Introduction
The RCA Standard Clean (SC), commonly referred to as SC-2 (Standard Clean 2) or HPM (Hydrogen Peroxide Mixture), is a mixture of hydrochloric acid (HCl) and hydrogen peroxide (H2O2). This solution is extensively used to remove ionic and metallic contaminants from silicon wafer surfaces, and comes into direct contact with the semiconductor devices, so it must be in its purest form. As such, ultra-high-purity HCl is required. According to the SEMI Standard C27-0918 Tier-D1 protocol, the contaminant level in high-purity HCl should be less than 10 parts per trillion (ppt) for each element.
Inductively coupled plasma mass spectrometry (ICP-MS) has been widely used for the determination of ultra-trace impurity levels in various chemicals. However, it can be subjected to interferences from polyatomic and isobaric ions originated from the plasma and/or matrix species.
This work demonstrates the ability of the NexION® 2200 ICP-MS to reliably and effectively quantify ultra-trace impurities at the ng/L level in concentrated HCl. The data displays the effectiveness of the proprietary Universal Cell Technology (UCT) in addressing Cl-based interferences. Using Reaction mode, impurities in 20% HCI can be directly measured at SEMI C27-0918 Tier-D levels. This approach eliminates the need for complex sample pre-treatment or dilution, thus minimizing the risk of contamination.
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