The role of oxide formation on insulating versus metallic substrates during Co and Ru selective ALD

Proximity Effects of the Selective Atomic Layer Deposition of Cobalt on the Nanoscale: Implications for Interconnects

“…In addition, nearly all of the nuclei are of a similar diameter, with 95% of particles being between 230–298 nm 2 with oblong disc shapes as observed in SEM and TEM imagery. From the work of Wolf et al, it is observed that selectivity on un-patterned SiO 2 during Co ALD with Co­( t Bu 2 DAD) 2 is consistent with the lack of molecular adsorption . Nuclei 2–4 nm tall are observed by AFM on blanket SiO 2 , but it is hypothesized that there are more hydroxyl groups on patterned SiO 2 due to defects formed during CMP of the surface compared with thermally grown SiO 2 , so that the proximity of the Co/Cu surfaces is more likely to result in unwanted adsorption of Co precursor on the hydroxyl groups and therefore, unwanted nucleation.…”

“…In this report, Co ALD was performed using the coreactants Co­( t Bu 2 DAD) 2 (EMD Performance Materials, Inc.) and TBA at 180 °C on a test pattern consisting of Cu stripes embedded in SiO 2 . , In this process, the Co­( t Bu 2 DAD) 2 precursor bound to the Cu metal surface engages in ligand exchange with the dosed TBA to form Co metal plus amine ligands, which are subsequently desorbed during pump-down as described in eq and Figure . …”

“…In this report, Co ALD was performed using the coreactants Co(tBu 2 DAD) 2 (EMD Performance Materials, Inc.) and TBA at 180 °C on a test pattern consisting of Cu stripes embedded in SiO 2 . 12,13 In this process, the Co(tBu 2 DAD) 2 precursor bound to the Cu metal surface engages in ligand exchange with the dosed TBA to form Co metal plus amine ligands, which are subsequently desorbed during pump-down as described in eq 1 and Figure 2a is a top-down SEM image (see the full image in Figure S1 in Supporting Information) of the test pattern prior to Co ALD, consisting of 85 nm wide strips of Cu deposited via electrodeposition on a TiN/Si substrate, then planarized by chemical−mechanical polishing (CMP). A degrease and 0.5% HF clean were performed on the post-CMP samples to minimize surface contamination.…”

“…Another novel application of such a selective Co ALD process is in the bonding of suspended Cu pads to form electrical contacts, enabling tighter-packed connections between bonded dies during packaging . Selective ALD of the Co metal has previously been reported using several precursors such as Co­(AMD) 2 and ( t Bu-Allyl)­Co­(CO) 3 . , Of special interest is one selective Co ALD process reported by the Winter group using bis­(1,4-di tert -butyl-1,3-diazadienyl) cobalt [Co­( t Bu 2 DAD) 2 ] and formic acid at 180 C, exhibiting a very high selectivity toward metals versus insulators. , Additional studies on the deposition of Co using Co­( t Bu 2 DAD) 2 were performed using tert -butylamine to avoid oxidation of metallic substrates. , …”

“…10,11 Additional studies on the deposition of Co using Co(tBu 2 DAD) 2 were performed using tert-butylamine to avoid oxidation of metallic substrates. 12,13 During area-selective ALD on conductors versus insulators, loss of selectivity can result from surface defects (such as hydroxyl groups) on insulators causing unwanted nucleation. 14 This problem is magnified by close proximity to the desired growth surface, where it is hypothesized that excess precursors remaining weakly bound to the growth surface may diffuse onto the insulator.…”