Indentation lithography enables complex 3-D Nano Patterns

Editor’s Note: This article was submitted by CSM Instruments and PI L.P. For the full article by J. Gong, D. Lipomi, J. Deng, Z. Nie, X. Chen, N. Randall, R. Nair and G. Whitesides, visit this link.

May 10, 2011—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 nanoscale. The motivation for this development was the ability to produce unique lithographical patterns of different shapes and sizes for use in research applications (e.g. lab on a chip) where conventional techniques such as electron-beam lithography cannot be used. 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 identers 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 3-D relief, which would be impossible to achieve using lithographic techniques in which features have a fixed depth and approximately vertical sidewalls.

   

• The CSM Nano-Scratch Tester setup and a PI P-733 planar flexure scanner stage.

  Resultant patterns can then be replicated as shown in Figure 1 (below) 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 1: Pattern produced with a diamond indenter can then be replicated by pouring a polymeric layer over the 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 between these modules is position synchronized so that any predefined area of a surface can be patterned in an automatic way and subsequently imaged in three dimensions.

   

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

  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.

  

• Figure 3: Typical 2-D array of split rings produced in epoxy with an outer diameter of 10µm, line width of 350nm and a 60˚ opening.

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

  For more information about this technology, visit the PI or CSM Instruments Web sites.