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Improvement of Temperature Uniformity in Rapid Thermal Processing Systems Using Multivariable Control1

Published online by Cambridge University Press:  28 February 2011

S. A. Norman,
C. D. Schaper and
S. P. Boyd
S. A. Norman
Affiliation:
Stanford University, Dept. of Electrical Engineering, Stanford CA 94305.
C. D. Schaper
Affiliation:
Stanford University, Dept. of Electrical Engineering, Stanford CA 94305.
S. P. Boyd
Affiliation:
Stanford University, Dept. of Electrical Engineering, Stanford CA 94305.
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Abstract

During rapid thermal processing (RTP) of a semiconductor wafer, maintenance of nearuniform wafer temperature distribution is necessary. This paper addresses the problem of insuring temperature uniformity in a cylindrical RTP system with multiple concentric circular lamps.

A numerical technique is presented for optimizing steady-state temperature distribution by independently varying the power radiated by each lamp. It is shown for a simulated system, over a wide range of temperature setpoints, that the temperature uniformity achievable with multivariable (“multiple knob”) control of lamp powers is significantly better than that achievable with scalar (“single knob”) control.

The difficulties of using scalar control in RTP are more severe in the case of temperature trajectory design than in the case of steady-state temperature maintenance. For example, with scalar control the rate of temperature increase during ramping is limited because temperature nonuniformity can cause slip defects in the wafer. A numerical technique is presented for designing multivariable lamp power trajectories to obtain near-optimal temperature uniformity while wafer temperature tracks a specified ramp, resulting in slip-free ramp rates much faster than those achievable with scalar control.

Information

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 224: Symposium F – Rapid Thermal and Integrated Processing I , 1991, 177
Copyright
Copyright © Materials Research Society 1991

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Footnotes

1

This research was supported by the Advanced Research Projects Agency of the Department of Defense and was monitored by the Air Force Office of Scientific Research under Contract No. F49620-90-0-0014. This manuscript is submitted for publication with the understanding that the US Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation hereon.

The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either express or implied, of the Advanced Research Projects Agency or the U.S. Government.

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