Advanced Process Control in Semiconductor Manufacturing
Kostas S. Tsakalis
Supported by SEMY Engineering Inc. (subsequently part of Semitool,
Brooks PRI, Applied Materials) under grant No. SEI-950815-MBTC-001,...,6
Best products Award (picture)
This work provides an integrated approach for modeling and robust
multivariable controller design, with application to temperature
control of diffusion and CVD furnaces. Modeling relies on input-output
data, collected in a preliminary identification experiment at the
desired operating conditions. An important component of the
identification is the computation of uncertainty bounds that describe
the confidence limits of the model, in a manner consistent with robust
control theory. The results of the identification are then used to
design an H-infinity controller with a cascade, hierarchical structure.
The final implementation of the controller also includes mechanisms to
prevent integrator wind-up. Special emphasis is placed on automating
the procedure --for classes of furnaces-- so that, potentially, it can
be used by non-experts on the field. Implementations include several
industrial furnaces. Experimental results demonstrate the success of
the approach as well as the good agreement between predicted and actual
- K. Tsakalis, J.-J. Flores-Godoy and K. Stoddard,
"Temperature Control of Diffusion/CVD Furnaces Using Robust
Multivariable Loop-Shaping Techniques," Proc. 38th Conf. Decision
and Contr., V.4, 4192-4197, Phoenix, AZ, Dec. 1999.
- S. Limanond, J. Si and K.S. Tsakalis, "Monitoring and Control of
Semiconductor Manufacturing Processes," IEEE Control Systems,
18, 6, 46-58, Dec. 1998.
- K. Tsakalis and K. Stoddard, "Integrated Identification and
Control for Diffusion/CVD Furnaces," 6th IEEE Int. Conference on
Emerging Technologies and Factory Automation, Los Angeles, Sept.
- K. Tsakalis and K. Stoddard, "Control Oriented Uncertainty
Estimation in System Identification," IASTED MIC'98 Conf., Grindelwald,
- M. Tucker, E. Valdez, K. Tsakalis, M. Warren, K. Stoddard,
"Improving Vertical Furnace Performance Using Model-Based Temperature
Control," SEMI/SEMATECH AEC/APC Symposium X Vail, Oct, 98.
- E. Grassi and K. Tsakalis, "PID Controller Tuning by Frequency
Loop-Shaping," Proc. 35th CDC, Kobe, Dec. 96.
M. Yelverton, K. Stoddard, B. Cusson, T. Timmons, "Improving
Diffusion Furnace Capability Using Model-Based Temperature Control in
Production Environment," 6th ISSM, San Francisco, Oct. 97.
(Brief description of the project and typical experimental results,
courtesy of SEMY Eng. Inc.)