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 (D0) with a 20–30 μm gap. A 540-nm-thick UVII-HS resist was used for the exposure experiment. With a proximity gap of 20 μm, a 100-nm-diam hole was replicated with a 200-nm-diam mask pattern by exposing it with 0.56 D0 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 D0.