Use of enclosed thin laminar liquid flows above ablation area for control of ejected material during excimer machining

Dowding, Colin and Lawrence, Jonathan (2009) Use of enclosed thin laminar liquid flows above ablation area for control of ejected material during excimer machining. In: ICALEO 2009, 2nd - 5th November 2009, Orlando, FL, USA..

Documents
Paper_M107.pdf
Final Published verision (I had to format it correctly myself for publication: the Laser Institute of America should have done no more formatting in their published version)
[img]
[Download]
Request a copy
[img] PDF
Paper_M107.pdf - Whole Document
Restricted to Repository staff only

2MB

Official URL: http://www.lia.org/store/product/ICAL09_M107

Abstract

The performance of laser ablation generated debris
control by means of open immersion techniques have
been shown to be limited by flow surface ripple effects
on the beam and the action of ablation plume pressure
loss by splashing of the immersion fluid. To eradicate
these issues a closed technique has been developed
which ensured a controlled geometry for both the
optical interfaces of the flowing liquid film. This had
the action of preventing splashing, ensuring repeatable
machining conditions and allowed for control of liquid
flow velocity. To investigate the performance benefits
of this closed immersion technique bisphenol A
polycarbonate samples have been machined using
filtered water at a number of flow velocities. The
results demonstrate the efficacy of the closed
immersion technique: a 93% decrease in debris is
produced when machining under closed filtered water
immersion; the average debris particle size becomes
larger, with an equal proportion of small and medium
sized debris being produced when laser machining
under closed flowing filtered water immersion; large
debris is shown to be displaced further by a given flow
velocity than smaller debris, showing that the action of
flow turbulence in the duct has more impact on smaller
debris. Low flow velocities were found to be less
effective at controlling the positional trend of
deposition of laser ablation generated debris than high
flow velocities; but, use of excessive flow velocities
resulted in turbulence motivated deposition. This work
is of interest to the laser micromachining community
and may aide in the manufacture of 2.5D laser etched
patterns covering large area wafers and could be
applied to a range of wavelengths and laser types.

Item Type:Conference or Workshop Item (Presentation)
Additional Information:The performance of laser ablation generated debris control by means of open immersion techniques have been shown to be limited by flow surface ripple effects on the beam and the action of ablation plume pressure loss by splashing of the immersion fluid. To eradicate these issues a closed technique has been developed which ensured a controlled geometry for both the optical interfaces of the flowing liquid film. This had the action of preventing splashing, ensuring repeatable machining conditions and allowed for control of liquid flow velocity. To investigate the performance benefits of this closed immersion technique bisphenol A polycarbonate samples have been machined using filtered water at a number of flow velocities. The results demonstrate the efficacy of the closed immersion technique: a 93% decrease in debris is produced when machining under closed filtered water immersion; the average debris particle size becomes larger, with an equal proportion of small and medium sized debris being produced when laser machining under closed flowing filtered water immersion; large debris is shown to be displaced further by a given flow velocity than smaller debris, showing that the action of flow turbulence in the duct has more impact on smaller debris. Low flow velocities were found to be less effective at controlling the positional trend of deposition of laser ablation generated debris than high flow velocities; but, use of excessive flow velocities resulted in turbulence motivated deposition. This work is of interest to the laser micromachining community and may aide in the manufacture of 2.5D laser etched patterns covering large area wafers and could be applied to a range of wavelengths and laser types.
Keywords:KrF excimer laser, Ablation, debris control, Closed Liquid Immersion, Flow Velocity
Subjects:H Engineering > H680 Optoelectronic Engineering
F Physical Sciences > F361 Laser Physics
H Engineering > H700 Production and Manufacturing Engineering
H Engineering > H300 Mechanical Engineering
Divisions:College of Science > School of Engineering
ID Code:4027
Deposited By: Colin Dowding
Deposited On:18 Feb 2011 09:20
Last Modified:13 Mar 2013 08:56

Repository Staff Only: item control page