Non-contact C-V measurements of ultra thin dielectrics

Abstract

In this paper, we present a non-contact C-V technique for ultra-thin dielectrics on silicon. The technique uses incremental corona charging of dielectric and a measurement of the surface potential with a vibrating capacitive electrode. A differential quasistatic C-V curve is generated using time-resolved measurements. The technique incorporates transconductance corrections that enable corresponding ultra-low electrical oxide thickness (EOT) determination down to the sub-nanometer range. It also provides a means for monitoring the flat band voltage, VFB, the interface trap spectrum, DIT, and the total dielectric charge, QTOT. This technique is seen as a replacement for not only MOS C-V measurements but also for mercury-probe C-V. In addition, EOT measurement by the corona C-V has a major advantage over optical thickness methods because it is not affected by water adsorption and molecular airborne contamination, MAC. These effects have been a problem for optical metrology of ultra-thin dielectrics.