Polysiloxanes with a Phenol Moiety for Bilayer Photoresist Applications

Abstract

Novel Polysiloxanes with a phenol pendant group were synthesized and applied to bilayer photoresists for g-line and deep-UV (248 nm) lithography. These polymers had adequate aqueous-base solubility and oxygen-RIE resistance to serve as the base resin component for top imaging resists in bilayer resist systems. One of these polysiloxanes was synthesized from chlorodiethoxyphenylsilane and m-trimethylsiloxychlobenzene. Others were synthesized from dichlorophenylsilane and phenol and phenols with a double bond moiety (eugenol, isoeugenol and m-isopropenylphenol). These polysiloxanes had from 9.8 wt.% to 13.1 wt.X Si content and displayed an oxygen-RIE resistance 10 times greater than novolak resin. The m.p. values for these polymers ranged from 30°C to 90°C. The UV transmittance value (at 248 nm, 1 micron thickness) were from 7 % to 76 X. Resists were prepared from these polysiloxanes and sensitizers. In g-line lithography, the sensitizer was naphthoquinonediazide. In deep-UV (248 nm) lithography, the sensitizer was selected from naphtoquinonediazide, diazide and diazo compounds. 0.5 micron line and space patterns were obtained, when the resist was exposed using a g-line stepper, and using a tetramethylammonium hydroxide solution (ca. 1.3 %). 0.4 micron line and space patterns were resolved, when the resist was exposed using a KrF excimer laser stepper, and developed using the same solution. The top layer pattern could be transferred to the bottom layer (hard baked positive resist OFPR-5000) using oxygen-RIE. The etching rate for the silicon containing resist was 35 nm/min, while that for OFPR-5000 was 555 nm/min. These polysiloxanes make it possible to obtain the fine pattern resolution required in VLSI processing.