Shear-Mode Piezoelectric Sensor for Lithographic Positioning
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Solution Overview
Problem
Current strain and acceleration sensors in lithographic apparatuses lack sufficient resolution and are sensitive to temperature and electromagnetic interference, affecting the accuracy of object positioning in high-speed applications.
Innovation Solution
A sensor comprising two shear-mode piezoelectric transducers with opposite polarization subtransducers and read-out electronics, including a charge amplifier with a feedback circuit, is used to reduce electromagnetic interference and enhance resolution, with a beam structure for additional stiffness and low thermal expansion materials to minimize thermal effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current strain and acceleration sensors are used in lithographic apparatuses, then the apparatus can perform basic positioning functions, but the sensors lack sufficient resolution and are sensitive to temperature and electromagnetic interference
Solution Approach 1:
The sensor is divided into multiple piezoelectric subtransducers arranged in a stack configuration. Each subtransducer contributes to the overall measurement capability, and the segmented structure allows for differential measurements that cancel out temperature and electromagnetic interference effects while maintaining high resolution strain and acceleration measurements.
Solution Approach 2:
The patent changes the physical parameters of the sensor by using piezoelectric materials with specific properties and configuring them in a stack arrangement. This parameter change enables the sensor to achieve higher resolution and reduced sensitivity to environmental factors compared to conventional sensor designs.
2Speed
If increasing accelerations are applied to objects to be positioned for increased speed, then positioning speed improves, but larger deformations of the objects occur which negatively impact position accuracy
Solution Approach 1:
The patent replaces conventional mechanical strain and acceleration sensors with piezoelectric transducers that convert mechanical deformation directly into electrical signals. This substitution enables high-speed measurements of both strain and acceleration, allowing the system to maintain position accuracy even when objects undergo large deformations during high-speed positioning.
Solution Approach 2:
The piezoelectric transducers act as intermediaries between the mechanical deformation of the object and the electrical measurement system. They provide a direct coupling that enables real-time measurement of deformation and acceleration, allowing the control system to compensate for positioning errors caused by object deformations during high-speed operation.
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 sensor provides improved resolution and reduced sensitivity to temperature and electromagnetic interference, enabling more accurate object positioning and deformation measurement in high-speed applications.
Implementation Method 1
two shear-mode piezoelectric transducers, wherein each piezoelectric transducer comprises a bottom surface and a top surface
Implementation Method 2
adjacent subtransducers have an opposite polarization so that a varying electromagnetic field has an opposite effect in the adjacent subtransducers
Data Source
AI summary
A sensor includes two shear-mode piezoelectric transducers, wherein each piezoelectric transducer has a bottom surface and a top surface, wherein the top surfaces of the piezoelectric transducers are rigidly connected to each other, and wherein the bottom surfaces of the piezoelectric transducers are configured to be attached to an object to be measured.