Piezo Stage Waveform Correction for Speed Stability
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Solution Overview
Problem
Conventional stage mechanisms in scanning electron microscopes suffer from low speed stability, leading to inaccuracies in positioning and operability issues when observing fine patterns, as they rely on stepping motors that cause backlash and elastic deformation, making precise and constant-speed movement challenging.
Innovation Solution
A stage apparatus with a drive unit driven by a waveform generation unit that outputs corrected voltage signals to maintain constant speed, using a walking-type piezo motor with correction data to adjust command voltage values and timing, ensuring high accuracy and stability by reducing speed fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a stepping motor with ball screw and nut is used to drive the stage, then the stage can be positioned with high accuracy, but backlash and elastic deformation occur causing speed instability and positioning errors
Solution Approach 1:
The patent replaces the conventional stepping motor and ball screw mechanical transmission system with a piezoelectric element-based direct drive system. The piezoelectric element converts electrical signals directly to mechanical displacement, eliminating the ball screw and nut mechanism that causes backlash and elastic deformation. This substitution resolves the contradiction by providing both high positioning accuracy and stable speed control without mechanical transmission errors.
Solution Approach 2:
The patent introduces a piezoelectric element as an intermediary between the electrical control system and the mechanical stage. This piezoelectric mediator directly couples the electrical drive signal to the stage movement, eliminating the need for mechanical transmission components. The intermediary piezoelectric element provides precise control while avoiding the backlash and elastic deformation problems of conventional mechanical systems.
2Productivity
If the stage is moved at high speed to improve observation efficiency, then productivity increases, but positioning accuracy and speed stability deteriorate
Solution Approach 1:
The patent employs dynamic control of the piezoelectric element through waveform generation units that can adjust drive parameters in real-time. The system dynamically adapts the drive waveform to maintain stable stage movement at various speeds, ensuring both high productivity and positioning accuracy. The dynamic control capability allows the stage to move efficiently while maintaining precision through electronic adjustment rather than mechanical means.
Solution Approach 2:
The patent changes the electrical drive parameters (voltage waveform, frequency, amplitude) of the piezoelectric element to optimize stage movement characteristics. By adjusting these parameters, the system achieves both high-speed operation for improved productivity and precise positioning control. The ability to modify drive parameters electronically allows simultaneous optimization of speed and accuracy without the compromises required by mechanical systems.
3Stability of the object's composition
If correction data is applied to adjust command voltage values and timing, then speed stability and positioning accuracy improve, but device complexity increases
Solution Approach 1:
The patent applies correction data in advance to pre-adjust the drive waveform parameters before actual stage movement. The waveform generation unit uses stored correction data to modify command voltage values and timing proactively, compensating for known system characteristics. This preliminary correction approach improves speed stability and positioning accuracy while avoiding the need for complex real-time feedback control systems.
Solution Approach 2:
The system performs self-correction by incorporating correction data into the drive waveform generation process. The waveform generation unit automatically adjusts command parameters based on pre-determined correction values, enabling the system to self-compensate for inaccuracies without external intervention or complex additional control mechanisms. This self-service approach enhances stability while keeping the control system relatively simple.
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 stage apparatus achieves high speed stability and accurate positioning, reducing the likelihood of overlooking details during observation, thereby enhancing operability and precision in high-magnification observations.
Implementation Method 1
a piezoelectric element is pressed against a drive transmission surface provided to a lower surface of the stage, and accordingly, the drive transmission surface is linearly moved in the direction of movement of the stage with use of the shearing deformation of the piezoelectric element when a power voltage is applied
Data Source
AI summary
In order to provide a stage apparatus with high speed stability in addition to being able to achieve positioning with a high degree of accuracy, and a sample observation apparatus, such as an optical microscope and a scanning electron microscope, including the stage apparatus, the stage apparatus and the sample observation apparatus of the present invention correct a command voltage value of standard waveform data or an output timing of a command voltage value such that a difference between a first time history response and a second time history response is reduced to zero, the first time history response for displacement or speed when the stage mechanism is driven with use of the standard waveform data showing the command voltage value at each predetermined time and the second time history response for displacement or speed when a speed of the stage mechanism is constant, to be set as drive waveform data to be outputted to a drive unit of the stage mechanism.