Material removal mechanism of copper chemical mechanical polishing in a periodate-based slurry

Applied Surface Science 337 (2015) 130–137

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Material removal mechanism of copper chemical mechanical polishing in a periodate-based slurry Jie Cheng, Tongqing Wang, Yongyong He, Xinchun Lu ∗ State Key Laboratory of Tribology, Tsinghua University, Beijing, 10084, China

a r t i c l e

i n f o

Article history: Received 15 December 2014 Received in revised form 16 January 2015 Accepted 11 February 2015 Available online 18 February 2015 Keywords: Chemical mechanical polishing Copper Periodate Surface chemistry Material removal mechanism

a b s t r a c t The material removal mechanism of copper in a periodate-based slurry during barrier layer chemical mechanical polishing (CMP) has not been intensively investigated. This paper presents a study of the copper surface film chemistry and mechanics in a periodate-based slurry. On this basis, the controlling factor of the copper CMP material removal mechanism is proposed. The results show that the chemical and electrochemical reaction products on the copper surface are complex and vary considerably as a function of the solution pH. Under acidic conditions (pH 4) the copper surface underwent strong chemical dissolution while the corrosion was mild and uniform under alkaline conditions (pH 11). The corrosion effect was the lowest in near neutral solutions because the surface was covered with non-uniform Cu(IO3 )2 ·H2 O/Cu-periodate/copper oxides films, which had better passivation effect. The surface film thickness and mechanical removal properties were studied by AES and AFM nano-scratch tests. Based on the combined surface film analysis and CMP experiment results, it can be concluded that the controlling factor during copper CMP in a periodate-based slurry is the chemical-enhanced mechanical removal of the surface films. The periodate-based slurry should be modified by the addition of corrosion inhibitors and complexing agents to achieve a good copper surface quality with moderate chemical dissolution. © 2015 Elsevier B.V. All rights reserved.

1. Introduction As the feature size of ultra-large scale integrated circuit continues to shrink below 22 nm, the conventional Ta/TaN bilayer barrier structure will be inadequate because of the large film thickness and gap filling problems [1,2]. To solve these problems, Ruthenium (Ru) has been considered as the most suitable candidate for replacing the Ta/TaN barrier layer in copper interconnect structures [3,4]. During the production process of microelectronic chips, the chemical mechanical polishing (CMP) process is the key for enabling both global and local planarization [5,6]. The CMP of Cu/Ru structure has been studied, especially the ruthenium polishing in a periodatebased slurry [7–9]. However, the copper polishing process in a barrier layer slurry has not been intensively investigated. The material removal mechanism, surface chemistry characteristics, galvanic corrosion problem, and chemical-mechanical interactions during the CMP process are not well known yet [10,11]. Y. Li et al. studied the material removal rate (MRR) of copper and tantalum as a function of pH value in an iodate-based slurry. The results showed that the polishing rate of copper at pH 2 was considerably higher

∗ Corresponding author. Tel./f ax: +86 010 62797362. E-mail address: [email protected] (X. Lu). http://dx.doi.org/10.1016/j.apsusc.2015.02.076 0169-4332/© 2015 Elsevier B.V. All rights reserved.

because the passivation film on the copper surface was more likely to exist at higher pH values [12]. L. Jiang et al. found that the copper MRR in a KIO4 -based slurry increased with the concentration of KIO4 increasing, which was due to the formation of Cu-periodate and Cu-iodate compounds [13]. Nevertheless, lots of work needs to be done to reveal the material removal mechanism of copper in a periodate-based slurry. Copper CMP can be identified as a transient chemical process with intermittent mechanical phenomena [14]. The total material loss during CMP process could be divided into three parts: the chemical dissolution, the mechanical removal and the chemical–mechanical interactions [15,16]. However, the situation may differ greatly due to different slurry compositions and polished materials [17]. T. Du et al. believed that at low H2 O2 concentrations, the copper material removal was caused by electrochemical dissolution, while it was due to the mechanical abrasion of the oxidized surface when the H2 O2 concentration was comparatively high [18]. J. Li et al. investigated the material removal mechanism of copper in a H2 O2 -based slurry. They found that the chemical-mechanical synergistic effect played an important role in near-neutral slurries, while the corrosion effect dominated when the slurry was strongly acidic or alkaline [19]. Little work has been done to study the material removal mechanism of copper with periodate as oxidant. Therefore, it is essential to find out the controlling factor of

