Detection of surface impurities on Si wafers using total reflection X-ray photoelectron spectroscopy

摘要

Total reflection x-ray photoelectron spectroscopy (TRXPS) has been applied to measure contamination elements on Si wafers using an x-ray photoelectron spectrometer. The radiated x-rays are limited by a slit placed in front of the Al anode, and the grazing angle is made shallow by using a crystal to make it possible for parallel x-rays to radiate the sample surface. In this experiment, the grazing angle of x-rays (Al Kα) was 1.1°, which satisfies the total reflection condition. The samples used are Si wafers contaminated with Fe and Cu. It is observed that the background intensity of photoelectron spectrum decreases with the penetration depth of x-rays, but the photoelectron peak intensity does not decrease remarkably. The detection limit of TRXPS was found to be 9×10~(10) atoms cm~(-2) for Fe and Cu contamination on Si wafers. As a result, the detection limit of TRXPS has been improved to more than 100 times in comparison with that of normal-type XPS. Accordingly, it can be said that TRXPS is a very effective method for the contamination analysis of Si wafers.