Methods of defect-engineering shallow junctions formed by B+-implantation in Si

Abstract

Control of dopant diffusion during high-temperature cycling is critical in forming shallow electrical junctions in silicon as needed in integrated-circuit manufacturing. However, junctions formed by implantation can be anomalously deep due to a transiency associated with ion-induced defects which greatly enhances dopant diffusion. The purpose of this work was to investigate methods of defect engineering the implantation process to control or eliminate transient-enhanced diffusion (TED). TED of boron has been attributed to excess interstitials introduced into the lattice during implantation, known as the plus-one model. Effects of pre-amorphization (i.e., amorphization prior to dopant implantation using isoelectric ions) on TED of boron, and particularly, the role of the end-of-range (EOR) defects at the amorphous-crystalline interface, are discussed. These EOR defects were varied by altering the implantation conditions during pre-amorphization. Also, other means of controlling the transiency are discussed, in particular, the use of high-energy ions to introduce excess vacancies into the lattice where dopant diffusion occurs. These vacancies are shown to interact with the excess interstitials introduced during dopant implantation to suppress TED.