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material loss during the copper CMP process in a periodate-based slurry. In our previous study, the passivation behavior of copper in KIO4 -based slurry at different pH values was investigated by tribo-corrosion experiments. The results revealed that the copper repassivation process is obviously faster in alkaline slurries than that in acidic slurries. Moreover, the CMP-chemical tests indicated that the corrosion current density during polishing (Icc ) reached the minimum at pH 7, and ascended when the pH value increased or decreased [20]. It can be inferred from the experimental data that the corrosion under acidic conditions was more severe than that under alkaline conditions. Raman spectroscopy experiments of the copper surface products showed that the copper surface was mainly passivated with copper oxides, copper hydroxide and copper iodide, but these varied as a function of the pH value of slurry. However, further complementary experiments should be performed to confirm this opinion. The existing investigations of copper in periodate-based slurry mainly focus on copper CMP performance rather than intensive surface property analysis and material removal mechanism. The surface chemistry of the copper oxidation films needs to be intensively investigated to determine the key factor dominating material removal during CMP in a periodate-based slurry. In this study, the copper surface reaction products were analyzed. The mechanical effect during the CMP process was evaluated as well. Finally, in order to indicate the controlling factor of material removal during the CMP process, CMP tests were carried out over a wide pH range of 4.0–11.0. 2. Experimental 2.1. CMP-electrochemical experiments CMP-electrochemical experiments were carried out to study the electrochemical behavior of copper during CMP. The apparatus was modified on a chemical mechanical polishing machine connected with an electrochemical workstation (CHI600C, Chenhua). The copper sample (99.99%) was 12.5 mm in diameter and about 1 mm in thickness. The pad was IC1010/Suba IV and the slurry contained 0.015 M KIO4 without any abrasives. The pH was adjusted to 4, 6, 7, 9, 10 and 11 respectively. The counter electrode was platinum and the reference was an Ag/AgCl (3.5 M) electrode. During the polishing process, the applied force on the copper sample was 2.9 psi. The copper sample was stationary and the pad rotated at a speed of 100 rpm. The potentiodynamic polarisation experiments were conducted at a scan rate of 1 mV/s. The corrosion current density under both the polishing and static conditions has been calculated using the linear fitting method of E and Log (I) in Tafel strong polarization region thereafter. 2.2. Surface chemistry characterization The chemical and electrochemical reaction products on the copper surface were analyzed using an X-ray microprobe (PHI Quantera Scanning XPS Microprobe, ULVAC-PHI Inc.). The copper samples were cut from electroplated copper on a wafer. Prior to the experiments, the copper samples were immersed in 0.05 M citric acid (pH ≈ 2) for 5 min to remove the native oxide layer, and then cleaned in absolute ethyl alcohol and dried using a N2 gas stream. The immersion solution contains 0.015 M KIO4 as oxidant. The pH value was adjusted to 4, 6, 9 and 11 with KOH and H2 SO4 as pH adjustors. The copper samples were immersed in the solutions for 5 min and cleaned in DI water. The Cu 2p and I 3d XPS peaks were analyzed and the data were fitted by the XPSPEAK software. The surface morphology of copper after the immersion experiments

