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

随着表面和薄膜功能的日益集成化和小型化，不仅需要新的材料，还需要用于局部修改、图案化和沉积的新的创新技术。在过去的几年里，激光技术已经被开发出来，以提高激光加工的精度，从而使新的应用成为可能。目前的激光加工优先利用激光诱导熔化、蒸发和烧蚀等物理过程。该项目的目标是研究激光诱导反应等离子体(LIP)，并评估其用于极高质量和低缺陷密度表面的微加工。LIP和表面之间的相互作用机制可以是化学的，也可以是物理的，然而，到目前为止，通常的物理相互作用已经被研究。因此，我们将重点放在激光诱导等离子体产生激发的化学反应自由基，这种等离子体应该被用来在特定形状的激光束的焦点下进行局部化学自由基刻蚀。要回答的主要问题包括：(I)脉冲高强度激光沿表面引导而不会造成表面损伤，同时能够在近表面形成LIP；(Ii)在大气压下，激光诱导等离子体优先从含有合适的前体分子的气体混合物中产生反应自由基；以及(Iii)LIP产生的反应物种传输到样品表面并与其发生化学反应。根据实验结果，通过研究表面改性和刻蚀对LIP工艺参数的依赖关系，以及优先利用光学原位诊断来研究反应产物的形成、传输和衰变，揭示了所涉及的过程，并建立了激光诱导等离子体刻蚀的机理。对选定进程的模拟应有助于核实这些进程和机制的相关性。这种激光诱导的反应等离子体可以在各种应用中实现局部分辨、化学支持的表面加工。

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.