Temperature-Dependent Physical and Memory Characteristics of Atomic-Layer-Deposited RuO x Metal Nanocrystal Capacitors

• Published in: Journal of nanomaterials 2011-12, Vol.2011, p.1-12
• Main Authors: Maikap, S., Banerjee, W., Tien, T. C., Wang, T. Y., Yang, J. R.
• Format: Article
• Language: English
• ISSN: 1687-4110; 1687-4129
• DOI: 10.1155/2011/810879

Physical and memory characteristics of the atomic-layer-deposited RuO x metal nanocrystal capacitors in an n-Si/SiO 2 /HfO 2 / RuO x /Al 2 O 3 /Pt structure with different postdeposition annealing temperatures from 850–1000 ° C have been investigated. The RuO x metal nanocrystals with an average diameter of 7 nm and a highdensity of 0.7 × 10 12 /cm 2 are observed by high-resolution transmission electron microscopy after a postdeposition annealing temperature at 1000 ° C. The density of RuO x nanocrystal is decreased (slightly) by increasing the annealing temperatures, due to agglomeration of multiple nanocrystals. The RuO 3 nanocrystals and Hf-silicate layer at the SiO 2 /HfO 2 interface are confirmed by X-ray photoelectron spectroscopy. For post-deposition annealing temperature of 1000 ° C, the memory capacitors with a small equivalent oxide thickness of ~9 nm possess a large hysteresis memory window of >5 V at a small sweeping gate voltage of ±5 V. A promising memory window under a small sweeping gate voltage of ~3 V is also observed due to charge trapping in the RuO x metal nanocrystals. The program/erase mechanism is modified Fowler-Nordheim (F-N) tunneling of the electrons and holes from Si substrate. The electrons and holes are trapped in the RuO x nanocrystals. Excellent program/erase endurance of 10 6 cycles and a large memory window of 4.3 V with a small charge loss of ~23% at 85 ° C are observed after 10 years of data retention time, due to the deep-level traps in the RuO x nanocrystals. The memory structure is very promising for future nanoscale nonvolatile memory applications.