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Applications of lasers for industrial cleaning in engineering

Objective


The above aims were achieved. Investigation of fundamental mechanisms of laser cleaning has resulted in the development of three new laser-cleaning methods (laser shock cleaning, angular cleaning, steam assisted cleaning). The degree of removal of contaminants from a wide range of contaminant / substrate combinations encountered in the fabrication of microelectronic components has been quantified and it has been shown that careful selection of laser wavelength and operational mechanism can significantly improve the cleaning efficiency in many cases. At the same time, substrate damage has been avoided. Laboratory prototypes based on Nd:YAG, excimer laser and operational parametric oscillator devices have been constructed and tested. Compact power supplies have been developed to enhance the portability of these devices and a novel diode laser has been designed and produced as a potential new laser source in such devices.
Objectives and content
Microcleaning is emerging as an essential aspect of the
achievement of these goals. As microelectronic devices
become smaller, the critical size of an adherent foreign
particle that can produce a "killer" defect similarly
reduces (since the critical size is about 1/10th of the
design linewidth) and particles as small as 0.1mm require
removal to ensure component viability. Many
microcomponents are contaminated during production with
surface deposits that require removal to ensure device
quality and performance.
Conventional techniques for the removal of such deposits
are currently severely limited. The more successful
techniques involve wet cleaning with organic solvents
such as carbon flurochloride (CFC) or trichloroethylene,
often used in conjunction with ultrasonic agitation.
These organic solvents are hazardous to human health as
potent cancer causing agents. The organic solvents also
pose a significant environmental risk by destruction of
atmospheric ozone. Hence, there is strong restriction on
the use of CFCs. These techniques are ineffective in
removing the very small (0.1mm) particles since
redeposition from the solution invariably takes place
because such small particles cannot be removed from the
bulk solution by filtration. At the same time, removal
becomes more difficult since the adhesion forces increase
as the inverse of the square of the particle diameter and
conventional techniques lack the selectivity of energy
input to remove such small particles.
Laser microcleaning (LMC) offers a revolutionary
approach, which exploits the unique capabilities of
lasers to remove surface contaminants in ambient
atmosphere without the need to use environmentally
contaminating solvents. Since no vacuum or special
protective atmospheres are required, LMC can be
unobtrusive in the production process, integrating in
continuous in-line systems. Significantly, the action a
tightly focussed laser is highly localised leading to
high surface specificity of the cleaning effect. This
capability is aided by very recent and ongoing
developments in the types of laser sources available
which, with the introduction of diode pumped solid state
lasers, offers increasing process efficiency and
flexibility at reduced cost compared with earlier non
solid state laser systems. As a result LMC is an
emerging technology with potential for the improvement in
the efficiency and capability of microcleaning
requirements.
In the ALICE programme, we will create the conditions for
the systematic exploitation of LMC by European industry.
Our industrial objectives will centre on the development
of LMC to meet the needs of the microtechnology sector.
The principal aim will be to reduce component wastage
rates by 50% as a result of the introduction of LMC
compared with current techniques. The secondary aim is
to show that this can be achieved in an environmentally
acceptable manner. Further, we will show that by the use
of diode pumped solid state systems the costs of LMC can
be reduced by over 100% compared with current excimer
lasers and result in instruments which are at least one
third the physical mass of the conventional flashlamp
pumped systems.
ALICE will proceed beyond current state of the art by
developing innovative LMC regimes for specific deposit
substrate combinations and microelectronic components.
We will also innovate through the development of
fundamental understanding of the mechanisms involved and
the characterisation of the effect of the cleaning regime
on the substrate material and its functional properties.
Targets will be to achieve 100% deposit removal with
maintenance of full component functionality.

Coordinator

THE UNIVERSITY OF LIVERPOOL
Address
Brownlow Hill
L69 3BX Liverpool
United Kingdom

Participants (5)

ARTT - Association for Research Technology and Training
Greece
Address

71110 Heraklion
INSTITUTO SUPERIOR TECNICO
Portugal
Address
Avenida Rovisco Pais
1049-001 Lisboa
Lynton Lasers Limited
United Kingdom
Address
Beech Lane
SK9 5ER Wilmslow
MATS (UK) Ltd.
United Kingdom
Address
4,Wavertree Boulevard South
L7 9PF Liverpool
Plasma Ireland Ltd.
Ireland
Address
Enterprise Centre
30 Cork