Detection of ultra-low-level surface contamination using Extreme Ultraviolet photoelectron spectroscopy

A new evaluation method in extreme ultraviolet (EUV) lithography is being developed. The method must have the ability to detect a 0.1% reflectivity drop at the wavelength of 13 nm. Until now, the most promising candidate is EUV excited photoelectron spectroscopy (EUPS). The performance of EUPS as a diagnostics of tin (Sn) contamination on a surface is studied using a 4.86-nm photon which is generated from boron nitride (BN) plasma. The electron energy spectrum is obtained by the time-of-flight method. The intensity change of Sn 4d electrons will be observed as a function of Sn deposition coverage ratio on a Si wafer. Furthermore, the sensitivity of this detection is affected by the oxygen peaks in the silicon wafer performing a SiO₂ binding. So, the use of hydrofluoric (HF) acid as a cleaner to this oxygen peaks is being examined.