Local confined laser-induced plasmas for direct writing of low damage patterns by precise reactive etching

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With increasing integration and miniaturisation for extending the functionality of surfaces and thin films new materials are required but also new, innovative technologies for local modification, patterning and deposition are requested. Within the last years laser technologies have been developed to increase the precision of laser machining for enabling new applications. The current laser processing preferentially makes use of physical processes like laser-induced melting and evaporation and ablation. The goal of the proposed project is to investigate laser induced reactive plasmas (LIP) and evaluate them for micromachining of surfaces with an extremely high quality and a low defect density. The interaction mechanism between the LIP and surfaces can be of chemical or physical nature however typically physical interactions have been investigated until now. Hence, we focus on the generation of excited chemical reactive radicals by laser induced plasmas that should be employed for local chemical radical etching beneath the focal point of a particular shaped laser beam. Main questions to be answered cover the areas of (i) guiding of the pulsed, high intense laser light along the surface without surface damage and enabling near surface LIP formation at the same time, (ii) generation of reactive radicals from a gas mixture containing suitable precursor molecules by laser induced plasmas preferentially at atmospheric pressure, and (iii) transport of the LIP generated reactive species to and chemical reaction of them with the samples surface. By the results of the experimental work that should be accomplished by studying the surface modification and etching in dependence on LIP process parameters and investigating the formation, transport and decay of reactive products by preferentially optical in situ diagnostics are utilized to expose the involved processes and establish a mechanism of laser induced plasma etching. The simulation of selected processes should provide help for verifying the relevance of these processes and mechanism. Such laser induced reactive plasmas could enable locally resolved, chemical supported machining of surfaces for a variety of applications.