Test Chip to Evaluate Measurement Methods for Small Capacitances

We designed and fabricated a test chip to evaluate the performance of new approaches to the measurement of small capacitances (femto-Farads to atto-Farads range). The test chip consists of an array of metal-oxide-semiconductor (MOS) capacitors, metal-insulator-metal (MIM) capacitors, and a series of systematically varying capacitance structures directly accessible by an atomic force microscope probe. Nominal capacitances of the test devices range from 0.3 fF (10^-15 F) to 1.2 pF (10^-12 F). Measurement of the complete array of capacitances by using an automatic probe station produces a "fingerprint" of capacitance values from which, after correction for pad and other stray capacitances, the relative accuracy and sensitivity of a capacitance measurement instrument can be evaluated..