The oxygen for interface W oxidation should come from the La2O3 film. It was proposed that the oxygen in W may diffuse into the La2O3 film to fill up the oxygen vacancies there . Oxygen vacancies are the major defect centers in La2O3 which result in several instability issues and enhance the gate leakage current [15–17]. The present result indicates that a reverse process may have been Selleck 3-deazaneplanocin A taken place in the present samples. That means a high-temperature process may
lead to the out-diffusion of oxygen to the W/La2O3 interface, and that increases oxygen vacancies in the La2O3 film. In addition, La-O-W bonding with a peak energy of 532.2 eV was found. For the case of WO x phase enhancement, it should not affect the EOT as it can be considered as part of the metal electrode; on the other hand, the effects of La-O-W bonding have never been explored, and it should have some impact in making the effective EOT thicker. Figure 1 W 4f XPS spectra with Gaussian
decomposition. This figure shows various oxidized states of tungsten near the W/La2O3 interface. (a) As-deposited film. (b) Sample with thermal annealing at 600°C for 30 min. check details A stronger WO x peak was observed. Figure 2 O 1s spectra taken near the W/La 2 O 3 interface. (a) Three oxidation states, corresponding to WO3, WO x , and La-O, were found for the as-deposited film. (b) After thermal annealing, an additional peak, attributing to La-O-W bonding, was found at an energy of 532.2 eV. Silicon/high-kinterface High-k can react, especially in the presence of a silicon oxide layer, with the silicon substrate, Phosphoprotein phosphatase and the electronic bonding structure at the La2O3/Si interface should be much more complicated than the SiO2/Si case. It was known that the interface bonding may lead to either an insulating layer (silicate bonding) or JNJ-26481585 conductive layer (silicide bonding) [1, 2]. Most of the high-k
silicides are conductive. The interfacial silicide layer will not affect the EOT but the interface metal-Si bonding in the interface trap precursors and results in the channel mobility degradation and other instabilities [1, 15, 16]. Most of the high-k materials including hafnium oxide and lanthanum oxide are only marginally stable against the formation of silicates. The device properties can be improved with the interfacial silicate layer . However, this layer has much smaller k values and becomes the lower bound of the thinnest EOT, and needs to be minimized for the subnanometer EOT dielectric. Figure 3 shows the La 3d XPS spectra at different depths. The different depths were obtained by argon sputtering for 2.5 to 8 min, and all the XPS analyses were made at a take-off angle of 45°. This treatment should be able to minimize the artifacts due to ion knock-on effects. The bulk La 3d3/2 XPS spectra shows a main peak energy of 851.9 eV and a satellite peak energy of 855.6 eV . As sputtered closer to the substrate, the main peak of La 3d3/2 shifts to an even higher energy side of 852.