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Self-assembled tungsten nanocrystals in high-k dielectric for nonvolatile memory application

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7 Author(s)
Samanta, S.K. ; Silicon Nano Device Laboratory, Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 ; Tan, Zerlinda Y.L. ; Won Jong Yoo ; Ganesh Samudra
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Discrete midgap tungsten nanocrystals (W-NCs) embedded in atomic layer deposited hafnium aluminate (HfAlO) film were fabricated by a self-assembly method using sputtering followed by rapid thermal annealing and integrated into transistors for nonvolatile memory application. Transmission electron microscopy and single electron diffraction analysis revealed the formation of crystalline W-NCs (∼5 nm) embedded in an amorphous HfAlO matrix. Effects of deposition of thin Al2O3 on the formation of W-NCs were investigated. Al2O3 was found to be effective to retain the amorphous property of the underlying HfAlO, assisting to form uniformly distributed and small W-NCs. Electrical characterization of the Si/HfAlO/W-NCs/HfAlO structure based memory device showed that clear memory effects (1.8 V memory window at operating bias of 7 V) and good retention properties (50 mV/dec threshold voltage decay rate) originate from the charge storage of electrons in W-NDs and deep quantum well of W-NDs embedded in the HfAlO+Al2O3 high-k structure.

Published in:

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures  (Volume:23 ,  Issue: 6 )