Multi-Wavelength Substrate Inspection for Depth-Resolved Defects
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Solution Overview
Problem
Existing substrate inspection technologies struggle to effectively detect defects at various depths within substrates using near-infrared nanosecond laser light, particularly in detecting particle contamination and damage in thin films.
Innovation Solution
A substrate inspection apparatus employing multiple illumination light sources with different wavelengths, including a first illumination light source providing light at a first depth and a second illumination light source providing light at a shallower depth, combined with a holographic phase pattern to increase focal depth and a digital delay pulse generator to enhance bandwidth, allowing for defect detection at multiple depths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single near-infrared nanosecond laser light source is used for substrate inspection, then the inspection system is simple, but it cannot effectively detect defects at various depths within the substrate
Solution Approach 1:
The illumination system is segmented into multiple independent laser light sources, each operating at different wavelengths. The first light source uses near-infrared nanosecond laser (e.g., 910 nm) for deep substrate inspection, while the second light source uses shorter wavelength laser (e.g., 800 nm) for shallow depth inspection. This segmentation allows each light source to target specific depth ranges, resolving the contradiction between detection capability and system simplicity.
Solution Approach 2:
The system changes the wavelength parameter of the illumination light to achieve different penetration depths. By using near-infrared nanosecond laser with longer wavelength for deeper penetration and shorter wavelength laser for shallower inspection, the system optimizes defect detection at various depths without requiring complex single-source solutions.
2Measurement precision
If multiple illumination light sources with different wavelengths are used to detect defects at various depths, then defect detection accuracy is improved, but the device complexity increases
Solution Approach 1:
Multiple laser light sources with different wavelengths are merged into a single inspection system, sharing common optical components such as the objective lens, beam splitter, and image sensor. This merging approach enables depth-resolved defect detection while minimizing the increase in overall system complexity by consolidating redundant components.
Solution Approach 2:
The inspection system is designed with multi-functionality, where a single optical path and image sensor can handle multiple wavelengths simultaneously. The beam splitter and optical components are configured to process both near-infrared and shorter wavelength light through the same pathway, allowing one system to perform multiple inspection functions at different depths.
3Length of stationary object
If near-infrared nanosecond laser light is used for deep substrate inspection, then penetration depth is improved, but the ability to detect shallow defects is reduced
Solution Approach 1:
The inspection depths are segmented into different ranges by assigning specific wavelength ranges to specific light sources. The near-infrared nanosecond laser (910 nm) is dedicated to deep substrate inspection, while the shorter wavelength laser (800 nm) is dedicated to shallow defect detection. This segmentation ensures optimal performance in both deep and shallow inspection without compromise.
Solution Approach 2:
The wavelength parameter of the illumination light is changed to control penetration depth. Longer wavelength near-infrared light is used for deeper penetration into the substrate, while shorter wavelength light is used for shallower inspection. This parameter change allows the system to optimize detection capability for different depth ranges by selecting appropriate wavelengths.
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 comprehensive detection of defects such as fume spouts, bridges, and voids in 3D NAND flash memory devices by distinguishing and measuring defects at different depths, enhancing the accuracy and depth penetration of defect detection.
Implementation Method 1
near-infrared nanosecond laser light has been widely employed as illumination for industrial semiconductor inspection apparatus
Implementation Method 2
playing a crucial role in inspection applications based on the thickness of a substrate and the thin film deposited on it
Implementation Method 3
nanosecond laser light has been effectively utilized as irradiation light for measuring particle contamination and detecting damage in thin films
Implementation Method 4
a first main beam splitter disposed between the imaging optical system and the objective lens; a first illumination light source disposed at one side of the first main beam splitter
Implementation Method 5
a holographic phase pattern disposed between the first main beam splitter and the objective lens and configured to increase in focal depth of each of the first and second illumination light
Implementation Method 6
an image sensor disposed on the stage; an objective lens disposed between the image sensor and the stage and configured to project an image of the substrate
Data Source
AI summary
Provided is a substrate inspection apparatus which includes a stage to accommodate a substrate, an image sensor disposed on the stage, an objective lens disposed between the image sensor and the stage to project an image of the substrate, an imaging optical system disposed between the objective lens and the image sensor, a first main beam splitter disposed between the imaging optical system and the objective lens, a first illumination light source disposed at one side of the first main beam splitter to provide first illumination light to a first depth of the substrate, and a second illumination light source disposed adjacent to the first illumination light source to provide second illumination light source, which has a wavelength shorter than that of the first illumination light source, to a second depth, which is shallower than the first depth, through the first main beam splitter.