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Browse Prior Art Database

Debris Elimination Following Laser Etching

IP.com Disclosure Number: IPCOM000119675D
Original Publication Date: 1991-Feb-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 3 page(s) / 95K

Publishing Venue

IBM

Related People

Dreyfus, RW: AUTHOR

Abstract

Laser etching removes material from solid surfaces by ejecting the material into the gas or vacuum space above the surface. The removed material may be ejected as species as small as individual atoms or as large as particles in the tens of micrometer diameters. These various products often return to the solid surface; some of the reasons for this are gas dynamic effects, gravity and electrostatic fields.

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Debris Elimination Following Laser Etching

      Laser etching removes material from solid surfaces by
ejecting the material into the gas or vacuum space above the surface.
The removed material may be ejected as species as small as individual
atoms or as large as particles in the tens of micrometer diameters.
These various products often return to the solid surface; some of the
reasons for this are gas dynamic effects, gravity and electrostatic
fields.

      These laser ablation products are often sufficiently dense that
the debris does not fly away from the etched surface without
hindrance, i.e., without collisions, but rather partially deposits
around and in the etch crater, or, alternately, as particulates on a
substrate being coated. This debris deposition is often a significant
handicap to the utilization of laser etching in microelectronic
production.  For instance, in the case of etching insulators,
polymers or metals from circuits, the debris may contaminate
surrounding areas, thus hindering further processing steps, e.g.,
shorting circuits, contaminating the chip, obstructing lithography,
or contaminating the final circuit extending beyond the encapsulated
chip stage.

      It is herein suggested that debris can be significantly
modified or eliminated by having very high (>> 2J/cm2) laser fluence
just above the etched surface (see Fig. 1). Furthermore, it is herein
detailed how these high fluences may be readily produced either by
grazing angle etching or by a second laser.  The debris modification
operates in the following ways.  First, high fluence in the above
surface region promotes the formation of a free electron plasma. This
plasma commonly produces chemical change, particularly the
decomposition of larger molecules into smaller molecules or even into
atoms.  Second, high fluence in the above surface region will have a
strong effect on particulates within this region.  The optical
absorption of substrate-like particulates will commonly simulate the
bulk mate...