Evaluation of halomethylated poly(methylphenylsilane)s as electron-beam resists

Polysilane analogues of halomethylated poly(styrene)s, chloromethylated and bromomethylated poly(methylphenylsilane), have been prepared from the parent polymer by reaction with the appropriate halomethyl methyl ether. The polymers undergo a single-stage crosslinking reaction when irradiated with 20 kV electrons. As electron beam resists they operate in negative-working mode but their performance is poor in comparison to the corresponding poly(styrene) derivatives. The low lithographic sensitivities and attainable contrasts are shown to arise as a consequence of a competitive chain scission reaction which in the case of the bromomethylated system increases with increasing bromomethyl content. The radiation chemistries of the systems are rationalised in terms of modifications of the crosslinking and scission mechanisms that are thought to operate in the corresponding resists based on poly(chloromethylstyrene-stat-styrene).