IMPROVING METAL-OXIDE-SEMICONDUCTOR DEVICE PERFORMANCE THROUGH THE USE OF ION EXCHANGE-PURIFIED HF

Ion-exchange purification systems were employed at two different semic onductor metal oxide semiconductor (MOS) wafer fabs to purify the dilu te hydrofluoric acid solutions used in cleaning silicon wafers. One fa b performed the HF cleans in immersion baths while the other fab used a spray cleaner. Both f abs observed improvements in device performanc e, as measured in split-lot gate oxide integrity tests, after they beg an using the ion exchange-purified HF One fab also observed a signific ant improvement in refresh characterization time, and a 5% yield impro vement at multiprobe. These improvements are believed due to the lower levels of metallic impurities in the ion exchange-purified HE Impurit y levels of over 30 elements in the treated HF are routinely below 1 p pb.