HBr Plasma Treatment Versus VUV Light Treatment to Improve 193 nm Photoresist Pattern Linewidth Roughness

We have studied the impact of HBr plasma treatment and the role of the VUV light emitted by this plasma on the chemical modifications and resulting roughness of both blanket and patterned photoresists. The experimental results show that both treatments lead to similar resist bulk chemical modifications that result in a decrease of the resist glass transition temperature (Tg). This drop in Tg allows polymer chain rearrangement that favors surface roughness smoothening. The smoothening effect is mainly attributed to main chain scission induced by plasma VUV light. For increased VUV light exposure time, the crosslinking mechanism dominates over main chain scission and limits surface roughness smoothening. In the case of the HBr plasma treatment, the synergy between Bromine radicals and VUV light leads to the formation of dense graphitized layers on top and sidewalls surfaces of the resist pattern. The presence of a dense layer on the HBr cured resist sidewalls prevents from resist pattern reflowing but on the counter side leads to increased surface roughness and linewidth roughness compared to VUV light treatment. magnified image