Material Removal Behavior of Nano-Sized Cerium Hydroxide Abrasive Slurry for Chemical Mechanical Polishing

Abstract

Microscratch induced by Chemical Mechanical Polishing (CMP) is a chronic problem to device yield-killing and its criticality becomes more important in sub-14nm device manufacturing. In order to mitigate scratching during CMP, minimizing abrasive particle size without sacrificing removal rate is the most important parameter. For this purpose, less than 5nm sized cerium hydroxide-based (nano-sized cerium hydroxide-based, NC) particle is utilized as oxide CMP slurry, which is much smaller than conventionally used calcined ceria slurry (100nm – 200nm in particle size). Although it shows more than 80% microscratch reduction obtained by NC slurry in poly CMP process, its polishing behavior is not well understood. In this study, tetraethyl orthosilicate (TEOS) oxide removal behavior with NC slurry is explored by a series of experiments involving tribological analysis. Based on experimental results, this study emphasizes surface reaction as a dominant parameter to determine removal rate rather than mechanical aspect of material removal.

Abrasive for Chemical Mechanical Polishing

“…Therefore, recent abrasive technology has focused on nano-sized abrasive synthesis with minimized agglomeration. For dielectric CMP, nano-sized cerium hydroxide (or ultrafine cerium hydroxide or nano-ceria) abrasive slurry has been introduced due to its potential scratch defect reduction [33][34][42][43]. The synthesis procedure of nano-sized cerium hydroxide abrasive is given in Figure 13.…”

“…Han et al reported polishing pad surface roughness control is critical to maintain removal rate stability with nano-sized cerium hydroxide abrasive [44]. Kim proposed particle coverage model on the wafer as material removal mechanism with nano-sized cerium hydroxide abrasive [43]. In order to apply nano-sized cerium hydroxide abrasive for dielectric CMP, role of chemistry to enhance removal rate with selectivity control needs to be further explored.…”