2011

Haatainen, Tomi

The nanoimprinting is a potential method for submicron scale patterning for various applications, for example, electric, photonic and optical devices. The patterns are created by mechanical deformation of imprint resist using a patterned imprinting mold called also a stamp. The bottle-neck for imprint lithography is availability of the stamps with nanometer-scale features, which are typically fabricated by electron beam lithography. Therefore, patterning of a large stamp is time consuming and expensive. Nanoimprint lithography can offer a low cost and a high through-put method to replicate these imprinting molds. In this work, stamp replication process was developed and demonstrated for three different types of imprint molds. Replication relies on sequential patterning method called step and stamp nanoimprint lithography (SSIL). In this method a small master mold is used to pattern large areas sequentially. The fabricated stamps are hard stamps for thermal imprinting, bendable metal stamps for roll embossing and transparent stamps for UV-imprinting. Silicon is a material often used for fabrication of hard stamps for thermal imprinting. Fabrication process of silicon stamps was demonstrated using both the imprinted resist and lift-off process for pattern transfer into silicon. Bendable metal stamp for roll-to-roll application was fabricated using sequential imprinting to fabricate a polymer mold. The polymer mold was used for fabrication of a nickel copy in subsequent electroplating process. Thus fabricated metal stamp was used in a roll-to-roll imprinting process to transfer the patterns onto a CA film successfully. Polymer stamp for UV-imprinting was fabricated by patterning fluorinated polymer templates using sequential imprinting and a silicon stamp. The imprinted polymer stamp was used succesfully for UV-NIL. In the stamp fabrication process the features of the silicon stamp were replicated with good fidelity, retaining the original dimensions in all of three stamp types. The results shows, that the sequential imprinting is as a potential stamp replication method for various applications.