Lithographic Evaluation of Phenolic Resin-Dimethyl Siloxane Block Copolymers

Reactive, functionally terminated poly(dimethyl siloxane) oligomers (PDMSX) have shown promise as the silicon-containing component in bilevel resists based on conventional novolac-diazonaphthoquinone chemistry. The ability to photoimage the novolac-siloxane block copolymers depends on the initial siloxane block length, the chemical structure of the novolac resin and the microphase separation of the system. Glass transition temperature measurements, transmission electron microscopy and Auger depth profiling experiments indicate that extensive microphase separation occurs if high molecular weight siloxane oligomers are used. When the phase mixing of the two components was promoted in an o-cresol novolac-siloxane copolymer (PDMSX=510 g/mole), 0.5micron L/S patterns could be resolved using deep-UV exposures (248 nm) at a dose of 156 mJ/cm sup 2. Good solubility in aqueous tetramethylammonium hydroxide was observed with the copolymer containing 10 wt % silicon and an 0 sub 2 reactive ion etching resistance of 1:18 compared to hard-baked HPR-204 was obtained. The 0.5micron L/S patterns were transferred through a 1.4micron thick planarizing layer yielding features with high aspect ratios.