Non-shrinkable and nanomolecular resists for DUV lithography

Abstract

To satisfy the updating demand of next generation of lithography, new chemically amplified resist materials should be developed that can perform at the limit where the image feature size is on the order of molecular dimensions. Amorphous dendritic materials have several advantages over linear systems. First, the limit of resolution can be extended to molecular level since the building block of image feature shrinks to small molecule. Second, molecular materials do not have strong intermolecular interaction like chain entanglement due to short chain length. Therefore the dendritic molecular resist helps to dissolve more uniformly during development. Third, resist molecules that are free of intermolecular chain entanglement may have implications in decreasing line edge roughness at very small feature sizes. Herein we studied several dendritic molecular resist materials for 193 nm photoresists. t-Butyl cholate was used as a dendrimer core and ester groups as peripheral parts. Ester groups are attached to 3-α, 7-α, 12-α positions of t-butyl cholate. These materials were synthesized using an acetal-protected anhydride derivative of 2,2-bis(hydroxymethyl)proponic acid as an acylating reagent. The t-butyl cholate has high etch-resistance and it acts as dissolution inhibitor. To give solubility change, t-BOC groups are attached to the end of peripheral parts. The number of t-BOC groups increases to $3^*2^n$ as generation goes to the higher level. The large number of t-BOC groups can give high sensitivity to the resist materials. Their peripheral parts are composed of ester groups. Because cholate has some hydrophobic property these ester groups can give resist materials hydrophilicity which gives adhesion property to the resist materials. We synthesized new amorphous nanomolecular reisist materials. They have adamantane as cores and t-butyl cholate as peripheral parts. Polycyclic structures of adamantane and cholate provide high dry-etch resistance. They are amorphous ...