IC inspection test masks: Experimental results

Integrated circuit inspection test photomasks were scanned with four automated inspection systems to determine if these masks could be used to test and calibrate automated inspection systems. It was found that the dimensions on the background die pattern of such masks must be accurate before an automated system, especially a scanning type, can be used to inspect them. When adjustments were made for the stepping error by the operator, an automated system found nearly twice as many defective die as were found during a manual inspection of the same mask. A better way to achieve randomly positioned defects would be to make them with a laser scribing machine and with chrome patching. Randomly positioned defects are desired if an automated inspection system is to be compared with a manual scan technique. If all that is desired is the calibration of the automated system, then the defects can be positioned in a regular manner but there must be a large number of them in a variety of sizes so that detection statistics can be accumulated.