Direct Determination of Metallic Contamination on and in Wafers Using Laser Ablation Inductively Coupled Plasma Mass Spectrometry

A new analytical technique was developed for determination of metallic impurities in wafers using LA-GED-MSAG-ICP-MS. Up to 300 mm wafer can be analyzed directly without using a small, enclosed chamber. Particles generated by a femto-second laser ablation were aspirated together with a particle free clean air by an ejector and introduced to the ICP-MS (Inductively Coupled Plasma Mass Spectrometry) via GED (Gas Exchange Device). The air was exchanged by Ar gas and the particles came out from GED in Ar gas stream. For quantitation of LA-ICP-MS, MSAG (Metal Standard Aerosol Generation) was used. MSAG could introduce nearly a 100% of aqueous multi-element standard solution to the plasma of ICP-MS, which allowed precise quantitation using the method of standard addition while ablating wafer samples. This paper describes how the new analytical technique works for ultra-trace level of metallic impurities in wafers.