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Abstract: The mechanism of copper (Cu) voids formation from electro-chemical plating (ECP) followed by Cu chemical mechanical polishing (CMP) are studied in Cu dual-damascene interconnection. The formation of Cu voids at metal lines is the main problem that causes not only the failure of via-induced metal-island corrosion but also yield loss. The galvanic theory and Cu lifting mechanism are proposed to explain the dependence of Cu-void performance on the Cu grain size and the benzotriazole (BTA, C6H5N3) flow rates. In the integration process of Cu interconnects, it is found that the smaller Cu grain size in ECP conditions and less BTA flow rate in CMP processes cannot only reduce the number of Cu voids but also improve the wafer yield. [Copyright &y& Elsevier]

Abstract: The reduction of the copper dishing was investigated by optimizing the copper CMP processes. The reduction method is a novel copper slurry with the organic passivation agent used during the copper polishing to reduce the copper dishing level. The passivation mechanism of the copper polishing was proposed. With the optimized condition of the copper ECD and CMP, the resistivity deviation of 180-μm square metal pads with 10–80% pattern densities was reduced from over 30% to less than 10%. The amount of the copper dishing was reduced from around 150 nm to less than 30 nm. Finally, 10% increase of wafer yield and better process reliability were achieved. [Copyright &y& Elsevier]

According to rapid development of CMP technology, the difference of polishing methods would be applied for copper damascene interconnect. These methods include conventional rotary, linear, oscillation platform. The advantages of these platform would highlighted in uniformity control, stability of removal rate, planarization efficiency, throughput promotion, lower cost of ownership, even dishing and erosion effect integrated with slurry. This paper presented our experience to compare the uniformity, removal rate and planarization efficiency of Cu-CMP between various polishing platforms. In convection, the rotary or oscillation platform would be usually applied in oxide and tungsten CMP, due to the robust air-back carrier and rigid platen to polish the wafer, which performs the good reliability on wafer-to-wafer thickness and endpoint detection. However, the linear polisher is made of the air-bearing moving belt and self-rotated carrier and would provide the wider uniformity and planarization control window than others. In addition, the simulation model would explain the difference from mechanic design and wafer moving paths between various polishing techniques. Hence, the trade-off advantage and application between various platforms would be compensated and integrated with slurry, conditioners and coming thickness profile from copper plating. It can achieve the optimization of Cu-CMP process. [Copyright &y& Elsevier]

The microstructures, interfaces, and physics properties of the devices with multifunctional barrier materials are investigated to achieve integration of perovskite oxide films with Cu film on Si for the application in nonvolatile Si-based ferroelectric random access memories (FeRAMs) with the on-chip copper metallization of advanced microelectronic devices. La 0.5 Sr 0.5 CoO 3 /Pb(Zr 0.4 Ti 0.6 )O 3 /La 0.5 Sr 0.5 CoO 3 (LSCO/PZT/LSCO) capacitors have been successfully fabricated on the Cu/Ni–Al/SiO 2 /Si stack structure for Cu interconnects using an amorphous Ni–Al (a-Ni–Al) film as the barrier layer for the Cu/SiO 2 interface and a mixed-phase nanocrystalline Ni–Al (n-Ni–Al)/a-Ni–Al ((n+a)-Ni–Al) bi-layer-like film as the oxygen diffusion barrier layer for the LSCO/Cu interface, respectively. The perfect structure compatibility and clear interfaces between thin films are achieved. Excellent physical properties of the capacitor, such as high remnant polarization (∼26 μC/cm 2 ), good reliability and dielectricity, powerfully confirm that Ni–Al film can be used as the barrier layer between Cu and SiO 2 or LSCO. The barrier properties of the (n+a)-Ni–Al can be understood as two aspects: n-Ni–Al component can level up the roughness of Cu/barrier/SiO 2 /Si surface and relax stresses in the multilayer stack heterostructure, and a-Ni–Al can inhibit oxygen penetration. Compared to the (n+a)-Ni–Al, only n-Ni–Al film without a-Ni–Al layer couldn't prevent Cu oxidation due to oxygen penetration leading to the failure of devices, whose failure mechanism can be ascribed to the reactions between Cu and complex oxides. The results fully illustrate the viability of the lead-based ferroelectric capacitors grown on Cu/Barrier/SiO 2 /Si stack structure with Ni–Al barrier for the future ferroelectric capacitor based devices with Cu metallization. [ABSTRACT FROM AUTHOR]

Abstract: Basing on the results of the scanning tunneling microscopy (STM) observations and density functional theory (DFT) calculations, the structural model for the Cu magic clusters formed on Si(111)7×7 surface has been proposed. Using STM, composition of the Cu magic clusters has been evaluated from the quantitative analysis of the Cu and Si mass transport occurring during magic cluster converting into the Si(111)‘5.5×5.5’-Cu reconstruction upon annealing. Evaluation yields that Cu magic cluster accommodates ∼20 Cu atoms with ∼20 Si atoms being expelled from the corresponding 7×7 half unit cell (HUC). In order to fit these values, it has been suggested that the Cu magic clusters resemble fragments of the Cu2Si-silicide monolayer incorporated into the rest-atom layer of the Si(111)7×7 HUCs. Using DFT calculations, stability of the nineteen models has been tested of which five models appeared to have formation energies lower than that of the original Si(111)7×7 surface. The three of five models having the lowest formation energies have been concluded to be the most plausible ones. They resemble well the evaluated composition and their counterparts are found in the experimental STM images. [Copyright &y& Elsevier]

Abstract: AlCoCrFeNiTi0.5 solid-solution alloy, which were designed by using the strategy of equi-atomic ratio and high entropy, possesses excellent room-temperature compressive mechanical properties even superior to most of the high-strength bulk metallic glasses. By Cu addition, the alloys still have body-centered cubic structure as its main phases just like the original AlCoCrFeNiTi0.5 alloy, but there is obvious Cu segregation preferential to the interdendritic regions at the same time, which impairs the mechanical properties of AlCoCrFeNiTi0.5 to a large extent. [Copyright &y& Elsevier]

A new Zr-based bulky amorphous alloys containing W are designed and prepared by using the combined technique of jet and water-cooled copper mold casting. XRD, DSC and SEM analysis are conducted to investigate the microstructure, the supercooled liquid region ΔTx (=Tx−Tg), and thermal stability of the new bulk metallic glass system. The effects of the addition of W and the increase of Cu content on the glass forming ability (GFA) and thermal stability are discussed. Compressive experiments were also carried out to study the Young''s modulus, compressive fracture strength and elongation of the new alloys. The fracture characterization and mechanism of the new bulk amorphous alloys are discussed in detail. [Copyright &y& Elsevier]