Nearly Epitaxial Low-Resistive Co Germanide Formed by Atomic Layer Deposited Cobalt and Laser Thermal Annealing

Abstract

With ALD-Co on n+ -Ge (ND of $2\times {10}^{{19}}\text {cm}^{\text {-3}}$ ) as the platform, annealing schemes including rapid thermal annealing (RTA) and laser thermal annealing (LTA) were employed to study its impact on the characteristics of CoGe2. CoGe2 formed by LTA shows no agglomeration and a low $\rho _{\text {c}}$ of $1.3\times {10}^{\text {-8}} \Omega $ -cm2 which is reduced by 54 % as compared to the counterpart RTA. In addition, a uniform and atomically smooth CoGe2 with nearly epitaxial crystal structure is also achieved by LTA. Furthermore, LTA-formed CoGe2 does not require any barrier layer during formation which is in stark difference to other germanides and would greatly improve line resistance of the ever scaled contact trench. The promising results mainly stem from the low thermal budget with significant thermal gradient/shallow heat distribution of LTA that effectively limits excess surface Co diffusion and grooving effect, proving the high contact performance enabler beyond 5 nm node.