Nanoimprint Lithography, NIL in short, is an attractive method for cost-effective nanoscale device fabrication. In addition, the application of mechanical deformation in the NIL process enables grayscale lithography with a single patterning step, which can’t be accomplished with any other traditional lithography technique. The exact and repeatable mirroring of nanoscale patterns using only one high resolution patterning process makes this method a lot more accomplished than other costly methods like e-beam and helium-ion-beam lithography.
Also, because of using mechanical deformation in the NIL process, grayscale lithography can be done using only one patterning step, which cannot be achieved using any other lithographic method. These qualities facilitate the fabrication of distinct nanoscale devices by NIL process for various applications such as optics, plasmonics, and biotechnology. The latest developments in throughput and outturn in NIL show the potential of being followed for main semiconductor device fabrication.
Older Definition of Nanoimprint Lithography
Nanoimprint lithography was initially defined as nanoscale lithography process with the potential for cost-effective and high throughput, over two decades ago. It has become a dependable alternative to traditional lithography techniques and has found usefulness in a number of areas of nanoscale device fabrication such as conventional semiconductor devices and bit patterned media, and more distinct applications in optics, plasmonics, and biometric structures.
Why is Mold Used in Nanoimprint Lithography?
In nanoimprint lithography, a mold is used to define nanoscale deformation of a resist that is cured by either heat or UV application. After the resist is cured, the mold is eliminated and the patterned resist is used as it is or further treated through processes such as etching and metal deposition in order to generate a final device or new mold for further processing. The technique widely classified into two types – hard nanoimprint lithography and soft nanoimprint lithography. Here, what we mean by hard and soft is the quality of the mold. Hard nanoimprint uses a mold made of stern material like silicon or quartz, complementing fine features as minute as 5 nm.
High resolution can be obtained but at the cost of higher defect rates from particles as well as trapped air bubbles on non-adhering mold and substrate. Soft nanoimprint lithography addresses this challenge using molds comprising elastomeric materials like PDMS [Poly (dimethylsiloxane)], polyimides, and polyurethanes, although Poly (dimethylsiloxane), is, by far, the most commonly used material. The elastomeric materials can be used either as a freestanding mold for applications or as attached to a hard substrate for enhanced durability.
