Application of Electron Projection Lithography to Via Formation in Two-Layer Metallization

Abstract

In this paper we showed electron projection lithography (EPL) applicability to via formation in a back-end-of-line (BEOL) process for 45-nm technology node through fabricating a two-layer metallization device. We developed a single-layer via-resist process for 45-nm technology node. In order to prevent resist profile deteriorations, we optimized process conditions of a bottom anti-reflective coating (BARC) and an electrical conductive film (ECF). As a result, fine 60-nm (1:1) via-patterns were obtained after low-k dry-etching and 67-nm via-holes filling with Cu could be confirmed by using cross-sectional transmission electron microscope (TEM). These results suggested the single-layer via-resist process we developed could be applied for 45-nm technology node. In addition, for 32-nm technology node, we developed a tri-layer via-resist process that had a high resolution compared with a single-layer resist process. There, we could obtain extremely fine 40-nm (1:1) top-layer via-resist patterns. We believe that EPL has high applicability to via formation in BEOL process for not only 45-nm but also 32-nm technology node.