Monitoring of an interlayer between Si(100) and a TiO2 layer formed during cyclic CVD

The growth of an interlayer between TiO2 and Si(100) during the cyclic CVD of TiO2 is investigated using X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). The interlayer, the thickness of which was estimated to be 21 angstrom at 300 degrees C and 26 angstrom at 400 degrees C, can be divided into two distinct regions, i.e., an SiOx layer, which grows during the initial four deposition cycles, and TiSiOx which grows in the subsequent four and ten deposition cycles. A TiO2 layer then grows during the following deposition cycles (> 10 cycles), but a sharp boundary is observed between TiO2 and the interlayer. Based on the HRTEM images, the two layers are seen to be distinct and not mixed. SiOx, which is formed on Si(100) during the initial four deposition cycles, promotes the decomposition of the Ti precursor, so the Ti concentration in the interlayer that is formed after the initial four cycles increases at a higher rate than that in the layer formed during the initial cycles. In this study, the thickness of the interlayer could be kept to less than 14 angstrom by reducing the amounts of O-2 used in each cycle.