A 5800 μm² Process Monitor Circuit for Measurement of in-Die Variation of Vth in 65nm

A compact 5800 μm ² process monitor circuit is demonstrated which can measure multiple threshold voltages (Vth) locally on a die. An accurate, process/voltage/temperatureindependent current source is provided to measure Vth using the constant current method to an accuracy of σ = 3.6 mV. The output is digitized by a sigma-delta modulator with a conversion time of 2ms. The circuit enables efficient and compact in-die variation monitoring of the key process parameters and is thus useful for the high-volume characterization of integrated circuit products. The circuit contains its own reference voltage, and thus can be used for calibration during testing or in the field.