Chapter 6

Chapter 6

Determination of Interface Trapped Charges in

Ultrathin Oxide MOSFETs

Traps at the SiSiO2 interface play an important role in determining the threshold voltage, inversionlayer mobility and lowfrequency
noise of MOSFETs. Proper device modeling requires the knowledge of the density of interface states throughout the bandgap.

In MOSFETs, interface traps have been characterized in three ways:

1) As an average value over both the surface energy bandgap and channel length, Nit (cm 2 ) [23, 5]
2) As an average over the bandgap, but not channel length, Nit(x) (cm 2 ) [5]
3) As an average over channel length, but not surface potential energy in the bandgap, Dit(y) (eV 1 cm 2 ) [24, 25 and 26]


Usually two methods are widely in use as deterministic tools for interface trapped charges. These are:

1) Charge Pumping or CP Method
2) CapacitanceVoltage or CV Method


To mention that in place of using CVmethod, we have employed an improved version of lowfrequency CV method.

This chapter deals with different experiments run on different ultrathin oxide MOSFETs with the above processes.