Capacitive Sensor Position Measurement for Lithography
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Solution Overview
Problem
Existing microlithographic exposure systems face challenges in achieving precise positioning of stage apparatus and imaging optical systems due to non-linear responses of fluid gauges, making calibration and servo-control complex and difficult.
Innovation Solution
The use of analog proximity sensors, such as air gauges, coupled with actuators and controllers, allows for accurate positioning of the sensor at a fixed distance from a known surface, enabling precise measurement of substrate height through known surface positions and position signals, while embodiments like modular air gauges and force actuators ensure repeatable and accurate positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fluid gauges are used for position measurement, then measurement capability is provided, but calibration complexity increases due to non-linear response
Solution Approach 1:
The patent replaces fluid gauges with a capacitive sensor system for position measurement. The capacitive sensor measures displacement through electrical field interaction rather than fluid pressure, providing a linear response that eliminates the calibration complexity associated with non-linear fluid gauge characteristics while maintaining high measurement precision
Solution Approach 2:
The invention changes the measurement parameter from fluid pressure (non-linear) to capacitive coupling (linear). By using the linear relationship between capacitive sensor output and plate displacement, the system achieves accurate position measurement without requiring complex non-linear calibration procedures
2Measurement precision
If fluid gauges with multiple air flows are used, then position measurement is achieved, but control system complexity increases
Solution Approach 1:
The patent extracts the measurement function from the complex multi-flow fluid gauge system and implements it using a single capacitive sensor. This eliminates the need for multiple air flows, mass-flow controllers, and differential pressure sensors, thereby reducing control system complexity while maintaining measurement precision
Solution Approach 2:
The capacitive sensor system is self-regulating through its linear electrical field interaction with the movable plate. The sensor automatically provides accurate position feedback without requiring complex servo-control mechanisms to manage multiple fluid flows, simplifying the overall control architecture
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 high-accuracy and precision in measuring substrate height, reducing complexity in servo-control and improving calibration processes, thereby enhancing the precision of microlithographic exposure systems.
Implementation Method 1
Analog proximity sensors, such as air gauges, coupled with actuators and controllers, allows for accurate positioning of the sensor at a fixed distance from a known surface
Data Source
AI summary
Apparatus are disclosed for measuring the position of an object surface along an axis. An exemplary apparatus has at least one actuator coupled to a fixed member such as a metrology frame. At least one analog proximity sensor is coupled to the at least one actuator. The at least one actuator is controllably operated to position the at least one proximity sensor at a fixed distance along the axis from a surface that is fixed relative to the fixed me+mber. A controller, coupled to the actuator and to the proximity sensor, is configured to compute a position of the object surface along the axis based on a known location of the fixed surface along the axis, the fixed distance from the fixed surface, and position signals from the at least one proximity sensor.