Electrochemical Delineation of Tungsten Films for Microelectronic Devices

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Abstract
A process is described for delineating high resolution patterns in tungsten films on semiconductor device wafers. The process is based on high‐speed anodic dissolution in alkaline ferricyanide electrolyte of exposed tungsten on a photoresist masked wafer. Slow chemical etching in the same solution occurs simultaneously with the electroetching to remove isolated residual areas of tungsten. The effects of important process variables are discussed, and optimized conditions are presented. The process is capable of accurately defining patterns in several‐micrometer thick tungsten suitable for metallization and intraconnection patterns on transistor and integrated circuit wafers The technique is also suitable for patterning tungsten and molybdenum foils. The capability and applicability of the process is illustrated with photomicrographs of representative devices.