Subthreshold drain leakage currents in MOS field-effect transistors

• Published in: IEEE transactions on electron devices 1972-02, Vol.19 (2), p.213-219
• Main Author: Gosney, W.M.
• Format: Article
• Language: English
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/T-ED.1972.17399

There are two contributions to the drain-source leakage current in MOS field-effect transistors for gate voltages below the extrapolated threshold voltage (V tx ) : 1) reverse-bias drain junction leakage current, and 2) a surface channel current that flows when the surface is weakly inverted. Nearly six orders of magnitude of drain-source current from the background limit imposed by the drain junction leakage to the lower limits of detection of most curve tracers (0.05 µA) are controlled by gate-source voltages below the extrapolated threshold voltage. It is shown that this current flows only for gate voltages above the intrinsic voltage V i , the gate voltage at which the silicon surface becomes intrinsic. For gate voltages between V i and V tx the surface is weakly inverted with the resulting channel conductivity being responsible for the drain-source current "tails" observed for gate voltages below V tx . The importance of the intrinsic voltage in designing low-leakage CMOS and standard PMOS circuitry is discussed.