Infrared Wafer Defect Imaging for Subsurface Depth Measurement
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Solution Overview
Problem
Conventional subsurface defect detection methods for silicon wafers face limitations such as low detectable energy of scattered light, requirements for transparent samples, high surface roughness, and inaccurate defect depth measurement, necessitating improved structures for enhanced defect detection capability.
Innovation Solution
A wafer defect analyzing device comprising a light source, imaging mechanism, and height adjusting mechanism, utilizing infrared light and a camera with a microscopic objective lens, gain element, and light filtering element, along with a processor to analyze defects by capturing multiple images at varying focal positions, enabling precise defect depth measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional laser scattering method is used to detect subsurface defects, then the detection setup is simple, but the scattered light energy is too small to be detected effectively
Solution Approach 1:
The patent introduces an infrared light source as an intermediary to illuminate subsurface defects, which then scatter infrared light that can be effectively detected by the imaging mechanism. This intermediary illumination source enables the detection of subsurface defects that would otherwise produce undetectably weak scattered light signals.
Solution Approach 2:
The patent changes the wavelength parameter of the light source to infrared range, which penetrates deeper into the wafer and produces stronger scattered signals from subsurface defects. This parameter change from visible light to infrared light fundamentally improves the detectability of subsurface defects.
2Device complexity
If conventional detection methods are used, then the device structure is simple, but the defect depth cannot be accurately measured
Solution Approach 1:
The patent segments the detection process into multiple focal positions along the optical axis, capturing images at different depths. By analyzing the focal position where defects appear sharpest or most prominent, the system can determine the depth of subsurface defects with high precision.
Solution Approach 2:
The patent adds the depth dimension (z-axis) to the traditional two-dimensional image capture by introducing focal position adjustment. This enables three-dimensional defect localization, allowing accurate measurement of defect depth in addition to lateral positioning.
3Adaptability or versatility
If conventional detection methods are used, then no special requirements are imposed, but the method requires transparent samples or high surface roughness
Solution Approach 1:
The patent uses infrared light with specific wavelength parameters that can penetrate silicon wafers effectively, eliminating the requirement for sample transparency in the visible range. The infrared wavelength parameter enables detection in opaque silicon materials, greatly expanding sample adaptability.
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 clear identification and accurate depth measurement of subsurface defects in silicon wafers, enhancing defect detection ability and ensuring reliable semiconductor manufacturing by identifying and quantifying defect depth.
Implementation Method 1
the light source emits an infrared light penetrating the wafer
Implementation Method 2
a microscopic objective lens located between the camera and the light source
Implementation Method 3
the imaging mechanism shoots a plurality of images respectively corresponding to a plurality of focal positions
Data Source
AI summary
A wafer defect analyzing device includes a light source, an imaging mechanism, a height adjusting mechanism and a processor. The light source is configured to carry a wafer and to emit an infrared light. The imaging mechanism includes a camera facing toward the light source for shooting the wafer, a microscopic objective lens located between the camera and the light source, a light filtering element located between the camera and the microscopic objective lens, and a gain element located between the camera and the light filtering element. The height adjusting mechanism is connected to the imaging mechanism and includes a motor. The processor is signally connected to the imaging mechanism. The height adjusting mechanism moves the imaging mechanism along a longitudinal axis, the imaging mechanism shoots a plurality of images of the wafer, and the processor receives and analyzes the images to analyze a defect on the wafer.