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Characterization of positive bias temperature instability of NMOSFET with high-k/metal gate last process

Shangqing Ren, Bo Tang, Hao Xu, Weichun Luo, Zhaoyun Tang, Yefeng Xu, Jing Xu, Dahai Wang, Junfeng Li, Jiang Yan, Chao Zhao, Dapeng Chen, Tianchun Ye and Wenwu Wang

+ Author Affiliations

 Corresponding author: Shangqing Ren, E-mail: renshangqing@ime.ac.cn; Wenwu Wang, E-mail: wangwenwu@ime.ac.cn

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Abstract: Positive bias temperature instability (PBTI) characteristics and degradation mechanisms of NMOSFET with high-k/metal gate last process have been systematically investigated. The time evolution of threshold voltage shift during PBTI stress still follows a power law. However, the exponent n decreases from 0.26 to 0.16 linearly as the gate stress voltage increases from 0.6 to 1.2 V. There is no interface state generation during stress because of the negligible sub-threshold swing change. Moreover, the activation energy is 0.1 eV, which implies that electrons directly tunnel into high-k bulk and are trapped by pre-existing traps resulting into PBTI degradation. During recovery the threshold voltage shift is linear in lgt, and a mathematical model is proposed to express threshold voltage shift.

Key words: positive bias temperature instability (PBTI)high-kmetal gate



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Fig. 1.  The structure chart of an NMOSFET.

Fig. 2.  (Color online) $I_{\rm d}$-$V_{\rm g}$ curves measured at different sweep ranges of gate voltage successively before stress voltage is applied.

Fig. 3.  Accumulation degradation measured at different voltage sweep ranges and fitted by power law. Two sets of data are shown and overlap well.

Fig. 4.  The time evolution of gate leakage during stress at different stress voltages. The gate leakage decreases gradually.

Fig. 5.  Sub-threshold swing versus time during stressing.

Fig. 6.  Normalized threshold voltage shift of NMOSFET versus time. The power law is fitted, and the power exponent $n$ decreases with increasing stress.

Fig. 7.  Temperature dependence of normalized threshold voltage shift of NMOSFET.

Fig. 8.  The thermal activation energy ($E_{\rm a}$ $=$ 0.10 eV) of threshold voltage shift extracted by an Arrhenius relationship.

Fig. 9.  The remaining threshold voltage shift versus time during recovery phase.

Fig. 10.  Stress dependence of fitting parameters during recovery period. The power law fits well.

Fig. 11.  Temperature dependence of fitting parameters during the recovery period. The exponential law fits well.

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    Received: 05 June 2014 Revised: Online: Published: 01 January 2015

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      Shangqing Ren, Bo Tang, Hao Xu, Weichun Luo, Zhaoyun Tang, Yefeng Xu, Jing Xu, Dahai Wang, Junfeng Li, Jiang Yan, Chao Zhao, Dapeng Chen, Tianchun Ye, Wenwu Wang. Characterization of positive bias temperature instability of NMOSFET with high-k/metal gate last process[J]. Journal of Semiconductors, 2015, 36(1): 014007. doi: 10.1088/1674-4926/36/1/014007 S Q Ren, B Tang, H Xu, W C Luo, Z Y Tang, Y F Xu, J Xu, D H Wang, J F Li, J Yan, C Zhao, D P Chen, T C Ye, W W Wang. Characterization of positive bias temperature instability of NMOSFET with high-k/metal gate last process[J]. J. Semicond., 2015, 36(1): 014007. doi: 10.1088/1674-4926/36/1/014007.Export: BibTex EndNote
      Citation:
      Shangqing Ren, Bo Tang, Hao Xu, Weichun Luo, Zhaoyun Tang, Yefeng Xu, Jing Xu, Dahai Wang, Junfeng Li, Jiang Yan, Chao Zhao, Dapeng Chen, Tianchun Ye, Wenwu Wang. Characterization of positive bias temperature instability of NMOSFET with high-k/metal gate last process[J]. Journal of Semiconductors, 2015, 36(1): 014007. doi: 10.1088/1674-4926/36/1/014007

      S Q Ren, B Tang, H Xu, W C Luo, Z Y Tang, Y F Xu, J Xu, D H Wang, J F Li, J Yan, C Zhao, D P Chen, T C Ye, W W Wang. Characterization of positive bias temperature instability of NMOSFET with high-k/metal gate last process[J]. J. Semicond., 2015, 36(1): 014007. doi: 10.1088/1674-4926/36/1/014007.
      Export: BibTex EndNote

      Characterization of positive bias temperature instability of NMOSFET with high-k/metal gate last process

      doi: 10.1088/1674-4926/36/1/014007
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      Project supported by the Important National Science & Technology Specific Projects (No. 2009ZX02035) and the National Natural Science Foundation of China (Nos. 61176091, 61306129).

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