Metallic Impurity Analysis in Ultra-Pure N-Methyl Pyrrolidone with the NexION 5000 ICP-MS

Introduction

As semiconductor devices have become smaller and more sophisticated, it has become essential to prevent metal contamination, which causes yield loss. Therefore, strict impurity control is required for chemicals used in the fabrication process. A variety of organic solvents are used in the fabrication process, including N-methyl-2-pyrrolidone (NMP), which is used as a typical stripper for photoresists. If metal in the stripper remains in the circuit pattern, it may affect the electrical and other characteristics of the semiconductor. Therefore, the NMP used must be of high purity.

Inductively coupled plasma mass spectrometry (ICP-MS) is commonly used for elemental impurities analysis in organic solvents and photoresists thanks to its ability to detect many elements on the order of ng/L (ppt) and pg/L (ppq). However, the concentration of elemental impurities in commercial organic solvents has been raised as a challenge. As the required impurity levels decreased, the impurity concentrations of some elements in widely used semiconductor-grade pure organic solvents is high and the ICP-MS system is required to have higher interference removal capability.

This work reports the results of analysis of 37 elements in ultra-pure NMP using the NexION^® 5000 multi-quadrupole ICP-MS. Equipped with the latest technologies, among which proprietary multi-quadrupole technology, the LumiCoil RF load coil, and a free-running RF generator, the NexION 5000 provides excellent trace-analysis performance, including superior spectral interference removal, in organic solvent measurements.