Fundamental Study of Chemical–Mechanical Polishing Slurry of Cobalt Barrier Metal for the Next-Generation Interconnect Process

Nishizawa, Hideyuki; Haruki, Nojo; Isobe, Akira

doi:10.1143/jjap.49.05fc03

Cited by 38 publications

(40 citation statements)

References 2 publications

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“…At pH 4 and 7, the postpolish surface had much higher P/V and Sq values compare to that at pH 8. The higher roughness in the acidic region can be attributed to localized corrosion that was also reported by other authors 18,53,54 for PVD films. Indeed Co coupons (∼2 × 2 cm 2 ) simply dipped in 200 ml of 1 wt% H 2 O 2 + 1 wt% citric acid solution (stirred at 300 rpm) at pH 4, 7, or 8 for three minutes showed pits again at pH 4 and 7 but not at pH 8, as shown Figure 7 (panels d, e and f).…”

Section: Resultssupporting

confidence: 81%

“…Several authors [18][19][20][21][22][23][24][25][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 ∼0.61 V, it is very important to lower this to ∼10-20 mV.…”

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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: Resultssupporting

confidence: 81%

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confidence: 99%

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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“…It was suggested to use alkaline slurry with low peroxide concentration. Nishizawa et al 13 reported the effects of H 2 O 2 and pH value on chemical mechanical polishing of cobalt. The results are similar as those of Ref.…”

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confidence: 99%

The Effect of H2O2 and 2-MT on the Chemical Mechanical Polishing of Cobalt Adhesion Layer in Acid Slurry

Wang

et al. 2012

Electrochem. Solid-State Lett.

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Cobalt has emerged as a potential adhesion layer for advanced copper metallization. This work investigates the role of oxidant and inhibitor on the corrosion and polishing properties of cobalt in the acid slurry. It is found that H 2 O 2 could greatly increase the static etch rate (SER) and removal rate (RR) of cobalt. The 2-Mercaptothiazoline (2-MT) is very efficient to inhibit cobalt corrosion and reduce the SER and RR of cobalt in the acid slurry. In the glycine based slurry at pH = 5, by using 2-MT, the corrosion potential difference between Co and Cu can be reduced to a very small value.

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“…Only in this way can the dishing defects caused by the copper overburden CMP step be corrected, the residual copper be removed, and the surface non-uniformity of the patterned wafer be controlled. 49 Fig. 15 presents the removal rate for ruthenium and copper obtained using the slurries with various components (the specific information of slurries is embodied in the title of Fig.…”

Section: Resultsmentioning

confidence: 99%

“…In order to achieve planarization during barrier CMP, copper dishing, which is the height difference of a copper with respect to the adjacent oxides, must be controlled. [45][46][47][48][49] This would require that the removal rate of barrier material is greater than that of copper. Only in this way can the dishing defects caused by the copper overburden CMP step be corrected, the residual copper be removed, and the surface non-uniformity of the patterned wafer be controlled.…”

Section: Removal Rate Selectivitymentioning

confidence: 99%

Effect of ethylenediamine on CMP performance of ruthenium in H₂O₂-based slurries

Liu

et al. 2022

RSC Adv.

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Fundamental Study of Chemical–Mechanical Polishing Slurry of Cobalt Barrier Metal for the Next-Generation Interconnect Process

Cited by 38 publications

References 2 publications

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

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

The Effect of H2O2 and 2-MT on the Chemical Mechanical Polishing of Cobalt Adhesion Layer in Acid Slurry

Effect of ethylenediamine on CMP performance of ruthenium in H₂O₂-based slurries

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Fundamental Study of Chemical–Mechanical Polishing Slurry of Cobalt Barrier Metal for the Next-Generation Interconnect Process

Cited by 38 publications

References 2 publications

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

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

The Effect of H2O2 and 2-MT on the Chemical Mechanical Polishing of Cobalt Adhesion Layer in Acid Slurry

Effect of ethylenediamine on CMP performance of ruthenium in H2O2-based slurries

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Effect of ethylenediamine on CMP performance of ruthenium in H₂O₂-based slurries