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was observed using AFM (Asylum Research MFP-3D) and scanning electron microscopy (SEM, FEI Quanta 200 FEG). The thickness of the copper surface passivation film was obtained by AES (Physical Electronics, Inc., PHI-700) with a coaxial cylindrical mirror analyzer (CMA). The sputtering rate was 5 nm/min or 18 nm/min according to the different surface film thickness. The preparation of the copper samples was identical to that discussed previously. The immersion solution contained 0.015 M KIO4 , and the immersion time was also 5 min. 2.3. Nano-scratch tests. Copper (99.99% purity) was cut into 20 mm × 20 mm × 2 mm squares. Before the experiments, the copper samples were polished on a Struers bench top polisher (TegraPol-35) until the surface roughness was below 3 nm, and then immersed into solutions containing 0.015 M KIO4 with different pH values for 5 min. The nano-scratch experiments were performed using AFM (Veeco Co., RTESP) with a silicon rectangular cantilever probe. The constant applied force during scratching was 0.126 ␮N. 2.4. CMP experiments. Electroplated copper on a 2 inch wafer was used. A polisher (CETR CP4) was used with a platen/carrier speed of 100/100 and a slurry flow rate of 100 mL/min at a down pressure of 4 psi. The slurry contained 5% Nexsil 85k-40 colloidal silica abrasive (Nyacol Nano Technologies Inc.), and 0.015 M KIO4 at different pH values. The pad was IC1010/Suba-IV (K-type groove, Dow Electronic Materials). The MRRs were measured using the weight-loss method after polishing for 1 min. Prior to the experiments, conditioning was carried out for 10 min. Between each polishing, a pad ex-situ conditioning was executed for 45 s. The surface morphology after CMP was observed using an optical interferometer surface-mapping microscope (MicroXAM, Veeco). 3. Results and discussion 3.1. Surface chemistry characterization During the corrosion of copper, the electrode potential is the key factor to control the ionization of copper while the pH value greatly affects the stability of the surface film. The relative stability regions of aqueous substances in a Cu-I-H2 O system are shown in the Pourbaix diagram (Eh-pH), presented in Fig. 1. The activities of I− and Cu2+ are assumed equal to their [I− ] and [Cu2+ ] concentrations, respectively. The equilibrium constant K used in Fig. 1 are listed in Table 2, which correspond well to the literature [21]. It is clear that the copper surface reaction products in the periodate-based slurry are significantly more complex than that in H2 O2 -based slurry [22–24]. The surface reaction products consist not only of copper oxides (CuO/Cu2 O/Cu(OH)2 ), but also copper iodide (CuI), iodine (I2 ) and copper iodate (Cu(IO3 )2 ·H2 O) [13,25]. However, as shown in Fig. 1, the copper surface film composition varies with different pH values. The Cu(IO3 )2 ·H2 O and I2 are more likely to be present in more acidic solutions whereas the copper surface tends to be covered with CuO and Cu2 O when the solution is extremely alkaline. The opinion mentioned above is supported by XPS experiments. Fig. 2 shows the XPS Cu 2p results on the copper surface immersed into KIO4 solutions with different pH values for 5 min. When the solution pH was 6 and 9, the Cu 2p3/2 peaks obviously shifted to higher binding energies. At the same time, satellite peaks were observed between 940 and 945 eV, indicating the formation of CuO and Cu(OH)2 [26,27]. The deconvolution of the Cu 2p3/2 spectra on the untreated copper surface showed two peaks, at 933.8 eV (peak

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(934.9 eV and 935.5 eV). There was insufficient supportive data to prove this, but the appearance of these two peaks was likely due to the formation of the Cu(IO3 )2 ·H2 O/Cu-periodate complex, which corresponded to previous Raman spectral data [20,30]. The deconvolution data of the I 3d XPS spectra are shown in Fig. 3. The XPS of the I 3d core levels revealed two sharp and well-resolved peaks, corresponding to 3d5/2 (∼620 eV) and 3d3/2 (∼630 eV) spinorbit split levels. The peaks appearing at 619.4 eV and 630.5 eV indicated the presence of CuI [31–33]. The peak located at 619.9 eV referred to chemisorbed I2 , which clearly existed on the copper surface under a pH 4 condition [34]. It has been reported in the literature that the binding energy of the I 3d in Cu(IO3 )2 is between 621.3 and 622.5 eV, but the binding energies for Cu-periodates are not clear because the reaction products are quite complex [35–38]. There was an apparent strong peak located at 624.2 eV, especially under the pH 6 and pH 9 conditions, which was the evidence for the presence of a Cu(IO3 )2 ·H2 O/Cu-periodate compound [39]. Table 3 shows the atomic concentrations of the Cu, O, and I on the copper surface. The I concentration reached the maximum at pH 6 and 9 (16.88% and 13.64%, respectively) due to the formation of the Cu(IO3 )2 ·H2 O and Cu(IO4 )2 complexes, as discussed earlier. The 11.20% I concentration under the pH 4 condition was caused by the formation of I2 and CuI on copper surface. However, when the solution was more alkaline, the element I on copper surface was negligible (only 3.76%). 3.2. Copper surface corrosion morphology

Fig. 1. Eh-pH diagram at 25 ◦ C for (a) the Cu-I-H2 O system and (b) the I-Cu-H2 O system. [Cu2+ ] = 10−2 M and [I− ] = 10−2 M.

