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Role of Molds for Nanoprint Lithography

Scope of Nanoprint Lithography 

The nanoprint lithography technology has drawn considerable attention in academic as well as industrial fields as one of the most eminent lithographic methods in the fabrication of nanoscale devices. Efficiently controllable shapes of fabricated components, very high resolution, and cost-effectiveness of this technique have shown limitless potential to be used for real-time applications.

Categorization of Lithography

In the last decade, numerous lithographic techniques have been developed, including electron beam lithography, photo lithography, and nanoimprint lithography. Nanoprint lithography, among them, has proven to have a number of benefits like other lithographic methods. Based on the molds for imprint with various pros and cons, nanoprint lithography can be classified into three different techniques – hard mold, soft mold, and hybrid nanoimprint. The nanoimprint lithography technique will be the next-generation lithographic technique that’ll change the patterning and fabrication in nanoscale devices in the industry.

Process Briefly Described

In order to overcome the challenges of electron beam lithography and photo lithography, nanoimprint lithography was proposed by Chou and others. Nanoimprint lithography makes the patterns through mechanical deformation of imprint resist and the following processes. The earliest version of this type of lithography, proposed by Chou and others is based on thermoplastic polymers as resist materials. In conventional thermoplastic nanoimprint lithography, a slim layer of imprint resist will be spin-coated on the sample substrate.

Subsequently, the mold that was predefined with topological patterns is pressed on to the resist-coated substrate with temperature above glass transition and increased pressure. Then, the impression on the mold is transferred on to the softened resist. Subsequently, it is cooled so that it becomes hard. The mold is then separated from the sample and the patterns resist remains on the substrate. Because the preliminary idea of this method was developed, a number of variations of the nanoimprint lithography technique have been proposed so as to substitute necessary high temperature in order to soften the thermoplastic resist into ultraviolet light to make the resist hard so as to transfer the pattern.

Depending on these two hardening methods, three types of nanoimprint lithography methods have been proposed so as to reach high resolution, large area and low cost patterning. These three types include soft-mold, hard-mold, and hybrid-mold nanoimprint lithography.

Traditional lithographic methods, including electron beam, photo and ATM (Atomic Force Lithography) Lithography are great options for lone-nano structure devices having resolution down to tens of nm. However, their restriction of comprehensive writing and patterning times restricts the application for high-volume production.

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