UV curing of resists for warm embossing
The basis of our investigation is a modified UV curable negative tone resist (mr-L 6000 XP), which allows for warm embossing at a temperature as low as 50 C. UV curing serves to stabilise the imprinted pattern, either in a flood exposure or an exposure through a photomask. The latter may be used to combine embossing with a subsequent UV lithography step to define either two-level or three-level patterns. In the case of a patterned resist, the standard UV curing process is not applicable since it affects the edge steepness of the embossed structure. Distinctive phase shifting effects are observed, depending on the lateral periodicity of the embossed structures, resulting in trenches below steep edges when the effective exposure happens within a narrow wavelengthband. Especially for polychromatic illumination, the absorption of the photoresist has to be taken into account to circumvent these trenches. This is verified by simulation of the UV intensity distribution within the patterned resist.
uv curing warm embossing nanoimprint lithography