Browsing by Author "Chien, W. C."

Now showing 1 - 7 of 7

Characterization of a nano-oxide layer in a pseudo spin valve by complex magneto-impedance spectroscopy
(2006-10-01)
Chien, W. C.
;
Peng, T. Y.
;
Hsieh, L. C.
;
Lo, C. K.
;
Yao, Y. D.
The ac properties of a pseudo spin valve (PSV) consisting of NOLtop/Co/Cu/Co/Ni80Fe20/NOLbottom with a top and bottom nanooxide layer (NOL) were studied as functions of NOL and thickness, d, by magneto impedance spectroscopy. The NOLs were formed by natural oxidizing the top and bottom ferromagnetic or Ta layers in situ. The increase in the thickness of NOL resulting in the increment of caused the shift of roll-off frequency from low to high. The frequency dependence behavior of this NOLtop/PSV/NOLbottom system can be modeled by equivalent circuit theory. PSV with a different NOL structure can be checked by such a nondestructive analysis method.
Enhancement and inverse behaviors of magnetoimpedance in a magnetotunneling junction by driving frequency
(2006-11-13)
Chien, W. C.
;
Lo, C. K.
;
Hsieh, L. C.
;
Yao, Y. D.
;
Han, X. F.
The magnetoimpedance effect was employed to study magnetotunneling junction (MTJ) with the structure of Ru(5 nm)/Cu(10 nm)/Ru(5 nm)/IrMn(10 nm)/CoFeB(4 nm)/Al(1.2 nm)-oxide/CoFeB(4 nm)/Ru(5 nm). A huge change of more than +/- 17 000% was observed in the imaginary part of the impedance between the magnetically parallel and antiparallel states of the MTJ. The inverse behavior of the magnetoimpedance (MI) loop occurs beyond 21.1 MHz; however, the normal MI at low frequency and the inverse MI at high frequency exhibit the same magnetization reversal as checked by the Kerr effect. The reversal in MI was due to the dominance of magnetocapacitance at high frequency. (c) 2006 American Institute of Physics.
High frequency impedance inverse in MTJ junction
(2007-03-01)
Hsieh, L. C.
;
Huang, Y. W.
;
Han, X. F.
;
Zeng, Z. M.
;
Chien, W. C.
The magnetoimpedance effect of magnetic tunnel junction ( MTJ) was investigated at room temperature in the frequency ranged from 100 Hz to 15 MHz. The MR loop with a ratio of 9.49% at 5MHz switches to - 11.51% at 7 MHz, respectively. This indicates the MR loop reverse shape and sign around 6 MHz. This inverse MR effect is explained by the impedance competition among Resistor- Inductor series circuit and Capacitor part. (c) 2006 Elsevier B. V. All rights reserved.
MULTI-LEVEL OPERATION OF FULLY CMOS COMPATIBLE WOX RESISTIVE RANDOM ACCESS MEMORY (RRAM)
(2009)
Chien, W. C.
;
Chen, Y. C.
;
Chang, K. P.
;
Lai, E. K.
;
Yao, Y. D.
The multi-level operation of WOX based RRAM has been investigated. Improvement of our WOX process has produced an extended linear R-V region for our devices. By adding an electrical forming process and a program-verify algorithm we have demonstrated stable 2-bit/cell operation, with potential for 3-bit/cell. The reliability of the MLC operation has been examined and very stable high temperature retention, robust read disturb immunity and initial cycling endurance of >1,000 times have been demonstrated.
Oscillating voltage dependence of high-frequency impedance in magnetic tunneling junctions
(2007-06-01)
Chien, W. C.
;
Hsieh, L. C.
;
Peng, T. Y.
;
Lo, C. K.
;
Yao, Y. D.
Oscillating voltage (V-Os), which depends on the frequency dependence of the magnetoimpedance (MI) effect, was applied to study a magnetic tunneling junction (MTJ) of Ru(5 mn)/Cu(10 nm)/Ru(5 nm)/IrMn(10 nm)/CoFeB(4 nm)/Al-2 O-3/CoFeB(4 nm)/Ru(5 nm) at frequencies up to 40 MHz. The MI ratio decreased as the V-Os. was increased. The MI ratio turned from positive to negative at a certain frequency. An equivalent circuit model was employed to analyze the results. The fact that MTJ can be regarded as the composition of a resistance component and two sets of parallel resistance (R) and capacitance (C) components in series has been utilized to describe the individual impedance contribution from the lead of cross pattern, barrier, and interface. The resistance (R-barrier) and capacitance (C-barrier) of the barrier effect are functions of V-Os. The R-barrier decreases as the V-Os increases, However, Cbarrier behaves the opposite way. The tendency is for interfacial resistance R-interface and interfacial capacitance C-interface to have opposite results with increasing V-Os. This work provides a detailed investigation of high-frequency transport behavior subjected to V-Os, especially useful for MTJ characterization.
Unipolar Switching Behaviors of RTO WO(X) RRAM
(2010-02-01)
Chien, W. C.
;
Chen, Y. C.
;
Lai, E. K.
;
Yao, Y. D.
;
Lin, P.
The microstructure and electrical properties of the WO(X)-based resistive random access memory are investigated in this letter. The WO(X) layer is formed by converting the surface of the W plug with a CMOS-compatible rapid thermal oxidation process. The conductive-atomic-force-microscopy result indicates that nanoscale conducting channels exist in the WO(X) layer and result in a low initial resistance. This letter studies the unipolar operation-the programming, reading, and reliability behaviors of the device are characterized systematically. The low programming voltages for RESET (3.3 V/50 ns) and fast SET speed (3 V/300 ns) are achieved along with cycling endurance greater than 10(7) times. In addition, the device is immune to read disturb. A 2-bit/cell operation is also demonstrated for high-density applications.
Unipolar Switching Behaviors of RTO WOX RRAM
(2010-02-01)
Chien, W. C.
;
Chen, Y. C.
;
Lai, E. K.
;
Yao, Y. D.
;
Lin, P.
The microstructure and electrical properties of the WOX-based resistive random access memory are investigated in this letter. The WOX layer is formed by converting the surface of the W plug with a CMOS-compatible rapid thermal oxidation process. The conductive-atomic-force-microscopy result indicates that nanoscale conducting channels exist in the WOX layer and result in a low initial resistance. This letter studies the unipolar operation-the programming, reading, and reliability behaviors of the device are characterized systematically. The low programming voltages for RESET (3.3 V/50 ns) and fast SET speed (3 V/300 ns) are achieved along with cycling endurance greater than 10(7) times. In addition, the device is immune to read disturb. A 2-bit/cell operation is also demonstrated for high-density applications.