Cost effective lithography approaches for ASIC circuits

摘要

It is suggested that the high cost of mask sets for 90nm and below technologies may restrict the application of technologies to a handful of high volume chips. Most of the cost for mask production is a result of the increased time to write and inspect (including defect disposition) a mask due to the large files that are created prior to mask writing. Stringent mask specifications needed for low k factor imaging drive protracted and costly yield learning curves for a mask maker. The cost of different steps in the flow from design tape-out to final wafer test are analyzed and it is shown that limiting the reticle field size on critical layers could reduce net costs. The net die cost is lower as long as the number of processed wafers stays below a cutoff number. Costs can be further decreased by reducing the overall "figure count" (and hence writing time) for an ASIC chip by restricting the amount of OPC done on critical layers.