Potassium Oleate as a Dissolution and Corrosion Inhibitor during Chemical Mechanical Planarization of Chemical Vapor Deposited Co Films for Interconnect Applications

Abstract

1,2-4 Triazole (TAZ), N-lauroylsarcosine sodium salt (NLS) and potassium oleate (PO) were tested as passivating additives to previously developed H 2 O 2 and citric acid-based silica dispersions for the polishing of chemical vapor deposited Co films for interconnect applications. In comparison to TAZ and NLS, Co corrosion currents are ∼1 to 2 order of magnitude lower (∼1-3 μA cm −2 ) at pH 7 with PO and post-polish surface quality was much better. The galvanic corrosion currents between Co-Ti and Ti-TiN couples with PO were also very low (∼0.1 μA cm −2 ), making the previously developed silica and citric acid-based dispersion, now containing PO, suitable for both bulk removal of Co (step I) and for planarizing Co/Ti/TiN structures (step II) with excellent selectivity while stopping on low-k dielectric. Langmuir adsorption isotherm model analysis showed that the standard free energies of adsorption values were ∼−40 kJ/mol for PO suggesting chemisorption. Fourier transform infra-red (FTIR) and attenuated FTIR spectroscopy data show bridging coordination between the carboxylate ligand of PO and the Co surface. Cobalt is being evaluated as a possible alternative to replace copper as an interconnect metal for 10 nm and smaller technology nodes.1-5 The fabrication of the interconnects starts with the formation of trenches in a low-k dielectric. Liner/barrier layer, typically Ti/TiN 6 , is then deposited, followed by the filling of the trenches with Co by physical vapor deposition (PVD), 7,8 chemical vapor deposition (CVD) 6 or electroplating (ECP), and then removing the metal overburden by chemical mechanical planarization (CMP). 9 To prevent damage to the underlying softer low-k structures, the polishing of the metal films has to be performed at low pressures (∼1-2 psi) requiring the chemical component of the CMP process to be more dominant. 10Typically, interconnect CMP is a two-step process.2 The first step involves removal of the overburden at ∼300 nm/min or more 11 till about 10-20 nm of it remains. Then, a second step removes the residual Co along with the underlying liner/barrier at a relatively slower rate of ∼20-50 nm/min 12,13 while, and more importantly, controlling the galvanic corrosion between Co-Ti (liner) and Ti-TiN (barrier) couples and achieving close to 1:1:1 removal rate (RR) selectivity for Co:Ti:TiN and stopping on the low-k dielectric.An important aspect of polishing the interconnects is to protect the recessed regions of the wafer surface from dissolution while the protruding areas are selectively planarized.14 Controlling dissolution during CMP minimizes dishing (Figure 1) and helps achieve effective planarization. It is known that Co corrodes very easily in aqueous solutions.15 For example, it was shown recently that pits were generated on the film surface even at neutral conditions of pH ∼7, when exposed to a mixture of H 2 O 2 and citric acid 9 caused by the soluble complexation reaction between CoO formed at the surface and the citrate ligands, creating localized cavities in the surface la...

Effect of potassium oleate on chemical structure-compression relationship of natural rubber foam

“…The results of the control sample showed the peak at 3036-2850 cm -1 of C-H stretching (CH3 and CH2), the peak at 1663 cm -1 of C=C stretching in the double bond of natural rubber molecules [3], the peak at 836 cm -1 of C=C wagging and the peak at 1127-928 cm -1 of C-H stretching, respectively. We also found a peak at 1562 cm −1 which represented the asymmetric stretching modes of the carboxylate ion from potassium oleate [5]. The chemical structure of PO was shown in Figure 3.…”

“…However, decreasing the PO concentration by more than 50% results in a material becomes too dense and inappropriate with natural rubber foam products. Meanwhile, when PO was decreased, the compression strength of the half-soap sample was greater than that of the control sample at 17 kPa and 15 kPa, respectively [5]. The ATR-FTIR results were studied in the chemical functional groups of both samples, as shown in Figure 2.…”

A review on chemical and mechanical phenomena at the wafer interface during chemical mechanical planarization

“…Although surfactants such as CTAB [106], ammonium dodecyl sulfate [65], and potassium oleate [107] were also investigated as corrosion inhibitors, BTA is the most common corrosion inhibitor used in CMP slurries. In any case, all these inhibitors can complex with metal ions and remain stable on the metal film as undesirable organic residues [108], and it has been very difficult to remove these organic residues during post-CMP cleaning [109,110].…”

Investigation of Effect of L-Aspartic Acid and H2O2 for Cobalt Chemical Mechanical Polishing

“…8 that the surface RMS roughness (Sq) value reaches 0.186 nm, which is far lower than other reported values. 15,24 A flat surface is essential for integrated circuit technology, which is a necessary premise for cobalt to be applied to the interconnect structure and process. There are some white spikes in the 3D image, which are estimated to be residual silica particles.…”

“…IBM introduced CMP technology into DRAM manufacturing in the 1980 s. It is currently the only global planarization process The process of achieving global planarization through chemical and mechanical cooperation effects almost covers the FEOL, BEOL, and packaging processes of the chip processing. [14][15][16] In order to obtain a higher removal rate (RR) and defect-free surface quality of Cobalt CMP, many complexing agents, oxidants and inhibitors are usually added to the slurry. [17][18][19][20][21] There shows so many researchers to do a plenty of works to enhance the RR in the Cobalt CMP processing.…”