Stamp deformation and its influence on residual layer homogeneity in thermal nanoimprint lithography

In thermal nanoimprint lithography (NIL), one of the key points to be addressed is the printing uniformity on large areas. During the process, the silicon stamp undergoes significant mechanical stress, function of different parameters and appear under the concurrent influence of both the applied pressure on the backside of the stamp and an opposite force due to the polymer viscoelastic behaviour. It leads to non-negligible deformations within patterned or unpatterned areas, which translates into non uniformity of the printing, stamp pattern break and degradation of the polymer surface. This work studies the relation between the residual layer thickness (RLT) and the patterned area size, fill factor (FF) and stamp thickness (ST) for stamps made in silicon. Important and different variations in the homogeneity of the residual layer are obtained in comparison with the values predicted by the theory. This will help to optimize stamp designs and choose appropriate process setups and parameters for nanoimprint with improved pattern transfer capability.