Non-differential integrated atofarad capacitor measurement system

On chip capacitance measurement with resolution below 10/sup -18/ F//spl radic/Hz is presented. The minimum value of the absolute capacitance starts at 20 fF. Test chip using standard CMOS process has been designed and evaluated. The measuring system can be used to evaluate extremely small capacitances on different nodes since the sensing nodes can be multiplexed. The system is therefore capable of using variable capacitance as sensor for either any electrical, mechanical or temperature value changing the capacitance being measured. The calibration of the measuring system is based on the absolute value of interlayer capacitance, which can be performed once for every fabrication lot.