<title>Negative resist systems using acid-catalyzed pinacol rearrangement reaction in a phenolic resin matrix</title>

Abstract

Acid-catalyzed dehydration of pinacols known as pinacol rearrangement has been utilized in the design of alkali developable, negative working resist systems. The resist systems are composed of a pinacol compound used as a dissolution inhibitor precursor, diphenyliodonium triflate and a novolak resin. The resist system using hydrobenzoin (HB) shows better lithographic performance than the resist systems using other pinacol compounds such as 1,1,2,2-tetramethylethylene glycol (TMEG), benzopinacole (BP), DL-(alpha) ,(beta) -di-(4-pyridyl) glycol (DPG), and 2,3-di-2-pyridyl-2,3-butanediol (DPB). In the unexposed region, HB acts as a dissolution promoter of novolak resin due to its hydrophilic property. HB reacts with acid to produce hydrophobic materials such as diphenyl-acetaldehyde. Therefore, the solubility of the HB resist film in alkaline developers decrease upon exposure to deep UV radiation and subsequent heating. The resist system has high contrast and high resolution capability. Line-and-space patterns of 0.3 micrometers are obtained using a KrF excimer laser stepper with a 5 mJ/cm2 dose.