1) and 932.8 eV (peak 2), corresponding to copper in the form of CuO and metallic copper (Cu0 ), respectively [28,29]. The similar analysis results were also obtained under pH 4 and 11 conditions, showing that the copper surface was mainly composed of metallic copper (peak 2, 932.8 eV). However, for the pH 6 and 9 solutions, two peaks (peak 3 and peak 4) appeared at higher binding energies

The copper surface morphology and surface average roughness after being immersed in the KIO4 solutions are shown in Fig. 4. At pH 11, the surface roughness remained almost unchanged from the untreated copper surface, indicating a uniform and mild corrosion proceeding on the copper surface (Fig. 4(d) and (e)). However, severe corrosion occurred when the solution was acidic, especially when the pH value was 6, as was shown in Fig. 4(a) and (b). These results correspond well with the SEM images of the immersed copper surface, as is demonstrated in Fig. 5. It is obvious that at pH 6 and pH 9, the copper surface was in the typical oxidized state, which is in line with the investigation by C. Liao et al. [40]. As can be seen in Fig. 5(b) and (c), the surface oxidation films were non-uniform, indicating that the Cu(IO3 )2 ·H2 O/Cu-periodate/copper oxide films have a poor surface quality. The corrosion current during the CMP at pH 4 provided the highest value (Table 1), due to the strong oxidative ability of KIO4 under acidic conditions, in addition to the poor passivation effect of the CuI/I2 surface films [41]. 3.3. Copper surface film thickness In order to characterize the corrosion products thickness on the copper surface in KIO4 -based solutions, a semi-quantitative analysis was done by AES experiments. Fig. 6(a) shows the element depth profiles of the copper surface films under a pH 6 condition. After 4 min, the Cu atomic concentration increased to greater than 90%, and the film thickness was estimated to about 72 nm [23]. Fig. 6(b) shows the calculated surface film thickness based on the AES data. It was evident that the surface film thickness increased as the pH value decreased, indicating that in acidic solutions the copper electrochemical and mechanical reaction products are more likely to adsorb on the surface rather than directly dissolute in the solution. 3.4. Nano-scratch experiments

Fig. 2. The XPS of Cu 2p on the copper surface in 0.015 M KIO4 -based solutions at different pH values.

In order to evaluate the mechanical removal properties of copper surface films in a periodate-based slurry, the nano-scratch tests were performed under a 0.126 ␮N force after immersing the samples into 0.015 M KIO4 solutions for 5 min. Fig. 7 shows the

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Fig. 3. The XPS of the I 3d on copper surface in 0.015 M KIO4 -based solutions at pH values of (a) 4, (b) 6, (c) 9, (d) 11 and the untreated copper surface.

Fig. 4. The copper surface morphology after a 5 min immersion in 0.015 M KIO4 at pH values of (a) 4, (b) 6, (c) 9, (d) 11, and (e) the untreated copper surface. The average roughness (Ra) was (a) 23.84 nm, (b) 24.97 nm, (c) 12.70 nm, (d) 0.28 nm, and (e) 0.39 nm.

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Fig. 5. SEM images of the copper surface after a 5 min immersion in 0.015 M KIO4 at pH values of (a) 4, (b) 6, (c) 9, (d) 11, and (e) the untreated copper surface. Table 1 The corrosion current density (Icc ) measured by potentiodynamic polarization curves, the material removal attributed to corrosion (MRRcc ) and the MRRcc /MRR from the CMP-chemical experiments. pH

4

6

7

9

Icc (␮A) MRRcc (nm/min) MRRcc /MRR

29.2388 0.649 1.45%

15.9281 0.354 1.37%

5.4806 0.122 0.39%

6.0502 0.122 0.32%

typical scratch morphology under a pH 9 condition. There was obvious pileup around the scratch trench due to the probe pushing the removed material. The average scratch depth is shown in Fig. 8. It was apparent that the scratch depth was comparatively low (∼ 2 nm) for copper surface that were untreated or treated in the pH 11 solution, similar to the results obtained

