Abstract:

Particle precursors, defined as a dissolved molecular compound, which may form particles when dried on the wafer surface, have been identified in multiple studies as a risk to semiconductor manufacturing yield (1,2). These compounds are anticipated to be primarily organic. Given the high use of polymers used in UPW and chemical distribution systems as well as ion exchange resins used in UPW systems and chemical purification, the concentration of these contaminants can be substantial. As device dimensions decrease, particles formed from particle precursors can reach the critical size identified as a yield risk (currently ~3.5 nm). Given that particle precursors are dissolved, they are difficult to remove with traditional filtration techniques and cannot be detected by traditional optical particle counters based on light-scattering.

The recent introduction of metrology based on nebulization and condensation particle counting has provided a tool for both online and offline measurement of particle precursors. These instruments use a measurement technique significantly different than traditional light-scattering particle counters and new procedures are required to standardize their measurement output and allow for instrument correlation. To this end, the SEMI UPW Task Force engaged in the preparation of a Guide for Evaluation of Metrology for Particle Precursors in Ultrapure Water. The purpose of this paper is to demonstrate the utility of this document by evaluating multiple instruments at multiple facilities following the guidelines and comparing outcomes. The paper will also demonstrate the ability to quantify particle precursor concentrations by normalizing the particle concentration data to mass concentration.