Activation of Implanted n-Type Dopants in Ge Over the Active Concentration of 1×10[sup 20] cm[sup −3] Using Coimplantation of Sb and P

Abstract

One of the greatest challenges in fabricating a Ge-channel n-MOSFET is achieving a high n-type dopant activation within the source and drain regions. Conventional approaches to increase the electrically active doping level have been proven to be unsatisfactory, and typically the highest activation of n-type dopants is 4 × 10 19 cm -3 using phosphorus. This article describes a method to enhance the activation level of n-type dopants in Ge. Coimplantation of phosphorus and antimony leads to dopant activation over 1 X 10 20 cm -3 at 500°C. The enhancement of n-type dopant activation is attributed to reducing the implantation damage upon annealing due to increase in solid solubility of the dopants.