Defect generation and activation processes in HfO2 thin films: Contributions to stress-induced leakage currents
Research output: Contribution to journal › Research article › Contributed › peer-review
Contributors
Abstract
An important source of degradation in thin dielectric material layers is the generation and migration of oxygen vacancies. We investigated the formation of Frenkel pairs (FPs) in HfO2 as the first structural step for the creation of new defects as well as the migration of preexisting and newly built oxygen vacancies by nudged elastic band (NEB) calculations and stress induced leakage current (SILC) experiments. The analysis indicates, that for neutral systems no stable intimate FPs are built, whereas for the charge states q = ± 2 FPs are formed at threefold and at fourfold coordinated oxygen lattice sites. Their generation and annihilation rate are in equilibrium according to the Boltzmann statistics. Distant FPs (stable defects) are unlikely to build due to high formation energies and therefore cannot be accounted for the measured gate leakage current increase of nMOSFETs under constant voltage stress. The negatively charged oxygen vacancies were found to be very immobile in contrast to positively charged V0's with a low migration barrier that coincides well with the experimentally obtained activation energy. We show that rather the activation of preexisting defects and migration towards the interface than the defect generation are the cause for the gate oxide degradation.
Details
Original language | English |
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Pages (from-to) | 547-553 |
Number of pages | 7 |
Journal | Physica Status Solidi (A) Applications and Materials Science |
Volume | 212 |
Issue number | 3 |
Publication status | Published - Mar 2015 |
Peer-reviewed | Yes |
External IDs
ORCID | /0000-0003-3814-0378/work/142256276 |
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Keywords
ASJC Scopus subject areas
Keywords
- density functional theory, HfO, high-κ materials, MOSFETs, stress induced leakage currents, vacancies