Encoder Head Liquid Residue Detection in Lithography
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Solution Overview
Problem
In lithography processes for semiconductor device manufacturing, existing exposure apparatuses face challenges with position detection precision due to liquid immersion methods, where residual liquid on encoder heads can lead to measurement errors and malfunction, affecting the accuracy and stability of positional information measurement.
Innovation Solution
An exposure apparatus and method that includes a liquid supply device, a pattern generation device with an optical system, and a measurement system with encoder heads. The apparatus detects residual liquid on the photodetection surface of encoder heads and outputs this information to the measurement system, allowing for the exclusion of non-functional encoder heads and enabling accurate positional measurement by using only heads with a good residual liquid state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If liquid immersion method is used to form liquid immersion area, then manufacturing precision is improved, but reliability deteriorates due to residual liquid on encoder heads causing measurement errors
Solution Approach 1:
The detection device performs preliminary detection of residual liquid on encoder heads before the measurement system uses them for position detection. This allows the system to identify and exclude encoder heads with excessive residual liquid in advance, preventing measurement errors while maintaining the benefits of liquid immersion exposure
Solution Approach 2:
The detection device provides feedback information about the residual liquid state of encoder heads to the measurement system. Based on this feedback, the measurement system can selectively use only those encoder heads that have acceptable residual liquid levels, ensuring reliable position detection while maintaining manufacturing precision
2Productivity
If encoder head enters liquid immersion area, then liquid supply is improved for optical system, but measurement precision deteriorates due to residual liquid on photodetection surface
Solution Approach 1:
The detection device detects residual liquid on encoder heads before they are used for position measurement. This preliminary detection allows the system to identify encoder heads that have been contaminated by liquid immersion and exclude them from measurement, preventing degradation of measurement precision while maintaining liquid supply efficiency
Solution Approach 2:
The detection device provides feedback about the liquid contamination state of encoder heads to the measurement system. This feedback mechanism enables the measurement system to selectively use only clean encoder heads, ensuring high measurement precision while the liquid supply device continues to efficiently supply liquid to the optical system
Data Source
AI summary
In an exposure apparatus of a liquid immersion exposure method, there is a case when a wafer table holding a wafer moves, a liquid immersion area formed by liquid supplied in a space between a wafer table and a projection optical system passes over a head mounted on the wafer table. Therefore, for a head over which the liquid immersion area has passed, the residual presence of the liquid is detected based on an amount of light of a reflected light received by the light receiving element which receives the reflected light from the wafer table surface. And, of a plurality of heads, positional information of the wafer table is measured, based on measurement values of a head that had no liquid remaining in the detection.