3D Datacube Metrology With Distortion-Corrected FIB Delayering
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Solution Overview
Problem
Conventional methods for delayering semiconductor structures face challenges in achieving uniform milling rates across regions with varying materials or structures, leading to inaccurate three-dimensional imaging and metrology.
Innovation Solution
A method and system that utilizes a scanning electron microscope (SEM) and focused ion beam (FIB) to acquire multiple two-dimensional images, correct distortions through inverse transformations, and generate a three-dimensional data cube by aligning and segmenting images based on known milling rates and ground truth geometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional delayering methods are used on regions with varying materials or structures, then the delayering process can be performed, but the milling rate becomes non-uniform across different portions of the region
Solution Approach 1:
The patent applies local quality by using material-specific milling rate information to selectively adjust processing parameters for different regions. The system identifies different materials in the region of interest and applies location-dependent corrections to achieve uniform milling across heterogeneous structures.
Solution Approach 2:
The patent changes processing parameters dynamically based on the local material composition. By modifying milling parameters according to the identified material types in different regions, the system compensates for varying milling rates and achieves uniform material removal across the entire region.
2Loss of information
If delayering is performed to expose subsurface features, then three-dimensional imaging can be achieved, but distortion occurs in the acquired images due to non-uniform milling
Solution Approach 1:
The patent implements feedback by using acquired images to identify material locations and milling rates, then using this information to correct distortions in subsequent images. The system continuously refines the three-dimensional reconstruction by incorporating feedback from previous measurement cycles.
Solution Approach 2:
The patent performs preliminary identification of material locations and milling rates before final three-dimensional reconstruction. By pre-characterizing the region's heterogeneous structure, the system can apply appropriate corrections during the imaging and reconstruction process to eliminate distortions.
3Difficulty of detecting and measuring
If multiple images are acquired during delayering to create a three-dimensional model, then subsurface features can be visualized, but the images contain distortions that reduce metrology accuracy
Solution Approach 1:
The patent segments the region of interest into distinct material regions based on identified milling rates. By dividing the heterogeneous structure into homogeneous segments, the system can apply region-specific correction factors to improve the accuracy of three-dimensional reconstruction and metrology measurements.
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 the creation of an accurate three-dimensional image of semiconductor wafers by correcting distortions and non-uniform milling rates, allowing for precise metrology and virtual slicing of the data cube.
Implementation Method 1
a ROI on a specimen can be bombarded with ions of Xenon, Gallium or other elements generated by a focused ion beam (FIB) column to erode the surface layer of the specimen in the ROI
Implementation Method 2
imaging a surface of the region of interest with the SEM column
Data Source
AI summary
A method of evaluating a region of interest of a sample including: positioning the sample within in a vacuum chamber of an evaluation tool that includes a scanning electron microscope (SEM) column and a focused ion beam (FIB) column; acquiring a plurality of two-dimensional images of the region of interest by alternating a sequence of delayering the region of interest with a charged particle beam from the FIB column and imaging a surface of the region of interest with the SEM column; generating an initial three-dimensional data cube representing the region of interest by stacking the plurality of two-dimensional images on top of each other in an order in which they were acquired; identifying distortions within the initial three-dimensional data cube; and creating an updated three-dimensional data cube that includes corrections for the identified distortions.