Sr/Si Template Formation for the Epitaxial Growth of SrTiO 3 on Silicon
- PDF / 195,477 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 80 Downloads / 159 Views
Sr/Si template formation for the epitaxial growth of SrTiO3 on silicon Xiaoming Hu*, Y. Liang, Yi Wei, J.L. Edwards Jr., R. Droopad, K. Moore, and W.J. Ooms Physical Science Research Laboratories – Motorola Labs, 7700 S. River Parkway, Tempe, Arizona 85284 ABSTRACT A novel silicon cleaning process using strontium metal thin films has been described. The silicon dioxide de-oxidation process using strontium as catalysts has been studied by X-ray Photoelectron Spectroscopy (XPS) and other in-situ techniques. A Sr/Si template for the epitaxial growth of SrTiO3 single crystals on silicon can be directly formed as a result of the above Sr-de-oxidation process. The de-oxidation mechanism can be explained after solving the interfacial structures of the Sr/SiO2/Si system with in-situ XPS. INTRODUCTION In the past few years, a lot of efforts have been spent on the searching for a replacement of the SiO2 as gate oxide [1]. One of the requirements for an alternative gate oxide is that the material should have a large band gap and a high dielectric constant (high-k). Figure 1 plots a selection of candidate materials by their energy band gap and kvalues.
… STO (200)
Figure 1. Plots of dielectric constant vs. energy band gap for some selected materials.
*
Email: [email protected]
B6.2.1 Downloaded from https://www.cambridge.org/core. Squire Law Library, on 03 Feb 2020 at 03:52:15, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/PROC-716-B6.2
Intensity (a.u)
Si (002)
STO (002)
Si (004) STO (001)
20
30
40 50 2*Theta (°)
60
70
Figure 2. XRD showing crystalline SrTiO3 film grown on Si(100). While SiO2 has a large band gap (about 9 eV), its dielectric constant value is relatively small (about 3.9). An intermediate solution for the replacement of SiO2 is to use medium-k materials such as ZrO2 or HfO2 which satisfy both large energy band gap and relatively large-k value requirements [2]. Strontium titanate (SrTiO3 or STO for short, dielectric constant about 200, band gap 3.3 eV) has been found to be able to grow expitaxially on silicon (100) surface [3] using MBE (Figures 2). The crystallographic relations between the SrTiO3 film and Si(100) are: STO(100) // Si(100) and STO // Si, i.e. STO has been rotated by 45° with respect to silicon. The first step towards STO epitaxial growth on silicon is the removal of SiO2 on silicon and the formation of a Sr/Si-2x1 template. EXPERIMENTAL DETAILS Experiments have been performed on a 3-inch DCA cluster tool consisting of MBE deposition chambers and in-situ analytical tools such as XPS, LEED (Low Energy Electron Diffraction), and UHV-STM (scanning tunneling microscope). The base vacuum is generally in the low 10-10 torr range and in some cases mid 10-11 torr can also be achieved. Silicon wafers of known orientation and off-cut angles were firstly UVO3 (ultra-violet ozone) cleaned to remove surface contaminations such as carbon and as a result some additional SiO2 has been re-grown on silicon. The cleanness of
Data Loading...
