Comparisons of measured linewidths of submicrometer lines using optical, electrical, and SEM metrologies

An investigation is being carried out to determine the ability of three methods of linewidth metrology to measure the dimensions of features of less than 0.5 micrometers . The three methods are transmitted-light optical microscopy, electrical test structure, and scanning electron microscopy (SEM). To permit the inclusion of transmitted-light optical microscopy in this investigation, 100-nm thick Ti films were patterned using normal VLSI processing techniques on a 150-mm diameter quartz wafer. The cross-bridge resistor test structure was used since this structure has been widely used in industry and it allows the results from all three metrological techniques to be compared. The design bridge widths of the test structures range from 0.4 micrometers to 1.0 micrometers . The results of these measurements show systematic and uniform offsets between the different techniques. In this paper we discuss the different techniques and describe the observed results.