Abstract
The
channel width-to-length ratio is an important transistor parameter
for integrated circuit design. Contact diffusion into the channel
during fabrication or operation alters the channel width and this
important parameter. A novel methodology combining atomic force microscopy
and scanning Kelvin probe microscopy (SKPM) with self-consistent modeling
is developed for the nondestructive detection of contact diffusion
on active devices. Scans of the surface potential are modeled using
physically based Technology Computer Aided Design (TCAD) simulations
when the transistor terminals are grounded and under biased conditions.
The simulations also incorporate the tip geometry to investigate its
effect on the measurements due to electrostatic tip–sample
interactions. The method is particularly useful for semiconductor–
and metal–semiconductor interfaces where the potential contrast
resulting from dopant diffusion is below that usually detectable with
scanning probe microscopy.