Cobalt polishing slurries for 10 nm and beyond

Wang, Luling; Mishra, Abhudaya; Cruz, Benjamín; Wen, Richard

doi:10.1109/icpt.2014.7017287

Cited by 8 publications

(11 citation statements)

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“…Dissolution.-Co coupons (2 × 2 cm) were dipped for 3 minutes in 200 ml of the desired solutions stirred at ∼300 rpm maintained at 45 • C, a temperature that is expected to be close to the polishing temperature 29,[31][32][33] using a digital hotplate with a temperature probe. The dissolution rates were determined from the change in the thickness, before and after dipping the coupons, obtained by measuring the resistance of these films using a four-point probe.…”

Section: Methodsmentioning

confidence: 99%

“…3 wt% of silica loading was used in the slurries so that the RRs of CVD cobalt films used in this study could be compared to those obtained with PVD cobalt films in a previous study. 19 Three different H 2 O 2 concentrations (0.1, 1, and 5 wt%), selected based on the amount used in commercial cobalt slurries reported recently in the patent literature, 29,[31][32][33][34] were investigated and the results are shown in Figures 1 and 2.…”

Section: Effect Of H 2 O 2 Concentration and Ph On Co Drs And Rrs-mentioning

confidence: 99%

“…29 Recent patent literature suggests several slurry compositions with the required higher removal rates along with the necessary removal rate selectivity toward other liner/barrier layers (Ta/TaN, Ti/TiN) and dielectrics (TEOS, SiN, low-k, and ultra-low-k films). 29,[31][32][33] For example, Wang et al 31 have developed a polishing composition comprising 3 wt% abrasives, a weak acid acting as a complexing agent, at least one-azole containing corrosion inhibitor, water, and a pH adjustor as needed in the pH range of 7-12. They claimed very high removal rates (500 nm/min) at 1.5 psi down pressure along with a relatively low dissolution rate (≤1 nm/min) at pH 7 and 8.…”

mentioning

confidence: 99%

“…Furthermore, during the polish step, the RRs for Co:Cu should be ∼1:1 to minimize Cu dishing. Therefore, the barrier slurries 27 were typically formulated in near neutral to highly alkaline 28 regions where the formation of compact and passive oxides 19,22,25 on the cobalt surface lowers the RRs and helps in minimizing corrosion.…”

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confidence: 99%

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Citric Acid as a Complexing Agent in Chemical Mechanical Polishing Slurries for Cobalt Films for Interconnect Applications

Popuri

Sagi

Alety

et al. 2017

ECS J. Solid State Sci. Technol.

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A colloidal silica-based slurry (3-10 wt%) containing H 2 O 2 (1 wt%) and citric acid (50 mM) was found to polish chemical vapordeposited (CVD) cobalt (Co) films with removal rates (RRs) of ∼180-500 nm/min and a dissolution rate (DR) of ∼0 nm/min at pH 8 along with an RMS roughness of ∼0.5 nm and a corrosion current of ∼50 μA/cm 2 . Our results suggest that, in the presence of H 2 O 2 , the Co film surface was covered with a passive film of CoO in acidic conditions and Co 3 O 4 in alkaline conditions. However, in the presence of H 2 O 2 and citric acid in acidic conditions, formation of the soluble complex [Co(C 6 H 5 O 7 ) 2 ] 3− from abraded Co enhanced the RRs significantly. The roles of H 2 O 2 , citric acid, and silica abrasives as well as the pH on the Co material removal process are discussed and a removal mechanism is proposed. Two inhibitors namely, 1, 2, 4-Triazole (TAZ) and Benzotriazole (BTA), were tested in the presence of 50 mM citric acid at pH 8 but were found to be ineffective even at concentrations of 100 mM in reducing the E corr of Co-Ti couple to minimize galvanic corrosion that is essential when the Co/Ti structure is polished after the removal of bulk of Co and requires further study. Sub-10 nm devices face several challenges with copper as an interconnect material for back-end-of-the-line (BEOL) processes during the manufacture of integrated circuits. These include increasing resistivity with decreasing thickness, 1 non-conformal deposition at narrow trench widths ∼20 nm or less, 2 and scaling limitations of the diffusion barrier/liner.3 This led to the investigation of new trench filling materials. Cobalt is a promising alternative to meet the challenges of interconnect lines at these lower nodes for the first two metal layers M1 and M2, due to its lower resistivity at smaller dimensions (∼10 nm) compared to copper. [4][5][6] Kamineni et al. 7 proposed the use of chemical vapor deposited (CVD) cobalt to replace the widely used tungsten for local interconnects for 10 nm and smaller nodes. They emphasized two main advantages of CVD Co metallization which are a) CVD Co precursors do not damage the Ti liner enabling barrier scaling and b) it achieves void free fill in high aspect ratio features without defects, something that is difficult to achieve with a conventional physical vapor deposited (PVD) Co process. 8,9 Hence, CVD-based Co metallization is an attractive option for the technology nodes below 10 nm.CVD-based cobalt has also gained prominence in the advanced copper interconnects below 22 nm as liner [10][11][12][13][14][15][16][17] to improve adhesion between the barrier (TaN, TiN) and Cu seed layer where the Co film thickness is only ∼2 nm. Several authors 18-26 have investigated cobalt polishing for such applications where RR requirements are typically <20 nm/min and Co loss due to corrosion has to be as close to zero as possible, since even a minute loss of Co material can degrade the device reliability significantly. Hence, since the potential gap between Co and Cu is a large ∼0...

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Section: Methodsmentioning

confidence: 99%

Section: Effect Of H 2 O 2 Concentration and Ph On Co Drs And Rrs-mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Citric Acid as a Complexing Agent in Chemical Mechanical Polishing Slurries for Cobalt Films for Interconnect Applications

Popuri

Sagi

Alety

et al. 2017

ECS J. Solid State Sci. Technol.

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show abstract

“…Advanced semiconductor fabrication techniques are driven to meet the requirements of leading functionalities and enhanced performances by introducing dramatically scaled feature sizes, innovative assembly architectures, and novel integrated circuit materials. With further shrinking in device dimensions, cobalt (Co) has been emerging as one of the most promising candidates for both diffusion barrier layers, interconnect metals, and contact plugs, replacing tantalum/tantalum nitride, the first two copper metal layers (M1/M2 Cu), as well as tungsten (W) in the middle of the line, respectively. − It is mainly related to multiple excellent properties of Co, involving relatively low resistivity (∼6.2 μΩ·cm), high electromigration performance, good gap-fill ability, conformal adhesion characteristic, and inexpensive commercial availability. − …”

Section: Introductionmentioning

confidence: 99%