A topcoat material plays a significant role in achieving technology nodes below 45 nm via ArF immersion lithography.
Switching the exposure medium between the lens and the photoresist (PR) film from gas (air, n=1) to liquid (H2O,
n=1.44) may lead to leaching of the polymer, the photoacid generator (PAG), or the solvent. These substances can
contaminate the lens or cause bubbles, which can lead to defects during the patterning. Previously reported topcoat
materials mainly use hydrophobic fluoro-compounds and carboxylic acids to provide high dissolution rates (DR) to basic
developers as well as high receding contact angles (RCA). Recently, the demand for a new top-coat material has risen
since current materials cause water-mark defects and decreases in scan speeds, due to insufficient RCA's. However,
RCA and DR are in a trade-off relationship as an increase in RCA generally results in a lower DR. To overcome this, a
novel polymer with high-fluorine content was synthesized to produce a topcoat material with improved DR (120 nm/s in 2.38 wt% TMAH) and RCA (>70°). In addition, a strategy to control the pattern profile according to needs of customers was found.