Reflection Tomographic Imaging for Semiconductor Inspection
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Solution Overview
Problem
Current optical inspection techniques for semiconductors and display devices face challenges in achieving high-resolution, non-destructive, three-dimensional internal imaging and surface profiling, especially for multilayer structures, due to limitations in resolution, aberration correction, and compatibility with various microscope configurations.
Innovation Solution
A high-resolution reflection tomographic imaging system utilizing temporally coherent and spatially incoherent light, which generates a reference beam on a conjugate image plane far from the sample, allowing for off-axis detection and interference-based 3D imaging without the need for specific objective lenses, thus enabling tomographic reconstruction of 3D objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If white light interferometry is used for high-resolution imaging, then surface profiling capability is improved, but depth-resolved imaging capability deteriorates
Solution Approach 1:
The patent merges white light interferometry and optical coherence tomography into a single system that can perform both surface profiling and depth-resolved imaging. The interferometric setup with a beam splitter combines the reference beam and sample beam paths, allowing simultaneous acquisition of both surface topography and internal depth structures through different detection modes.
Solution Approach 2:
The system dynamically switches between different imaging modes (surface profiling and depth-resolved imaging) by adjusting the detection configuration. The focal point can be scanned along the optical axis to access different depths, and the detection system can adapt between measuring surface heights and reconstructing internal 3D structures based on the required measurement type.
2Measurement precision
If confocal microscopy is used for depth sectioning, then resolution is improved, but imaging speed deteriorates
Solution Approach 1:
The patent replaces the mechanical point-by-point scanning mechanism of confocal microscopy with a non-scanning interferometric approach. Instead of moving the focal point mechanically to scan the sample, the system uses optical interference patterns and digital processing to achieve depth sectioning and 3D reconstruction, significantly improving imaging speed while maintaining resolution.
Solution Approach 2:
The system employs periodic modulation of the reference beam path length to encode depth information in the interference signal. By sweeping the reference mirror position periodically and detecting the interference patterns at different path lengths, the system achieves depth-resolved imaging without mechanical scanning of the sample, enabling faster acquisition through parallel detection.
3Measurement precision
If Mirau objective lens is used for white light interferometry, then surface measurement capability is improved, but resolution and aberration correction deteriorate
Solution Approach 1:
The patent extracts the interferometric measurement function from the specialized Mirau objective lens and implements it using a separate beam splitter and reference mirror assembly. This allows the use of high-quality, aberration-corrected objective lenses for sample illumination while performing interference measurements through a dedicated optical path that does not compromise the objective lens's imaging quality.
Solution Approach 2:
The system introduces a beam splitter as an intermediary element that separates the illumination path (through the high-quality objective lens) from the interference measurement path (through the beam splitter and reference mirror). This intermediary allows the objective lens to provide aberration-corrected illumination while the interferometric setup independently performs surface measurements without introducing additional aberrations.
4Adaptability or versatility
If Linnik interferometer configuration is used for white light interferometry, then flexibility in optics selection is improved, but alignment complexity deteriorates
Solution Approach 1:
The patent creates a universal interferometric setup that can work with various objective lenses and optical configurations. The beam splitter-based design is compatible with different microscope types and objective lenses, providing flexibility in optics selection while maintaining a standardized, easier-to-align interferometric measurement path that does not require the complex dual-objective alignment of Linnik configuration.
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 system achieves high-resolution, non-destructive 3D imaging of semiconductor and display device structures, enhancing inspection capabilities with improved resolution, flexibility, and ease of alignment, while being adaptable to various wavelengths and microscope configurations.
Implementation Method 1
temporally coherent and spatially incoherent light
Implementation Method 2
temporally coherent and spatially incoherent light
Implementation Method 3
a semi-reflective surface element configured to split the light into a sample and a reference beam
Implementation Method 4
a sample beam from the sample and the reference beam cause interference for tomographic imaging
Implementation Method 5
an objective lens
Implementation Method 6
an objective lens
Data Source
AI summary
Provided is a high-resolution reflection tomographic imaging system and method. The high-resolution reflection tomographic imaging system of the present disclosure may include an objective lens, a tube lens, a camera, an illumination element configured to introduce temporally coherent and spatially incoherent light, and a semi-reflective surface element configured to split the light into a sample and a reference beam between the tube lens and the camera, such that a sample beam from the sample and the reference beam cause interference for tomographic imaging.