Polymer Engineering & Science

Soluble polysilanes: An interesting new class of radiation sensitive materials

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All high molecular weight polysilane derivatives are characterized by a very strong electronic absorption in the‐UV spectral region. The position of this absorption and the molar extinction coefficients are functions of both the nature of the substituent and the molecular weight. In this regard, both the λmax and the ϵsi‐si increase rapidly at first with increased catenation and approach limiting values al around 100 to 150 monomer units. Irradiation of these polysilane derivatives leads predominantly to chain scission and molecular weight reduction although the scission ing/crosslinking ratio is dependent on the nature of the substituents. The mechanism of the photodegradation involves both the extrusion of substituted silylene fragments and the formation of silyl radicals. Lithographically, we have exercised the polysilanes in two configurations: (1) O2‐RlE etch resistant barriers in multilayer structures and, (2) thin imaginable layers for O2‐RIE image transfer. In each case, the stability of the silicon polymers to O2‐RIE conditions is due to the formation of a thin skin of oxide. In the case of the bilayer configurations, the images have been developed both by conventional wet development and by excimer laser ablation at either 308 or 248 nm prior to image transfer. Using either mode, we have been able to generate and transfer submicron images without difficulty. Finally, the strong optical absorption of the polysilanes, coupled with the observed bleaching upon irradiation, suggests potential as contrast enhancing materials. The contrast enhancement gained by the use of a polysilane layer has been modeled by computer simulation and demonstrated experimentally. Copyright © 1986 Society of Plastics Engineers