Detecting CD error or transmission error of photomask patterns

Whereas critical-dimension (CD) error below 35 nm and transmission error below 3.5% are required for 256 M DRAM, a present-day cutting-edge inspection system may fail to detect 150 nm CD error or 6% transmission error. Improvement of defect inspection is, therefore, necessary to raise yields of semiconductor devices. A new inspection algorithm has been developed for CD error and transmission error of photomask patterns by calculating the average transmission error. Experimental results show as small as 4% transmission error or over 25 nm CD error of hole pattern will be detected without any false alarms.