New fast-etching bottom antireflective coatings for 248-nm lithography

Abstract

As the critical dimensions for the feature sizes shrink, the thickness of the photoresist layer decreases to enable patterning without collapse of the photoresist structure. Simultaneously, the use of an antireflective coating underneath the photoresist layer becomes imperative for achieving good critical dimension control. The thickness of the bottom antireflective coating (BARC) and its etch rate relative to the photoresist determine how much resist is lost during the dry etch step. In order to minimize resist loss during BARC etch, we have designed BARC compositions that have high etch selectivity and optical constants (high n and high k) that make it possible for the BARC to be used much thinner than the existing BARCs. Furthermore, the new BARC compositions are single component systems and are therefore relatively simple to produce compared to typical BARCs. The polymer that forms the coating has high absorbance at 248nm and is also capable of crosslinking in the presence of an acid catalyst at elevated temperatures. These organic coatings are immiscible with photoresists and are not affected by the base developer. In this paper, we will report the etch properties, optical properties and compatibility with photoresists of these new coatings.