| AVS 65th International Symposium & Exhibition | |
| Thin Films Division | Wednesday Sessions |
| Session TF+EM+MI-WeM |
| Session: | Thin Film Processes for Electronics and Optics I |
| Presenter: | SungYeon Ryu, Seoul National University of Science and Technology, Republic of Korea |
| Authors: | S.Y. Ryu, Seoul National University of Science and Technology, Republic of Korea Y. Kim, Seoul National University of Science and Technology, Republic of Korea W.Y. Park, SK Hynix Inc., Republic of Korea S.G. Kim, SK Hynix Inc., Republic of Korea B.J. Choi, Seoul National University of Science and Technology, Republic of Korea |
| Correspondent: | Click to Email |
Bipolar type resistive switching random access memories (RRAMs) utilized by TaOx and HfOx as switching materials, have been demonstrated superior to unipolar type RRAMs owing to the low switching current and better reliability. Bias-polarity-dependent valence change mechanism in HfOx is attributed to the repeated generation and rupture of conducting filaments (CF), which could be the clusters of oxygen vacancies (Vo). As the device size scales down to 2x nm, the dimension of CF and the whole device area become comparable, and thus the involvement of oxygen loss or unintended VO incorporation, that is, intrinsic defects may significantly degrade the device reliability. On the other hand, extrinsic defects by doping metallic elements may also change the switching characteristics and device variability depending on the fabrication methods, such as, co-sputtering, implantation, thermal and photo-assisted diffusion, etc.
In this study, influence of both intrinsic and extrinsic defects was investigated systematically. The device having TiN contact-plug with 28 to 2000-nm-diamenter formed in SiO2 inter-layer was fabricated. 1.2-nm-thick HfOx layer was deposited by atomic layer deposition (ALD). At first, for the control of intrinsic defect, the fabricated RRAM devices were post-annealed in both air and vacuum (~10mTorr) at a wafer temperature of 150 to 250 oC for 20 min, respectively. Electrical property is measured by semiconductor parameter analyzer (HP-4155) and function generator (AFG-3102) for DC and AC measurements. More reliable switching and free-from abnormal switching behavior, such as reset-failure, were observed in the vacuum-annealed device.
Secondly, Al- and Ga-doped HfOx films are grown by using thermal ALD to change the structural and chemical properties of HfO2 film via incorporating extrinsic defects. Dopant concentration and location were controlled by the ALD cycle ratio and sequence. Through Al doping, pristine resistance and forming voltage of the device were increased with increasing Al cycle ratio. On the other hand, Ga-doped HfO2 device showed reverse switching polarity. The resistive switching characteristics caused by intrinsic and extrinsic defects in HfOx films will be presented in detail.
Acknowledgment
This paper was result of the research project supported by SK hynix Inc.