Scheduling cluster tools with independent dual-arms for chamber cleaning

Abstract

In semiconductor industry, cluster tools are widely used in wafer manufacturing, especially in wafer fabrication. Many previous researches have dealt with conventional architecture of cluster tools, which are single-arm and dual-arm. Recently, a new cluster tool architecture has been introduced to improve productivity and quality of wafers. The new architecture is called independent dual-arm. Previously, three independent dual-arm robot sequences, which are Modified Swap, Dual Backward, and Disjunct Backward, have been proposed. However, independent dual-arm cluster tools have never been studied with chamber cleaning operation. By extending the three independent dual-arm robot sequences, we propose Modified Swap(z), Dual Backward(z), and Disjunct Backward(z) sequences that allow partial loading for parallel chambers, where vector z specifies how many chambers z$_i$ of each process step i are kept empty for cleaning. We then examine three sequences based upon cycle time and wafer delay. We propose a new robot sequence, called Hybrid Backward(s,z). The sequence optimizes both cycle time and wafer delay. We verify by graph analysis and optimal results given by MIP model.