A batch-based run-to-run process control scheme for semiconductor manufacturing

Run-to-Run (R2R) control has been widely used in semiconductor manufacturing to compensate for process disturbance and to improve quality. The traditional R2R controller only takes the process output in a previous run as its input and generates an optimal recipe for the next run. In a multistage semiconductor manufacturing process, variations in upstream stations are propagated to downstream stations. However, the information from upstream stations is not considered by existing controllers. In addition, most R2R processes have a limited capacity; the products must be processed in batches. Therefore, if the incoming materials could be grouped with small within-batch variations and large batch-to-batch variations and the recipes are customized for each batch to drive all batch averages toward the same target value, the output variation could be reduced and quality improved. A batch Exponentially Weighted Moving Average (EWMA) controller is proposed in this article. It employs a modified K-means algorithm to group the incoming materials into batches with a fixed and equal size while minimizing the within-batch variation. The controller then generates the control settings by taking both the batch information and the feedback quality information into account. Simulation studies show that the proposed controller could significantly reduce output variation and improve quality.