Advanced CO2 laser-induced plasma processing and its application

Chen-Kuei Chung, Shih Lung Lin

Research output: Chapter in Book/Report/Conference proceedingChapter

Abstract

The CO2 laser of 10.6 μm in wavelength is an inexpensive, rapid and flexible one forthe soft polymer and hard glass and ceramic related materials processing. It has beenwidely applied to the fabrication of microchannel ablation, cutting, microhole drilling,material annealing and modification in the categories of MEMS, bio-chip, optical/optoelectronic devices, displays and laser dentistry. The basic CO2 laser physics is photothermalmechanism for material removal therefore some defects of debris, bulges, cracksand scorches around ablated microstructure are formed during laser processing in airwhich degrades the device yield and quality for bonding. In this article, some advancedlaser processing methods have been proposed for improving the microstructure quality offabrication including Liquid Assisted Laser Processing (LALP), cover-layer protectionprocessing and Glass Assisted CO2 Laser Processing (GACLAP) for eliminating thecracks and scorches defects, diminishing bulges height and reducing feature size, evenmaking the transparent-in-nature silicon material to be etched, drilled and cut. LALP caneffectively reduce the temperature, heat-affected zone, thermal gradient and stress viawater for hindering the crack and scorch formation together with the laser heatinginduced stronger natural convection in water for carrying debris away to reduce bulgeheight. The feature size can be reduced from 400-500 μm via traditional processing in airto 150-200 μm even smaller via LALP. Combing LALP and low-temperature bondingtechniques have been used for the fabrication of capillary-driven glass-based microfluidicchip for the application of low-to-high viscosity fluid actuating and biomedical bloodcoagulation testing. GACLAP can change light absorption behavior of Si and make Si beetched from the top surface toward the interface whose new mechanism is discussed inviewpoint of the variation of electronic band structure, surface oxidation and lightabsorption of Si at high temperature. A simple thermal model and ANSYS software areadopted for the analysis of thermal and stress distribution on specimen during the laserirradiation in air and water ambient. Also, a simple CO2 laser annealing process fortitanium dioxide treatment has also been developed instead of conventional expensiveshort wavelength laser annealing and non-selective high-temperature furnace annealing. Both crystalline rutile and anatase titanium dioxide transformation from amorphoustitanium oxide can be controlled by the sol-gel composition and laser annealingparameters for material property adjustment which is potentially used for thephotocatalyst and optoelectronic application. The relationship between process,microstructure and phase transformation of titanium oxide is discussed and established.

Original languageEnglish
Title of host publicationLaser-Induced Plasmas
Subtitle of host publicationTheory and Applications
PublisherNova Science Publishers, Inc.
Pages231-292
Number of pages62
ISBN (Print)9781613248515
Publication statusPublished - 2013 Jan

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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