10 8.5894 0.191 0.70%

11 9.4843 0.211 0.86%

in H2 O2 -based solutions [19]. When the pH value of the solutions were 4, 6 and 9, the scratch depth sharply increased to more than 50 nm, with the maximum (79.29 nm) obtained at pH 6. These results can be explained by two reasons. First, the surface films produced in the KIO4 -based solutions (at pH values of 4, 6, and 9) were significantly thicker than that under

Fig. 6. AES results of the copper surface after a 5 min immersion in 0.015 M KIO4 with (a) element depth profiles at pH 6 and (b) the calculated surface film thickness according to the data.

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Fig. 9. The MRR and COF of copper as a function of the slurry pH during the CMP experiments.

pH 11 and untreated conditions. Second, it was reported that the Cu(IO3 )2 /Cu-periodate formed on a copper surface was nonuniform and could be easily removed due to its low mechanical strength [13,42,43]. 3.5. Mechanism of the chemical enhanced mechanical material removal during the CMP To investigate the controlling factor of material removal during the copper CMP process, CMP experiments were conducted to compare the MRR and coefficient of friction (COF) as a function of solution pH. Fig. 9 shows the MRR and COF in the CMP experiments as a function of pH. It is clear that the MRR of copper was the lowest at pH 11 (24.43 nm/min), whereas it reached the maximum when the pH value was 4 (44.80 nm/min). Based on the aforementioned analysis, it is surmised that the high MRR of the copper under pH 4 is due to the strong chemical dissolution. However, the MRR resulting from the total corrosion (MRRcc ) is shown in Table 1, which is calculated by the equation [44]: MRRcc = Icc M/nF

Fig. 7. Typical nano-scratch of the copper surface at pH 9 with (a) AFM 2D image and (b) cross-sectional profile of the scratch depth.

Fig. 8. The nano-scratch depth variation of the copper surface under different pH conditions.

(1)

where Icc is the corrosion current during the CMP process measured by the potentiodynamic polarization curve, F is the Faraday constant, n is the valence of copper in the research system under examination,  is the density and M is the atomic mass of copper. The MRRcc and MRRcc /MRR are listed in Table 1. It is interesting that although the copper surface was severely corroded in by the CuIO4 − redox reaction at pH 4, the MRRcc contributed to only a small portion of the total MRR (1.45%). The MRRcc /MRR at other pH values were even less, at no more than 2% of the total. These results are completely different from those in a copper CMP slurry with H2 O2 as the oxidant, where the chemical corrosion occupied a major portion of the total material loss when the chemical dissolution was strong [19,44]. Based on the above analysis, it could be concluded that during the copper CMP in a KIO4 -based slurry, the controlling factor of material loss was the chemical-enhanced mechanical removal of the surface films. The COF in near neutral conditions was comparatively high, which is due to the removal of the non-uniform Cu(IO3 )2 ·H2 O/Cu-periodate/copper oxide surface films. The copper surface quality after the CMP in Fig. 10 indicated that the resultant surface was not desirable, especially when the slurry was acidic, because the chemical and electromechanical reaction products on the surface were heterogeneous with a poor passivation effect.

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Fig. 10. The copper surface morphology after CMP experiments at (a) pH 4, (b) pH 6, (c) pH 9, and (d) pH 11.

Table 2 Thermodynamic data for the Eh-pH diagrams of the Cu-I-H2 O system. Reactions

Log K

−

Cu + 2e →Cu 2Cu2+ + H2 O + 2e− →Cu2 O (s) + 2H+ Cu2 O (s) + 2H+ + 2e− →2Cu + H2 O CuO (s) + 2H+ →Cu2+ + H2 O Cu2+ + I- + e- →CuI (s) IO4 − + 2e- + 2H+ →IO3 - + H2 O IO4 − + 8e- + 8H+ →I- + 4H2 O Cu2+ + 2IO3 − + H2 O→Cu(IO3 )2 ·H2 O (s) IO4 − + 7e- + 8H+ →I2 (s) + 4H2 O IO3 − + 6H+ + 6e− →I− + 3H2 O I2 (s) + 2e− →2I− 2IO3 − + 12H+ + 10e− →I2 (s) + 6H2 O 2+

