A Wafer Design Problem in Semiconductor Manufacturing for Reliable Customer Service

Abstract

Suppose a set of several different types of chips are needed in a specified number and unless all the chips are available in the right proportion, shipment cannot be made. Uncertainties in wafer fabrication process, especially random yield, poses a major challenge for the reliable production of chips. We present models which explicitly take account of yield losses and show how available chip sites should be allocated among various types of chips to meet the demand of a set with the maximum probability. A key result is that the proportion of sites allocated to each chip type varies with the total number of available sites. The allocation model also provides a tradeoff curve between the total number of chip sites assigned for the production of a set and the highest attainable level of confidence in meeting the demand; this is valuable when more than one set is competing for the same resources. The influence of wafer loss and rework is considered for the determination of job size. The models presented here are specially useful when reliable delivery of a set of chips by an impending due date is of prime concern in a congested fabrication line. © 1990 IEEE.