Value-based dispatching for semiconductor wafer fabrication

Abstract

The semiconductor industry has primarily emphasized lot dispatching decisions in order to achieve customer on-time delivery (OTD) satisfaction. Other dispatch objectives include reaching throughput and cycle time goals. However, the overall purpose of any commercial endeavor is to make money now and in the future. This paper presents a prototype lot dispatching system with the objective of "Value-Based Dispatching" (VBD) that proposes additional objectives such as profit maximization, market share growth, technology development along with achieving manufacturing goals. Required inputs for value-based dispatching beyond conventional OTD data include wafer costs, lot size, die count, net yield, and average selling price. This system utilizes a multi-rule based criteria to calculate the current value for each lot in a semiconductor wafer fab. This lot value is used in place of typical slack-time or critical ratio. Manufacturing objectives such as bottleneck starvation avoidance and resource utilization are also embedded into the dispatching system. A comparison of outputs such as profit and on-time delivery are also presented for VBD vs. OTD lot dispatching systems.