Image Capture Position Correction for Sample Thermal Expansion
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Solution Overview
Problem
Existing image capturing apparatuses struggle to accurately capture images of highly integrated circuit patterns due to poor field-of-view position accuracy, particularly when thermal expansion by the sample itself is not considered, leading to position errors and reduced throughput.
Innovation Solution
An image capturing apparatus and method that includes a temperature sensor, a chuck with a back surface secured to a table, a column for capturing images, a mirror, a laser interferometer, and a control unit to calculate and correct for thermal expansion by both the table and the sample, ensuring precise image capturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If image capturing is performed twice to correct position deviation, then position accuracy is improved, but throughput decreases
Solution Approach 1:
The patent applies preliminary action by calculating and correcting for thermal expansion effects before performing image capturing. The system predicts position deviations caused by thermal expansion of the stage and sample based on temperature measurements, and pre-adjusts the image capturing position to compensate for these deviations. This eliminates the need for a second image capturing pass, thereby maintaining high throughput while achieving accurate positioning.
2Manufacturing precision
If field-of-view range is narrowed for high magnification, then manufacturing precision is improved, but field-of-view position accuracy becomes more critical
Solution Approach 1:
The patent implements feedback by continuously monitoring the temperature of the stage and sample using temperature sensors, and using this information to dynamically calculate and correct for thermal expansion effects. The system measures actual temperature conditions, computes the resulting position deviations, and adjusts the image capturing position accordingly. This closed-loop feedback mechanism ensures high field-of-view position accuracy even when operating at high magnification with narrow field-of-view ranges.
3Device complexity
If thermal expansion by sample is not considered, then device complexity is reduced, but position accuracy deteriorates
Solution Approach 1:
The patent applies parameter changes by incorporating temperature as a key parameter in the position correction calculation. The system measures temperature changes in the stage and sample, and uses these temperature parameters to calculate thermal expansion effects. By adding temperature measurement and thermal expansion calculation to the correction model, the system achieves high position accuracy without excessive complexity, as the calculation uses straightforward thermal expansion formulas based on measured temperature data.
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 enables accurate image capturing of samples despite thermal expansion, improving position accuracy and enabling high-throughput inspection by correcting for thermal expansion, thereby ensuring precise alignment and efficient image capture.
Implementation Method 1
a laser interferometer that emits laser light onto the mirror and measures a distance to the mirror
Implementation Method 2
there is the spread or dissipation of heat due to radiant heat transfer or heat conduction by a solid... the temperature distribution changes and thermal deformation in conjunction therewith arises
Data Source
AI summary
[Object]To provide an image capturing apparatus and an image capturing method that can accurately capture an image of a sample irrespective of the presence or absence of thermal expansion by the sample.[Solving Means]An image capturing apparatus includes a table, a chuck having a back surface secured to the table and a front surface for holding a sample under suction, a temperature sensor that obtains a temperature of the chuck, a column that captures an image of the sample mounted on the chuck, a mirror provided on the table, a laser interferometer that emits laser light onto the mirror and measures a distance to the mirror, and a control unit that calculates an amount of position correction for an image capturing location on the basis of the temperature of the chuck. The control unit calculates a temperature of the table on the basis of the temperature of the chuck, calculates an amount of thermal expansion by the table on the basis of the temperature of the table, calculates an amount of thermal expansion by the sample on the basis of the temperature of the chuck, and calculates the amount of position correction for the image capturing location on the basis of the amount of thermal expansion by the table and the amount of thermal expansion by the sample.