11.49 7.36 15.625 7.59 15.30 53.73 164.97 7.27 155.87 111.27 18.20 204.28

Table 3 Atomic concentrations obtained by XPS of the copper surface. (%)

pH 4

pH 6

pH 9

pH 10

Untreated

Cu O I

41.09 47.71 11.20

19.69 63.43 16.88

18.59 67.77 13.64

36.33 59.91 3.76

24.90 73.10 2.00

4. Conclusions The copper material removal mechanism in a periodate-based slurry during CMP was investigated by surface film chemistry and

mechanical analysis. Eventually the controlling factor of copper material removal during polishing was determined. It was found that additives such as inhibitors and complexing agents should be added to optimize the KIO4 -based slurry in order to achieve a good MRR and surface quality. The following conclusions have been drawn:

1. The surface chemical and electrochemical reaction products on copper in a periodate-based slurry are complex. In acidic conditions, the surface is primarily covered with CuI/I2 composite films. In near neutral regions, the surface films comprise Cu(IO3 )2 ·H2 O/Cu-periodate/copper oxides. In alkaline conditions, the copper surface is covered with CuO/Cu2 O. 2. Under acidic conditions (pH 4) the copper surface undergoes strong chemical dissolution while the corrosion is mild and uniform under alkaline conditions (pH 11). The corrosion effect is the lowest in near neutral solutions because the surface is passivated with non-uniform Cu(IO3 )2 ·H2 O/Cu-periodate/copper oxides films. 3. The surface film thickness increases with the decreasing solution pH. The nano-scratch tests show that under near neutral conditions, the copper surface films are easily removed because the surface films are mechanically weak. 4. During copper CMP in a KIO4 -based slurry, the controlling factor of material loss is the chemical-enhanced mechanical removal of the surface films.

