Photomask Flatness Measurement Using Multi-Angle Interferometry
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Solution Overview
Problem
The accuracy of pattern transfer in semiconductor materials is compromised by deviations in the flatness of photomasks from the ideal plane, leading to errors in physical patterning.
Innovation Solution
A method involving the measurement of photomask flatness at various orientations and tilt angles using interferometers, followed by calculations to determine true flatness by removing gravitational error components, ensuring accurate patterning without induced errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photomask flatness is measured at single orientation and tilt angle, then measurement process is simple, but gravitational errors contaminate the measurement results
Solution Approach 1:
The measurement process is segmented into multiple discrete measurements at different orientations and tilt angles. The photomask is measured at least twice at different orientations (e.g., 0度和90度) and/or different tilt angles, with each measurement providing a separate data point. This segmentation allows gravitational effects to be differentiated and eliminated through subsequent calculations, resolving the contradiction between measurement simplicity and accuracy.
Solution Approach 2:
The measurement approach transitions from a single-point measurement to a multi-dimensional measurement space by introducing orientation and tilt angle as additional dimensions. By measuring at multiple orientations and tilt angles, the system creates a dimensional framework where gravitational errors can be mathematically separated from true flatness, enabling high-precision measurement without complex equipment.
2Reliability
If multiple measurements at different orientations and tilt angles are performed, then gravitational errors can be eliminated, but measurement time and process complexity increase
Solution Approach 1:
The methodology performs preliminary measurements at multiple orientations and tilt angles before final flatness determination. By collecting multiple measurement datasets in advance and storing them for processing, the system eliminates the need for repeated real-time measurements. The preliminary action of gathering multi-angle data enables subsequent mathematical processing to remove gravitational errors, improving reliability while managing measurement time through efficient data collection and processing workflows.
3Manufacturing precision
If gravitational effects are not accounted for, then measurement process is straightforward, but patterning accuracy of semiconductor materials deteriorates
Solution Approach 1:
The patent replaces complex mechanical compensation systems with a mathematical approach. Instead of physically eliminating gravitational effects through complex mechanical adjustments, the system uses mathematical models and calculations to substitute and remove gravitational error components from measurement data. By processing measurements through algorithms that account for gravitational effects at different orientations and tilt angles, the system achieves high patterning accuracy without requiring complex mechanical correction mechanisms.
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 approach provides a gravitationally error-resistant measurement of photomask flatness, enabling accurate patterning of semiconductor materials by accounting for and correcting deviations in flatness, thus preventing errors in the patterned substrate.
Implementation Method 1
measuring a first flatness measurement of the substrate at a first orientation and a first tilt angle, measuring a second flatness measurement of the substrate at the first orientation and a second tilt angle different from the first tilt angle
Data Source
AI summary
A method of determining a flatness of a substrate, the method including measuring a first flatness measurement of the substrate at a first orientation and a first tilt angle, measuring a second flatness measurement of the substrate at the first orientation and a second tilt angle different from the first tilt angle, generating a difference measurement between the first flatness measurement and the second flatness measurement, fitting the difference measurement to an orthogonal polynomial, generating an estimation of error based at least in part on using a scale factor and the difference measurement, the scale factor based on extracting orthogonal factors associated with the orthogonal polynomial, and generating a true flatness of the substrate by removing the estimation of error from the first flatness measurement.