Profile Monitoring of Batch Processes with PI Controllers in Semiconductor Manufacturing

• Activity Number: 361
• Type: Contributed
• Date/Time: Tuesday, August 2, 2011 : 10:30 AM to 12:20 PM
• Sponsor: International Chinese Statistical Association
• Author(s): Shui-Pin Lee*+
• Companies: Ching Yun University
• Keywords: profile monitoring ; batch process ; proportional-integral controller ; health index ; state space ; average run length

Abstract

A modern semiconductor manufacturing line contains hundreds of sequential batch processing stages. Each of these operation stages consists of many steps carried out by expensive tools with several PI controllers to adjust the recipes, which are monitored by numerous sensors capable of sampling at intervals of seconds. The heterogeneous variations at different profile points are mainly due to on-off recipe actions of the PI controllers at specific points. In addition, the analysis of these profiles is further complicated by long-term trends due to tool aging and short-term effects specific to the first wafer in a lot-cycle. Statistical process control methods that fail to take these effects into consideration will lead to frequent false alarms. A systematic method is proposed to address these challenges. At first, each of these PI controllers is described by a state space model, its output matrix is used to capture and remove intrinsic variations due to long-term aging trends and the short-term first-wafer effects. The residuals are used to formulate a health index, and this index can be used to monitor the health of the equipment and detect faulty wafers efficiently.