Cross-Sectional Imaging of Directed Self Assembled Block Copolymers

摘要

In this paper we address an important topic for the development of block copolymer directed self assembly, which is the lack of the third dimensional information. The three-dimensional shape of the DSA feature directly impacts the ability to transfer the DSA pattern into etched patterns. Through TEM sample preparation by in-situ focused ion beam (FIB) Pt deposition and milling, we show cross-sectional images for the two most elemental building blocks of directed self assembled block copolymers, namely, the single and double-hole (peanut shape) etched in Si structures with great contrast at the interface formed by PS and PMMA. Additionally, a hard-mask single hole structure processed with a different template material is shown as well. Elemental mapping with energy filtered TEM (EFTEM) was shown to assist interpretation of images. 3D reconstruction of the holes formed in the hard-mask sample was performed using dark field (DF) STEM. A reduction in the SOC and SOG thickness was observed post in-situ Pt deposition for the hard mask structure. Further TEM sample preparation improvements will be needed to minimize the compression observed.