Investigation on the work function of tungsten and thermal stability of W/SiO2/Si, W/SiON/Si and W/HfO2/Si gate stacks

Pei Chuen Jiang, Jen Sue Chen, K. H. Cheng, T. J. Hu, K. B. Huang, F. S. Lee

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Replacement of poly-Si and SiO2 with new gate electrode and high k gate oxide is an inevitable trend for next-generation CMOS integrated circuits. Therefore, work function (Φm) of gate electrodes as well as the thermal stability and electrical behaviors of MOS capacitors should be understood. In this study, tungsten (W) is applied as the gate electrode and the gate dielectric materials are SiO2, SiON and HfO2. Φ of W and electrical properties of the MOS structures are investigated. Φm,measured of W is calculated from the flat-band voltage (V m,measured) of MOS capacitors with dielectrics of various thicknesse. For W/SiO2/Si structure, the Φm,measured of W is 4.67 V; however, the Φm,measured of W in W/SiON/Si and W/HfO 2/Si structures is 4.60 V and 4.84 V, respectively. The result means that the Φm,measured of W in W/HfO2/Si structures has extrinsic contributions to Fermi level pinning. The phase of as-deposited W is β-W (or β-W+α-W) phase and transfers to α-W+WO3 mix phase after annealing at 500°C in N2+H2 ambient for 30 min. The trapped charges and oxide charges of dielectric are reduced after annealing. However, the EOT of W/SiO2/Si increases significantly after annealing, indicating the thermal stability of this capacitor is poor.

Original languageEnglish
Title of host publicationGate Stack Scaling
Subtitle of host publicationMaterials Selection, Role of Interfaces, and Reliability Implications
PublisherMaterials Research Society
Number of pages7
ISBN (Print)1558998748, 9781558998742
Publication statusPublished - 2006
Event2006 MRS Spring Meeting - San Francisco, CA, United States
Duration: 2006 Apr 172006 Apr 21

Publication series

NameMaterials Research Society Symposium Proceedings
ISSN (Print)0272-9172


Other2006 MRS Spring Meeting
CountryUnited States
CitySan Francisco, CA

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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