A Discrepancy in Hydrogen Peroxide Air Sample Results for a CMP Maintenance Task – Case Study
Cole, Krista S.
(University of California)
Hydrogen peroxide airborne emissions were sampled during a routine maintenance task for CMP equipment. The direct reading measurements made with the Zellweger ChemKey TLD fluctuated between 0.2 to 0.4 ppm, with spikes to 0.5 ppm. These results conflicted with the integrated sample result, which returned from the analytical laboratory as “non-detect”, lower limit of detection 0.068 ppm. Possible causes for this discrepancy in results were evaluated. The evaluation led to the hypothesis that the Tygon tubing placed upstream of the sample media cause a negative interference with the integrated sample. A mathematical model was constructed to calculate the expected H2O2 concentrations in the breathing zone. The model results agreed with the real-time readings made with the direct reading instrument. Recommendations are provided to help avoid similar discrepancies in the future.