3D determination of a MOSFET gate morphology by FIB tomography

The construction of today's extremely complex modem electronic devices involves a large number of sequential processing steps, many of which require sub-micron spatial accuracy. A misalignment or error in a processing step resulting in significantly altered device geometry may render part of the device inoperable. In order to characterise the construction and degradation of devices with complex inhomogeneous microstructures, methods of three-dimensional (3D) structural and chemical analysis are becoming increasingly important. At present there are a range of 3D analysis techniques available for determining the morphology of individual device components, each with varying spatial and chemical resolution. The 3D morphology of the gate electrode in a Si-Ge metal oxide semiconductor field effect transistors device has been determined by 3D focused ion beam (FIB) tomographic analysis. Sequential two-dimensional FIB sectioning, imaging, and computer reconstruction enables the gate electrode shape and location with respect to the neighbouring source and drain to be determined in 3D.