Acid-catalyzed pinacol rearrangement: chemically amplified reverse polarity change

The reverse polarity change from a polar to a nonpolar state has been successfully incorporated in the design of chemical amplification resists. The imaging mechanism is based on the pinacol-pinacolone rearrangement, wherein vic-diols (pinacols) are converted to ketones or aldehydes with photochemically generated acid as a catalyst. In addition to a polymeric pinacol which undergoes the rearrangement very cleanly in the solid state, aqueous base developable three-component negative deep UV resist systems are described, which are based on phenolic resins, small pinacols, and triphenylsulfonium hexafluoroantimonate as the acid generator.