Enhanced Depth of Lift-off Pattern Defined with Soft Mold Ultraviolet Nanoimprint by Multi-Layer Masks

The traditional lift-off process can hardly be carried out in ultraviolet nanoimprint defined patterns due to the poor solubility of the ultraviolet resist. Moreover, the depth of lift-off pattern defined by an ultraviolet nanoimprint is limited by that of the soft mold. In this work, a modified nanoimprint process by a multi-layer mask method is introduced to enhance the depth of the final lift-off pattern. Pillar photonic crystal is fabricated from the hole pattern defined by NIL to prove the pattern-reversal capability. On its basis, combining the features of overetching technology and the lateral diffusion phenomenon in the metal depositing process, pillar-shaped photonic crystal stamps with different duty cycles have been fabricated by adjusting the etching time of the lift-off layer. Based on this process, a 50-nm line width metal grating is fabricated from a soft stamp with an aspect ratio as low as 1.