A batch study of trace metal impurities in high-k semiconductor precursors

Abstract

Advanced electronic materials called precursor molecules are designed for the deposition of thin films that are expected to be reliable, contamination free and pristine. Deleterious effects of metallic contamination have been demonstrated in dielectric properties of thermal oxides grown on silicon [1]. In order to achieve ultra-high purity products, essentially free from trace metals (TM) and organic impurities, they need to be fully qualified. Upfront, TM analysis allows detection, identification and quantification of these contaminants to help control the quality of these precursors thus making them the preferred candidates for atomic layer deposition of high-k materials as storage capacitors in DRAM applications, or gate stacks of MOS-transistors. In this paper, we will demonstrate the inherent variability of trace metal concentrations in precursors, that necessitates the quantification for evaluation, qualification and periodic monitoring of suppliers. We will reveal the presence of high levels of TM contaminants that are present in varying amounts from batch to batch and supplier to supplier for the same precursor. Additionally, the same precursor from two different suppliers may contain totally different TM contaminants.