Ion Beam Delayering With Topography for IC Imaging Contrast
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Solution Overview
Problem
Current methods for delayering integrated circuits, such as scanning electron microscopy, face challenges in distinguishing different materials due to low contrast in substantially planar surfaces, making it difficult to reverse engineer and analyze the internal structures and interconnections of high-tech microchips.
Innovation Solution
An ion beam delayering system and method that introduces topographical enhancements on the delayered sample surfaces by selectively milling materials at different rates, using an ion beam mill to create features that improve imaging contrast in scanning electron microscopy, allowing for better delineation of material locations and connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If scanning electron microscopy is used to image delayered surfaces, then imaging capability is provided, but image contrast is low due to substantially planar surfaces
Solution Approach 1:
The ion beam mill is used to create topographical features (ridges, edges, and relief structures) on the delayered sample surfaces before imaging. This preliminary topographical enhancement ensures that when SEM imaging is performed, the surfaces already contain visible features that provide contrast, eliminating the need for post-imaging processing and directly resolving the low contrast problem
Solution Approach 2:
The ion beam milling process creates curved and elevated topographical features such as ridges and rounded edges on the otherwise planar surfaces. These curved features scatter electrons differently during SEM imaging, creating contrast variations that allow clear delineation of material boundaries and circuit features
2Illumination intensity
If ion beam mill is used to create topographical features, then imaging contrast is improved, but additional processing time is required
Solution Approach 1:
The patent combines the delayering process with topographical feature creation in a single integrated ion beam milling step. By adjusting ion beam parameters (energy, current, angle) and using selective masking, the system simultaneously removes material to expose new layers and creates contrasting topographical features, eliminating the need for separate imaging preparation steps and reducing total processing time
Solution Approach 2:
The ion beam milling parameters (acceleration voltage, beam current, incident angle) are optimized to achieve both delayering and topographical enhancement at controlled rates. By precisely controlling these parameters, the process creates sufficient contrast features within minimal milling time, balancing the trade-off between contrast improvement and processing duration
3Measurement precision
If selective ion beam milling is used to create topography, then material differentiation is improved, but device complexity increases
Solution Approach 1:
The ion beam mill is configured to apply different milling conditions to different regions of the sample. By using selective masking and adjusting beam parameters locally, the system creates distinct topographical features for different materials (such as metal interconnects versus dielectric layers), enabling clear material differentiation without requiring complex multi-step processes
Solution Approach 2:
The patent introduces masking layers as intermediaries that selectively protect certain regions during ion beam milling. These masks allow the ion beam to create topographical features only in specific areas, enabling material differentiation through simple binary presence/absence of features rather than requiring complex real-time parameter adjustment
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
The ion beam delayering process enhances imaging contrast and accuracy, facilitating reverse engineering efforts by creating visible edges and ridges between materials, thereby improving the ability to identify circuit connections and interlayer relationships in integrated circuits.
Implementation Method 1
operating the ion beam mill in accordance with the predetermined operational characteristics to simultaneously remove the materials, using an ion beam from the ion beam mill, such that the at least one of the materials is milled at the substantially different ion beam removal rate so to introduce or enhance a topography
Data Source
AI summary
Described are various embodiments of an ion beam delayering system and method, topographically enhanced sample produced thereby, and imaging methods and systems related thereto. In one embodiment, a method comprises: identifying at least two materials in an exposed surface of the sample and predetermined operational characteristics of an ion beam mill that correspond with a substantially different ion beam mill removal rate for at least one of the materials; operating the ion beam mill in accordance with the predetermined operational characteristics to simultaneously remove the materials and introduce or enhance a topography associated with the materials and surface features defined thereby; acquiring surface data; and repeating the operating and acquiring steps for at least one more layer.