Precilab offers silicon wafer surface analysis using liquid phase decomposition of the silicon oxide layer followed by trace element analysis using ICP-MS (LP-ICP-MS) for 36 elements. Although similar to vapor phase decomposition methodologies, liquid phase decomposition allows for improved precision, repeatability, and lower detection limits. Liquid phase decomposition makes the best use of ultra-pure reagents and water with sub-ppt (pg/g) element levels, preparation under Class One cleanroom (ISO Class 3) conditions, and analysis using an ICP-MS dedicated to wafer analysis.
Accurate characterization of wafer surface contamination depends entirely on the skilled handling of the wafer once it is time for preparation. In our experience the use of dilute ultra-pure reagents for precise decomposition of the oxide layer avoids the complication of surface etching and excessive volatilization of important elements such as Boron and Arsenic. For many wafers the small volume of liquid scanning solutions remains on the surface for less than one minute. Upon completion of the decomposition step the liquid is removed and isolated prior to analysis.
Class 1 Cleanroom Conditions
Liquid phase decomposition avoids the use of chambers and machines that are known to add contaminants and are sources of cross contamination from previously analyzed wafers. Decomposition of the oxide layers under cleanroom conditions prevents airborne contamination and spurious false-positive results. Exposure time of the surface is reduced and the overall recovery of all elements of interest is enhanced. We used the highest purity hydrofluoric acid-hydrogen peroxide (HF-H2O2) available for our scanning solution.
The sample solutions isolated off the wafer surface are analyzed using a dedicated ICP-MS. This instrument is optimized for scanning solution analysis. Wafer analysis demands the very best in contamination control of the analysis tool. Analysis of the sample solutions benefits from the elimination of instrument memory effects as the required quantitation levels continue to go lower. When fast-turn analysis is needed our instrument is ready and your sample are not “waiting” for instrument time to be made available.