| AVS 61st International Symposium & Exhibition | |
| Electronic Materials and Processing | Thursday Sessions |
| Session EM1-ThA |
| Session: | Materials for Quantum Computation |
| Presenter: | Pini Shekhter, Technion Israel Institute of Technology, Israel |
| Authors: | P. Shekhter, Technion Israel Institute of Technology, Israel A.R. Chaudhuri, Leibniz University, Germany A. Laha, Indian Institute of Technology Bombay, India H.J. Osten, Leibniz University, Germany M. Eizenberg, Technion Israel Institute of Technology, Israel |
| Correspondent: | Click to Email |
High k dielectric materials receive great attention in recent years due to the downscaling of metal-oxide-semiconductor (MOS) devices leading to the need in replacing the traditionally used SiO2 gate oxide. Rare earth oxides are leading candidates as high-k dielectrics. Introduction of different elements into the bulk of such oxides can drastically alter the behavior of the MOS stack.
Here we present the results of incorporation of carbon into the bulk of Gd2O3 on the electrical properties of the Pt/Gd2O3:C/Si stack. Crystalline layers of stoichiometric Gd2O3 were MBE deposited together with elemental C on Si (100) substrates. Four samples with different concentration of elemental C were prepared: 0%, 0.10%, 0.67%C and 1.89%. MOS capacitors were prepared by in-vacuo (in the MBE tool) evaporating Pt through a shadow mask.
Capacitance voltage (C-V) measurements revealed an increase in the flatband voltage (Vfb) for the carbon rich sample. While the three samples with the lower carbon content all showed Vfb voltages of -0.1 ÷ +0.2 V, the sample with 1.89% carbon presented a significant increase to 2.25 V.
X ray diffraction (XRD) revealed that all the layers hold the same structure and that no orientation differences are present in the layers, ruling out the option of structural differences leading to such a change in Vfb. Time of flight secondary ion mass spectroscopy (ToF-SIMS) depth profiles revealed an uneven concentration profile for the carbon in the 0.67% and 1.89% samples. For both samples, the same concentration was found in the bulk of the layer, indicating the existence of a certain solubility limit that had been exceeded. This led to some segregation for the 0.67% sample to the inner interface while substantial segregation was observed in the 1.89% sample to the inner interface and some to the outer surface. Transmission electron microscope (TEM) micrographs show a thin amorphous interface layer that is formed between the Gd2O3 and Si that most likely plays a role in the capturing of the segregating carbon atoms.
We propose that the carbon segregation causes a modification of Vfb which is an important property of the MOS stack. By using carbon incorporation it might be possible to develop an effective method for controlling Vfb without changing the process or materials for any of the MOS gate components.