Characteristics of a chemically amplified silicone-based negative resist in KrF excimer laser lithography

A chemically amplified silicone-based negative resist, CSNR, composed of an alkali-soluble silicone polymer (ASSP) and an acid generator has been developed for two-layer resist systems. ASSP is obtained by a sol-gel reaction of organotrimethoxysilane and has numerous silanol groups that make it alkali-soluble. The resist chemistry of CSNR is based on the acid- catalyzed condensation of the silanol groups during post-exposure bake (PEB). A 0.5 micrometers - thick CSNR is used as the top imaging layer. The sensitivity (D50) is 30 mJ/cm2 and the (gamma) value is 4. A linear relationship between mask and resist pattern linewidths is maintained down to 0.25 micrometers line and space (l&s) patterns with steep profiles. The CSNR includes silicon atoms in such abundance that it exhibits high resistance to oxygen reactive ion etching (RIE). Using oxygen RIE, two-layer resist processing can be easily accomplished down to 0.22 micrometers l&s patterns with vertical walls.