Critical Organics Risk Assessment of High-Purity Polymer Piping
Gary Van Schooneveld, Larry Zazzera - CT Associates, Inc.
Ali Altun - UNISERS AG
Bob McIntosh - Enviro-Energy Solutions
Organic contamination present in Ultrapure Water (UPW) and other liquids pose a risk of depositing on the wafer surface during processing and cleaning. These depositions can be in the form of a film, a particle or combination. Of greatest concern are those deposits that are non-volatile. These are designated as “Critical Organics”.
Within the IRDS roadmap there are multiple references and requirements related to Critical Organics. There are as well, multiple definitions primarily related to the boiling point of the organic. For example, the Critical Components IRDS definition use a boiling point > 150oC while UPW IRDS uses 200oC.
The objectives of this study are to quantify the extraction of critical organics from high-purity piping in hot UPW; specifically, PFA and PVDF, assess the affinity of the organic contaminants to the wafer surface during spin processing and to determine the relative concentrations of organic contamination remaining on the wafer surface as a function of temperature.
In the first phase of the testing, PFA and PVDF extract was prepare with hot (85oC) UPW using an extended SEMI F40 extraction with an elevated surface area to UPW ratio. The extraction period was extended to 14 days to ensure an adequate level of contamination and to allow time for lower diffusion rate extract constituents to migrate. The extracts were analyzed for total organic carbon (TOC) concentration by UV reduction and particle and particle precursor concentrations by nebulization and aerosol particle counting (Liquid Nanoparticle Sizing (LNS)).
Aqueous solutions of PFA and PVDF extract were prepared at two concentrations in UPW and deposited on wafers via spin coating. These wafers were analyzed for critical organics at UNISERS (Zurich, Switzerland) via surface enhanced particle sizing (minimum particle diameter 8 nm) and surface enhanced Raman spectroscopy.
CTA publication #148: Ultrapure Micro Conference, Tempe, AZ, 2022