VPD-DSE-STUDIES OF METAL IMPURITIES ON SILICON: A COMPARISON OF DIFFERENT CONTAMINATION METHODS

摘要

Combining TXRF (total reflection x-ray fluorescence spectrometry) with VPD-DSE as preconcentration method (vapour phase decomposition-droplet surface etching) improves the detection limits of straight TXRF from E10 atoms/cm2 to the region of E8 atoms/cm2 or below, depending on the wafer diameter. VPD-DSE TXRF can meet the detection limits currently required in the semiconductor industry'. However, a closer look at the method reveals inconsistencies. Previous studies showed the shortcomings of VPD-TXRF caused by variations of the properties of the DSE residue. Others revealed discrepancies between TXRF and AAS (Atomic Absorption Spectrometry) due to a calibration difference between film-type and particle-type contaminations in TXRF. This study is a further investigation of factors which cause discrepancies in the results viz. the method of contamination of the sample and the influence of the angle of incidence in TXRF based on the contaminants Mn and Fe. A comparison is also drawn between radiotracer techniques and straight TXRF as analytical methods. Deviations of 20 to 40% between both analytical methods were found.