Abstract:

Trace organic contamination in Ultrapure Water (UPW) and high purity materials pose a risk of depositing on wafers during wafer processing. Organic contaminants include relatively low molecular weight particle precursors and higher molecular weights polymers of various chemical functionality which influence reactivity, volatility and adhesion. “Critical organics” which remain adhered to the wafer surface pose the greatest risk to yield.

To aid the industry in mitigating the risk from critical organic contaminants, the SEMI UPW Task Force is developing a particle precursor challenge, specifically ion exchange resin extract, for inclusion in SEMI C79, Guide to Evaluate the Efficacy of Sub-15 nm Filters used in UPW distribution systems. Additional risk mitigation efforts regarding high purity materials include the IRDS Critical Components team goal to establish critical organics extraction limits for PVDF and PFA components.

Vibrational spectroscopy methods (FTIR-ATR, SERS and AFM-IR) speciate semi-volatile and non-volatile contaminants present as thin films and image and size nanoparticles on surfaces. All three of these analytical methods can detect specific chemical bonds in a wide range of organic and inorganic contaminants. However, the underlying physics and instrumentation of these analytical techniques are different. This operational diversity will be valuable if vibrational spectroscopy can evolve to fill gaps in analytical capabilities that are still needed to understand particle precursors and defects on wafers. Currently, data from vibrational spectroscopies are run in parallel with spectrometry, microscopy, chromatography and particle sizing to ascertain the risk of trace amounts of low molecular weight monomers and larger molecular weight nanoparticles in UPW and on wafers.

Particle precursors from ion exchange leachates in UPW and chemical pathways to particles on wafers have been studied. One pathway involves reactants that are a less obvious source of particles based on their low molecular weight. Another investigation studied non-volatile and semi-volatile portions of the PFA and PVDF extracts that remain adhered to wafers. Before this work we did not know if organics from polymer components met the definition of critical organics, now we know these components are potential sources of critical organics.

We will present composition and size data from FTIR-ATR, SERS, AFM-IR and additional analytical techniques that identify particle precursors and potential transformations to nanoparticles on wafers. Our results will highlight analytical capabilities, challenges and opportunities in the use of vibrational spectroscopy to obtain fundamental knowledge on critical organics. Discussion of these results is important because it could help identify analytical capability improvements needed to better quantify and manage risks to wafer yield.