Impact of elevated oxygen concentration on in-situ doped sub-50 nm SiGe and SiGeC base strained layer NPN HBT

Abstract

This paper presents the results of studies on oxygen concentration levels in in-situ boron doped sub-50 nm SiGe and SiGeC base strained layer NPN HBTs. The layers were characterized using four-point probe, secondary ion mass spectrometry and X-ray diffraction. The effect of oxygen concentration levels on boron sheet resistance, minority carrier lifetime, and device performance were investigated. It was found that oxygen can incorporate in SiGe by an order of magnitude over silicon. It is also determined that elevated oxygen can reduce the substitutional electrically active boron concentration and/or degrade the mobility, resulting in reduced sheet resistance. Similarly for elevated-oxygen concentration levels greater than 3/spl times/10/sup 18/ at/cc, device performance was found to be degraded.