Düsseldorf, Germany: Analysis at the 1nm level is now possible thanks to a recent breakthrough in imaging electron-carrier paths and impurities in semiconductors. Accomplished by Toshiba Corp., the advance, based on scanning spreading resistance microscopy (SSRM), is seen as an essential step toward achieving LSI at the 45nm generation and beyond.
SSRM is a technology for twodimensional profiling of localised resistance on a semiconductor cross-sectional surface, allowing for analysis of the distribution of electron carriers and impurities. The fine tolerances required for 45nm-generation LSI makes it crucial to understand electroncarrier density in the carrier channel, and to be able to control doping with 1nm-level precision. That's because slight differences in electrical characteristics can lead to increased current leakage and the risk of short-circuiting.
SSRM employs a scanning probe to produce twodimensional images of carriers in a semiconductor device. These images reveal impurity-induced resistance variation and enable analysis of electron-flow paths. However, the level of precision and repeatable generation of high-resolution SSRM images with conventional available probes has remained at around 5nm.
Problems with SSRM stem from two sources: degraded imaging accuracy due to the influence of water vapour on the sample, and the difficulty of controlling a sufficiently stable contact between the sample and the probe. To overcome these factors, Toshiba installed the SSRM in a vacuum environment and refined the positioning of the probe.
