Browse Prior Art Database

Double Masks for Laser Ablation and Drilling

IP.com Disclosure Number: IPCOM000112256D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Ehrenberg, SG: AUTHOR [+4]

Abstract

Disclosed is a combination of multilayer dielectric mask, followed by another mask, which can be used to laser etch or expose patterns in substrates. If the holes or features to be exposed or etched are always in certain allowed positions in a regular array, and some holes or features are missing in the various part numbers to be etched, we use an expensive multilayer dielectric mask 1 with holes etched in every possible position that might be required. For a typical pattern with 4 thousandths holes with center to center spacing of 8 thousandths, for example, only 17% of the light 2 from laser 3 that is incident on the mask 1 is transmitted through the holes 4 in the mask 1 to the lens 5 which focuses the light from holes 4 through holes 6 in a second mask 7 held in proximity to part 8.

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Double Masks for Laser Ablation and Drilling

      Disclosed is a combination of multilayer dielectric mask,
followed by another mask, which can be used to laser etch or expose
patterns in substrates.  If the holes or features to be exposed or
etched are always in certain allowed positions in a regular array,
and some holes or features are missing in the various part numbers to
be etched, we use an expensive multilayer dielectric mask 1 with
holes etched in every possible position that might be required.  For
a typical pattern with 4 thousandths holes with center to center
spacing of 8 thousandths, for example, only 17%  of the light 2 from
laser 3 that is incident on the mask 1 is transmitted through the
holes 4 in the mask 1 to the lens 5 which focuses the light from
holes 4 through holes 6 in a second mask 7 held in proximity to part
8.  Mask 4 is made with the hole pattern desired.  The light from the
holes in the dielectric mask 1 passes through the holes in mask 7
without touching the mask 7, and hence do not contribute to heating
the mask 7.  Only where the light is blocked in mask 7 does the mask
become heated.  In the extreme case of only few holes drilled, the
mask 7 is heated at 17%  of the rate it would be heated in absence of
mask 1.  Typically, half the allowed positions are drilled, and the
rate of heating of the metal mask is cute down by an order of
magnitude.

      Since the only purpose of the mask 7 is to stop the light from
impinging o...