A Proximity Effect Measuring Test Chip - Design and Application

An electrical tester has been designed for measuring the proximity effect e-beam lithography. The tester consists of a clover-shaped van der Pauw resistor for sheet resistance measurement, a four-terminal resistor for linewidth measurement, and a second four-terminal resistor of identical width but with adjacent bars for evaluating changes due to proximity effect. The test chip is composed of a set of testers with various combinations of linewidth, bar size, and the space between them, ranging in dimension from 0.5 micron to 2.0 micron. Computer software has been developed to interface a commercial computer to the probe station for fully automated data acquisition, statistical analysis, and graphic display. The test chip yields very high precision in both the sheet resistance (3 sigma is equivalent to 3% of nominal) and electrical linewidth (3 sigma is equivalent ti 5%). The chip can serve as a general purpose metrology tool to evaluate the efficacy of different proximity correction techniques in e-beam lithography, to complement SEM linewidth measurements which suffer from resist profile threshold dependence especially for rounded resist profiles, and to monitor linewidth control for submicron process development.