Lens-Free Digital Holography Microscope for High-Speed Wafer Inspection
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Solution Overview
Problem
Conventional inspection methods, such as electron microscopes and ellipsometry, face limitations in speed and accuracy for defect detection on objects like wafers, particularly in achieving high resolution while maintaining a wide field of view and efficient inspection processes.
Innovation Solution
A digital holography microscope (DHM) with a lens-free path from the light source to the detector, utilizing coherent light and a beam splitter to generate and analyze interference patterns, allowing for high-speed and high-resolution inspection by detecting defects through hologram generation and analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical microscopes are used for inspection, then the device complexity is low, but the measurement precision and resolution are limited by the diffraction limit
Solution Approach 1:
The patent replaces conventional optical lenses with a digital sensor array that directly captures interference patterns. The lens-free digital holographic microscope uses a coherent light source and detector array to record holograms, eliminating the need for traditional optical focusing components while achieving super-resolution through computational reconstruction methods.
Solution Approach 2:
The patent creates a digital copy (hologram) of the object's light field that contains both amplitude and phase information. This digital holographic copy can be reconstructed computationally to achieve high resolution without physical lenses, allowing the inspection of semiconductor wafers at resolutions beyond conventional optical limits.
2Measurement precision
If electron microscopes are used for high-resolution inspection, then the measurement precision is improved, but the inspection speed and productivity decrease
Solution Approach 1:
The patent enables continuous inspection by capturing holographic information from the entire field of view simultaneously using a detector array. Unlike sequential scanning methods, the lens-free digital holographic microscope records complete wavefront information across the entire wafer surface at once, allowing high-speed inspection without sacrificing resolution.
Solution Approach 2:
The patent transitions from conventional 2D intensity imaging to 3D complex amplitude holographic recording. By capturing the full wavefront information (amplitude and phase) in four-dimensional space-time, the system can reconstruct images at multiple focal depths and achieve high resolution across the entire field of view simultaneously, dramatically increasing inspection speed.
3Measurement precision
If conventional microscopes increase resolution, then the measurement precision is improved, but the field of view decreases
Solution Approach 1:
The patent uses digital holography to capture four-dimensional information (x, y, amplitude, phase) simultaneously across the entire field of view. This allows computational reconstruction at multiple focal planes and super-resolution imaging without reducing the field of view, as the resolution enhancement is achieved through wavefront analysis rather than optical magnification.
Solution Approach 2:
The patent replaces optical magnification with computational reconstruction. Instead of using high-numerical-aperture lenses that reduce field of view, the system uses a lens-free detector array to capture interference patterns that encode high-resolution information across the entire field of view, with resolution achieved through digital processing rather than optical physics.
4Loss of information
If ellipsometry is used for wafer inspection, then information about sample properties is obtained, but the ability to detect surface defects is limited
Solution Approach 1:
The patent creates a multi-functional inspection system that can simultaneously perform both ellipsometry (for material properties) and defect detection. The lens-free digital holographic microscope captures complete wavefront information that can be analyzed for both quantitative material characterization and qualitative defect identification, providing universal inspection capability in a single system.
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 DHM enables accurate and rapid inspection of objects at high resolution without the trade-offs of resolution and field of view seen in traditional systems, allowing for efficient defect detection and improved semiconductor device manufacturing processes.
Implementation Method 1
the detector generates a hologram when the reflected light includes interference light
Implementation Method 2
utilizing coherent light and a beam splitter to generate and analyze interference patterns
Data Source
AI summary
A low-cost digital holography microscope (DHM) that is capable of performing inspection at high speed while accurately inspecting an inspection object at high resolution, an inspection method using the DHM, and a method of manufacturing a semiconductor device by using the DHM are provided. The DHM includes: a light source configured to generate and output light; a beam splitter configured to cause the light to be incident on an inspection object and output reflected light from the inspection object; and a detector configured to detect the reflected light, wherein, when the reflected light includes interference light, the detector generates a hologram of the interference light, and wherein no lens is present in a path from the light source to the detector.