Photocaid Generator Bound Polymer Resists for Electron Beam Lithography

Abstract

Photoacid generators (PAGs) are a essential component and have been broadly used to apply in chemically amplified resist system. PAGs were imported to not only KrF excimer laser lithography system but also ArF and the electron beam lithography due to high resolution and high sensitivity properties. A new PAG monomer, triphenylsulfonium acylate (TPSMA) was designed for being bounding in the main polymer backbone and synthesized. The acrylic resist containing PAG were employed for synthesis by free radical terpolymerization with PAG monomers, methylmethacrylate (MMA) and glycidylmethacrylate (GMA) monomers using AIBN. For blending test with TPSMA and triphenylsulfonium triflate are prepared with a resin poly (GMA-co-MMA). Terpolymers with various ratio of TPSMA with fixed GMA ratio were synthesized and characterized by nuclear magnetic resonance spectroscopy. All resists were analyzed by thermogravimetric analysis (TGA), differential scanning calorimeter (DSC) which show thermal stability. Molecular weight (Mw) and distribution of polymers was checked by gel permeation chromatography (GPC) using CHCl3 as eluent. We have applied electron beam lithography and ArF excimer laser lithography in order to demonstrate the effects of PAG bound resists. In bounding system, pinhole phenomenon was deleted after soft baking on surface and low PAG loaded resist shows high efficiency in patterning and line edge roughness (LER) is improved. When thickness is low about below 50nm, sub 35 nm (L:S=1:2) resolution is always possible to be made in low sensitivity (300 μC/cm2) regardless of PAG concentration. PAG bounding resists including GMA and MMA were well qualified and successfully applied for fabrication of crosslinked negative-type nano-scale patterns.