Semiconductor Crack Detection via Edge Light Scattering
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Solution Overview
Problem
Existing methods for detecting cracks in semiconductor substrates face challenges such as mechanical stress and strong background signals, making them inefficient for accurate crack detection.
Innovation Solution
A method and apparatus that utilize infrared light directed along the edges of semiconductor substrates, where the light is partially transmitted and reflected, allowing an imaging optical detector to capture scattered light from cracks, thereby avoiding total reflection and reducing background noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical methods are used to detect cracks by comparing resonant frequencies, then crack detection is achieved, but mechanical stress may cause breaking of even intact wafers
Solution Approach 1:
The patent replaces mechanical detection methods with optical methods. Instead of using mechanical excitation and resonant frequency comparison, the invention uses light sources to illuminate the wafer and optical detectors to capture reflected light patterns, thereby detecting cracks without applying mechanical stress to the substrate
Solution Approach 2:
The patent introduces light as an intermediary between the detection system and the wafer. Light serves as a non-contact probe that interacts with the wafer surface and cracks, carrying information about crack locations to the optical detector without physically touching or stressing the substrate
2Measurement precision
If optical methods with backlight arrangement are used, then crack detection is possible, but the crack must extend through the wafer or be deep enough for light penetration
Solution Approach 1:
Instead of shining light through the wafer from the back (transmission mode), the patent inverts the approach by illuminating from the front surface and detecting reflected light. This reflection-mode approach allows detection of cracks that do not extend through the entire wafer thickness, as the light interacts with cracks near the surface and reflects back to the detector
Solution Approach 2:
The patent changes the detection dimension from transmission (through-thickness) to reflection (surface-level). By detecting light reflected from the front surface, the system can identify cracks at various depths without requiring complete light penetration through the wafer, thus expanding the detectable crack depth range
3Measurement precision
If bright-field observation is used with light transmission through the wafer, then the wafer can be optically analyzed, but the transmittance variation signal is superimposed by a much stronger background signal
Solution Approach 1:
The patent extracts only the reflected light component from the optical interaction, excluding the transmitted light that creates the strong background signal. By using optical filters and detection geometry that selectively capture reflected light at specific angles, the system isolates the crack-related signal from the overwhelming transmitted light background
Solution Approach 2:
The patent applies local quality by using optical filters and detection geometry tailored to capture only the reflected light component. The detection system is optimized to respond specifically to light reflected from crack sites, while ignoring the transmitted light that would otherwise create a strong background signal
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 high signal-to-noise ratio, enabling quick and accurate detection of cracks with minimal mechanical stress and background interference, suitable for inspecting semiconductor wafers and solar cells.
Implementation Method 1
the electromagnetic radiation is directed from its point of incidence at the edge surface for at least half the distance to the opposite point of the edge surface by reflection at the faces
Implementation Method 2
radiation is detected by means of an imaging optical detector which is sensitive to the introduced electromagnetic radiation, preferably the introduced light, which is scattered by a crack and exits from one of the faces at the crack site
Data Source
AI summary
A method and an apparatus for detecting cracks in semiconductor substrates, such as silicon wafers and solar cells, are provided. The method and apparatus are based on the detection of light deflected at a crack.