Dip Pen Nanolithography (DPN) and Nanoimprint Lithography (NIL)

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Dip Pen Nanolithography (DPN), a direct-write soft lithography method, is used to develop nanostructures on a preferred substrate by offering sets of molecules through capillary transport from an Atomic Force Microscope (AFM) tip to a surface.

Developing nanostructures using DPN is a single-step process that eliminates the need for using resists. A traditional atomic force microscope can be used to realize ultra-high-resolution features as small as 15-nm line widths and a spatial resolution of approximately 5 nm. In the case of nanotechnology applications, it is necessary to pattern molecules in high resolution as well as to functionalize surfaces with patterns of two or more parts.

The most vital characteristic of DPN is that as the same device is used to image and write a pattern, patterns of multiple molecular inks can be produced on the same substrate in very high alignment.

Nanoimprint Lithography (NIL)

Nanoimprint is one of the most economical nanolithography methods for laboratories, and the resolution achieved can be as low as 10 nm. The principle of this method is the imprinting of a patterned mold in a heated resist.

The three pillars of nanoimprint lithography are a stamp with appropriate feature sizes, the sufficient polymer material to be printed, and equipment for printing with sufficient temperature and pressure control.

The First Step in Nanoimprinting

In nanoimprinting, the first step is to construct a silicon relief mold with the help of direct-write e-beam equipment. This is a gradual process in which each feature is described by rastering an electron beam over the wafer. However, after defining the imprint mold, it can be employed to remove features with the same parallel speed of the mask-based exposure process.

Thus, NIL can obtain sub-10-nm structures across vast regions with high throughput and low cost, a triumph that is presently unattainable using current lithographies. The successful growth of NIL can eliminate the main barrier—cost—to nanostructure commercialization and will make nanostructures easily accessible for industrial applications.

UV Imprint and EUV Lithography

The imprint forces are decreased to less than 1 bar by using UV resist. In a UV nanoimprint process, the resist toughens due to UV, eliminating the need for long heating and cooling phases.

This results in shorter process times, prevents any unwanted expansion of the material, and enables a gentle imprint of pre-structured substrates and work in step-and-repeat mode. Visual adjustments can be made with the help of the transparent stamp.