Assisted research into creating direct-write photomasks from bimetallic thermal resists. One of the main tasks was to develop a method to quickly calculate the Optical Density (OD) of patterns written onto a sample. Until recently the only way to do this was to create a 1cm by 1cm square pattern and take it to a UV spectrometer. Due to the limited size of the glass slides used, this meant that only a handful of patterns could be placed onto any given slide. More complex patterns such as v-grooves and patterns with small features could not be measured. My implementation involved backlighting a sample and taking pictures with a microscope. The OD level could then be mapped to a corresponding intensity level in the image using image analysis in Matlab. These measurements could then be used to create a calibration file for the laser direct-write system.
The laser direct-write setup:
The measurement setup:
The Matlab script developed:
James M. Dykes, Calin Plesa, and Glenn H. Chapman, “Enhancing direct-write laser control techniques for bimetallic grayscale photomasks.” Proc. of SPIE, Vol 6883, 688312:1-12. 2008. [PDF]
James M. Dykes, Calin Plesa, Chinheng Choo, and Glenn H. Chapman, “Bimetallic thermal resists potential for double-exposure immersion lithography and grayscale photomasks.” Proc. of SPIE, Vol 6730, 673040:1-10. 2007. [PDF]