Coincident Detection Scanning Apparatus
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
Rough or patterned surfaces on semiconductor wafers can be inspected for particulate contamination or defects by grazing angle detection of scattered normally incident illumination. With this apparatus, a circularly polarized laser beam of small spot size, roughly 5 microns, is projected normally incident onto a wafer surface. Four detectors at incremental angles (i.e., 45o, 135o, 225o, 315o) surround the wafer and are located 0 to 5o above the wafer's surface. In operation, the laser scans and is scattered off the surface of the wafer. The detectors measure the scatter at a preset grazing angle depending on the height threshold for acceptable particulate contamination.