Temperature-reduced nanoimprint lithography for thin and uniform residual layers

Wavelength interrogation of grating-based optical biosensors in the input coupler configuration

“…Atomic Force Microscopy (AFM) analysis of the stamp and imprint indicated that the imprint had typically 50-60% of the depth profile of the stamp (Fig. 3b and c), suggesting that our low temperature imprint was performed in the so-called underfilling conditions [19]. During thermal NIL the resist flows and behaves as an uncompressible fluid; at our process temperature, the stamp cavities to be filled by the fluid have a larger volume than the available fluid so they become partially filled.…”

“…During thermal NIL the resist flows and behaves as an uncompressible fluid; at our process temperature, the stamp cavities to be filled by the fluid have a larger volume than the available fluid so they become partially filled. A result of imprinting in underfilling condition is a relatively thick (∼40-50%) but uniform residual resist layer which is less prone to defect formation [19]. The residual resist was uniformly removed in a dry plasma-etch process before the pattern transfer would take place, and a high quality 12 mm × 12 mm grating pattern was obtained.…”

Residual Layer Self‐Removal in Imprint Lithography

“…Further reductions in edge roughness, which should translate directly toward enhanced preservation of critical dimensions, are expected as resist materials and chemistry are optimized. Resist thickness at point of failure 11 13…”

“…[7] Minimizing these issues or eliminating the residual layer altogether is an important area of research, and various attempts have been made toward this end. Among these include (1) the addition of some aspects of photolithography such as selective UV-curing through a hybrid mask-mold followed by a development step, [8,9] (2) contrast-modified exposure followed by development, [10] (3) reducing the initial volume of resist to induce incomplete filling of the mold, [11] (4) using high pressure to squeeze excess resin out from between the mold and the substrate, [12,13] and (5) optimization of droplet positioning in the case of a liquid resin system. [14] While the addition of a development step in (1) and (2) is perhaps the best proposed solution up to this point because developer solvents can completely remove the residual layer without loss of critical dimension control, it nevertheless deprives imprint lithography of one of its intrinsic advantages as a completely dry process.…”

Recovery prevention via pressure control in thermal nanoimprint lithography

“…Secondly, the initial layer thickness delicately controls the final thickness of the residual layer and, even more critical, its uniformity. [12][13][14] This is due to the fact that imprint is a mechanical process, where, during stamp intrusion, the polymeric volume is locally transferred from an initial location to a final one, the volume of the polymer remaining conserved.…”