Nanopatterning of Inorganic and Polymeric Substrates by Indentation Lithography

Physik Instrumente (PI), L.P., Auburn, Massachusetts; Harvard University, Cambridge, Massachusetts; and CSM Instruments, Needham, Massachusetts

A recent collaboration between the Whitesides Group at Harvard University and CSM Instruments has culminated in an important advance in lithography of different materials at the nano scale. The motivation for this

development was the ability to produce unique lithographical patterns of different shapes and sizes for use in research applications, such as lab-on-a-chip, where conventional techniques such as electron-beam lithography (EBL) and photolithography cannot be used.

Figure 1. Pattern produced with a diamond indenter can then be replicated by pouring a polymeric layer over the substrate.

The new method utilizes the standard Ultra Nanoindentation Tester (UNHT) and the Nano Scratch Tester (NST) without any modification. The methodology has the following advantages:

It can generate multiple levels of relief (height) by altering the applied load.
It can control the shape of the pattern by using indenters of different shapes.
It can produce patterns in very hard materials if a diamond indenter is used.
It can produce features with a wide range of depths, from a few to several hundred nanometers.

These characteristics produce patterns with three-dimensional relief, which would be impossible to achieve using lithographic techniques in which features have a fixed depth and approximately vertical sidewalls. Resultant patterns can then be replicated as shown in Figure 1 to produce a stamp bearing an inverse replica of the original pattern. Such replicas can in turn be used to pattern other materials in an efficient and cost-effective manner.

Figure 2: Continuous channels with 70μm length and 5μm spacing produced in an epoxy substrate.

The experimental setup consists of a standard CSM Instruments Open Platform fitted with Ultra Nanoindentation (UNHT), Nano Scratch (NST), Atomic Force Microscope (AFM), and Optical Video Microscope modules. Translation of the sample among these modules is positionally synchronized so that any predefined area of a surface can be patterned in an automatic way and subsequently imaged in three dimensions.

The actual shape of the patterns is achieved with a Physik Instrumente (PI) P-733.2CD stage, which is mounted directly on the Open Platform, and allows sub-nanometer positioning resolution in the X and Y axes.

The combination of nanopositioning, accurate load control, and choice of indenter geometry means that almost any shape and depth of feature can be achieved in a fast and reproducible manner.

This work was done by Jinlong Gong, Darren J. Lipomi, Jiangdong Deng, Zhihong Nie, Xin Chen, Nicholas X. Randall, and George M. Whitesides of Harvard University; and Rahul Nair of CSM Instruments. For more information, Click Here .