Calibrating grayscale direct write bimetallic photomasks to create 3D photoresist structures

Abstract

Bimetallic thin films were previously shown to create laser direct write binary and analog gray scale photomasks. DCsputtered Sn/In (5at.% Sn, 80 nm) oxidize under laser exposure, modifying the optical density at 365 nm from >3OD to <0.22OD. Bimetallic Sn/In thin film grayscale photomasks have been successfully used to create concave and convex 3D structures using mask aligners with Shipley photoresists. To produce precise 3D structures in the organic photoresists, every mask making step was studied. Compensations during the mask making process were necessary because that the relationship between the optical density of the exposed bimetallic films and the laser writing power is not accurately linear, and also that the response of the photoresists is not linear to the exposure. V-grooves with straight slope profile were produced with calibrations taken into account. X-ray diffraction analysis indicates that structure of laser exposed Sn/In bimetallic films is similar to that of ITO films, suggesting new directions for improvement of bimetallic film optical properties, and that the theoretical maximum transmission should approach pure ITO's ~0.05OD in the visible wavelength.

Development of novel segmented-plate linearly tunable MEMS capacitors

“…Figures 7(b) and (c) represent fabricated samples with two different scenarios: ramp patterning and step patterning. One should notice that the linearity of the C-V response in a segmented-plate capacitor depends on the step heights and hence, the process should be calibrated to achieve high accuracy [20] which may require several trials.…”

“…At the end of RIE, an insulator layer with variable thickness is obtained. Figures 7(b depends on the step heights and hence, the process should be calibrated to achieve high accuracy [20] which may require several trials.…”

Programmable Chemical Gradient Patterns by Soft Grayscale Lithography

“…The opacity of the resulting mask elements is precisely correlated to the length and intensity of the e‐beam exposure at each location. Other techniques for grayscale photomask fabrication involve laser exposure of bimetallic thermal resists (such as Sn/In, Bi/In, Bi/In/O, or Zn alloys) to form transparent (at 365 nm and above) alloy oxides, the opacity of which drops as a function of increased laser power 35, 38. While direct writing by e‐beam or laser exposure is limited in resolution only by the width of the exposure source (e‐beam or laser) itself, the pixel‐by‐pixel serial writing required by this technique is massively time intensive and the associated materials systems (i.e., HEBS glass) are expensive, all of which contribute to impractical scale‐up for mass production of large‐area samples.…”