Multi-Wavelength Interference Die Defect Detection
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Solution Overview
Problem
Conventional apparatuses for die defect detection in Wafer Level Packaging (WLP) face challenges with low accuracy and efficiency in inspecting three-dimensional surface characteristics such as bump height, RDL thickness, and TSV depth, which are crucial for high-yield chip fabrication.
Innovation Solution
An apparatus and method utilizing a light source emitting at least two wavelengths, with a beam splitter to create a detection beam and a reference beam that form interference signals on a detection unit, allowing for precise 3D measurement by analyzing interference fringes, and optionally employing multiple detectors and a reflective element inclined at an angle to enhance signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional 3D die measurement apparatuses are used, then the inspection process is simple, but the measurement precision and efficiency are low
Solution Approach 1:
The patent employs periodic action by using multiple wavelengths of light (λ1, λ2, λ3) sequentially or in combination to illuminate the die surface. Each wavelength generates interference patterns that are detected and processed to extract 3D surface information. This periodic illumination approach enables precise measurement of bump height, RDL thickness, and TSV depth while maintaining high inspection efficiency through the use of superpixels that process multiple pixels together for faster data acquisition
Solution Approach 2:
The patent applies parameter changes by varying the wavelength parameter of the light source to achieve different measurement objectives. The shorter wavelength (λ1) provides high-resolution surface topology information, while the longer wavelengths (λ2, λ3) provide broader measurement range for 3D characteristics. By changing the wavelength parameter, the system optimizes both measurement precision and efficiency for different defect detection requirements
2Measurement precision
If multiple wavelengths are used for 3D measurement, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent merges multiple wavelengths of light into a single optical path using beam splitters and combiners. The light source unit generates multiple wavelengths (λ1, λ2, λ3) that are combined and directed onto the die surface through a unified optical system. The detection unit receives all wavelength components and processes them together using superpixel algorithms, thereby reducing optical system complexity while maintaining high measurement precision
Solution Approach 2:
The detection unit is designed with multi-functionality to handle multiple wavelengths simultaneously. The same detector and processing unit can analyze interference patterns from different wavelengths to extract various 3D surface characteristics. This universal approach eliminates the need for separate detection systems for each wavelength, reducing device complexity while achieving precise 3D measurement
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 improved accuracy and efficiency in 3D die defect detection, suitable for large dies, by determining defect parameters based on interference signals, thus addressing the limitations of conventional systems.
Implementation Method 1
the reference beam crosses the detection beam at an angle and thus forming interference signals on a sensing surface of the detection unit
Data Source
AI summary
An apparatus and method for die defect detection are disclosed. The apparatus includes: a light source unit (10) for emitting light of at least two wavelengths; a beam splitter (40) for receiving the light emitted by the light source unit (10) and splitting it into a first portion and a second portion, the first portion of the light reflected by a die (60) surface under inspection and thereby forming a detection beam; a reference unit (70) for receiving the second portion of the light and processing it into a reference beam; and a detection unit (90) for receiving the detection beam and the reference beam. The reference beam crosses the detection beam at an angle and thus produces interference fringes on a sensing surface of the detection unit (90), based on which a defect parameter of the die (60) surface under inspection is determined. This apparatus is capable of measuring a die with improved accuracy and efficiency and is suitable for the measurement of large dies.