Nanoscale post-breakdown conduction of HfO/sub 2//SiO/sub 2/ MOS gate stacks studied by enhanced-CAFM

An enhanced conductive atomic force microscope has enabled a measurement of the conduction through a HfO/sub 2//SiO/sub 2/ gate stack until breakdown (BD) in a single measurement, with nanometer resolution. Before the stack BD, the current-voltage characteristic shows several conduction modes. After BD, switchings between different conduction states were observed, showing that BD is a reversible phenomenon.