Mechanical Removal in CMP of Copper Using Alumina Abrasives

Guo, Lirong; Subramanian, R. Shankar

doi:10.1149/1.1640632

Cited by 37 publications

(30 citation statements)

References 11 publications

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“…This effect of reaching a limiting value for the metal RR has been proposed to reflect a maximum in the extent of mechanical abrasion of the metal surface by the abrasive particles. 31 The Cu RR in 75 mM KBrO 3 and 2 wt % titania at pH 2 was 285 nm/min, and was not suppressed to a significant extent by the addition of 65 mM benzotriazole. Further work is necessary to identify a Cu corrosion inhibitor suitable for this slurry.…”

Section: Resultsmentioning

confidence: 93%

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Potassium Bromate as an Oxidizing Agent in a Titania-Based Ru CMP Slurry

Victoria

Sharma

Suni

et al. 2010

Electrochem. Solid-State Lett.

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Ru chemical mechanical planarization ͑CMP͒ was studied in slurries containing titania and potassium bromate at different pH values, showing that the Ru removal rate is enhanced at pH 2 or less. Potentiodynamic polarization studies indicate that the corrosion current is enhanced in the presence of bromate, while the static etch rate experiments show that the etch rate is low. Potassium bromate increases Ru removal only at anodic potentials or during mechanical abrasion. Studies at different concentrations of abrasive and oxidizing agent reveal that the removal rate enhancement saturates at 0.75 mM bromate and 4 wt % titania.Cu is used as interconnect material in integrated circuits, and a thin barrier layer is used to prevent the diffusion of Cu through the interlayer dielectric. 1,2 During damascene and dual damascene fabrication of the interconnect structures, the excess Cu and barrier are removed by a process of chemical mechanical planarization ͑CMP͒. Currently, Ta and TaN are used as barrier metals 1 and a thin Cu seed layer is deposited by physical vapor deposition ͑PVD͒, followed by electrodeposition of Cu. However, as feature dimensions shrink, the PVD Cu is not scalable and Ru is proposed as a suitable seed layer. It has low resistivity as well as negligible solid solubility with Cu. 3,4 Although the introduction of Ru would likely require the development of CMP techniques, only a few articles have appeared that describe the Ru CMP methods. 5-17 Ru is a noble metal with high chemical resistance and mechanical hardness, which makes Ru CMP challenging. Sodium periodate, 5-9 hydrogen peroxide, 10-12 persulfate, 11 Ce͑IV͒, 10,13-16 and perborate 17 have been suggested as suitable oxidizing agents for Ru CMP. Here, we report potassium bromate ͑KBrO 3 ͒ as an oxidizing agent and titania as an abrasive for Ru CMP. Titania was chosen as candidate abrasive because it was reported to yield a higher Ru removal rate ͑RR͒ when compared to silica-and alumina-based slurries. 18 The effect of abrasive loading, oxidizing agent concentration, and pH is systematically studied. ExperimentalRu CMP was studied with a laboratory-scale polishing instrument ͑Struers LaboPol-5/LaboForce 3͒ using a 25 mm diameter, 3 mm thick Ru disk ͑99.9% purity, William Gregor, Ltd., U.K.͒. Electrochemical grade copper disk of 25 mm diameter was used for copper CMP. A constant downward pressure of 5.8 psi was applied, the platen was rotated at 150 rpm, the disk was rotated at 250 rpm, and a slurry flow rate of 100 mL/min was maintained. The slurry contained deionized water and titania abrasives ͑Ϫ300 mesh, DCW, India͒, and pH was adjusted using HNO 3 or KOH. Each run was conducted for 3 min, and at least three runs were performed at each polishing condition. The RR was calculated by the weight loss method. The average RRs along with the standard deviation are reported. For static etch rate experiments, the Ru disk was kept in 100 mL solution for 10 min with stirring and the concentration of Ru in the solution was measured using a Perkin-Elmer Opt...

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Section: Resultsmentioning

confidence: 93%

“…3 for Cu and W CMP. [27][28][29][30][31] The limiting value for the RR can be increased by changing either the chemical or mechanical parameters governing CMP. 29 Our results follow this trend, because without an oxidizing agent, the Ru RR saturates at 18 nm/min, while upon addition of 100 mM KBrO 3 , the Ru RR saturates at 104 nm/min.…”

Section: Resultsmentioning

confidence: 99%

Potassium Bromate as an Oxidizing Agent in a Titania-Based Ru CMP Slurry

Victoria

Sharma

Suni

et al. 2010

Electrochem. Solid-State Lett.

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“…7 shows the simulated and measured coupling efficiencies as the function of curvatures in vertical directions. The 980-nm laser-to-fiber coupling model was based on the diffraction theory [4], [15]. From the lasers to the HM, the Fresnel diffraction theory was used for beam propagation through free space.…”

Section: Measurements and Resultsmentioning

confidence: 99%

New Scheme of Hyperboloid Microlens for High-Average and High-Yield Coupling High-Power Lasers to Single-Mode Fibers

Huang

Hsieh

Hsu

et al. 2013

J. Lightwave Technol.

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A new scheme of hyperboloid microlens (HM) employing automatic grinding and precise fusing techniques to achieve high-average and high-yield coupling efficiency from high-power 980-nm lasers into single mode fibers is proposed and demonstrated. The fiber endface of the HM exhibited a double-variable curvature in the major and minor axes that was characterized as a hyperboloid. By selecting half transverse length of the hyperbola and using fusing process to precise and quantitative controlling the required minor radius of curvature within 2.4-2.8 m and offset within 0.8 m, the HMs exhibited a high-average coupling efficiency of 83%. For fabricated high-coupling HMs, the result was also found that the tolerance of minor radius of curvature decreased as the offset increased. This study demonstrates that the proposed HMs through both automatic grinding and precise fusing techniques can achieve high-average and high-yield coupling efficiency better than any other grinding techniques to form asymmetric microlenses for utilizing in many low-cost lightwave interconnection applications.

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“…2. Chemical reactions: It has been suggested [4,37,38] that the chemicals in the slurry serve to enhance abrasive wear of the wafer by the particle. Therefore, the model in this study assumed that the input material properties can be specified as a function of the slurry chemistry.…”

Section: Modeling Assumptionsmentioning

confidence: 99%

Analysis of Feature-Scale Wear in Chemical Mechanical Polishing: Modeling and Experiments

2009

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An asperity-scale wear model was developed to predict feature-scale wear in chemical-mechanical polishing (CMP), and was compared to the measured evolution of a lithographically patterned feature during full-scale CMP tests. To conduct this study, a lithographic technique was used to pattern a set of raised square features into a Cu-coated silicon wafer. Two-dimensional contact profilometry was used to measure the topography of an isolated feature on each wafer both before polishing and at various intervals throughout the polishing process. In the wear modeling formulation, a pad deflection-based contact mechanics model was developed and combined with a particle-based wear model to predict the wear evolution of the sample during CMP. The predicted wear of the sample feature was found to agree well to experimental results.

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Mechanical Removal in CMP of Copper Using Alumina Abrasives

Cited by 37 publications

References 11 publications

Potassium Bromate as an Oxidizing Agent in a Titania-Based Ru CMP Slurry

Potassium Bromate as an Oxidizing Agent in a Titania-Based Ru CMP Slurry

New Scheme of Hyperboloid Microlens for High-Average and High-Yield Coupling High-Power Lasers to Single-Mode Fibers

Analysis of Feature-Scale Wear in Chemical Mechanical Polishing: Modeling and Experiments

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