Use of a segmentation technique to analyze the variability of the yield of a mature CMOS SRAM

The authors use a segmentation technique to correlate the chip yield of SRAMs with several parameters such as wafer number, chip radial and angular position on the wafer, lot number and manufacturing date. From a large database corresponding to a mature 1 μm CMOS process, it is shown that the wafer to wafer variability is the most important variable explaining the spread of chip yield, followed by the radial position of the chip on the wafer. Variables such as angular position, lot number and data do not impact the yield variability