Negative Bleaching Photoresist (BLEST) For Mid-UV Exposure

Abstract

The design and preparation of a mid-UV negative bleaching photoresist (BLEST) are described. This two-component resist system is composed of a cresol novolac resin and 4,4'-diazido-3,3'-dimethoxybiphenyl. BLEST is a negative working resist which has the advantage of alleviating optical interference effects caused by reflection from the topograhic features on the substrate surface. The resist is characterized by its photobleaching controllability which helps incident UV light to penetrate more deeply, thus realizing a high aspect ratio. BLEST was exposed to mid-UV light and developed in a tetramethylammoniumhydroxide aqueous solution. The sensitivity of the resist was about 150 mJ/cm2 and contrast was 1.7. A good resist profile was obtained by printing on a Perkin-Elmer Micralign 500 system.