Abstract

MOSFET devices are routinely measured at the probe pad level with conventional capacitance-voltage (CV) measurement instruments. Such measurements are done at the front end of line (FEOL) and back end of line (BEOL) process completion levels. The CV data is used to monitor the process and verify certain parametrics such as effective oxide thickness (EOT), Tox, gate drain overlap capacitance (Miller capacitance), trapped charge, diffusion/halo implant oxide leakage, doping concentration, threshold implant level and many others. This type of testing is treated at length in the classic text of Nichollian and Brews [1]. The introduction of Nanoprobe Capacitance Voltage Spectroscopy (NCVS) of discrete MOSFET devices and the method of performing scanning capacitance imaging (SCM) have been previously presented [2]. In that work, the authors used a capacitance sensor to measure the capacitance of an individual failing embedded DRAM capacitor. This paper will describe nanoprobe CV measurements of a discrete finger device from a multiple finger test structure and show comparable results obtained at the probe pad level, using an improved version of the earlier capacitance sensor. By comparing the BEOL test structure measurements with NCVS results from a single finger, we will verify and calibrate the nanoprobing technique.

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