The interfacial states of the HfO 2 thin film grown on the Si100 substrate by the pulsed laser deposition method is investigated in situ using x-ray photoelectron spectroscopy. They are found to depend on the HfO 2 film thickness, oxygen pressure during the pulsed laser deposition growth, and the deposition process. The hafnium silicide is formed in an oxygen-deficient condition, and it can be most effectively controlled by the ambient oxygen pressure during film growth. The close relation between the silicide formation and abundance of the silicon suboxides at the interface is presented. © 2005 American Institute of Physics. Recently high-k materials have been extensively studied as an alternative gate dielectric in the complementary metal– oxide–semiconductor devices. Among those materials, HfO 2 is considered to be a good candidate since it has a relatively large dielectric constant about 25—Ref. 1, and the heat of formation −271 kcal/ mol 2 is higher than that of SiO 2 −217.7 kcal/ mol. 3 It is also known to be thermodynami-cally stable in contact with Si, 4,5 and its band gap is rela-tively large. 2 But the actual performance as a device will depend critically on how the interfacial state is formed be-tween the HfO 2 layer and Si. When HfO 2 is stacked on Si or SiO 2 / Si with various growth techniques, it has been found that there exist "by-products" such as silicateHf x Si y O 4 or silicide Hf x Si y or compounds containing other elements like nitrogen. 6,7 Among these, Hf-silicide is probably most detrimental since it is metallic and degrades the capacitor performance. Metal-lic Hf-silicide formation has been reported in the interface region of HfO 2 / Si structures prepared by the pulsed laser deposition PLD method 8 and by remote plasma oxidation of Hf metal. 7 In this letter, we focus on identifying major parameters which control hafnium silicide formation in the HfO 2 /Si100 stack grown by the PLD method. We per-formed an x-ray photoelectron spectroscopy study on HfO 2 / SiO 2 /Si100 grown in situ by PLD, while varying the deposition thickness, oxygen pressure, and deposition method. We found that among them the ambient oxygen pressure during PLD is the most important factor controlling the silicide formation. Another important parameter that could control the interfacial states is the substrate tempera-ture during PLD. 9,10 But Ikeda et al. found that the interlayer formation depends more strongly on the oxygen pressure than on the deposition temperature, 2 so we fixed the substrate temperature during PLD growth in this investigation. The interface states of HfO 2 thin films on Si substrate with its native oxide layers have been investigated before by Wang et al.. 8 They reported that the oxygen-deficient HfO x2 layer absorbs the oxygen from the native SiO 2 layer to form fully oxidized metal oxide film and the silicate layer is de-composed with the progress of HfO x2 deposition. They also verified by a sputter-depth profile study that a thin Hf-silicide layer is formed at the interface of the 8.75-nm-thick HfO 2 film. They, however, did not investigate in detail how this Hf-silicide formation is affected by various deposition con-ditions, and whether this silicide layer can be removed by a suitable deposition condition. We will report the results of our investigation on this important topic. HfO 2 films were deposited on p-Si100 at the substrate temperature 700 ° C by the PLD method using 3 Hz pulses of an Eximer laser = 248 nm of intensity 0.75 J / cm 2 , with a base pressure of 2 10 −8 mbar. The sample was then moved into the analysis chamber without breaking the vacuum. The XPS measurement was performed using a Mg K 1253.6 eV source and a hemispherical electron energy analyzer. The overall energy resolution was better than 1 eV, and the pressure was kept below 2 10 −9 mbar throughout the measurements. To find out the essential parameter which controls the silicide formation, we performed several series of experi-ments. First we investigated the film thickness dependence. Figure 1 shows a Si 2p, b O 1s, c Hf 4f spectra with various HfO 2 deposition times. To prevent oxygen defi-ciency, we introduced oxygen to maintain a partial pressure p O =2 10 −6 mbar during growth. For each set of measure-ments, we used a different Si substrate but identically pre-pared to grow a HfO 2 thin film for a given period of time 1, 2, 5, or 10 min rather than perform the deposition-measurement-deposition-measurement sequence on the same substrate. This was to prevent possible side-effects such as the adhesion of other molecules between subsequent deposi-tion processes.