WHERE:  Advanced Light Source  BL5.3.2 Scanning Transmission X-ray Microscope (STXM)
 
WHEN:   August 2005                        POSTED:  31 December 2005; updated 10-April 2006

WHAT: The large differences in X-ray absorption among different polymers provides a mechanism to use the bright, monochromated, focused STXM beam for chemically selective soft X-ray lithography. Although secondary mechanisms (electrons and radicals) conspire to destroy the chemical selectivity by transferring energy among chemical species, this can be circumvented by use of appropriate radical barriers. In conjunction with pattern generation programs, we are writing multi-color patterns into polymer thin film structures:

* to demonstrate this novel type of lithography,
* to improve spatial resolution, currently limited to ~100 nm due to radical spreading,
* to improve chemical selectivity and versatility.

The image shows a 2-color pattern written into a PAN, PMMA bi-layer at the peaks of their C 1s absorption energies (see C 1s spectra). The selectivity is demonstrated by the C 1s image sequence (movie). The color composite was generated by assigning red to the signal from PMMA-damage and blue to the signal from PAN-damage, determined by spectral analysis of the image sequence.

Three color patterns have been achieved using a tri-layer structure.

OTHER INFORMATION: A disclosure has been filed. Please contact Adam Hitchcock or Harald Stover if interested in possible applications of this technology.