Reflective X-Ray CT Imaging for 3D NAND Defect Inspection
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Solution Overview
Problem
Existing methods for inspecting semiconductor devices are often destructive and cannot effectively identify embedded defects in three-dimensional structures like 3D NAND strings.
Innovation Solution
A non-destructive inspection system using reflective X-ray microscope computed tomographic (CT) imaging, which directs an X-ray beam at an oblique angle to pass through and reflect off semiconductor substrates, rotating the wafer to capture images at multiple angles and reconstructing device structures for defect detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If destructive inspection methods are used, then defect detection capability is improved, but device integrity is worsened
Solution Approach 1:
The patent creates a virtual 3D copy of the semiconductor device interior through X-ray CT imaging. The system generates a reconstructed image that is a digital replica of the internal structure, allowing defect detection without physically damaging the actual device. This copying approach enables inspection while preserving device integrity.
Solution Approach 2:
The patent replaces destructive mechanical inspection methods with non-destructive X-ray imaging. Instead of physically cutting or disassembling devices to inspect internal structures, the system uses X-ray radiation to penetrate and image the interior, substituting mechanical destruction with electromagnetic wave-based visualization.
2Productivity
If conventional imaging methods are used, then inspection speed is improved, but ability to detect embedded defects in 3D structures is worsened
Solution Approach 1:
The patent transitions from 2D surface imaging to 3D volumetric imaging by implementing computed tomography. The system collects X-ray attenuation data from multiple projection angles and reconstructs a three-dimensional representation of the device interior, enabling detection of embedded defects that cannot be seen in conventional 2D images.
Solution Approach 2:
The patent implements a dynamic inspection process where the wafer is rotated during X-ray imaging to capture projections from multiple angles. This dynamic approach, combined with helical scanning patterns, enables comprehensive 3D reconstruction while maintaining efficient inspection throughput.
3Measurement precision
If oblique angle X-ray imaging is used, then 3D structure visualization is improved, but system complexity is worsened
Solution Approach 1:
The patent designs the X-ray imaging system to perform multiple functions: it can image various semiconductor device types (2D, 3D NAND, FinFET), accommodate different wafer sizes, and provide both 2D projection and 3D reconstructed images from the same hardware platform. This multi-functionality reduces the need for multiple specialized systems.
Solution Approach 2:
The patent introduces a computational reconstruction algorithm as an intermediary between the raw X-ray projection data and the final 3D image. This software-based mediator processes the attenuation data from multiple angles and generates the volumetric representation, separating the complexity of 3D reconstruction from the hardware imaging process.
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 non-destructive inspection of semiconductor devices, particularly 3D NAND strings, identifying embedded defects with high accuracy and preserving the integrity of the structures.
Implementation Method 1
at least a portion of the beam of X-ray radiation is reflected by the semiconductor substrate of the semiconductor wafer
Implementation Method 2
X-ray radiation that is attenuated by the device structures and reflected by the semiconductor substrate
Implementation Method 3
an X-ray detector configured to detect X-ray radiation that is attenuated by the device structures and reflected by the semiconductor substrate
Implementation Method 4
reflective X-ray microscope computed tomographic (CT) imaging
Data Source
AI summary
Systems and methods for non-destructive inspection of semiconductor devices, such as three-dimensional NAND memory device, using reflective X-ray microscope computed tomographic (CT) imaging. An X-ray microscope directs a focused beam of X-ray radiation at an oblique angle onto the surface of a semiconductor wafer such that the beam passes through device structures and at least a portion of the beam is reflected by a semiconductor substrate of the wafer and detected by an X-ray detector. The wafer may be rotated about a rotation axis to obtain X-ray images of a region-of-interest (ROI) at different projection angles. A processing unit uses detected X-ray image data obtained by the X-ray detector at the different projection angles to generate a CT reconstructed image of the ROI. The CT reconstructed image may enable inspection of internal structural features, including embedded defects, in the semiconductor device in a non-destructive manner.