Laser Sensor Head Positioning for Stage Edge Mirror Metrology
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Solution Overview
Problem
Conventional interferometer systems for determining the position of an optical tool head relative to a substrate are prone to measurement inaccuracies due to environmental changes, thermal gradients, and angular deviations, which affect the precision of pattern generation and inspection on substrates.
Innovation Solution
A substrate pattern system with sensor heads attached to the tool head, emitting laser beams towards mirrors along the edges of the stage, and using optical fibers to connect the sensor heads to the laser source, reducing the spatial separation and exposure to environmental variations, thereby improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional interferometer systems use multiple optical components and mirrors to guide laser beams for position measurement, then the system can determine the position of the tool head, but the measurement accuracy is affected by environmental changes, thermal gradients, and angular deviations
Solution Approach 1:
The patent extracts the measurement function from the tool head by placing sensors on the stage to measure the position of the tool head relative to the stage. This separates the measurement system from the tool head, reducing the number of optical components exposed to environmental changes and thermal gradients in the measurement path.
Solution Approach 2:
The patent introduces an intermediary measurement system using sensors on the stage to detect tool head position, rather than using complex interferometer paths with multiple mirrors. This intermediary approach reduces the measurement path exposure to harmful environmental factors.
2Reliability
If conventional interferometer systems use a large number of optical components to guide laser beams, then the system can function, but the system requires very stable support structures and is sensitive to minor displacements
Solution Approach 1:
The patent removes the complex interferometer system with multiple optical components from the tool head and replaces it with a simplified sensor-based measurement system on the stage. This extraction reduces device complexity while maintaining reliability through direct sensor measurement.
Solution Approach 2:
The patent replaces the mechanical/optical interferometer system with electronic sensors that directly measure position. This substitution eliminates the need for stable support structures for multiple optical components while achieving the same positioning function.
3Measurement precision
If the measurement system uses laser beams exposed to environmental changes over long paths, then the system can measure position, but the measurement accuracy deteriorates due to thermal gradients and environmental variations
Solution Approach 1:
The patent extracts the measurement function from the tool head and implements it on the stage with sensors that measure tool head position directly. This shortens the measurement path and reduces exposure to thermal gradients and environmental variations.
Solution Approach 2:
The patent uses sensors on the stage to create a measurement reference frame that copies the stage's coordinate system, allowing direct measurement of tool head position without long laser paths exposed to environmental changes.
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
The system enhances positioning accuracy by minimizing Abbe errors and reducing the impact of environmental disturbances, ensuring precise alignment and measurement of patterns on substrates, particularly in microlithography and nanolithography processes.
Implementation Method 1
The first sensor head is configured to receive a first laser beam from the laser source, emit the first laser beam as a first measurement laser beam toward the first mirror, and receive a first reflected laser beam from the first mirror
Implementation Method 2
receive a first reflected laser beam from the first mirror
Implementation Method 3
The first sensor head is optically connected to the laser source via a first optical fiber
Data Source
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AI summary
A substrate pattern system (100) is provided. The substrate pattern system comprises a stage (150), a tool head (120), and a positioning system (170). The stage is configured to support a substrate (160). The tool head comprises an objective lens (122) having a focal point at a substrate supported by the stage. The tool head and/or the stage is movable to provide relative motion between the tool head and the stage along a first axis (X) and a second axis (Y). The positioning system comprises a first mirror (174x) arranged along a first edge of the stage. The first mirror has a first mirror surface facing the stage. The positioning system first comprises a second mirror (174Y) arranged along a second edge of the stage. The second edge is adjacent to the first edge. The second mirror has a second mirror surface facing the stage. The positioning system further comprises a laser source (171), a first sensor head (173x), a second sensor head (173Y), a detector (177), and a processor (176). The first sensor head is attached to the tool head. The first sensor head is configured to receive a first laser beam from the laser source, emit the first laser beam as a first measurement laser beam (Mx) toward the first mirror, and receive a first reflected laser beam from the first mirror. The second sensor head is attached to the tool head. The second sensor head is configured to receive a second laser beam from the laser source, emit the second laser beam as a second measurement laser beam (MY) toward the second mirror, and receive a second reflected laser beam from the second mirror. The detector is arranged to detect the first reflected laser beam and the second reflected laser beam. The processor is configured to determine a first position (x) along the first axis and a second position (y) along the second axis of the objective lens relative to the stage based on the first reflected laser beam and the second reflected laser beam.