Browsing by Author "Wang, Pai-Syuan"

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Formation and composition of titanium oxinitride nanocrystals synthesized via nitridizing titanium oxide for nonvolatile memory applications
(2011-09-01)
Feng, Li-Wei
;
Chang, Chun-Yen
;
Chang, Ting-Chang
;
Tu, Chun-Hao
;
Wang, Pai-Syuan
Formation and composition analyses of titanium oxinitride nanocrystals (NCs) fabricated via treating a magnetron co-sputtered thin film of titanium and silicon dioxide with a rapid thermal annealing in nitrogen ambient were demonstrated for nonvolatile memory applications. Phase separation characteristics with different annealing conditions were examined by transmission electron microscopy and chemical bonding characteristics were confirmed by X-ray photon emission spectra. It was observed that a blanket layer composed mainly of titanium oxide was still present as annealing temperature was increased to 700 degrees C, associated with the thermodynamically stable phase of titanium oxide. Furthermore, a higher thermal treatment of 900 degrees C induced formation of a well-separated NC structure and caused simultaneously partial nitridation of the titanium oxide, thereby forming titanium oxinitride NCs. A significant capacitance-voltage hysteresis in threshold voltage shift at 1 V was easily achieved under a small sweeping voltage range of + 2 V/-2 V, and a memory window retention of 2.2 V was obtained after 10(7) s by extrapolation under a 1 s initial-program/erase condition of +5 V/-5 V, respectively. (C) 2011 Elsevier B.V. All rights reserved.
Low temperature synthesis and electrical characterization of germanium doped Ti-based nanocrystals for nonvolatile memory
(2011-11-30)
Feng, Li-Wei
;
Chang, Chun-Yen
;
Chang, Ting-Chang
;
Tu, Chun-Hao
;
Wang, Pai-Syuan
Chemical and electrical characteristics of Ti-based nanocrystals containing germanium, fabricated by annealing the co-sputtered thin film with titanium silicide and germanium targets, were demonstrated for low temperature applications of nonvolatile memory. Formation and composition characteristics of nanocrystals (NCs) at various annealing temperatures were examined by transmission electron microscopy and X-ray photon-emission spectroscopy, respectively. It was observed that the addition of germanium (Ge) significantly reduces the proposed thermal budget necessary for Ti-based NC formation due to the rise of morphological instability and agglomeration properties during annealing. NC structures formed after annealing at 500 degrees C, and separated well at 600 degrees C annealing. However, it was also observed that significant thermal desorption of Ge atoms occurs at 600 degrees C due to the sublimation of formatted GeO phase and results in a serious decrease of memory window. Therefore, an approach to effectively restrain Ge thermal desorption is proposed by encapsulating the Ti-based trapping layer with a thick silicon oxide layer before 600 degrees C annealing. The electrical characteristics of data retention in the sample with the 600 degrees C annealing exhibited better performance than the 500 C-annealed sample, a result associated with the better separation and better crystallization of the NC structures. (C) 2011 Elsevier B.V. All rights reserved.
Role of germanium in the reduced temperature dependence of Ti-based nanocrystals formation for nonvolatile memory applications
(2009-12-28)
Feng, Li-Wei
;
Chang, Chun-Yen
;
Chang, Ting-Chang
;
Tu, Chun-Hao
;
Wang, Pai-Syuan
We investigated the physical and electrical characteristics of Ti-based nanocrystals (NCs) with composition of germanium fabricated by cosputtering titanium silicide and germanium targets for low temperature applications of nonvolatile memory. The addition of Ge significantly reduces the thermal budget necessary for Ti-based NCs formation to 500 degrees C in 2 min due to the rise of its morphological instability and agglomeration properties. Compositions characteristics were analyzed by x-ray photon-emission spectroscopy and formations of NCs were observed by transmission electron microscopy. Additionally, capacitance-voltage characteristics, data retention, and endurance properties are characterized to demonstrate its advantages for nonvolatile memory device applications.