Throughput Estimation Model of Cluster Tool in Semiconductor Manufacturing

Abstract

Semiconductor manufacturing management system was developed and grown up over the past decades. In order to increase the product yield and enhance the production productivity, cluster tools became the main stream in modern wafer fabrication factories which occupies over 50% of production equipment. Generally, cluster tools are integrated by several components including robots, vacuum chambers (Load locks) and single-wafer process chambers in a module and can be treated as a small factory. The throughput estimation before recipe release is very difficult. However, it is necessary and important for the planning activity. In this work, a throughput estimation model for cluster tools is proposed. The Multiple Regression Analysis is applied to develop a set of throughput estimation equations. A simulation model of cluster equipment including 3 single-wafer process chambers are built to get the historical throughput data for the regression analysis. From the Multiple Regression Analysis, it reveals that different numbers of recipes processed in the same time have to develop different regression model. The major factors in the regression model include numbers of load ports and process time of each recipe. Furthermore, a set of recipes are used to test the accuracy of estimation. Based on the testing results, they revealed that the MAPE is under 3% and the estimation model is accepted in practice to forecast the throughput of recipes for the planning activities.

Short-Term Scheduling Model of Cluster Tool in Wafer Fabrication

“…Basically, the main goal in this scheduling model is to maximize the output without exceeding the time constraint. It leads to the latest time that WIP must be processed on the machine should be first calculated and indicated, and then the efficiency table of the machine processing combination [4] (it is called as combination efficiency table) is applied to arrange the future 3-h schedule for each machine. It is well known that the status of the shop floor is varied quickly, to re-schedule every half hour to respond to the on-site conditions is necessary.…”

“…For validating the performance of proposed model, a simplified simulation model with a parallel cluster tool is established and to compare the performance results with FIFO rule. Although there is only one cluster tool in the system, the behaviors of cluster tool are established as the production tool and has been validated [4]. Besides, an arrival list of wafer lots for 33 days is created in advance for expediting the validation process and the lookahead function is ignored in such a situation.…”

“…In order to maximize the output, this research is not only considering the current WIP in front of the machine, but also calculates and adds the WIP that will reach the machine in the upcoming three hours. In addition, the WIP with the time constraint is calculated and marked at the latest time that must be processed on the machine, and then the efficiency table of the machine processing combination developed in the previous studies [4,5] is used to arrange each machine within the next three hours processing schedule to guarantee that the resulting schedule is the best schedule in the current situation. Under this procedure, the best short-term schedule of the cluster tool can be arranged accordingly.…”