Mirror Support Module Thermal Expansion Compensation
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Solution Overview
Problem
Scanning electron microscopes (SEM) experience X-axis and Y-axis distance errors due to thermal expansion differences in materials like the SEM column, mechanical stage, and chuck interface, leading to incorrect beam positioning and false location corrections.
Innovation Solution
A mirror support module with a body made of alloys like Kovar or Invar, featuring internal and external portions, apertures, and intermediate regions that move to reduce aperture area, maintaining stability and minimizing thermal expansion effects on mirror locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the SEM column, mechanical stage, and chuck interface are made of different materials with different thermal expansion coefficients, then each component can be optimized for its specific function, but thermal expansion differences cause X-axis and Y-axis distance errors between mirrors
Solution Approach 1:
A mirror support module is introduced as an intermediary component between the SEM column and the mirrors. This module is made of a material with a thermal expansion coefficient matched to the SEM column, acting as a mediator that absorbs thermal expansion differences and prevents them from affecting mirror positions and distance measurements.
Solution Approach 2:
The patent changes the material parameter (thermal expansion coefficient) of the mirror support module to match the SEM column. By selecting a material whose thermal expansion characteristics align with the SEM column, the system compensates for thermal expansion differences in other components, maintaining measurement accuracy despite temperature variations.
2Stability of the object's composition
If the mirror support module uses a rigid structure, then mirror positions are stable, but thermal expansion of the SEM column cannot be accommodated, leading to distance errors
Solution Approach 1:
The patent changes the material parameter (thermal expansion coefficient) of the mirror support module to match the SEM column. This allows the module to expand and contract with the SEM column during temperature changes, maintaining stable mirror positions relative to the column while accommodating thermal expansion.
Solution Approach 2:
The patent utilizes thermal expansion by selecting a material for the mirror support module that has a thermal expansion coefficient matched to the SEM column. This allows the module to naturally expand and contract with the column during temperature variations, maintaining stable relative positions without requiring active compensation mechanisms.
3Measurement precision
If the mirror support module is made of a material with low thermal expansion coefficient, then thermal expansion effects are minimized, but the material selection becomes more restricted and manufacturing more difficult
Solution Approach 1:
Instead of requiring extremely low thermal expansion coefficients, the patent changes the approach by matching the thermal expansion coefficient of the mirror support module to the SEM column. This uses a more practical parameter range that is easier to manufacture while still achieving the goal of minimizing differential thermal expansion effects.
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 solution significantly reduces X-axis and Y-axis distance errors by keeping mirror positions stable despite SEM column expansion, ensuring accurate beam positioning and reducing errors to tolerable thresholds.
Implementation Method 1
One or more of the SEM column, the mechanical stage, the mechanical couplers and the chuck interface tend to heat during the operation of the SEM. The heating causes the SEM column, the mechanical stage, the mechanical couplers and the chuck interface to expand.
Data Source
AI summary
A mirror support module having a body that includes an internal portion surrounding an inner space, an external portion, an aperture formed in the body and an intermediate region that extends between a segment of the internal portion and the aperture. When the intermediate region is subjected to a force directed in a first direction, the intermediate region can be moved in the first direction towards the aperture to reduce an area of the aperture while the external portion remains stable regardless of movement of the intermediate region.