Maskless Laser Etching of Alumina and Ceramic Substrates
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MASKLESS LASER ETCHING OF ALUMINA AND CERAMIC SUBSTRATES
JAMAL KHAN Digital Equipment Corporation, Shrewsbury, MA 01545.
ABSTRACT Maskless patterning of alumina (A1203) films of various thicknesses and ceramic (TiC-A1203) substrate material was accomplished by using pulsed excimer and Nd:YAG laser systems. Etched structure size was defined through the computer software which also controls the workpiece position and laser operating parameters. Etch profile, materials removal rate and surface roughness was found to be dependent on laser emission wavelength, fluence, pulse rate and relative scan speed. Smoother etching was obtained with the excimer lasers. The etch characteristics are compared with those of the polymeric and metallic materials. Various potential applications of this laser based etching process in microelectronic and micromagnetic device fabrication are identified.
INTRODUCTION Ceramic film and substrate materials are key components in many of the modern electronic, magnetic and optical devices. Therefore, development of new cost effective processing techniques for these materials is of paramount importance. Most of the literature on laser processing of ceramic materials deals with machining and hole drilling [1-5] and for the most part CO2 and YAG lasers were used. Extended heat-spread zone, formation of resolidified layer at the edges and appearance of micro-cracks were found to be major problems in the laser etching of ceramics. Better etch profiles were obtained when the etching was performed in water or a liquid chemical etchant [7,8]. Chemically assisted laser etching of glasses and Si3N4 has been done by using a reactive gas environment to either selectively enhance [9-11] or suppress [12] the etch operation. Conventionally, pattern etching in ceramic materials in the semiconductor device fabrication is achieved by vacuum sputter etching through photoresist masks. However, the mask define and stripping steps are time consuming and these processes are not always practical in the etching of patterns in certain materials due to limited etch selectivity. Laser etching of patterns through masks has been reported by some researchers [8,13,14]. We now describe a totally maskless laser etch process without using any chemical reagents.
PRINCIPLE AND SPECIAL FEATURES OF THE NEW PROCESS Computer controlled laser etching systems are used in this process such that the dimensions of the structure, location of patterns and operation of laser parameters (beam energy, pulse rate, etc.) are controlled via the software. A thin film of the desired workpiece material is deposited on the substrate by using conventional methods after completing prior process steps. Laser system is chosen such that the material to be etched has sufficient absorption at the laser emission wavelength. Absorptive characteristics of materials can be investigated by spectroscopic techniques and laser etching parameters can be optimized separately for each material. Mat. Res. Soc. Symp. Proc. Vol. 201.
1991 Materials Research Society
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