Edge direct tunneling current in nano‐scale MOSFET with high‐K dielectrics

Abstract

Purpose

Choosing suitable high‐K gate dielectrics to reduce the off‐state leakage (I_off) by edge direct tunneling mechanism, demonstrating that the decreased I_off increase significantly when the gate dielectrics permittivity are above 25. The purpose of this paper is to report that HfSiON and HfLaO are promising gate dielectrics.

Design/methodology/approach

The off‐state gate current, drain current, and substrate current are investigated. The I_d‐V_gs characteristics for the 50 and 90 nm NMOSFET with various gate dielectrics are studied. Edge direct tunneling current (I_EDT) with various gate dielectrics including SiO₂, Si₃N₄ and HfO₂ are compared and this paper also examines the I_EDT with HfSiON and HfLaO gate dielectrics.

Findings

I_EDT prevails over conventional gate‐induced drain‐leakage current (I_GIDL), subthreshold leakage current (I_SUB), band‐to‐band tunneling current (I_BTBT) and it dominates off‐state leakage current. A large increase in off‐state leakage current occurs for smaller devices due to increase in I_EDT at high V_dd. Although I_EDT is decreased with increase in gate dielectrics permittivity K. The authors found fringing induced barrier lowering (FIBL) which could introduce significant off‐state leakage current for K>25. Fortunately, the I_EDT with HfSiON and HfLaO gate dielectrics which are two‐five orders of magnitude lower than that of SiO₂, furthermore, FIBL for HfSiON and HfLaO gate dielectrics are inconspicuous. Moreover, HfLaO and HfSiON have superior electrical performance and thermal stability.

Originality/value

Both edge direct tunneling and FIBL are considered to alternate high‐K gate dielectrics for nano‐scale MOSFET.

Citation

Yang, J., Li, G. and Liu, H. (2008), "Edge direct tunneling current in nano‐scale MOSFET with high‐K dielectrics", Microelectronics International, Vol. 25 No. 1, pp. 30-33. https://doi.org/10.1108/13565360810846626