Low-dose exposure technique for 100-nm-diam hole replication in x-ray lithography

In this article, we describe a new exposure technique for printing hole patterns with diameters of 100 nm or below in x-ray lithography. By using mask patterns approximately twice the size of the required resist patterns, 100-nm-diam holes can be replicated with doses less than those required to clear a large exposed area (D-0) with a 20-30 mu m gap. A 540-nm-thick UVII-HS resist was used for the exposure experiment. With a proximity gap of 20 mu m, a 100-nm-diam hole was replicated with a 200-nm-diam mask pattern by exposing it with 0.56 D-0 dose. Both the experimental and the simulation results indicated that this technique provides a higher resolution and a larger exposure latitude compared to normal-dose exposure. In terms of mask biasing, this technique corresponds to the mask bias optimization at doses below D-0. (C) 1998 American Vacuum Society. [S0734-211X(98)07606-9].