Pergamon zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Ekcfrochimica Acm, Vol. 42, Nos 20-22, pp. 3007-3013, 1997 0 1997 Published by Elsevier Science Ltd. All rights reserved. Printed in Great Britain PII: s6013-4686(97)00147-3 001%4686/97 $17.00 + 0.00 Electrochemical micromachining: An environmentally friendly, high speed processing technology Madhav Datta* and Derek Harris? IBM Corporation, T. J. Watson Research Center, Yorktown Heights, NY 10598, U.S.A. (Received 16 December 1996; in revised form 28 February 1997) Abstract-Wet chemical etching processes are employed in the manufacturing of a variety of microelectronic components. These processes use etchants that generally contain aggressive and toxic chemicals, generate hazardous waste and have limited resolution. Electrochemical metal removal is an evolving alternate processing technique that involves controlled metal shaping by an external current, thereby requiring less aggressive and nontoxic electrolytes. The application of controlled electrochemical metal removal in the fabrication of microstructures and microcomponents is referred to as electrochemical micromachining (EMM). In this paper a recently developed EMM process and tool for metal mask fabrication is discussed. EMM performance is compared to that obtained by the conventional chemical etching process. Obtained results demonstrate the opportunities offered by EMM particularly as a high-speed, environmentally friendly processing technology. 0 1997 Published by Elsevier Science Ltd Key words: Electrochemical micromaching, chemical etching, high speed etching, microfabrication, greener processing. INTRODUCTION Metal etching techniques by both dry and wet methods are widely employed in the fabrication of microelectronic packages, metallic components and microengineered structures. Dry etching techniques are used for precision etching of thin films involving very small amounts of material removal whereas wet etching processes are predominantly used in large scale production of metallic parts involving bulk metal removal. Dry processes for thin film etching are based on plasma assisted processes and include ion etching, plasma etching and reactive ion etching [l]. These processes are particularly employed in the semiconductor industry for ultralarge scale inte- gration (ULSI) because of their ability to remove material with precision. However, some of the disadvantages that are inherent zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFED in dry etching techniques include high equipment cost, lack of selectivity, and problems arising from redeposition on the sample and deposition on the vacuum chamber. *Author to whom correspondence should be addressed. tPresent address: BMC Industries, Inc., P.O. Box 189, Cortland, NY 13045. U.S.A. Lately, concern has intensified about the safety, environmental impact, and disposal of the toxic gases used in plasma assisted dry etching. Wet chemical etching methods are used in microfabrication because of their selectivity, high etch rates and relatively low capital investment as compared to competing dry etching technologies. However, in many wet etching manufacturing processes, waste treatment and disposal contribute significantly to the product cost. The present paper describes some of the attributes of chemical etching and discusses advances made in the development of electrochemical metal removal as an environmentally friendly processing technology for microfabrication. CHEMICAL ETCHING Wet chemical etching involves removal of un- wanted material by the exposure of the workpiece to an etchant whereby the exposed material is oxidized by the reactivity of the etchant to produce reaction products that are carried away from the surface by the medium. Chemical etching involves conversion of a solid insoluble material to a soluble form. For this purpose, the extended lattice of metal atoms in the 3007