300 mm-wafer metrology for area-selective deposition in nanoscale patterns: A case study for ruthenium atomic layer deposition

Abstract

Area-selective deposition (ASD) is a possible enabler for the fabrication of various future semiconductor devices. However, it remains challenging to characterize and optimize ASD processes in patterns with nanoscale di-mensions, as required for semiconductor device applications. Therefore, we study Ru ASD on different types of nanopatterns on 300 mm-wafers and assess the role of the pattern geometry and density on selectivity. As selectivity is often improved by means of passivation-deposition-etch cycles, we investigate an ASD cycle con-sisting of passivation by (N,N-dimethylamino)trimethylsilane, deposition by (ethylbenzyl)(1-ethyl-1,4-cyclo-hexadienyl)Ru/O2 atomic layer deposition (ALD) and an O/Cl plasma etch. On line-space patterns with a 32 nm critical dimension, the passivation-deposition-etch cycle yields a lower defectivity level than the passivation-deposition approach for a given Ru ASD thickness. The comparison of Ru ASD on line-space and hole nano -patterns reveals the pattern-dependent selectivity, that is explained by accumulation of Ru nanoparticles at pattern edges. 300 mm-wafer uniformity is also investigated and related to reactor design. The investigation of ASD on nanopatterned 300 mm-wafers is enabled by ASD-specific developments of X-ray photoelectron spec-troscopy, optical critical dimension scatterometry, and scanning electron microscopy. This research highlights the possibilities and challenges in developing ASD processes in an industrial setting.