Method of extracting effective channel length for nano-scale n-MOSFETs

This paper proposes a method of extracting the effective channel length Leff of nano-scale n-MOSFETs. This method requires only one MOSFET; therefore, the Leff extraction is not affected either by variation of carrier mobility due to differences in gate length or by changes in MOSFET parameters due to differences in fabrication processes. The method is based on the facts that the gate tunneling current Igb to the substrate depends on Leff, and that the gate tunneling current Igsd to the source and drain depends on the gate–source/drain overlap length ΔL. Curves of Igb and Igsd versus the gate dielectric voltage Vox were obtained from the measured curves of Igb and Igsd versus gate voltage Vg in n-MOSFETs fabricated using a 90 nm CMOS technology. Leff was extracted from the ratio Igb/Igsd for a given Vox. Comparison of the drain current Id versus Vd curves calculated using the extracted Leffs with the same curves obtained using previous methods shows that the proposed method is much more accurate than the previous ones.