OPTIMIZING THE MATCH IN WEAKLY INVERTED MOSFETS BY GATED LATERAL BIPOLAR ACTION

The on-chip n-type MOSFET current mirror circuit with different drawn gate widths and lengths has been fabricated, and has been characterize d across the wafer with back gate slightly forward biased. The weakly inverted MOSFET device with a small back-gate forward bias represents equivalently the high-gain gated lateral bipolar transistor in low-lev el injection, Experimental results have exhibited a substantial improv ement in the match of the drain current in weak inversion due to actio n of the gated lateral bipolar transistor, especially for the small si ze devices. The extensively measured mismatch of the weak inversion dr ain current has been successfully reproduced by an analytic statistica l model with back-gate forward bias and device size both as input para meters. The experimentally extracted variations in process parameters such as the Rat band voltage and the body effect coefficient each have been found to follow the inverse square root of the device area, The mismatch model thus can serve as a quantitative design tool, and has b een used to optimize the trade-off between the device area and the mat ch with the forward back-gate bias as a parameter.