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Metal Film/Diamond Membrane Mask for Excimer Laser Ablation Projection Etching

IP.com Disclosure Number: IPCOM000106572D
Original Publication Date: 1993-Nov-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 80K

Publishing Venue

IBM

Related People

Cuomo, JJ: AUTHOR [+4]

Abstract

Disclosed is a new, high-performance, potentially low cost mask structure for excimer laser projection etching. It is based on the use of patterned metal films on a transparent and highly thermally conductive polycrystalline diamond membrane. Patterned metal films are relatively inexpensive, and diamond membranes with the desired characteristics for mask substrates (relatively large area, defect-free, double-sided polished, VIS-UV-transparent, and highly thermally conductive) are expected to soon be available at reasonable cost.

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Metal Film/Diamond Membrane Mask for Excimer Laser Ablation Projection Etching

      Disclosed is a new, high-performance, potentially low cost mask
structure for excimer laser projection etching.  It is based on the
use of patterned metal films on a transparent and highly thermally
conductive polycrystalline diamond membrane.  Patterned metal films
are relatively inexpensive, and diamond membranes with the desired
characteristics for mask substrates (relatively large area,
defect-free, double-sided polished, VIS-UV-transparent, and highly
thermally conductive) are expected to soon be available at reasonable
cost.

The disclosed mask consists of:

o   a transparent, highly thermally conductive diamond membrane
    (e.g., polycrystalline diamond of thickness 2 to 8 mu m) which
    (1) efficiently heat-sinks the laser energy absorbed by the metal

    on the time scale of the laser pulse duration, (2) provides a
    low-resistance thermal path for steady-state removal of the heat
    to the mask periphery, and (3) provides mechanical support,

o   an antireflection coating on one or both sides of such a
    membrane, and

o   opaque features consisting of patterned metal films optionally
    overcoated for oxidation resistance (e.g., Al coated with a
    half-wavelength optical thickness layer of MgF sub 2).

      An anti-reflecting (AR) coating is required on at least one
side of the diamond membrane for satisfactory transmission, due to
diamond's high refractive index ( 'n' sub 'diamond' % approx % 2.5 ).
A suitable AR coating would be a UV-transparent film with refractive
index
 'n' sub 'AR' % approx
 ('n' sub 'diamond' ) sup 1/2 % approx
 1.6 pm 0.1  having a thickness L given by  'n' sub 'AR' 'L' % = %
lambda /4 , where
 lambda is the laser wavelength.  The addition of a single AR coating
will increase the minimum diamond membrane transmission to around
80%, and reduce the interference-related oscillations in transmission
caused by small variations in membrane thickness from around  pm 26 %
to around  pm 0.9% for  'n' sub 'AR' % =  1.6 (and to around  pm 3.7
% for  'n' sub 'AR' % =  1.5).  The addition...