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Browse Prior Art Database

Phase Compensation Method for Phase-Shifting Lithography

IP.com Disclosure Number: IPCOM000119456D
Original Publication Date: 1991-Jan-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 1 page(s) / 51K

Publishing Venue

IBM

Related People

Bell, AE: AUTHOR [+4]

Abstract

Disclosed is a method to adjust the apparent phase thickness of a phase-shifting lithography mask. The method compensates phase errors introduced by phase mask fabrication errors, illuminator-lamp aging and photoresist spectral-sensitivity changes.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 85% of the total text.

Phase Compensation Method for Phase-Shifting Lithography

      Disclosed is a method to adjust the apparent phase thickness of
a phase-shifting lithography mask.  The method compensates phase
errors introduced by phase mask fabrication errors, illuminator-lamp
aging and photoresist spectral-sensitivity changes.

      In fabricating phase masks, errors in the mask, illumination
wavelength shifts due to lamp aging, and variations in wavelength
sensitivity in the imaging layers, all lead to phase errors.

      The use of a tunable wavelength filter in the projector
illumination system can correct these residual phase errors. The
wavelength tuning would correct residual phase error by shifting the
illumination spectrum D(g).  The figure shows an optical schematic of
one embodiment of the proposed lithographic system.  The discharge
lamp is imaged onto the entrance pupil of the imaging system.  A
tiltable interference filter and optical compensator plate are placed
in the illumination system.  Since the spectral transmission of
optical interference filters shifts towards shorter wavelength as
angle of incidence is increased, tilting the filter tunes the
transmitted spectrum D(g) so that the mean phase <D> of the mask is
at the design value.  The tiltable filter has spectral transmission
envelope shifted towards longer wavelengths than the desired portion
of the lamp spectrum.  By shifting the nominal spectrum towards
longer wavelengths, both positive and neg...