Establishing a sidewall image transfer chemo-epitaxial DSA process using 193 nm immersion lithography

Directed Self-Assembly (DSA) of Block Copolymers (BCP) by chemo-epitaxial alignment is a promising high resolution lithography technique compatible with CMOS high-volume manufacturing. It allows overcoming limitations in resolution and local stochasticity by conventional, imaging based, lithography. However, for BCP with pitches below 20 nm and guide patterning by immersion lithography (193i), multiplication factors ≥ 4 become necessary, imposing stringent requirements on the guides and defectivity becomes hard to control. The Arkema-CEA (ACE) process flow overcomes this limit by creating the guides by a self-aligned double patterning (SADP) process flow, followed by the deposition of a cross-linkable neutral mat and selective grafting of the guides. This paper reports on the transfer of the process flow to immersion lithography, details challenges encountered in process optimization, notably the dependence of the wetting of the neutral layer on the surface energy and the morphology of the spacers. Last, the paper presents a metrology and defectivity roadmap combined with preliminary, promising results.