Line Edge Roughness of Directed Self-Assembly PS-PMMA Block Copolymers—A Candidate for Future Lithography

Abstract

Directed self‐assembly (DSA) of block copolymers (BCPs) is a technology that combines lithographically defined physical or chemical features to guide self‐assembled polymers to create features smaller than those possible with conventional lithography. To the semiconductor industry DSA represents a possible lithography solution below 22–16 nm node where the targeted line edge roughness (LER) is 1.4 nm or less. This LER requirement presents a challenge for DSA to become a viable lithography solution. Hitherto the LER of DSA block copolymers was measured mostly using SEM and AFM, hence the results represent only the top surface characteristics. In addition, the observed LER using SEM or AFM is often greater than 1.3 nm. The purpose of this work is to demonstrate the use of transmission X‐ray scattering to quantify LER as well as the critical dimensions in BCP patterns created with the DSA technique. Experimental results from poly(styrene‐b‐methyl methacrylate) copolymer line gratings with 23 nm half pitch will be presented and the theoretical developments needed to extract LER from X‐ray scattering will also be discussed.