Advances in Cross-Contamination Control Using Single-Wafer High-Current Implantation

摘要

The Varian VIISta-80 is a single-wafer high-current implanter, which uses a ribbon beam, and a single-direction mechanical scan for implantation. The placement of the wafers on an electrostatic platen and the absence of end-station parts in the vicinity of the wafer during implant translate into an expected advantage in implanter memory over batch tools. This paper focuses on P-in-As cross-contamination and compares the performance of the VIISta 80 to a representative of the batch family of high-current tools - the Varian VIISion 80. The results of experiments designed to understand the mechanisms of phosphorus build-up in machine parts exposed to the P~+ beam, as well as their clean-up by a variety of subsequent ion beams are discussed in detail. Phosphorus levels in arsenic-implanted wafers are assessed using secondary ion mass spectrometry (SIMS) and four-point probe sheet resistance measurements. Typical cross-contamination performance is presented and recommendations on further reduction of the memory effects are made. Additionally, data on P-in-B, B-in-As, and B-in-P cross-contamination modes are reported.