In this work, we report the improved performance of TiO2 based MOS capacitor by inserting a thin layer of Al2O3 (5 nm) in between TiO2dielectric layer and Si substrate. Al2O3 is a stable dielectric material and act as an efficient barrier to reduce the down diffusion of O2 into Si substrate and possible formation of uncontrolled SiOxlayer. This is useful in two ways, first it will provide a large conduction and valence band offset to Si, and second TiO2 stoichiometry will be maintained. The dielectric constant of such bilayer MOS gate stack was estimated 31 from accumulation capacitance with improved leakage performance. The leakage current density was found 1.69×10-8 A/cm2 at + 1 V. The interface states density were extracted from DLTS method and found 2.9x1011 eV-1cm-2, which is reasonably low for Si/high-k system. In addition to that, various other parameters such as flat band voltage (VFB), change in flat band voltage during bidirectional sweep (∆VFB), oxide trapped charges (Qot), and equivalent oxide thickness (EOT) are found -0.48 V, 50 mV, 2.97x1011/cm2, and 5.66 nm, respectively. In conclusion, bilayer gate stacks based on TiO2 and Al2O3 can be useful in future CMOS technology.
APS March Meeting Abstracts
- Pub Date: