A modified sliding wire potentiometer test structure for mapping nanometer-level distances

Present a modified voltage-dividing potentiometer test structure which overcomes a problem typical in scaling electrical test structures: it provides a correction for electrical length shortening of a resistor strip caused by the attachment of voltage taps of nonnegligible width. The test structure was implemented in chrome on quartz, and measurements of displacements between 10 and 500 nm with ±12-nm random error were made using available test equipment. The enhanced precision of the measurement derives from reducing the size of the structure from previous design methods. The enhanced accuracy of the displacement measurement derives from scaling the length of the potentiometer bridge while simultaneously providing for nonscaled widths of the voltage taps. Measurements using these corrections demonstrate an improvement of up to 20% in measurement accuracy, and further improvements can be expected with optimized designs