Patterned, low-temperature growth of transition metal dichalcogenides for low resistance raised contacts

Transition metal dichalcogenide (TMD) monolayers are promising channel
materials for next-generation electronic devices. A challenge is the high
contact resistance between monolayer TMDs and metal contacts, especially
for holes. In this regard, raised source/drain contacts are promising.
However, the direct, patterned growth of raised contacts at
CMOS-compatible temperatures remains largely unresolved. We present
plasma-free selenization and sulfurization of metal-oxides at substrate
temperatures down to 400 °C, compatible with back-end-of-line (BEOL)
thermal budgets. To achieve growth at such temperatures, gas-phase
chalcogen precursors are first thermally activated at 950 °C. Films grown
on single-crystal monolayer TMDs exhibit high crystal quality as
confirmed by transmission electron microscopy. Raised contacts on
WSe2 monolayers fabricated using this approach yield a low hole contact
resistance of 0.3 kΩ·μm after chemical doping. This process is shown to be
applicable to growing various TMDs, including WS2, MoSe2, MoS2, PtSe2, and
NbS2.