Digital forensic atomic force microscopy of semiconductor memory arrays

Abstract

Atomic force microscopy is an analytical technique that provides very high spatial resolution with independent measurements of surface topography and electrical properties. This chapter assesses the potential for atomic force microscopy to read data stored as local charges in the cells of memory chips, with an emphasis on simple sample preparation (“delidding”) and imaging of the topsides of chip structures, thereby avoiding complex and destructive techniques such as backside etching and polishing. Atomic force microscopy measurements of a vintage EPROM chip demonstrate that imaging is possible even when sample cleanliness, stability and topographical roughness are decidedly sub-optimal. As feature sizes slip below the resolution limits of optical microscopy, atomic force microscopy offers a promising route for functional characterization of semiconductor memory structures in RAM chips, microprocessors and cryptographic hardware.