  Wafer-level testing is an important step for process and quality control of
electronic chips in integrated circuit (IC) manufacturing which occurs before
packaging. The process of wafer probing in its conventional contacting schemes,
becomes more complicated as ICs move to smaller technology nodes and more
compact designs, greatly increasing testing costs. Non-contact optical wafer
probing can overcome physical probing complications, reducing costs, and
increasing throughput and reliability. In this paper, a CMOS compatible,
broadband (22 GHz), small footprint (5 {\mu}m dia.) plasmonic electro-optic
modulator of low insertion loss (4 dB) and wide optical working bandwidth (100
nm) is proposed and demonstrated as a potential solution for wafer-level
optical testing. The device modulates in reflection an incident optical carrier
emerging from an optical fiber in a non-contact arrangement, to work as a data
output channel from the wafer. A modulation depth of over 2% is achieved which
should be sufficient to meet the requirements of wafer-level testing. The
device can be placed anywhere on wafer.
