Bright Field Optical Inspection for Semiconductor Defect Detection
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Solution Overview
Problem
Current methods for inspecting semiconductor substrates are inefficient and costly, as they often require destructive or time-consuming techniques to detect internal defects like cracks and bumps, which can lead to field failures and significant financial losses.
Innovation Solution
A system and method utilizing a partially blocking bright field unit and a non-blocking bright field unit for automated optical inspection, which includes optical components like aperture stops and a spatial light modulator to block or pass specular reflections, enabling fast, cost-effective, and non-destructive detection of internal defects within the numerical aperture of bright-field optical and imaging channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If expensive methods like X-Ray light imaging, IR or UV light imaging, or SEM sampling are used to detect internal defects, then measurement precision is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent replaces complex mechanical and expensive imaging systems (X-Ray, IR, UV, SEM) with a simplified optical inspection system using visible light and a camera. The key substitution is using a rotating aperture stop mechanism instead of expensive fixed imaging equipment, achieving comparable or superior detection capability with simpler, more versatile equipment.
Solution Approach 2:
The patent introduces dynamic elements by using a rotating aperture stop that changes the numerical aperture (NA) of the optical system during inspection. This dynamic adjustment allows the same optical system to detect different types of defects (internal cracks, bumps, voids) by varying the NA, replacing the need for multiple fixed systems.
2Reliability
If destructive or time-consuming inspection methods are used, then reliability of defect detection is improved, but productivity decreases
Solution Approach 1:
The patent replaces destructive physical sampling (SEM cross-sections) and time-consuming imaging methods with a rapid optical inspection system that provides real-time defect detection without damaging the substrate, thereby maintaining high reliability while dramatically improving throughput.
Solution Approach 2:
The inspection system operates continuously by rotating the aperture stop to different NA settings during a single pass over the substrate, eliminating the need for multiple separate inspection steps and enabling uninterrupted high-speed defect detection.
3Ease of operation
If regular AOI techniques are used, then ease of operation is maintained, but measurement precision deteriorates as inside layers' defects become invisible
Solution Approach 1:
The patent enhances regular AOI by dynamically adjusting the numerical aperture through a rotating aperture stop, allowing the same easy-to-operate system to detect internal defects that would otherwise be invisible with fixed NA optics, thus improving precision without sacrificing ease of use.
Solution Approach 2:
The system changes the optical parameter (numerical aperture) dynamically during inspection, allowing detection of different defect types at different NA settings. This parameter variation enables the detection of internal cracks, bumps, and voids that are invisible with conventional fixed-NA AOI systems.
4Reliability
If multiple inspection methods are used to detect all hidden defects, then reliability is improved, but loss of time increases
Solution Approach 1:
The patent creates a universal inspection system where a single optical setup with a rotating aperture stop can detect multiple types of defects (internal cracks, bumps, voids) that would otherwise require multiple specialized inspection methods, achieving comprehensive detection in one pass.
Solution Approach 2:
The patent merges multiple inspection functions into a single system by combining different NA settings in one rotating aperture stop mechanism, allowing the detection of various defect types that would normally require separate inspection procedures to be performed simultaneously.
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 allows for high-throughput, non-destructive detection of internal defects, reducing the risk of field failures and improving the reliability of semiconductor substrates by identifying cracks and bumps without the need for expensive or time-consuming methods.
Implementation Method 1
a partially blocking bright field unit and a non-blocking bright field unit for automated optical inspection, which includes optical components like aperture stops and a spatial light modulator to block or pass specular reflections
Implementation Method 2
optical components like aperture stops and a spatial light modulator to block or pass specular reflections
Data Source
AI summary
An inspection system for inspecting a semiconductor substrate, the inspection system may include an inspection unit that comprises a partially blocking bright field unit and a non-blocking bright field unit; wherein the partially blocking bright field unit is configured to block any specular reflection that fulfills the following: (a) the specular reflection is caused by illuminating, along a first axis, of an area of the wafer, (b) the specular reflection propagates along a second axis, (c) the first axis and the second axis are symmetrical about a normal to the area of the wafer, and (d) the normal is parallel to an optical axis of the partially blocking bright field unit; and wherein the non-blocking bright field unit is configured to pass to the image plane any specular reflection that fulfills the following: (a) the specular reflection is caused by illuminating, along the first axis, of an area of the wafer, (b) the specular reflection propagates along the second axis, (c) the first axis and the second axis are symmetrical about the normal, and (d) the normal is parallel to the optical axis of the partially blocking bright field unit.