Impact of molybdenum contamination on stacking faults in epitaxial silicon

While contamination of BF₂⁺ implants by double charged molybdenum has been well documented, the impact of that contamination on antimony implants has not been investigated and is the subject of this study. Many advanced power processes incorporate buried p and n regions created by implanting the substrate prior to growing the final epitaxial silicon layer. One such process is our 0.35um 80V HV CMOS process used in this study. For n-type regions, either arsenic or antimony is typically implanted. Antimony has the advantage of lower diffusion coefficients and therefore less auto-doping issues during the epitaxial silicon process compared with arsenic. While low levels of molybdenum contamination during the antimony implant will not impact the process, it was found that higher levels of contamination, above 3.2 ×10¹¹ ions/cm², can create both `mound´ defects (Figure 2) and planar stacking faults (Figure 3) in the epitaxial silicon layer. For the specific process studied, the estimated yield impact is approximately 0.5%.