Highlights

Scanning Confocal Electron Microscopy of Integrated Circuits

Scientific Achievement

Today, the operation and performance of technologically important engineered materials is governed by the complex internal arrangement and interaction of their constituent building blocks.  The process of 3D characterization in composite microstructures has always been a difficult and/or time-consuming task, and has been largely relegated to technologically complex instrumentation having highly penetrating radiation or it has involved the time-consuming and expensive preparation of very thin cross-section slices for study and/or reverse engineering.  In the former high energy x-rays typically from synchrotron facilities have been employed to successfully view the internal arrangements of thick materials, while in the latter atomic resolution analysis has been achieved using electron microscopy albeit at the expense of destructive and time consuming examination via tomography.  Scanning Confocal Electron Microscopy (SCEM) is a technique invented in the EMC which straddles these two extremes and permits study of thick sections of materials at  nanometer scale resolutions.  Traditionally, the use of TEM or STEM in the study of internal structure of semi-conductors has been applied to relatively thin specimens ( < 500 nm ).  The development of the scanning confocal electron microscope (SCEM) by Argonne has extended the potential range of application of EM to extremely thick specimens.  Previous work (2003) has demonstrated the application in biological and materials systems to ~5000 nm thick samples a ten-fold increase over traditional limitations.  Current research and developments in optimization of SCEM have extended this range to facilitate  imaging structures in integrated circuits  of ~ 11.5 µm in thickness. In this regime the SCEM can visualize deep buried structures in devices, without having to perform cross-sections or slicing, and it complements traditional thick section work done by X-ray Microscopy.  

Significance

There is a developing need to be able to characterize the circuitry of integrated circuits used in critical infrastructures particularly in the area of security and/or military applications.  This  need may become acute if device manufacturing is moved offshore.  In this situation, there is a desire on the part of a number of government organizations to be able to confirm, after the fact, that a particular circuit layout has not been compromised by individuals seeking to covertly modify these devices.  As modern complex circuitry is now 4-12 multi-layer construction the ability to image and confirm device conformance to the design specifications at 10-15 nm level in thicknesses that can exceed 10 µm in an modern electron microscope is a significant advancement. 

Performers