Error analysis and compensation method of focus detection in exposure apparatus
Yasuhiro Hidaka1, Kiyoshi Uchikawa, Daniel G Smith
1Precision Equipment Company, Nikon Corporation, Saitama, Japan. hidaka.y@nikon.co.jp
Summary
Measurement errors in integrated circuit lithography focus sensors stem from optical system imperfections and wafer surface variations. Novel techniques were developed and demonstrated to significantly reduce these critical measurement errors.
Area of Science:
- Semiconductor Manufacturing
- Optical Metrology
- Integrated Circuit Lithography
Background:
- Focus sensors are critical for precision in integrated circuit (IC) lithography.
- Existing focus sensors face challenges with measurement accuracy due to system and wafer surface interactions.
- Accurate focus measurement is essential for yield and performance in semiconductor fabrication.
Purpose of the Study:
- To introduce an original approach for analyzing measurement accuracy in typical focus sensors used in IC lithography.
- To theoretically analyze the primary causes of measurement errors in focus sensors.
- To develop and demonstrate novel techniques for reducing these measurement errors.
Main Methods:
- Theoretical analysis of focus sensor measurement errors.
- Derivation of mathematical formulations for error analysis.
- Experimental validation using a dedicated optical setup with reproduced wafer surface conditions.
Main Results:
- Identified key error sources: interactions between optical system imperfections and wafer surface conditions.
- Mathematical models accurately described the observed measurement errors.
- Demonstrated successful implementation of novel techniques to mitigate focus sensor errors.
Conclusions:
- The study provides a theoretical and experimental framework for understanding focus sensor errors in IC lithography.
- The developed techniques offer practical solutions for enhancing measurement accuracy.
- Improved focus sensor accuracy is crucial for advancing semiconductor manufacturing processes.
