Improving Metal Oxide Semiconductor Device Performance Through the Use of Ion Exchange‐Purified HF

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Abstract
Ion‐exchange purification systems were employed at two different semiconductor metal oxide semiconductor (MOS) wafer fabs to purify the dilute hydrofluoric acid solutions used in cleaning silicon wafers. One fab performed the cleans in immersion baths while the other fab used a spray cleaner. Both fabs observed improvements in device performance, as measured in split‐lot gate oxide integrity tests; after they began using the ion exchange‐purified . One fab also observed a significant improvement in refresh characterization time, and a 5% yield improvement at multiprobe. These improvements are believed due to the lower levels of metallic impurities in the ion exchange‐purified . Impurity levels of over 30 elements in the treated are routinely below 1 ppb.
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