Semiconductor Substrate Reflectance Inspection for Defect Depth Separation
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Solution Overview
Problem
Existing inspection methods for semiconductor substrates, particularly those using silicon carbide (SiC) and silicon (Si), struggle to accurately distinguish between crystal defects and other defects due to the limitations of high NA lenses with small depth of focus, leading to extraction loss and reduced reliability of semiconductor devices.
Innovation Solution
An inspection apparatus and method that utilizes a light source, lens system, and detection units to calculate reflectance and adjust the distance between the lens and substrate, enabling identification of defects by varying reflectance patterns, distinguishing between surface and internal defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a high NA lens with small depth of focus is used to capture reflected light from the substrate, then the ability to suppress back surface reflection is improved, but the ability to distinguish internal defects from surface defects deteriorates
Solution Approach 1:
The patent dynamically adjusts the numerical aperture (NA) of the lens according to the inspection depth requirements. When inspecting internal defects, the system uses a smaller NA to increase depth of focus, allowing light to penetrate deeper into the substrate. When inspecting surface defects, the system switches to a larger NA to reduce depth of focus and suppress back surface reflections. This dynamic adjustment resolves the contradiction by making the optical parameters adaptable to different inspection needs rather than fixed.
Solution Approach 2:
The system changes the optical parameters (specifically numerical aperture and wavelength) based on the inspection requirements. By switching between different NA values and wavelengths, the system can optimize the depth of focus for each inspection scenario. This parameter change approach allows the same inspection apparatus to handle both surface defect inspection (requiring small depth of focus) and internal defect inspection (requiring large depth of focus) without compromising either capability.
2Device complexity
If visible light or photoluminescence method is used to observe crystal state, then the inspection method is simple, but reflection from back surface and inspection stage occurs causing inspection accuracy to deteriorate
Solution Approach 1:
The system dynamically switches between different light sources (visible light and ultraviolet light) and adjusts optical parameters based on the inspection target. For crystal state observation, visible light is used with appropriate NA settings. For internal defect detection, ultraviolet light with smaller NA is employed to increase penetration depth and reduce unwanted reflections. This dynamic adaptation maintains relative simplicity while improving accuracy for different inspection scenarios.
Solution Approach 2:
The patent changes multiple parameters including light wavelength, numerical aperture, and focal position to optimize inspection accuracy. By using wavelength switching (visible/UV) and NA adjustment, the system can suppress back surface reflections and stage reflections while maintaining the ability to observe crystal states. These parameter changes transform a potentially inaccurate simple method into a versatile and accurate inspection 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
Enhances the ability to grasp the substrate state by identifying and distinguishing between different types of defects, improving the reliability of semiconductor devices by reducing extraction loss and identifying process improvements.
Implementation Method 1
capture the light emitted to and reflected by the substrate
Data Source
AI summary
An inspection apparatus includes a light source that generates and emits light to a substrate to be inspected, a lens that captures the light emitted to and reflected by the substrate, a detection unit that detects the light captured by the lens, and a determination unit that calculates a reflectance of light of the substrate based on an intensity of the light generated by the light source and an intensity of the light detected by the detection unit, and performs an abnormality determination of the substrate based on the calculated reflectance.