Abstract
A first-principles study of native point defects in monoclinic, cubic, two different tetragonal, and five different orthorhombic phases of hafnia (HfO2) is presented. They include vacancy of tri-coordinated and tetra-coordinated oxygen, metal vacancy, interstitial metal, and interstitial oxygen. Defect formation energy, trap depth, and relaxation energy upon optical excitation of defects are listed. The trap depth of oxygen vacancies shows little variation among different phases compared to other defects. Results of the trap depth are compared against measurements and found to have reasonable agreement.
Highlights
Hafnia (HfO2) is probably the most important high-κ insulator in today’s CMOS industry that has been introduced as a replacement for silicon-dioxide as the gate oxide of MOSFETs
A multitude of prospective applications of hafnia appeared, thanks to its multiple crystallographic phases that can be stabilized by tuning their growth conditions
We present a density functional theory (DFT) study of different possible point defects in nine lowest energy crystallographic phases of HfO2.11 We model Bias Temperature Instability (BTI)-like electrical measurements with COMPHY [from “nonradiative multi-phonon (NMP) theory”]12 to extract parameters defining the shallow defect band in 10 nm polyphase HfO2
Summary
Hafnia (HfO2) is probably the most important high-κ insulator in today’s CMOS industry that has been introduced as a replacement for silicon-dioxide as the gate oxide of MOSFETs. The low temperature phase, i.e., the monoclinic (m) HfO2, has been used in the CMOS gate stack for the last 10 years. A multitude of prospective applications of hafnia appeared, thanks to its multiple crystallographic phases that can be stabilized by tuning their growth conditions.. One of the phases that attracted attention is the metastable orthorhombic one that exhibits ferroelectricity. Its discovery opened the door for the exploration of ferroelectric (FE) capacitor for FE-RAM (analogous to DRAM), FE-FET for non-volatile-memory, etc. The metastable phase is stabilized by the doping of the oxide and/or strain engineering, etc.
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