Browsing by Author "Tang, DD"

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A novel transient characterization technique to investigate trap properties in HfSiON gate dielectric MOSFETs - From single electron emission to PBTI recovery transient
(2006-05-01)
Wang, TH
;
Chan, CT
;
Tang, CJ
;
Tsai, CW
;
Wang, HCH
A positive bias temperature instability (PBTI) recovery transient technique is presented to investigate trap properties in HfSiON as high-k gate dielectric in nMOSFETs. Both large and small-area nMOSFETs are characterized. In a large-area device, the post-PBTI drain current exhibits a recovery transient and follows logarithmic time dependence. In a small-area device, individual trapped electron emission from HfSiON gate dielectric, which is manifested by a staircase-like drain current evolution with time, is observed during recovery. By measuring the temperature and gate voltage dependence of trapped electron emission times, the physical mechanism for PBTI recovery is developed. An analytical model based on thermally assisted tunneling can successfully reproduce measured transient characteristics. In addition, HfSiON trap properties, such as trap density and activation energy, are characterized by this method.
Positive bias and temperature stress induced two-stage drain current degradation in HfSiON nMOSFET's
(2005)
Chan, CT
;
Tang, CJ
;
Wang, T
;
Wang, HCH
;
Tang, DD
Positive bias and temperature (PBTI) stress induced drain current degradation in HfSiON gate dielectric nMOSFETs is investigated by using a transient measurement technique. The degradation exhibits two stages, featuring different degradation rate and stress temperature dependence. The drain current degradation in the first stage is attributed to the charging of pre-existing high-k dielectric traps while the degradation in the second stage is mainly due to additional high-k trap creation. Process effect on high-k trap growth is evaluated.
Study of annealing and exchange bias effects in PtMn based magnetic tunnel junction system
(2004)
Peng, TY
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Yao, YD
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Chen, SY
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Wang, YH
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Chen, WC
The crystallization structure and thickness of PtMn layer in a magnetic tunnel junction system are important factors to improve its exchange bias effect. This study shows that the PtMn layer could be changed from a FCC (111) structure to a FCT (111) structure after annealing above 270 degreesC. The minimum thickness of PtMn layer is found to be 10 nm for exchange coupling effect to be occurred in our MTJ system. The magnetic exchange effect between PtMn and SAF layers is near 4,300 Oe. Annealing temperatures can be higher than 400 degreesC for samples without patterning; however, temperature at 275 degreesC is too high for samples after patterning. This may be due to the breakdown of edges of the patterned samples as well as the complicated environments around the patterned samples. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
The impact of uniaxial strain engineering on channel backscattering in nanoscale MOSFETs
(2005)
Lin, HN
;
Chen, HW
;
Ko, CH
;
Ge, CH
;
Lin, HC
The influence of uniaxial process-induced strain on carrier channel backscattering in nanoscale MOSFETs is reported for the first time. It is observed that the backscattering ratio can be reduced by uniaxial tensile strain while it is increased by uniaxial compressive strain mainly due to strain-induced modulation in mean-free-path for backscattering and slight decrease in k(B)T layer thickness. Nevertheless, both strain polarities improve source-side injection velocity because of reduced carrier effective mass. Impact to current drive under uniaxial strain is analyzed in terms of mean-free-path, k(B)T layer thickness, ballistic efficiency and injection velocity.