Thermal Oxidation of Tungsten Coatings for Detection by Infrared Spectrometry Method

Abstract

Physical vapor deposition (PVD) of metallic thin films is used extensively in the fabrication of semiconductor technology devices - use as of lately for them have grown. Tungsten (W) is a low resistivity, refractory metal, that is often deposited by PVD methods for use as a gate contact to semiconductor devices and due to the low work function and high thermal stability, W can be used for the fabrication of field emitters in microelectronics [1-3]. In order to monitor quality of the synthesized thin films by magnetron sputtering method, it is necessary to develop methodology suitable for the analysis of these thin films. Infrared spectrometry is a sensitive method for the analysis of chemical bonds, but W thin films contain weakly polar and non-polar W-W bonds, that cannot be directly detected by infrared spectrometry, therefore oxidation of W is selected as thermal oxidation method for detecting oxidized products for thin films of thickness 150 nm, for instance, W-O bonds. After oxidation, it was observed, that the oxidation of W thin films takes place already at a 600 °C in the air atmosphere. The Fourier transform infrared spectrometry (FTIR) spectra of modified coatings showed formation of additional new signals in the region of 700-900 cm−1 attributed to W-O, O-W-O, W=O bonds - formation of W-oxygen bonds on Si-SiO2 substrate was achieved. For coating homogeneity and production quality formation, additionally synthesized control samples are recommended for FTIR analysis.