A new modified HF-last cleaning process for high-performance gate dielectrics

A cleaning mixture which consists of HF with minute amounts of IPA added is discussed. This solution prevents the deposition of particles on the Si surface during HF-dipping and subsequent deionized-water rinsing and does not change the chemical state of the surface significantly. The characteristics of a thin gate oxide grown after this treatment show a markedly improved performance over the standard HF-last or RCA-cleaned samples. The addition of IPA to the HF mixture gives electrical breakdown results which are comparable to or better than the best results for HF-last samples. This demonstrates that the physisorbed IPA poses no problem for the gate oxide growth. It was observed that the contact angle directly correlates with the gate oxide yield. It is, therefore, a very powerful and fast technique for characterizing the Si surface after various treatments.<>