Wafer 3D Reconstruction by Diagonal FIB Milling and SEM Metrology
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Solution Overview
Problem
Current 3D metrology methods for wafers, such as CD-SAXS, optical scatterometry, and TEM, are either limited in application scope, time-consuming, or destructive, failing to provide high-resolution, non-destructive, and in-line 3D inspection of 3D structural elements.
Innovation Solution
A method and system integrating FIB and SEM technologies to perform diagonal milling and imaging, allowing for high-resolution 3D reconstruction of wafer structures with minimal destructive impact, using a FIB-tool to make diagonal cuts at controlled angles and SEM imaging to reconstruct layers, enabling fast and non-destructive 3D metrology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If FIB is used for high-resolution imaging and sectioning, then imaging resolution and sectioning capability are improved, but the specimen is destroyed and the process is time-consuming
Solution Approach 1:
The specimen is divided into multiple thin sections through controlled FIB milling at diagonal angles, allowing sequential imaging of different depths. This segmentation enables high-resolution 3D reconstruction while preserving the ability to stop at any depth level without completely destroying the specimen.
Solution Approach 2:
The FIB tool performs preliminary sectioning and preparation of the specimen surface before SEM imaging. By pre-milling diagonal sections and exposing internal structures, the specimen is prepared in advance for optimal SEM imaging, reducing the need for repeated destructive sectioning.
2Measurement precision
If traditional FIB-SEM imaging is used, then high-resolution imaging is achieved, but the process is destructive and cannot be conducted in-line
Solution Approach 1:
The system dynamically adjusts the FIB beam parameters (current, angle, duration) based on real-time feedback from SEM imaging. This dynamic control allows the process to be optimized for minimal material removal while achieving diagnostic quality images, enabling in-line implementation where time and material conservation are critical.
Solution Approach 2:
The FIB imaging parameters (beam current, scanning speed, milling depth) are changed and optimized to achieve the minimum necessary material removal for diagnostic imaging. By adjusting these parameters, the system balances image quality with specimen preservation, making the process suitable for in-line production environments.
3Adaptability or versatility
If multiple imaging methods (CD-SAXS, TEM, Scatterometry) are used for 3D metrology, then comprehensive coverage is achieved, but the process becomes time-consuming and complex
Solution Approach 1:
The patent combines FIB sectioning capability with SEM imaging in a single integrated system, eliminating the need to transfer specimens between multiple separate instruments (TEM, SAXS, scatterometry). This merging of functions into one platform maintains versatile application coverage while dramatically reducing measurement time and process complexity.
Solution Approach 2:
The FIB-SEM system is designed to perform multiple functions: high-resolution imaging, precise sectioning, 3D reconstruction, and various analytical techniques all in one instrument. This multi-functionality replaces multiple specialized instruments, reducing both time loss from specimen handling and the complexity of coordinating multiple measurement systems.
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 high-resolution, fast, and non-destructive 3D reconstruction of wafer structures with nanometric precision, suitable for in-line integration in manufacturing processes, with minimal wafer damage.
Implementation Method 1
a FIB-tool configured to mill an area of the wafer at a predetermined diagonal angle to thereby generate one or more diagonal cuts in the 3D structural elements
Implementation Method 2
the exposed layers can then be scanned using high-quality SEM to obtain one or more high-resolution images
Data Source
AI summary
Disclosed are system and method for metrology of 3D structural elements of a wafer by projecting, on a subset of the 3D structural elements, a focused ion beam (FIB) at a predefined diagonal angle, thereby generating a diagonal cut in each of the subset of sites, scanning each of the diagonal cuts using a scanning electron microscope (SEM), generating a reconstruction of the one or more 3D structural elements or a component thereof based on the SEM image and performing metrology measurements on the reconstruction.