Bonded Wafer Overlay Measurement Using AOI Brightness Patterns
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Solution Overview
Problem
Current methods for monitoring wafer bonding shift in 3DIC structures rely on visual inspection, which is inaccurate and time-consuming, hindering productivity.
Innovation Solution
A method using automatic optical inspection (AOI) to measure overlay shift by aligning and bonding wafers with specific patterns, allowing precise measurement through optical detection of brightness changes to determine shifting amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If visual inspection from naked-eye is used to monitor wafer bonding shift, then the measurement process is simple, but the measurement accuracy is rough and productivity is slow
Solution Approach 1:
The patent replaces the mechanical/visual inspection system with an optical measurement system. Specifically, it uses scatterometry techniques where light is directed at the measurement pattern on the bonded wafer, and the scattered light intensity is analyzed to determine overlay shift. This substitution of optical detection for visual inspection simultaneously improves measurement precision and enables automated high-throughput measurement, resolving the contradiction between accuracy and productivity.
Solution Approach 2:
The patent introduces a measurement pattern as an intermediary element between the wafer bonding process and the measurement system. This pattern includes specific structures (such as mandrels and openings) that modulate light scattering in a way that encodes overlay shift information. The intermediary measurement pattern enables precise, automated optical detection without requiring direct visual inspection of the actual device features, thereby improving both accuracy and throughput.
2Measurement precision
If visual inspection method is used, then the device complexity is low, but the measurement accuracy is insufficient
Solution Approach 1:
The patent replaces simple visual inspection with a sophisticated optical measurement system based on scatterometry. The system includes light sources, optical paths with mirrors and lenses, detectors for measuring scattered light intensity, and processing systems for analyzing the data. This increased device complexity enables precise, automated measurement of overlay shift by analyzing light scattering patterns from the measurement structures, thereby achieving high measurement accuracy.
Solution Approach 2:
The patent measures overlay shift indirectly through optical scattering characteristics rather than direct spatial measurement. By analyzing the intensity of scattered light at different angles and wavelengths, the system extracts overlay shift information from the optical domain, adding a dimensional approach that enables precise measurement without requiring complex mechanical positioning or direct imaging systems.
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 accurate and efficient measurement of overlay shift, improving productivity by automating the process and reducing manual errors, ensuring high throughput and quality control.
Implementation Method 1
measuring a measurement pattern including a top wafer pattern and a bottom wafer pattern... optical detection of brightness changes
Data Source
AI summary
A measurement pattern for monitoring overlay shift of bonded wafers includes a top wafer pattern and a bottom wafer pattern. The top wafer pattern includes a first portion with a width Wx1 measured along a first axis. The bottom wafer pattern includes a first part with a width Wx2 measured along the first axis, wherein the first portion of the top wafer pattern and the first part of the bottom wafer pattern are separated by a target distance Dx, and wherein the measurement pattern satisfies the following measurement formulas:Tx>Dx-Sx;Tx<Dx-Sx+Wx2;Tx>Sx;Tx<Dx-Sx+Wx1;wherein, Tx represents a searching distance for finding an end-point of the first portion or an end-point of the first part; and Sx represents an actual shifting amount of the first portion.