Allocating Reticles in an Automated Stocker for Semiconductor Manufacturing Facility

This article addresses the problem of reticle allocation in a stocker of an existing photolithography workshop of a 200 mm semiconductor wafer manufacturing facility. A reticle stocker generally consists of two internal storage zones: the retpod, where reticles are stored with pods and have short retrieval times, and the carousel, a bare reticle stocker with longer retrieval time. The reticle is an auxiliary resource in photolithography workshop operations. Thus, if the right reticles are not stored in the right places in the reticle stocker, it can quickly become a bottleneck. The purpose of the article is to determine the right reticles to store inside the right place of the reticle stocker. This is a knapsack problem. Three heuristics considering the arrival of lots in the upstream steps of the photolithography workshop are proposed and tested on real instances.