Ultra-Low ρc Extraction for Recessed and Non-Recessed Contacts: Generalized Transmission Line Model

A universal transmission line model (TLM) is developed to provide an accurate extraction of specific contact resistivity ρ
_c
for both recessed and non-recessed contacts. This new model eliminates the need for the assumption that semiconductor sheet resistance under the contact R
_shc
is equal to that in the contact gap region R
_sh
which has been used for decades and expands the application of TLM-based methods for alloyed contacts for the first time. The model was verified experimentally by applying it to directly extract ρ
_c
, R
_shc
, and metal sheet resistance R
_m
of alloyed p
⁺
-GeSn contact. The change of R
_shc
due to alloying or recess-etching is well captured and ultra-low ρ
_c
values of 1.0×10
^-9
Ω-cm
²
are extracted. In contrast, conventional TLM-based methods lead to a large variation in ρ
_c
extraction and miscalculate ρ
_c
by neglecting the deviation of Rshc from R
_sh
.