Defect Scatter Analysis (DSA) provides a fast, accurate method for evaluating the random errors made by defect scanners when a wafer is loaded, aligned, scanned, and unloaded multiple times. The DSA tool includes a 200 mm or 300 mm wafer that has a series of patterned defects; the defects can be located by the inspection scanner and the patterns detected even if there are many other defects present. The DSA software analyses multiple scans, locates the pattern at each site for every scan, and compares the distributions of the pattern at each site to the average reported position, as well as to the known site position. Plots of the predicted positions show the scatter in terms of x, y and rotational errors. The composite plot for all scans and sites represents a figure of merit for the scanner.
By itself, DSA is useful for evaluating which scanner makes the smallest set of random errors, and the effects of modifying a scanner to minimize these errors. In addition, the software also generates a defect file in the same format as the input files, showing the average reported positions for the sites of the programmed defects. This file and the wafer provide the best input to the JEOL in-fab microscopes for the LMLS/SSBWA procedures that correct for most of the systematic differences between the predicted positions and the defect positions as relocated on the SEMs1.
The tool consists of one 200mm or 300mm wafer and the analysis software, provided in both UNIX (either 9.05 or 10.2) and Windows 2000. The software will accept defect files in standard KLA, Tencor, and Inspex formats.