Recent progress in electron-beam a resists for advanced mask-making

Resists for advanced mask-making with high-voltage electron-beam writing to ols have undergone dramatic changes over the last three decades. From PMMA and the other early chain-scission resists for micron dimensions to the aqu eous-base-developable, dry-etchable chemically amplified systems being deve loped today, careful tuning of the chemistry and processing conditions of t hese resist systems has allowed the patterning of photomasks; of increasing complexity containing increasingly finer features. Most recently, our rese arch efforts have been focused on a low-activation-energy chemically amplif ied resist based on ketal-protected poly(hydroxystyrene). These ketal resis t systems, or KRSs, have undergone a series of optimization and evaluation cycles in order to fine-tune their performance for advanced mask-fabricatio n applications using the 75-kV IBM EL4+ vector scan e-beam exposure system. The experiments have led to an optimized formulation, KRS-XE, that exhibit s superior lithographic performance and has a high level of processing robu stness. In addition, we describe advanced formulations of KRS-XE incorporat ing organometallic species, which have shown superior dry-etch resistance t o novolak-based resists in the Cr etch process while maintaining excellent lithographic performance. Finally, current challenges facing the implementa tion of a chemically amplified resist in the photomask manufacturing proces s are outlined, along with current approaches being pursued to extend the c apabilities of KRS technology.