Co Silicide With Low Contact Resistivity Formed by Atomic Layer Deposited Cobalt and Subsequent Annealing

Abstract

Co silicide on $\text{n}^{+}$ -Si substrate ( $\text{N}_{\text {D}}= {8}\times {10}^{{{19}}}$ cm $^{{-{3}}}$ ) formed by atomic layer deposition (ALD) Co deposition and subsequent rapid thermal annealing (RTA) was proposed as the contact silicide for aggressively scaled contact technology. ALD-Co silicide formed by RTA of 750° C shows the best contact resistivity ( $\rho _{text{c}}$ ) of ${1.0}\times {10}^{{-{8}}} \Omega $ -cm2 with crystallinity in CoSi2 phase, highly-oriented crystal structure and smooth surface. Compared to physical vapor deposition (PVD, sputter)-Co silicide, ALD-Co silicide shows greatly reduced $\rho _{\text {c}}$ by 76 %. The major difference between ALD- and PVD-Co silicide is the interface roughness between silicide and Si substrate which is 1.004 nm and 2.645 nm respectively. The much reduced interface roughness stems from the atomically smooth Co deposition by ALD and it is the much smoother interface that makes less pronounced roughness induced scattering effect and consequently a lower $\rho _{\text {c}}$ . As the technology scales, contact silicide plays an essential role in determining parasitic resistance and ALD-Co silicide exhibits the great potential as the contact silicide beyond 5 nm technology node.