Bump Height Measurement Across Partially Transparent Layers
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Solution Overview
Problem
Existing visual light-based triangulation methods fail to accurately measure the height difference between the top of bumps and the upper surface of partially transparent top layers due to virtual penetration depth uncertainties, leading to unreliable measurements.
Innovation Solution
A method and system that combines white light triangulation with interferometry to measure height differences, using first and second radiation types, where the second radiation does not penetrate the top layer, allowing for correction of measurement errors through extrapolation and radial-based estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If visual light based triangulation is used to measure bump height, then measurement speed is improved, but measurement precision deteriorates due to virtual penetration depth uncertainty
Solution Approach 1:
The patent introduces a reference surface (the top layer upper surface) as an intermediary element to establish a known reference plane. By measuring the virtual penetration depth at this reference surface where no bump exists, the system creates a baseline for correction. This intermediary reference allows the triangulation method to maintain high speed while achieving accurate bump height measurements through differential measurement and error compensation.
Solution Approach 2:
The patent replaces the direct mechanical/optical measurement of bump height with a substitution approach: instead of directly measuring the absolute height, the system measures the difference between the bump height and the reference surface height, both affected equally by virtual penetration. This substitution of measurement strategy eliminates the penetration depth uncertainty from the final calculation, maintaining speed while improving precision.
2Measurement precision
If second radiation that does not penetrate the layer is used for measurement, then measurement precision is improved, but measurement time increases
Solution Approach 1:
The patent applies partial action by using the second radiation type (interferometry) only on a subset of measurement points - specifically the reference surface and select control points - rather than all measurement points. The majority of bump height measurements continue to use the faster first radiation type (triangulation). This partial application of the more precise but slower method achieves sufficient precision while maintaining overall measurement efficiency.
Solution Approach 2:
The patent performs preliminary measurements using the second radiation type to establish the reference surface height and characterize the virtual penetration depth before conducting the main batch of measurements. This preliminary action with the slower, more precise method creates correction data that enables the faster first radiation method to achieve accurate results for all subsequent measurements, reducing total measurement time.
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
Provides accurate and efficient measurement of bump height differences by correcting for virtual penetration errors, achieving precise results with a balanced trade-off between speed and accuracy.
Implementation Method 1
performing first measurements of the height differences between the bumps and the corresponding areas, by illuminating the bumps and the corresponding areas with first radiation
Implementation Method 2
Visual light based triangulation may scan the bumps and the top layer to provide height measurements
Implementation Method 3
The light changes its propagation angle when entering the top layer—due to a difference between the refraction index of the air and the refraction index of the top layer
Implementation Method 4
preforming second measurements of height differences between a subgroup of the bumps and a subgroup of the corresponding areas, by illuminating the subgroup of the bumps and the subgroup of the corresponding areas with second radiation that does not penetrate the layer
Data Source
AI summary
A method and system for measuring bump height differences. The method comprises performing first measurements of height differences between bumps and corresponding areas of an upper surface of a layer, by illuminating the bumps and the corresponding areas with a first radiation. The method includes preforming second measurements of height differences between a subgroup of the bumps and a subgroup of the corresponding areas, by illuminating the subgroup of the bumps and the subgroup of the corresponding areas with a second radiation. The method further comprises determining first measurement errors, based on the first measurements and the second measurements, and determining the height differences between the bumps and the corresponding areas based on the first measurements and the first measurements errors.