J. Snauwaert et al., TOWARDS A PHYSICAL UNDERSTANDING OF SPREADING RESISTANCE PROBE TECHNIQUE PROFILING, Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena, 12(1), 1994, pp. 304-311
Spreading resistance has become a standard in semiconductor resistivit
y determination. The method is based on metal-semiconductor point cont
act measurements. The resulting spreading resistance is generally desc
ribed by R(s) = rho/4a, wherein rho refers to the bulk resistivity and
a to the radius of the contact area. This relation is only valid in t
he ideal case where the contact area can be considered as a homogenous
circular contact. New contact models have introduced the concept of m
ultiple microcontacts in spreading resistance probe technique (SRP) me
asurements. The physical nature of these contacts has now been studied
by an atomic force microscope (AFM). The AFM images show indentations
of multiple point contacts penetrating 10-100 nm into the silicon dep
ending on the applied force and the probe characteristics. Time-depend
ent measurements at constant force revealed a gradual increase in pene
tration depth and in contact area. An AFM with conducting tip has been
developed to study the behavior of a single contact point. I-V curves
for such a metallic tip are compared with I-V curves for standard SRP
probes.