9612274 Walz Removal of particulate contamination from solid surfaces is a major concern in the fabrication of integrated circuits (IC's), high density magnetic storage, large area displays, high power laser and astronomical optics, and other electronic and optical devices. With the trend toward smaller scale device technology, the need for improved particle removal techniques has become critical. In previous work, Allen developed an innovative technique called Laser Assisted Particle Removal (LAPR) to remove particulates from solid surfaces using a laser and a medium to transfer energy from the laser beam to kinetic energy in the particles. In this project, a two-prolonged-effort will be used to identify experimentally the important variables in controlling the LAPR process and to integrate the resulting information into a physically meaningful model to predict and optimize LAPR for different particle/substrate/ambient systems. This combined empirical and mechanistic approach will allow efficient technology transfer to, for example, semiconductor process equipment manufacturers. The primary objective is to develop a model of the LAPR process that can be used to optimize the design of a particle removal process module for cleaning critical surfaces. Toward that end, collaborations with industrial partners will be continued. An important step in reaching this objective is to develop a model for predicting the strength of the adhesion force binding specific contaminants to surfaces. This will be accomplished using the novel optical techniques developed by Walz to measure colloidal interaction forces. Also proposed is the development of a new technique for removing adhered particles based on the principle of radiation pressure. Here, a tightly focused laser beam will be used to "push" particles off transparent substrates. The technique would be especially useful for cleaning high energy optical devices. A major advantage of the technique is that it should be possible to perform the cleaning without the use of any liquids. Since the applied radiation force can be measured independently, the technique could also be used for measuring directly the adhesion force, which would be an extremely useful research tool. ***
