Lasers clean dirty surfaces

17 Jun 2002

New surface technique removes stubborn microparticles in a flash

Lasers can provide an effective method for cleaning microscopic particles from certain polymeric surfaces, report scientists at Linz University, Austria, and Konstanz University, Germany. The researchers found that common problems associated with conventional techniques like ultrasound, wiping or high-pressure spraying, which often fail to remove micron- and submicron-sized dirt particles, can be avoided with certain particle-polymer combinations. In particular, highly absorbent materials were cleaned more effectively than highly reflective ones and the efficiency was increased further when the cleaning took place at a higher humidity.

The scientists removed small, spherical particles from polymer surfaces with the help of a 193 nm ArF laser and a 248 nm KrF laser. Polystyrene particles with diameters of 110 and 1700 nm and quartz particles with diameters of 400 and 800 nm were successfully removed from polyimide and polymethyl methacrylate. The tests took place in air at 23°C and a relative humidity of 24-28% and in an environment with 90% relative humidity.

The researchers believe that the technique will be useful for cleaning sensitive substrates, such as in semiconductor component production, provided that the substrates absorb the incoming light adequately.