Acousto-Optical Metrology for Substrate Stack Defect Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing metrology methods for substrate stacks face challenges such as the need for wetting with liquids, limited penetration depth of electromagnetic radiation due to metallic components, and time-consuming scanning methods, which are undesirable for precision, cost-effectiveness, and efficiency.
Innovation Solution
A metrology device and method that simultaneously impinges sound waves and electromagnetic waves on a substrate stack, using interference patterns to generate a three-dimensional image for defect detection, eliminating the need for liquid and enabling non-destructive, rapid, and precise measurements without scanning the entire surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acoustic measurement methods are used with liquid coupling, then sound signal coupling is achieved, but the substrate stack must be dried after measurement and liquid can penetrate substrate interfaces
Solution Approach 1:
The patent introduces a coupling medium that acoustically couples the sound source to the substrate stack without requiring direct liquid contact with the substrate surfaces. This intermediary medium enables effective acoustic coupling while preventing liquid penetration into substrate interfaces and eliminating drying requirements.
Solution Approach 2:
The patent replaces the traditional liquid immersion method with an alternative acoustic coupling mechanism that does not require the substrate stack to be submerged in liquid. This substitution eliminates the harmful effects of liquid while maintaining effective sound signal coupling for defect detection.
2Ease of operation
If electromagnetic radiation is used for measurement, then non-contact measurement is achieved, but penetration depth is limited by metallic components with high absorption
Solution Approach 1:
The patent changes the measurement parameter from electromagnetic radiation to acoustic waves. Acoustic waves have different interaction characteristics with metallic components, allowing them to penetrate deeper into substrate stacks and provide measurement information from greater depths without being strongly absorbed by metals.
3Measurement precision
If scanning methods are used with focused beams, then measurement precision is improved, but the substrate stack must move relative to the beam which is extremely time-consuming
Solution Approach 1:
The patent inverts the traditional scanning approach by keeping the measurement beam stationary and broadened to cover the entire substrate surface, while using acoustic wave propagation and interference patterns to obtain measurement information from all points simultaneously. This eliminates the need for mechanical scanning and relative movement between the beam and substrate.
Solution Approach 2:
The patent transitions from one-dimensional scanning (point-by-point measurement) to two-dimensional simultaneous measurement by broadening the beam and using acoustic interference patterns. This dimensional change allows parallel measurement of the entire substrate surface, dramatically increasing measurement speed while maintaining precision through interference-based detection.
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
Enables quick, dry, and precise measurement of substrate stacks with high reliability and reduced costs, overcoming limitations of traditional methods by using acousto-optical interference to identify defects across the entire substrate surface.
Implementation Method 1
a sound wave is coupled, in particular over the entire surface, onto a first substrate stack surface
Implementation Method 2
The sound waves generated propagate through the substrate stack to the second substrate stack surface, the substrate stack measurement surface, opposite the first substrate stack surface
Implementation Method 3
Electromagnetic beams are introduced into the substrate stack and their reflection is measured
Implementation Method 4
creating interference with the first beam path. In other words, the invention teaches in particular a system and a method for generating a three-dimensional image of a substrate stack by (ultra) sound excitation and interference measurement
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3
AI summary
The invention relates to a metrological device for examining a substrate, in particular a substrate stack (14), having the following features: sound application means for applying sound waves to a first substrate stack surface () of the substrate, in particular the substrate stack (14), an optical system having a) a source for emitting electromagnetic radiation, which is divided into at least a first beam path and a second beam path, b) means for applying the first beam path to a substrate stack measurement surface (14m) of the substrate, in particular the substrate stack (14), c) interference means for forming interference radiation from the first and second beam paths, and d) a detector (5) for sensing the interference radiation, evaluating means for evaluating the interference radiation sensed at the detector (5). The invention further relates to a metrological method for examining a bonded substrate, in particular a substrate stack (14), having the following steps, in particular the following sequence: applying sound waves to a first substrate stack surface () of the substrate, in particular the substrate stack (14), applying a first beam path of electromagnetic radiation emitted from a source to a substrate stack measurement surface (14m) of the sound-wave-loaded substrate, in particular substrate stack (14), forming interference radiation from the first and second beam paths of the electromagnetic radiation, sensing the interference radiation at a detector (5), evaluating the interference radiation sensed at the detector.