses be kept less than 3×10⁹ atoms per square centimeters. When doping semiconductorsusing conventional beam line accelerator technology, the implantation isvery pure because bending the beam with a magnetic field veryefficiently selects a single mass species. In order to provide a similarpurity implantation for PSII a process utilizing ion cyclotron resonancefor plasma purification prior to implantation is being investigated. Inorder to purify the plasma a DC magnetic field is imposed in the plasmaand an RF electric field is imposed perpendicular to the magnetic field.If the frequency of the RF electric field is selected to be at thecyclotron frequency of a contaminant ion, the contaminant ion will gainenergy efficiently and be diffused out of the plasma faster thannoncontaminant ions, and its increased diffusion rate will be primarilyperpendicular to the magnetic field. Once a contaminant ion is expelledfrom the plasma it is neutralized upon collision with a wall and is nolonger an implantation hazard. We present simulation results showingnecessary field strengths and uniformity for plasma purification,cleaning efficiency of the described system, and frequency/massresolution of the method