Positive-tone EUV resists: complexes of platinum and palladium

The EUV photoreactivity of platinum and palladium mononuclear complexes has been investigated. Many platinum and palladium complexes show little or no EUV sensitivity, however, we have found that metal carbonates and metal oxalates (L2M(CO3) and L2M(C2O4); M = Pt or Pd) are sensitive to EUV. The metal-carbonates give negative tone behavior. The most interesting result is that the metal oxalates give the first positive-tone EUV resists based on mono-nuclear organometallic compounds. In particular, (dppm)Pd(C2O4) (dppm = 1,1-Bis(diphenylphosphino)methane) (25) prints 30-nm dense lines with E-size of 50 mJ/cm(2). To improve the lithographic performance of (25), the processing conditions were studied. A bake study showed that bake affected sensitivity and dark loss very little, while dark loss worsened with development time. Derivatives of (25) were synthesized to explore the effect of molecular weight on resist sensitivity, but the study showed no correlation between molecular weight and sensitivity.