On-Line Monitoring When the Process Yields a Linear Profile

Abstract

Control charts monitor processes where performance is measured by one or multiple quality characteristics. Some processes, however, are characterized by a profile or a function. Here we focus on monitoring a process in semiconductor manufacturing that is characterized by a linear function. While the linear function is the simplest, it occurs frequently, for example in calibration studies. Two monitoring approaches are proposed: (1) monitor parameters, slope and intercept, with multivariate T² and (2) monitor average residuals between sample and reference lines with EWMA and R charts. Simulation studies indicate that both methods work well. Both methods are extendable to complex functions.

• Calibration
• Exponentially Weighted Moving Average Control Charts
• Multivariate Control Charts
• Process Control

Additional information

Notes on contributors

Lan Kang

Ms. Kang is a Doctoral student in the Department of Industrial Engineering.

Susan L. Albin

Dr. Albin is a Professor in the Department of Industrial Engineering. She is a Senior Member of ASQ. Her email address is [email protected].