Influence of the Seed Layer and Electrolyte on the Epitaxial Electrodeposition of Co(0001) for the Fabrication of Single Crystal Interconnects

Co electrodeposition was performed onto single crystal Ru(0001) and polycrystalline Ru films to study the influence of such seed layers on the growth of epitaxial Co(0001). The effect of misfit strain on the electrodeposited Co(0001) films was studied using 60 and 10 nm-thick Ru(0001) seed layers, where the misfit strains of the Co layer on the two Ru(0001) seed layers are 7.9% and 9.6%, respectively. Despite a large misfit strain of 7.9%, the planar growth of Co(0001) was achieved up to a thickness of 42 nm before a transition to island growth was observed. Epitaxial Co films electrodeposited onto 10 nm Ru(0001) showed increased roughness when compared with Co electrodeposited onto the 60 nm seed layer. Co electrodeposition onto polycrystalline Ru resulted in a rough, polycrystalline film with faceted growth. Electrochemical experiments and simulations were used to study the influence of [Co2+] and solution pH on the throughput of the electrodeposition process. By increasing [Co2+] from 1 to 20 mM, the deposition rate of Co(0001) increased from 0.23 nm min−1to 0.88 nm min−1at an applied current density of −80μA cm−2.

Authors:
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Publication Date:
NSF-PAR ID:
10204129
Journal Name:
Journal of The Electrochemical Society
Volume:
167
Issue:
16
Page Range or eLocation-ID:
Article No. 162503
ISSN:
0013-4651
Publisher:
The Electrochemical Society
2. The electrodeposition of Ru was investigated from solutions of ruthenium(III) nitrosyl sulfate and ruthenium(III) chloride onto seed layers of epitaxial and polycrystalline Ru and epitaxial Au. Using both galvanostatic and potentiostatic deposition modes, metallic Ru was found to electrodeposit as a porous layer comprised of (0001) oriented Ru crystallites, the presence of which was discovered and confirmed by X-ray and scanning transmission and transmission electron microscope (S/TEM) analyses. This finding was independent of the Ru salt and seed layer used. Using X-ray reflectivity (XRR), the average film density$ρeff$of the porous electrodeposited Ru layer was measured as less than the density of bulk Ru$ρRu,bulk$(14.414 g cm−3). Increasing the magnitude of the applied current density from −100μA cm−2to −10 mA cm−2in solutions of Ru nitrosyl sulfate increased the$ρeff$from 7.4 g cm−3to 9.7 g cm−2while the current efficiency decreased from 9.4% to 4.3%.