<title>Novolak design for high-resolution positive photoresists (IV): tandem-type novolak resin for high-performance positive photoresists</title>

Abstract

A new type of novolak resins is proposed for high performance positive photoresists. This novolak resin has a molecular weight distribution different from the existing materials and is characterized by its low content of middle molecular weight components. We call this novolak resin 'Tandem type novolak resin'. The positive photoresists that contain Tandem type novolak resins exhibit improved performance in resolution, sensitivity, and heat resistance which are usually balanced in trade-off relationships. The characteristics, syntheses, and advantages of Tandem type novolak resins are described. The mechanism of resist performance improvement will also be discussed.