Thick film positive photoresist: Development and resolution enhancement technique

Abstract

The development of a positive, thick film photoresist consisting of a diazonaphthoquinone sensitizer and a novolac resin is described which has the capability of meeting a wide range of thick film requirements necessary for magnetic recording head fabrication. This photoresist system can coat 4–15-μm-thick films over various types of topography on a variety of different metal and dielectric surfaces (copper, Permalloy, and alumina). Moreover, this resist is compatible with copper, permalloy, and gold plating baths as well as different metal etchants. The photoresist can be used to produce images with wall profiles greater than 80° with a resolution capability approaching 2 μm lines and spaces in a 7.5-μm-thick film. Process latitude is demonstrated over a wide range of exposure doses and focus positions. Enhancement of thick film photoresist resolution has been achieved using a method which involves the treatment of photoresist films with dilute surfactant solutions. A number of factors have been found to effect the outcome of this method including the surfactant structure and concentration, the method and period of application, and the order of processing steps. Under proper conditions significant enhancement of photoresist contrast is observed which is accompanied by improvement of photoresist image profile and resolution. The method is particularly useful in electroplating applications.