Silylation of novolac based resists: Influence of deep-ultraviolet induced crosslinking

Abstract

Most surface imaging resist schemes are based on the selective diffusion of a Si-containing compound into the resist. In the diffusion enhanced silylated resist process hexamethyldisilazane is being incorporated in the exposed regions during the silylation treatment. Upon deep ultraviolet irradiation (at 248 nm), novolac based resists will however crosslink to some extent. The crosslinking reaction influences the degree of silicon incorporation in the exposed resist and hence plays an important role in the imaging properties. The crosslinking reaction has been studied in detail in this work for two types of Plasmask deep-ultraviolet resists, along with its consequences on resist imaging. A decrease in silicon incorporation due to crosslinking puts a serious limitation on the useful process window for Plasmask 150u, but the process window is not limited by crosslinking for Plasmask 301 u. A thorough investigation of the influence of crosslinking on the pattern deformation is also carried out.

Wet silylation and oxygen plasma development of photoresists: A mature and versatile lithographic process for microelectronics and microfabrication

“…8 The selective incorporation of Si based on the difference in diffusivity was made widely known when the DESIRE process by Coopmans et al 9 appeared. Since then intense activity in the field has started, with applications for example in I-line lithography, 10 DUV lithography, 11,12 DUV and 193 nm lithography, 13-15 even vacuum UV and x-ray lithography. 16 Finally, in 1991 the idea of true surface imaging as opposed to near-surface imaging was proposed by Calvert et al 17 Si incorporation in the resist was done by diffusion from the gas phase ͑dry silylation͒.…”

Resist material requirements for 256m and 1g bit dram fabrication.

“…Key issue is not a base material but a silylating agent. Many works have been reported on the silylation results in i-line [18] and KrF [19] lithography with gas [20] and liquid [21] phase silylation agent but not so many in ArF lithography.…”