Browsing by Author "Lai, Chao Sung"

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Current transport mechanism for HfO2 gate dielectrics with fluorine incorporation
(2008)
Wu, Woei Cherng
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Lai, Chao Sung
;
Wang, Tzu Ming
;
Wang, Jer Chyi
;
Hsu, Chih Wei
In this article, the current transport mechanism of fluorinated HfO2 gate dielectrics is investigated. Based on the experimental results of the temperature dependence of gate leakage current and Fowler-Nordheim tunneling characteristics at 77 K, we have extracted the energy band diagrams and current transport mechanisms for TaN/HfOF/fluorinated-interfacial layer (IL)/Si structures. In particular, we have obtained the following quantities that will be useful for modeling and simulation: (i) fluorinated IL/Si barrier height (or conduction band offset): 3.2 eV; (ii) TaN/HfOF barrier height: 2.6 eV; and (iii) trap levels at 1.3 eV (under both gate and substrate injections) below the HfOF conduction band which contributes to Frenkel-Poole conduction. (C) 2007 The Electrochemical Society.
Dimensional Dependences of the Dynamic-NBTI with 1.2 nm N20-ISSG oxynitrides
(2007)
Lai, Chao Sung
;
Huang, D. C.
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Chung, S. S.
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電機學院
;
College of Electrical and Computer Engineering
Electrical and reliability improvement in polyoxide by fluorine implantation
(2007)
Kao, Chyuan Haur
;
Lai, Chao Sung
;
Lee, Chung Len
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We show that the incorporation of fluorine into the oxide grown on polysilicon (polyoxide) not only improves the electrical characteristics (i.e., lower leakage current, higher electrical breakdown field), but also improves the reliability (lower electron trapping rate, larger Q(bd)). This improvement is believed to be due to the stress relaxation of the polyoxide and smoother polysilicon/polyoxide interface by the fluorine incorporation. The optimum fluorine dose (2x10(14)) shows the best characteristics such as E-bd over 12 MV/cm and Q(bd)similar to 2 C/cm(2). However, excessive fluorination (1x10(15)) seems to result in performance degradation due to the generation of nonbridging oxygen centers. (c) 2007 The Electrochemical Society.
High-performance HfO2 gate dielectrics fluorinated by postdeposition CF4 plasma treatment
(2007)
Wu, Woei Cherng
;
Lai, Chao Sung
;
Wang, Jer Chyi
;
Chen, Jian Hao
;
Ma, Ming Wen
The superior characteristics of fluorinated HfO2 gate dielectrics were investigated. Fluorine was incorporated into HfO2 thin film by postdeposition CF4 plasma treatment to form fluorinated HfO2 gate dielectrics. Secondary-ion mass spectroscopy results showed that there was a significant incorporation of fluorine atoms at the TaN/HfO2 and HfO2/Si interface. Improvement of the gate leakage current, breakdown voltage, capacitance-voltage hysteresis, and charge trapping characteristics was observed in the fluorinated HfO2 gate dielectrics, with no increase of interfacial layer thickness. A physical model is presented to explain the improvement of hysteresis and the elimination of charge trapping. These results indicate that the fluorinated HfO2 gate dielectrics appear to be useful technology for future ultrathin gate dielectrics. (C) 2007 The Electrochemical Society.
Nitrogen effects on the integrity of silicon dioxide grown on polycrystalline silicon
(2007)
Lai, Chao Sung
;
Kao, Chyuan Haur
;
Lee, Chung Len
;
Lei, Tan Fu
;
電子工程學系及電子研究所
In this paper, we describe a simple technique to achieve a thin nitrided polyoxide film, only requiring an extra nitrogen implantation to be compatible with the floating gate nonvolatile memory process. The integrity of polyoxides is improved by using the through-silicon-gate nitrogen implantation. Nitridation can be achieved by implanting nitrogen into polysilicon gate followed by a high temperature annealing to drive the nitrogen atoms across the polysilicon, through the polyoxide, and to incorporate nitrogen at the polyoxide/polysilicon interface. The nitrogen-rich layer formed during the driven-in process not only strengthens the polyoxide structure but also improves the polyoxide quality. Improvements of electrical characteristics such as a low leakage current, a low electron trapping, and a high breakdown field for both positive and negative biases have been observed. (c) 2007 The Electrochemical Society.
Polarity asymmetry of polyoxide grown on phosphorus in situ doped polysilicon
(2006)
Kao, Chyuan Haur
;
Lai, Chao Sung
;
Lee, Chung Len
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We show that polyoxides grown on phosphorus in situ doped polysilicon have larger polarity asymmetry than that on the POCl3-doped polysilicon. It may be not only the surface roughness between the polysilicon/polyoxide interfaces, but also the phosphorus distribution in the interfaces. For the phosphorus in situ doped poly film, the phosphorus piled up at the poly-1/polyoxide interface should result from the out-diffusion of the poly-1 doping during the tetraethyl orthosilicate oxide deposition process. However, the phosphorus concentration near the polyoxide/top poly-2 interface was lower than the bulk concentration of the polysilicon film, which may result from insufficient phosphorus concentration near the polyoxide/top poly-2 interface without subsequent annealing and dopant activation. Therefore, this may affect the polarity asymmetry of the electrical characteristics for the phosphorus in situ doped samples. Especially, the thermal polyoxide had the largest polarity asymmetry due to very high phosphorus concentration piled up in the bottom poly-1/polyoxide interface. We also show that the top poly-2 doping process affects the phosphorus distribution in the polysilicon/polyoxide interfaces, and further, affects the polyoxide performance.
Suppression of interfacial reaction for HfO2 on silicon by pre-CF4 plasma treatment
(2006-08-14)
Lai, Chao Sung
;
Wu, Woei Cherng
;
Chao, Tien Sheng
;
Chen, Jian Hao
;
Wang, Jer Chyi
In this letter, the effects of pre-CF4 plasma treatment on Si for sputtered HfO2 gate dielectrics are investigated. The significant fluorine was incorporated at the HfO2/Si substrate interface for a sample with the CF4 plasma pretreatment. The Hf silicide was suppressed and Hf-F bonding was observed for the CF4 plasma pretreated sample. Compared with the as-deposited sample, the effective oxide thickness was much reduced for the pre-CF4 plasma treated sample due to the elimination of the interfacial layer between HfO2 and Si substrate. These improved characteristics of the HfO2 gate dielectrics can be explained in terms of the fluorine atoms blocking oxygen diffusion through the HfO2 film into the Si substrate. (c) 2006 American Institute of Physics.