Individual Wafer Control
Problem: Until now, in the production of DRAM, for example, wafers have usually been processed in lots of 25 (i.e., in wafer carrier units). The switch, however, towards high-diversity, low-volume production (e.g., custom LSI) has made individual wafer control necessary. In order to avoid reducing the number of IC chips produced per wafer, the markings used for individual wafer control must be as small as possible. Mark the back surface of each wafer with wafer ID (2-dimensional code) satisfying the specifications of the SEMI T7 standards using a laser marker. (The surface can be marked with a wafer ID consisting of 13 alphanumeric characters in an area of 4 Ã— 1 mm.) When the wafers are introduced into the processing equipment, read the wafer ID (2-dimensional code) with a 2-Dimensional Code Reader and send the information to the equipment.