Hybrid Encoder Interferometer Calibration for Stage Positioning
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Solution Overview
Problem
Current lithography processes face challenges in achieving high precision and long-term stability in position control of stages due to temperature fluctuations affecting laser interferometers and the mechanical instability of encoders used for position measurement in semiconductor device manufacturing.
Innovation Solution
A movable body drive method that employs a calibration process using a combination of measurement units, including encoders and interferometers, to correct measurement values and ensure accurate and stable positional information, allowing for precise movement of stages in uniaxial and two-dimensional directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a laser interferometer is used for position measurement, then measurement stability is improved, but measurement precision deteriorates due to temperature fluctuation
Solution Approach 1:
The patent combines two measurement units (encoder and laser interferometer) into a hybrid measurement system. The encoder provides high-resolution position data while the interferometer corrects for systematic errors, achieving both high precision and stability by merging the strengths of both measurement technologies.
Solution Approach 2:
The system uses feedback from the laser interferometer to correct encoder measurement values. The interferometer's stable measurements serve as a reference to compensate for encoder drift and temperature-induced errors, continuously adjusting the position data to maintain both precision and stability.
2Measurement precision
If an encoder is used for position measurement, then measurement resolution is improved, but long-term stability deteriorates due to mechanical drift
Solution Approach 1:
The laser interferometer acts as an intermediary reference system that mediates the encoder's measurements. It provides a stable optical reference that corrects the encoder's mechanical drift, allowing the high-resolution encoder data to be stabilized against long-term mechanical variations.
3Manufacturing precision
If higher precision position control is implemented, then manufacturing precision is improved, but system complexity increases
Solution Approach 1:
The hybrid measurement system serves multiple functions: the encoder provides primary position feedback for high-resolution control, while the interferometer simultaneously performs calibration and error compensation. This multi-functionality achieves high manufacturing precision without proportionally increasing system complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables accurate and stable movement of stages, improving the precision and long-term stability of pattern formation and exposure processes in semiconductor manufacturing, overcoming the limitations of traditional measurement methods.
Implementation Method 1
Position measurement of the reticle stage and the wafer stage is normally performed using a laser interferometer
Implementation Method 2
an encoder that has a measurement resolution of the same level or higher than a laser interferometer has been introduced
Data Source
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AI summary
Positional information of a movable body (RST) in a Y-axis direction is measured using an interferometer (16y) and an encoder ((24A, 26A1), (24B, 26B1)) whose short-term stability of measurement values excels when compared with the interferometer, and based on the measurement results, a predetermined calibration operation for obtaining correction information for correcting measurement values of the encoder is performed. Accordingly, by using measurement values of the interferometer, correction information for correcting the measurement values of the encoder whose short-term stability of the measurement values excels the interferometer is obtained. Then, based on the measurement values of the encoder and the correction information, the movable body is driven in the Y-axis direction with good precision.