Nano-structure stiction during drying has often occurred due to scaling of semiconductor devices. For less stiction drying technology, lower surface tension liquids such as isopropyl alcohol (IPA) or super critical fluid (SCF) have been developed, but are lacking in enough performance or maturity for 300 mm leading-edge device wafer treatment. Thus, we have focused on the surface energy reduction process which enables separation of the once adhering structures. We have evaluated the effect of the surface energy on the stiction with both calculation and experimental data, and have successfully demonstrated that the surface energy reduction process can suppress high aspect-ratio nano-structure stiction.
Scaling of semiconductor devices has caused nano-structure stiction issues during the drying step of wafer cleaning. We have already proposed a surface modification process to reduce the surface energy, and we have demonstrated this process is more effective for preventing nano-structure stiction than conventional IPA (isopropyl alcohol) drying. In this paper, the proper molecular structure is investigated for surface modification agents. It is important for the suppression of stiction to reduce a surface free energy rather than to increase a water contact angle. We have attained stiction free drying of a high aspect ratio pattern with 15 nm half pitch line and space using agents with shorter alkyl groups.
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