Measurement of femto-farad gate capacitance of a silicon nanowire FET using time-domain pulse response

We present the direct measurement of the gate capacitance of a silicon nanowire field effect transistor using time-domain monitoring of the source current when the gate pulses with various frequencies and amplitudes are applied. The displacement current induced at the gate capacitance is proportional to the derivative of the gate pulse, and it becomes measurable when the rise time of the gate pulse is small enough. The gate capacitance of fF range was successfully measured using our method.

I. Introduction

With rapid and continuous scaling of silicon devices, their present channel length is in the range of 20 nm. Another recent trend is the advent of the devices with 3-dimensional gate structures [1] to achieve a better gate control. The area of these devices, and thus the gate capacitance is too small, and it is difficult to obtain the gate capacitances by usual AC capacitance measurements.