| AVS 64th International Symposium & Exhibition | |
| Electronic Materials and Photonics Division | Thursday Sessions |
| Session EM-ThP |
| Session: | Electronic Materials and Photonics Poster Session |
| Presenter: | Duane McCrory, Penn State University |
| Authors: | D.J. McCrory, Penn State University P.M. Lenahan, Penn State University D. Nminibapiel, National Institute of Standards and Technology D. Veksler, National Institute of Standards and Technology J.T. Ryan, National Institute of Standards and Technology J.P. Campbell, National Institute of Standards and Technology |
| Correspondent: | Click to Email |
Resistive Random Access Memory (RRAM) is a leading candidate for future non-volatile memory applications. These devices may be extremely useful for space applications. However, at the present time there is virtually no direct experimental evidence identifying the atomic scale defects involved in RRAM radiation damage or the underlying atomic scale conduction mechanisms. One of the most promising systems for RRAM is HfO2 metal-insulator-metal based devices. In these devices, it is believed that the switching mechanism is derived from filamentary conduction paths within the oxide. One widely accepted mechanism involves the migration of oxygen vacancies within the transition-metal-oxide insulator, forming the conducting filament [1]. However, to the best of our knowledge, no direct experimental evidence establishes this transport mechanism.
By far the most powerful analytical tool available for identifying atomic scale defects is electron paramagnetic resonance (EPR). Using conventional EPR, Ryan et. al. have identified two atomic scale defects directly involved in gamma-irradiation damage; an O2- coupled to a hafnium ion, and an oxygen vacancy center [2]. However, conventional EPR is not sensitive enough to observe defects within the RRAM. We must look elsewhere to identify the defects and transport mechanisms. The most sensitive technique for identifying these defects is electrically detected magnetic resonance (EDMR) [3].
In this study we have subjected the TiN/Ti/HfO2/TiN RRAM devices to 1 MRAD of 60Co gamma irradiation. These 100x100 nm devices are cross-point type RRAM with 5nm thick HfO2. We have made EDMR measurements before and after gamma irradiation. We observe the radiation induced generation of two strong spectra that appear in both the in-phase and quadrature. We believe that this response is due to two different trap assisted tunneling mechanisms within the oxide. Both spectra appear to be reasonably consistent with the earlier observations of Ryan et. al [2]. A DFT study by Muñez et. al. linked this defect earlier observed for the Ryan et. al. as an oxygen vacancy [4]. DFT calculations by Bradley et. al. have linked two di-vacancy sites near the middle of the HfO2 bandgap that may contribute to transport in HfO2 [5]. Our results provide strong evidence linking electronic transport and radiation damage mechanisms to transport through oxygen vacancy related centers.
[1] R. Waser, Nat. Mater., vol. 6, 2007.
[2] J. T. Ryan, IEEE Trans. Nucl. Sci., vol. 52, 2005.
[3] D. J. Lepine, Phys. Rev. B, vol. 6, 1972.
[4] D. Muñoz Ramo, Phys. Rev. B - Condens. Matter Mater. Phys., vol. 75, 2007.
[5] S. R. Bradley, J. Phys. Condens. Matter, vol. 27, 2015.