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http://dx.doi.org/10.7464/ksct.2017.23.4.357

Study of Supercritical Carbon Dioxide/n-Butyl Acetate Co-solvent System with High Selectivity in Photoresist Removal Process  

Kim, Dong Woo (Department of Display & Engineering, Pukyong National University)
Heo, Hoon (Department of Display & Engineering, Pukyong National University)
Lim, Kwon Teak (Department of Display & Engineering, Pukyong National University)
Publication Information
Clean Technology / v.23, no.4, 2017 , pp. 357-363 More about this Journal
Abstract
In this study, the supercritical carbon dioxide ($scCO_2$)/ n-butyl acetate (n-BA) co-solvent system was employed to remove an unexposed negative photoresist (PR) from the surface of a silicon wafer. In addition, the selectivity of the $scCO_2$/n-BA co-solvent system was confirmed for the unexposed and exposed negative PR. Optimum conditions for removal of the unexposed PR were obtained from various conditions such as pressure, temperature and n-BA ratio. The n-BA was highly soluble in $scCO_2$ without cloud point and phase separation in mostly experimental conditions. However, the $scCO_2$/n-BA co-solvent was phase separated at 100 bar, above $80^{\circ}C$. The unexposed and exposed PR was swelled in $scCO_2$ solvent at all experimental conditions. The complete removal of unexposed PR was achieved from the reaction condition of 160 bar, 10 min, $40^{\circ}C$ and 75 wt% n-BA in $scCO_2$, as measured by ellipsometry. The exposed photoresist showed high stability in the $scCO_2$/n-BA co-solvent system, which indicated that the $scCO_2$/n-BA co-solvent system has high selectivity for the PR removal in photo lithograph process. The $scCO_2$/n-BA co-solvent system not only prevent swelling of exposed PR, but also provide efficient and powful performance to removal unexposed PR.
Keywords
Supercritical carbon dioxide; Co-solvent; Negative photoresist; n-butyl acetate;
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