Silicides of ruthenium and osmium: Thin film reactions, diffusion, nucleation, and stability

Abstract

The reactions of ruthenium and osmium thin films with their silicon substrates lead to the formation of the following phases: the isomorphous Ru2Si3 and Os2Si3, and OsSi2. Ru2Si3 forms by a diffusion controlled mechanism from approximately 450 to 525 °C; the activation energy is 1.8 eV. Os2Si3 grows by the same process and with the same activation energy as Ru2Si3, but at slightly higher temperatures (for equivalent rates). OsSi2 grows at about 750 °C by a nucleation controlled mechanism. With an alloy of ruthenium containing 33 at.% rhodium, one obtains RuSi, which forms by a diffusion controlled mechanism with an activation energy of 2.4 eV from 400 to 475 °C, and Ru2Si3. In the case of the ruthenium alloy, the formation of Ru2Si3 is not diffusion controlled; the controlling process is akin to a nucleation mechanism. Ru2Si3 and Os2Si3 form by silicon motion. This is also true of OsSi2, but the high formation temperature results in some metal motion also during the formation of that phase. The diffusion processes are discussed on the basis of simple ideas about diffusion in intermetallic compounds. The nucleation processes are shown to occur for the phases OsSi2 and Ru2Si3 (with rhodium), as in other nucleated phases, when the enthalpy contribution to the driving force is close to zero. The observation leads one to anticipate that for most (perhaps all) platinum-like metals the silicides with the highest silicon content should be unstable at low temperatures.

Atomic layer deposited ultrathin metal nitride barrier layers for ruthenium interconnect applications

“…A Kissinger analysis by repeating the RTA measurement at 3 different ramp rates yields Ea ~ 1.6 eV which is close to the value reported earlier 46 . Similar kinetics studies on CVD Ru (3nm)/ALD MN (x nm)/Si (M=Ti, Ta; x = 0, 0.5) film stacks yields Ea ~ 2.1 -2.3 eV which is consistent with previous measurements 37 . Although significant improvement in surface coverage for Ru was achieved after incorporation of 0.5 nm of TiN and TaN layers ( fig.…”

“…As semiconductor devices become even smaller at sub-7 nm nodes, Ru may be a strong candidate for replacing some of the back end and middle of the line Cu as the interconnect material. Since literature on experimental studies of ruthenium silicide formation in thin 37,47,48 and ultra-thin films is very limited, the detailed study of barrier failure via ruthenium silicide formation reported in this work is highly relevant for barrier and interconnect process development for sub-7 nm technology nodes. In the future, the properties of the barrier layer may be tailored in order to see how it affects the microstructure of the ruthenium overlayer in high aspect ratio structures with ALD TaN liner and CVD Ru and its relationship to device performance.…”

“…The XRD peak positions match well with a tetragonal structure (P4 c2) with a = 5.53 Å and c = 8.82 Å (PDF #01-070-9281) 36 . The structure of Ru2Si3 may equally well be explained by an orthorhombic unit cell (Pbcn) with a = 11.06 Å, b = 8.93 Å and c = 5.53 Å (PDF #32-0978) 36 which is approximately half of the tetragonal structure (with P4 c2) 37 . But that orthorhombic phase is usually observed at lower temperatures 37 .…”

Silicide Formation of Atomic Layer Deposition Co Using Ti and Ru Capping Layer

“…The reason is that Si is dominant diffusing species when Ru silicide is formed though RTA. 18) In Fig. 5b of EELS spectra, Ru is diffused into the Co film and closed to Si substrate while some of the Co is slipped out after RTA process.…”

(Ba,Sr)TiO3 Thin Films for Dram’s

“…Many of the potential bottom electrode materials such as Pt and Ru form silicides at low temperatures [79][80][81][82]. In general, a diffusion barrier must be used between the oxygen stable material and the Si in order to prevent silicide formation.…”