Stage Apparatus Abbe Error Correction via Vertical Scale Measurement
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Solution Overview
Problem
Existing stage apparatuses in charged particle beam systems face challenges in reducing Abbe error and mirror weight, leading to increased costs and positioning errors due to the need for additional interferometers and enlarged mirrors, which also cause vibration and thermal deformation issues.
Innovation Solution
A stage apparatus configuration that includes linear scales at different heights from the laser interferometers' optical axes to measure tilt and correct Abbe error, reducing the need for additional interferometers and minimizing mirror size and weight, while maintaining high field-of-view positioning accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional interferometers are used to measure tilt and correct Abbe error, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The single interferometer is designed to perform multiple functions: both position measurement and tilt measurement. By measuring positions at two different heights and calculating the difference, the system achieves tilt measurement capability without requiring a second interferometer, thus reducing device complexity while maintaining measurement precision
Solution Approach 2:
Instead of using a second interferometer to directly measure tilt, the system creates a virtual copy of the position measurement at a different height. By calculating the position difference between two heights, the tilt information is derived indirectly, avoiding the need for additional expensive and complex interferometer hardware
2Measurement precision
If mirror height is enlarged to accommodate tilt measurement, then measurement capability is improved, but weight of mirror increases
Solution Approach 1:
The system transitions from measuring tilt directly at a single mirror height to measuring positions at two different heights (vertical dimension). This dimensional approach allows tilt calculation without requiring the mirror itself to be taller, maintaining mirror weight while achieving tilt measurement capability through spatial differentiation
3Measurement precision
If two interferometers are laterally arranged for tilt measurement, then tilt measurement accuracy is improved, but length of mirror and table increases
Solution Approach 1:
Instead of arranging measurement points laterally (horizontal dimension), the system places measurement points at different vertical heights. This vertical arrangement enables tilt measurement without increasing the lateral dimensions of the mirror or table, avoiding the associated weight and manufacturing cost increases
4Measurement precision
If mirror size is increased to improve tilt measurement, then measurement precision is improved, but vibration increases
Solution Approach 1:
The system measures positions at two different vertical heights rather than using a larger lateral mirror area. This approach achieves tilt measurement precision without increasing mirror size, thereby avoiding the vibration problems that arise from larger, more massive mirrors
5Stability of the object's composition
If movable mass is increased to support larger mirror, then structural stability is improved, but motor heat generation increases leading to positioning error
Solution Approach 1:
The system achieves tilt measurement capability by measuring at different vertical heights rather than using a larger mirror that would increase movable mass. This keeps the mirror and table dimensions small, reducing movable mass and consequently reducing motor heat generation and thermal deformation while maintaining structural stability
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 configuration effectively reduces Abbe error and mirror weight, improving field-of-view positioning accuracy without increasing the stage's dimensions or movable mass, thus enhancing the overall performance and reducing manufacturing costs.
Implementation Method 1
a laser interferometer is used for position measurement of the stage
Implementation Method 2
a scale element having a scale measurement axis that is parallel to a first measurement axis in the first direction based on the position measurement element and is different from the first measurement axis in height, and measuring the position of the sample table in the first direction
Data Source
AI summary
A stage includes a sample table on which a sample is placed, a first drive mechanism moving the sample table in a first direction; a position measurement element measuring a position in the first direction that is a driving direction of the sample table. The stage also has a scale element having a scale measurement axis that is parallel to a first measurement axis in the first direction based on the position measurement element and is different from the first measurement axis in height, and measuring the position of the sample table in the first direction. A controller calculates the orientation of the sample table by using a measurement value by the position measurement element and a measurement value by the scale element and correcting the Abbe error of the sample table.