  Surface damage caused by ionizing radiation in SiO$_2$ passivated silicon
particle detectors consists mainly of the accumulation of a positively charged
layer along with trapped-oxide-charge and interface traps inside the oxide and
close to the Si/SiO$_2$-interface. High density positive interface net charge
can be detrimental to the operation of a multi-channel $n$-on-$p$ sensor since
the inversion layer generated under the Si/SiO$_2$-interface can cause loss of
position resolution by creating a conduction channel between the electrodes. In
the investigation of the radiation-induced accumulation of oxide charge and
interface traps, a capacitance-voltage characterization study of n/$\gamma$-
and $\gamma$-irradiated Metal-Oxide-Semiconductor (MOS) capacitors showed that
close agreement between measurement and simulation were possible when oxide
charge density was complemented by both acceptor- and donor-type deep interface
traps with densities comparable to the oxide charges. Corresponding inter-strip
resistance simulations of a $n$-on-$p$ sensor with the tuned oxide charge
density and interface traps show close agreement with experimental results. The
beneficial impact of radiation-induced accumulation of deep interface traps on
inter-electrode isolation may be considered in the optimization of the
processing parameters of isolation implants on $n$-on-$p$ sensors for the
extreme radiation environments.