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Acknowledgements The authors greatly appreciate financial support from the Science Fund for Creative Research Groups (51321092), the National Natural Science Foundation of China (51205226, 91323302), and the National Basic Research Program of China (2015CB057203) Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.apsusc. 2015.02.076. References [1] A. Roule, M. Amuntencei, E. Deronzier, P.H. Haumesser, S. Da Silva, X. Avale, O. Pollet, R. Baskaran, G. Passemard, Seed layer enhancement by electrochemical deposition: The copper seed solution for beyond 45 nm, Microelectron. Eng. 84 (2007) 2610–2614. [2] R. Chan, T.N. Arunagiri, Y. Zhang, O. Chyan, R.M. Wallace, M.J. Kim, T.Q. Hurd, Diffusion studies of copper on ruthenium thin film a plateable copper diffusion barrier, Electrochem. Solid-State Lett. 7 (2004) G154–G157. [3] C. Wu, Y. Wang, W. Lee, Copper electrodeposition on Ru-N barrier with various nitrogen content for 22 nm semiconductor manufacturing application, J. Electrochem. Soc. 159 (2012) D684–D689. [4] L.D. Urzo, S. Schaltin, A. Shkurankov, H. Plank, G. Kothleitner, C. Gspan, K. Binnemans, J. Fransaer, Direct-on-barrier copper electroplating on ruthenium from the ionic liquid 1-ethyl-3-methylimidazolium dicyanamide, J. Mater. Sci. Mater. Electron. 23 (2012) 945–951. [5] M. Sivanandini, M.K. Dhami, S.S. Dhami, B.S. Pabla, Enhancement in surface finish by modification of basic colloidal silica with silane in chemical mechanical polishing, ECS J. Solid State Sci. Technol. 3 (2014) P324–P329. [6] Y.G. Wang, L.C. Zhang, A. Biddut, Chemical effect on the material removal rate in the CMP of silicon wafers, Wear 270 (2011) 312–316. [7] L. Jiang, Y. He, Y. Li, J. Luo, Effect of ionic strength on ruthenium CMP in H2 O2 based slurries, Appl. Surf. Sci. 317 (2014) 332–337. [8] H. Cui, J. Park, J. Park, Corrosion inhibitors in sodium periodate slurry for chemical mechanical planarization of ruthenium film, ECS J. Solid State Sci. Technol. 2 (2013) P71–P75. [9] M.C. Turk, S.E. Rock, H.P. Amanapu, L.G. Teugels, D. Roy, Investigation of percarbonate based slurry chemistry for controlling galvanic corrosion during CMP of ruthenium, ECS J. Solid State Sci. Technol. 2 (2013) P205–P213. [10] A.M. Chockalingam, U.R.K. Lagudu, S.V. Babu, Potassium periodate-based solutions for minimizing galvanic corrosion at the Cu-Mn interface and for polishing the associated Cu interconnect structures, ECS J. Solid State Sci. Technol. 2 (2013) P160–P165. [11] K. Yu, N. Thomas, S.S. Venkataraman, K.S. Pillai, T. Hurd, K. Boggs, O. Chyan, Study of Cu bimetallic corrosion in CMP chemical environments using optical scanning and micropattern corrosion screening, ECS Trans. 35 (2011) 173–184. [12] Y. Li, S.V. Babu, Chemical mechanical polishing of copper and tantalum in potassium iodate-based slurries, Electrochem. Solid-State Lett. 4 (2001) G20–G22. [13] L. Jiang, Y. He, X. Niu, Y. Li, J. Luo, Synergetic effect of benzotriazole and non-ionic surfactant on copper chemical mechanical polishing in KIO4 -based slurries, Thin Solid Films 558 (2014) 272–278. [14] J. Jiang, M.M. Stack, A. Neville, Modelling the tribo-corrosion interaction in aqueous sliding conditions, Tribol. Int. 35 (2002) 669–679. [15] M. Krishnan, J.W. Nalaskowski, L.M. Cook, Chemical mechanical planarization: slurry chemistry, materials, and mechanisms, Chem. Rev. 110 (2009) 178–204. [16] Y. Zhao, L. Chang, S.H. Kim, A mathematical model for chemical-mechanical polishing based on formation and removal of weakly bonded molecular species, Wear 254 (2003) 332–339. [17] X. Zhang, I. Odnevall Wallinder, C. Leygraf, Mechanistic studies of corrosion product flaking on copper and copper-based alloys in marine environments, Corros. Sci. 85 (2014) 15–25. [18] T. Du, D. Tamboli, V. Desai, S. Seal, Mechanism of copper removal during CMP in acidic H2 O2 slurry, J. Electrochem. Soc. 151 (2004) G230–G235.

