An in-situ temperature measurement system for DUV lithography

Spatial uniformity of temperature across a silicon wafer is an important requirement during the post-exposure bake step of the deep-ultra-violet lithography process. Closed-loop temperature control provides a means by which the stringent temperature specifications can be achieved, provided that accu...

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Bibliographic Details
Published in:IEEE transactions on instrumentation and measurement 2003-08, Vol.52 (4), p.1136-1142
Main Authors: Woei Wan Tan, Li, R.F.Y.
Format: Article
Language:English
Subjects:
Algorithms
Contact
Control systems
Control theory
Feedback
Lithography
Monitoring
Resists
Semiconductor device manufacture
Sensor phenomena and characterization
Sensors
Temperature control
Temperature measurement
Temperature sensors
Thermal sensors
Wafers
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Summary:Spatial uniformity of temperature across a silicon wafer is an important requirement during the post-exposure bake step of the deep-ultra-violet lithography process. Closed-loop temperature control provides a means by which the stringent temperature specifications can be achieved, provided that accurate feedback signal is available. As each new wafer is loaded for processing, its level of thermal contact with the temperature sensor may vary, leading to erroneous measurement of the wafer temperature. Such variation in thermal contact manifests itself as changes in the time constant of the sensor. This paper describes a method for in-situ estimation of the sensor parameters, and proposes an algorithm for post-processing the sensor output to improve measurement accuracy. Experimental results are presented to demonstrate the effectiveness of the algorithm in improving the accuracy of the feedback signal, thereby reducing the undesirable influence of poor thermal contact on the performance of the closed-loop temperature control system.
ISSN:0018-9456
1557-9662
DOI:10.1109/TIM.2003.815987