ToF-SIMS Applications in Microelectronics: Quantification of Organic Surface Contamination

Abstract

An overview of our main Time‐Of‐Flight Secondary Ion Mass Spectroscopy (ToF‐SIMS) applications is first given that highlights the strengths but also reveals some development needs for this technique especially where it comes to contaminants quantification. In this work, as a step towards better quantified data, we have elaborated a method to quantify Airborne Molecular Contamination (AMC) on Silicon. For this a protocol using liquid nitrogen sample cooling was set up to reduce the desorption of the most volatile species under the Ultra High Vacuum (UHV) of the ToF‐SIMS analysis chamber and thus to enable a more stable, reliable and representative measurement. Using this protocol for the ToF‐SIMS analysis and a careful analytical sequence, good correlation between Wafer Thermal Desorption Gas Chromatography Mass Spectroscopy (W‐TDGCMS) and ToF‐SIMS results on wafers exposed for varying time under the clean‐room air flow containing 2,2,4‐trimethyl 1,3‐pentanediol diisobutyrate (TXIB) and Phthalates — two main organic clean‐room contaminants — is obtained. Relative Sensitivity Factors (RSF) are deduced. With the used measurement setups, the ToF‐SIMS low detection limits (DL) lie around 1E11 – 1E12 atoms Carbon/cm2 (atC/cm2) depending on species and are comparable to that of W‐TDGCMS at 1E11 atC/cm2.