Actuator Capacitance Measurement via Mechanical Coupling
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Solution Overview
Problem
In projection exposure apparatuses for semiconductor lithography, especially those using EUV and DUV systems, there is a lack of effective sensors to determine the topography of optically active surfaces due to limited installation space, leading to undetectable changes in actuator relationships and potential defects, which are difficult to diagnose using existing methods like impedance spectroscopy.
Innovation Solution
A method involving mechanically coupled piezoelectric or electrostrictive actuators, where one actuator is driven with a constant control signal, causing deflection in another, allowing capacitance changes to be measured, enabling conclusions about the mechanical coupling and integrity of the actuators, and potentially identifying defects by comparing capacitance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If no sensors are installed on the actuators due to limited installation space, then the device complexity is reduced, but the measurement precision and reliability of actuator monitoring deteriorates
Solution Approach 1:
The patent uses a capacitor as an intermediary element to indirectly measure actuator deflection. Instead of directly measuring the actuator surface topography with sensors, the capacitor's capacitance changes in response to actuator deflection, providing an indirect but accurate measurement method that avoids installation space constraints
Solution Approach 2:
The patent replaces direct mechanical/optical sensing systems with an electrical capacitance measurement system. By measuring the electrical property (capacitance) that changes with mechanical deflection, the system achieves measurement without requiring physical sensors on the actuator surface
2Device complexity
If actuators are driven in an open control loop without sensors, then the device complexity is reduced, but the reliability of detecting actuator defects and relationship changes deteriorates
Solution Approach 1:
The patent implements a feedback mechanism by continuously monitoring capacitance changes of the actuator. This capacitance information provides feedback about the actuator's actual state, enabling detection of defects and relationship changes while maintaining relatively simple control system architecture
Solution Approach 2:
The actuator itself serves its own measurement function through its capacitive properties. The actuator's electrical characteristics inherently provide information about its mechanical state, eliminating the need for separate dedicated sensing systems
3Measurement precision
If impedance spectroscopy is used to measure actuators, then the measurement precision is improved, but the ease of manufacture and device complexity worsens due to high cost and technical difficulty
Solution Approach 1:
The patent employs a simple, inexpensive capacitor-based measurement approach instead of complex impedance spectroscopy equipment. The capacitance measurement system is much easier to manufacture and implement, providing adequate measurement precision without the high costs and technical complexities of impedance spectroscopy
Solution Approach 2:
The patent measures a different electrical parameter (capacitance) compared to impedance spectroscopy. By focusing on capacitance changes rather than full impedance spectrum analysis, the system achieves sufficient measurement precision with simpler, more manufacturable equipment
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 method provides a means to accurately assess the condition and performance of actuators, improving the detection of defects and mechanical coupling, thereby enhancing the reliability of actuator operations in projection exposure apparatuses, with the ability to measure capacitance with high resolution and account for temperature influences.
Implementation Method 1
mechanically coupled piezoelectric or electrostrictive actuators
Implementation Method 2
mechanically coupled piezoelectric or electrostrictive actuators
Implementation Method 3
determining the change in capacitance of the further actuator
Data Source
AI summary
A method for measuring an actuator in a projection exposure apparatus for semiconductor lithography, comprises: driving and deflecting a first actuator with a constant control signal; deflecting a further actuator by way of the mechanical coupling; and determining the capacitance of the further actuator, which was deflected by way of the coupling. A projection exposure apparatus for semiconductor lithography comprises a control device and a measuring device, wherein the measuring device is configured to determine the capacitance of at least one actuator in the projection exposure apparatus.