pn -junction delineation in Si devices using scanning capacitance spectroscopy

The scanning capacitance microscope (SCM) is a carrier-sensitive imaging tool based upon the well-known scanning-probe microscope (SPM). As reported in Edwards et al. [Appl. Phys. Lett. 72, 698 (1998)], scanning capacitance spectroscopy (SCS) is a new data-taking method employing an SCM. SCS produces a two-dimensional map of the electrical pn junctions in a Si device and also provides an estimate of the depletion width. In this article, we report a series of microelectronics applications of SCS in which we image submicron transistors, Si bipolar transistors, and shallow-trench isolation structures. We describe two failure-analysis applications involving submicron transistors and shallow-trench isolation. We show a process-development application in which SCS provides microscopic evidence of the physical origins of the narrow-emitter effect in Si bipolar transistors. We image the depletion width in a Si bipolar transistor to explain an electric field-induced hot-carrier reliability failure. We show two sample geometries that can be used to examine different device properties.