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Transmissive Phase-Grating Fabrication Quality Measurement Method

IP.com Disclosure Number: IPCOM000118785D
Original Publication Date: 1997-Jul-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Sanford, JL: AUTHOR

Abstract

Transmissive phase shift and phase grating ablation mask fabrication requires tight control of the exposure and etching processes. Including a phase grating test site on the masks and using an apertured spectraphotometer will allow the depth (1) and grating duty factor (2) over (3) errors to be determined.

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Transmissive Phase-Grating Fabrication Quality Measurement Method

      Transmissive phase shift and phase grating ablation mask
fabrication requires tight control of the exposure and etching
processes.  Including a phase grating test site on the masks and
using an apertured spectraphotometer will allow the depth (1) and
grating duty factor (2) over (3) errors to be determined.

      The spectraphotometer aperture must be small enough to block
out the first and higher diffraction orders.  Upon scanning the
grating, the grating depth can be determined from the output minimum
wavelength and index of refraction of the grating media.  To a
first-order approximation, the phase error is 1.8 times the percent
error of the output minimum wavelength from the operational
wavelength of the mask.  The zero order intensity grating equation
can be used to determine  the magnitude of grating duty factor error
given the intensity of the spectraphotometer output minimum and
maximum.