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We have recently reported the formation of scum-free subhalf micron images in a bilayer composed of a thin (l500A) imaging layer of poly(cyclohexylmethylsilane) coated over a thick planarizing layer of a hardbaked diazoquinone-novalac type photoresist using deep UV exposure.2 Although excellent resolution was achieved ( < 0.5 urn) in this process, the exposure doses required (125-150 rnJ/cin2) were higher than desirable for commercial DUV imaging tools. We have addressed this problem using two approaches: (i) the synthesis of new polysilanes which are intrinsically more sensitive to photodegradation in the solid state and (ii) the incorporation of additives which enhance the photosensitivity. Regarding the former, a number of aryl substituted polysilane homopolyrners which are significantly more photolabile than the standard poly(methylphenylsilane), as assayed by the rate of spectral photobleaching upon exposure to DUV radiation, have been prepared and tested. In addition, a number of small molecule additives which quantitatively quench the polymer fluorescence in the solid state have been identified. Some of the additives which efficiently quench the polymer fluorescence in the solid state also accelerate the rate of photodegradation. The combination of the new polysilane materials with sensitizing additives has allowed submicron DUV imaging at exposure doses as low as 20 mJ/cm2 or less in a bilayer configuration employing 02-RIE for image transfer of the wet-developed images.

A series of sensitizing additives for polysilane bilayer photoresists have been identified. These compounds effectively quench the fluorescence of aromatic polysilanes and greatly increase the rate of photooxidation and spectral bleaching in the solid state. Resists formulated with sensitizers such as phthalimidotriflate show increased photospeed in imaging experiments at both 248 and 193 nm. Characteristics of the resist reactions are described.