Status monitoring of ion sputter relevant parameters of an XPS depth profiling instrument

An X-ray photoelectron spectroscopy (XPS) instrument is utilized for sputter depth profiling of thin films. Relevant instrumental parameters are the ion gun sputter rate, the contamination level of the sputter ion gun, and the purity of the sputter ion gun gas supply as well as the vacuum quality of the instrument at the sample position. A long-term recording of these instrumental parameters ensures the reliability of the measured depth profile data. The ion gun sputter rate was estimated using the standard ISO conform depth profiling of a SiO₂ reference layer of known thickness. Two new procedures are developed to determine the other relevant parameters. Gases that are emitted by the ion sputter gun get implanted into a Si target. An analysis of the implanted gases allows judging on the contamination level of the sputter gun and the purity of the sputter gun gas supply. The vacuum condition of an XPS microprobe at the sample position is monitored by the recontamination of a sputtered Ti surface by adsorbed residual gas particles.