Dynamic reliability characteristics of ultra-thin HfO/sub 2/

In this work, we present time-to-breakdown characteristics of HfO/sub 2/ under unipolar AC voltage stress on MOS capacitors. It is shown that HfO/sub 2/ displays a longer lifetime under AC stress than constant voltage stress. Higher frequency and lower duty cycle in the AC stress resulted in a longer lifetime enhancement. As the thickness decreases, the amount of lifetime enhancement decreases. The enhancement of unipolar t/sub BD/ is attributed to less charge trapping during the "on time", t/sub on/ and charge detrapping during the off time, t/sub off/. It is proposed that the characteristic time (/spl tau//sub in/) for charge to be trapped in HfO/sub 2/ is longer than t/sub on/ of unipolar stress. Also, we found a strong correlation between t/sub on/ and t/sub off/ with regard to how it leads to lifetime enhancement.

[1]  Gabriella Ghidini,et al.  Charge trapping mechanism under dynamic stress and its effect on failure time [gate oxides] , 1999, 1999 IEEE International Reliability Physics Symposium Proceedings. 37th Annual (Cat. No.99CH36296).

[2]  Jack C. Lee,et al.  MOSFET devices with polysilicon on single-layer HfO/sub 2/ high-K dielectrics , 2000, International Electron Devices Meeting 2000. Technical Digest. IEDM (Cat. No.00CH37138).

[3]  J.C. Lee,et al.  Area dependence of TDDB characteristics for HfO2 gate dielectrics , 2002, IEEE Electron Device Letters.

[4]  C. Hu,et al.  Dynamic stressing of thin oxides , 1986, 1986 International Electron Devices Meeting.

[5]  Wen-Jie Qi,et al.  Characteristics of TaN gate MOSFET with ultrathin hafnium oxide (8 /spl Aring/-12 /spl Aring/) , 2000, International Electron Devices Meeting 2000. Technical Digest. IEDM (Cat. No.00CH37138).

[6]  Guido Groeseneken,et al.  A consistent model for the thickness dependence of intrinsic breakdown in ultra-thin oxides , 1995, Proceedings of International Electron Devices Meeting.

[7]  K. Onishi,et al.  Hard and soft-breakdown characteristics of ultra-thin HfO/sub 2/ under dynamic and constant voltage stress , 2002, Digest. International Electron Devices Meeting,.

[8]  J. Stathis.  Percolation models for gate oxide breakdown , 1999 .

[9]  K. Onishi,et al.  Reliability characteristics, including NBTI, of polysilicon gate HfO/sub 2/ MOSFET's , 2001, International Electron Devices Meeting. Technical Digest (Cat. No.01CH37224).

[10]  R. Degraeve,et al.  Constant current charge-to-breakdown: Still a valid tool to study the reliability of MOS structures? , 1998, 1998 IEEE International Reliability Physics Symposium Proceedings. 36th Annual (Cat. No.98CH36173).

[11]  R. Degraeve,et al.  Low Weibull slope of breakdown distributions in high-k layers , 2002, IEEE Electron Device Letters.

[12]  Elyse Rosenbaum,et al.  Silicon dioxide breakdown lifetime enhancement under bipolar bias conditions , 1993 .