The effect of Fowler–Nordheim tunneling current on thin SiO2 metal-oxide-semiconductor capacitors

Abstract

p‐type metal‐oxide‐semiconductor (MOS) capacitors with various oxide thickness (less than 200 Å) are stressed by Fowler–Nordheim (F–N) tunneling constant current with negative gate bias, and high frequency and low frequency capacitance‐voltage (C‐V) characteristics have been used to investigate the charge trapping phenomenon in thermally grown thin SiO₂ films. Under constant current stress, high frequency C‐V curve shifts negatively, and flatband votage shifts ΔV_FB don’t saturate even at large injected charge F. In order to explain this behavior, we propose the expression, ΔV_FB =A[1− exp(−σF)]+KF. The first term indicates hole trapping by the preexisting traps and the second term means the generation factor due to traps generated under stress. A fitting parameter A is nearly in proportion to the square of SiO₂ thickness. This can be interpreted with the uniform distribution of bulk hole traps throughout the SiO₂. Both capture cross section σ and generation factor K rapidly decrease with decreasing SiO₂ thickness. From the results of low frequency C‐V characteristics, the interface states with very high density of the order of 10¹³/cm² eV are generated over a wide range of band gap.