Browse Prior Art Database

Phase Grating Blank for the Fabrication of Ablation Masks

IP.com Disclosure Number: IPCOM000117761D
Original Publication Date: 1996-May-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 118K

Publishing Venue

IBM

Related People

Dove, D: AUTHOR [+2]

Abstract

The patterning of polymeric or similar layers by an ablation process using a high power laser and mask is an important manufacturing process. Typically, ablation masks are prepared by depositing thin film dielectric multilayer stacks to block out the beam from regions that are not to be exposed. Such masks are expensive to produce and difficult to process. More recently, (1), it has been proposed that the main beam blocking be achieved by engraving the plate with a fine pitch diffraction grating. This approach works very well but introduces the possibility that the data set to be written in creating the mask may become quite large.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Phase Grating Blank for the Fabrication of Ablation Masks

      The patterning of polymeric or similar layers by an ablation
process using a high power laser and mask is an important
manufacturing process.  Typically, ablation masks are prepared by
depositing thin film dielectric multilayer stacks to block out the
beam from regions that are not to be exposed.  Such masks are
expensive to produce and difficult to process.  More recently, (1),
it has been proposed that the main beam blocking be achieved by
engraving the plate with a fine pitch diffraction grating.  This
approach works very well but introduces the possibility that the data
set to be written in creating the mask may become quite large.  To
overcome this problem, a blank structure is described that allows the
grating to be processed first and inspected, and the desired via or
other pattern may be processed as a second, independent, pattern
defining step.

      The blank disclosed consists of a quartz substrate plate to
which is applied a layer of material to be patterned so as to form a
phase grating.  Beneath this layer is an etch stop layer so that the
outer layer may be readily etched to a depth determined by the
thickness of the layer.  This allows a diffraction phase grating to
be etched into the surface with good control of etch depth.  In order
to ensure good rejection of the zero order beam it is important that
the phase grating introduces an optical path difference of a half
wavelength between adjacent elements of the grating and in addition
the amount of light transmitted between adjoining elements should be
equal.  These requirements need not be met very precisely since some
level of directly transmitted beam (zero order beam) may be
tolerated.  This is because the ablation process possesses a
threshold intensity below which ablation does not occur.

Fig. 2  Cross-section view (a), and plan view (b) of ablation mask,
showing transparent region formed by removing a small region of the
diffraction grating.

      The phase grating blank consists of a plate that has been
patterned and etched to produce a uniform phase grating consisting of
parallel lines or a two dimensional array of dots or of other very
closely spaced periodically repeating features.  The blank can be
fabricated by standard lithographic and etch techniques.

      In order to fabricate an ablation mask, the phase grating blank
is coated with resist and the resist is...