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[19] J. Li, Y. Liu, X. Lu, J. Luo, Y. Dai, Material removal mechanism of copper CMP from a chemical-mechanical synergy perspective, Tribol. Lett. 49 (2013) 11–19. [20] J. Cheng, T., Wang, Z., Chai, X. Lu, Tribocorrosion Study of Copper during Chemical Mechanical Polishing in Potassium Periodate-based Slurry, Tribol. Lett. http://dx.doi.org/10.1007/s11249-015-0474-9 [21] M. Anik, Selection of an oxidant for copper chemical mechanical polishing: Copper-iodate system, J. Appl. Electrochem. 35 (2005) 1–7. [22] V. Brusic, M.A. Frisch, B.N. Eldridge, F.P. Novak, F.B. Kaufman, B.M. Rush, G.S. Frankel, Copper corrosion with and without inhibitors, J. Electrochem. Soc. 138 (1991) 2253–2259. [23] D.Q. Zhang, H. Goun Joo, K. Yong Lee, Investigation of molybdate-benzotriazole surface treatment against copper tarnishing, Surf. Interface Anal. 41 (2009) 164–169. [24] M.M. Antonijevic, M.B. Petrovic, Copper corrosion inhibitors. A review, Int. J. Electrochem. Sci. 3 (2008) 1–28. [25] Q. Luo, Copper dissolution behavior in acidic iodate solutions, Langmuir 16 (2000) 5154–5158. [26] S. Deshpande, S.C. Kuiry, M. Klimov, Y. Obeng, S. Seal, Chemical mechanical planarization of copper: role of oxidants and inhibitors, J. Electrochem. Soc. 151 (2004) G788–G794. [27] J. Hernandez, P. Wrschka, G.S. Oehrlein, Surface chemistry studies of copper chemical mechanical planarization, J. Electrochem. Soc. 148 (2001) G389–G397. [28] T. Du, Y. Luo, V. Desai, The combinatorial effect of complexing agent and inhibitor on chemical-mechanical planarization of copper, Microelectron. Eng. 71 (2004) 90–97. [29] E. Cano, M.F. López, J. Simancas, J.M. Bastidas, X-ray photoelectron spectroscopy study on the chemical composition of copper tarnish products formed at low humidities, J. Electrochem. Soc. 148 (2001) E26–E30. [30] P.M. Sherwood, X-ray photoelectron spectroscopic studies of some iodine compounds, Journal of the Chemical Society, Faraday Transactions 2: Molecular and Chemical Physics 72 (1976) 1805–1820. [31] J.A. Lipton Duffin, O. Ivasenko, D.F. Perepichka, F. Rosei, Synthesis of polyphenylene molecular wires by surface-confined polymerization, Small 5 (2009) 592–597. [32] W. Wijekoon, M. Lyktey, P.N. Prasad, J.F. Garvey, The nature of copper in thin films of copper iodide grown by laser-assisted molecular beam deposition: comparative ESCA and EDXS studies, J. Phys. D 27 (1994) 1548. [33] S.W. Gaarenstroom, N. Winograd, Initial and final state effects in the ESCA spectra of cadmium and silver oxides, J. Chem. Phys. 67 (1977) 3500–3506. [34] A.F. Carley, M. Coughlin, P.R. Davies, D.J. Morgan, M. Wyn Roberts, Chemisorption and reaction of phenyl iodide at Cu (110) surfaces: a combined STM and XPS study, Surf. Sci. 555 (2004) L138–L142. [35] T. Du, D. Tamboli, Y. Luo, V. Desai, Electrochemical characterization of copper chemical mechanical planarization in KIO3 slurry, Appl. Surf. Sci. 229 (2004) 167–174. [36] R. Näsänen, Studies on copper (II) periodates, Acta Chem. Scand. 8 (1954) 1587–1592. [37] Z. Wu, Z. Zhang, L. Liu, Electrochemical studies of a Cu (II)-Cu (III) couple: Cyclic voltammetry and chronoamperometry in a strong alkaline medium and in the presence of periodate anions, Electrochim. Acta 42 (1997) 2719–2723. [38] Y. Zhou, F. Xu, X. Mo, F. Ye, Calorimetric studies for the dissolution of orthoperiodate salt of the type: M2 HIO6 ·nH2 O (M = Cu2+ , Zn2+ , Cd2+ ), Thermochim. Acta 398 (2003) 23–26. [39] G.M. Berry, B.G. Bravo, M.E. Bothwell, G.J. Cali, J.E. Harris, T. Mebrahtu, S.L. Michelhaugh, J.F. Rodriguez, M.P. Soriaga, Spectroscopic and electrochemical studies of iodine coordinated to noble-metal electrode surfaces, Langmuir 5 (1989) 707–713. [40] C. Liao, D. Guo, S. Wen, J. Luo, Effects of chemical additives of CMP slurry on surface mechanical characteristics and material removal of copper, Tribol. Lett. 45 (2012) 309–317. [41] M. Pourbaix, Atlas of Electrochemical Equilibria in Aqueous Solutions, 2nd ed., National Association of Corrosion Engineers, Houston, 1974. [42] S. Mischler, A. Spiegel, D. Landolt, The role of passive oxide films on the degradation of steel in tribocorrosion systems, Wear 225 (1999) 1078–1087. [43] T.K. Varadarajan, T.V. Ramakrishna, C. Kalidas, Ion solvation of some copper (II) salts in water+ N-Methyl-2-pyrrolidinone solvent mixtures at 30 ◦ C, J. Chem. Eng. Data 42 (1997) 453–457. [44] J. Li, Y. Liu, T. Wang, X. Lu, J. Luo, Electrochemical investigation of copper passivation kinetics and its application to low-pressure CMP modeling, Appl. Surf. Sci. 265 (2013) 764–770.