Comparison of interface trap density measured by capacitance/subthreshold/charge-pumping methods for n-MOSFETs with Si-implanted gate-SiO/sub 2/

Effects of channel B-implantation before gate oxidation and heavy Si-implantation into the gate-SiO/sub 2/ on interface trap density D/sub it/ distribution in the energy gap for n-MOSFETs are analyzed by three different measurement methods: (I) high-low frequency capacitance, (II) subthreshold current, and (III) charge pumping. These three methods produce similar results for D/sub it/. They indicate that the channel B/sup +/-dose scarcely has any effect on D/sub it/ at midgap and increases as larger Si-doses give an increase in D/sub it/. Method I can provide the D/sub it/ distribution across the majority of the bandgap and may cause an underestimation of D/sub it/. Method II is convenient with reasonable accuracy due to the simple DC measurement.

1. Introduction

One of the most important parameters for the evaluation of fabrication quality of MOS devices is the interface trap density is located at the interface with energy states within Si bandgap, and can change charge state by exchange of carriers with Si, resulting in significant degradation of the MOS device performance.