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Selective Deposition with "Dry" Vaporizable Lift-Off Mask

IP.com Disclosure Number: IPCOM000108471D
Original Publication Date: 1992-Jun-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 88K

Publishing Venue

IBM

Related People

Cuomo, JJ: AUTHOR [+4]

Abstract

Disclosed is an improved lift-off process for pattern deposition, which involves the in-situ deposition and patterning of the medium forming the lift-off mask. Unwanted material deposited on the lift-off mask can be removed by ablation concurrently with the deposition or removed afterwards, by warming.

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Selective Deposition with "Dry" Vaporizable Lift-Off Mask

       Disclosed is an improved lift-off process for pattern
deposition, which involves the in-situ deposition and patterning of
the medium forming the lift-off mask.  Unwanted material deposited on
the lift-off mask can be removed by ablation concurrently with the
deposition or removed afterwards, by warming.

      The lift-off mask medium can be any of a variety of condensible
vapors.  We found that water, acetone, and chlorobenzene each
condense onto a liquid nitrogen cooled surface in vacuum and produce
a solid film that is continuous, smooth and patternable down to the
substrate. The patterned structure is then exposed to material
deposited by evaporation or sputtering.  When the composite is warmed
after the deposition, the lift-off mask vaporizes, delaminating the
unwanted material deposits, which can then be blown off with a small
air burst.  The warming can be in-situ or ex-situ. High resolution
patterns have been prepared this way.

      In-situ patterning of the "ice" mask can be achieved in several
ways, all typically requiring some type of pulsed laser ablation
through a projection mask.  The patterning is easiest when the mask
medium is highly absorbing to the laser irradiation, and the mask
material can be ablated directly, e.g., chlorobenzene at the ArF
laser wavelength of 193 nm. In this case, the absorption depth is
calculated to be approximately 0.25 mm, comparable to polyimide at
that wavelength.  Acetone at 193 nm can also be patterned by direct
ablation, although with slightly more difficulty due to its lower
absorption (absorption depth calculated to be approximately 1.1 mm).
The absorbance of the mask medium may be increased by changing the
laser wavelength, or by doping the medium with an absorber.

      In-situ patterning of non-absorbing materials (e.g., water ice
at the 193 nm wavelength) can be achieved in three ways, the first
two of which we have demonstrated.  In the first, the ice mask is
deposited on a s...