Mechanical Polishing Of Copper Research Articles

Electrochemical Mechanical Polishing of Copper with High Permittivity Abrasives

Electro-Chemical Mechanical Polishing (ECMP) is a promising low-pressure copper planarization method for the interconnection containing low-k material. ECMP utilizes anodic dissolution of copper to raise the material removal rate. However, the surface roughness is usually not acceptable in ECMP because the selective removal ability of electrochemical dissolution is poor. Different permittivity abrasives have different influence on surface quality in ECMP. High permittivity abrasives can enhance selective removal ability to get better polishing results through aggrandizing the potential drop in electrode/electrolyte interface. In this article, three abrasives with different permittivity are compared using polishing experiments. The results show that rutile TiO2, permittivity of which is larger than anatase TiO2 and SiO2, gets the best surface quality among the three abrasives. The composition of electrolyte with rutile TiO2 was also optimized to improve polishing performance. The chosen electrolyte contains 0.5 mol/L glycine, 0.1 mol/L TSA, 1 wt% rutile TiO2. The material removal rate got by using this electrolyte is 0.06 mg/min and the surface roughness is Ra8.9 nm.

Effect of Nano-Size Silica Abrasives in Chemical Mechanical Polishing of Copper

AbstractThe effect of nano-size silica abrasives in chemical mechanical polishing (CMP) of copper is studied in order to reduce mechanical stresses during polishing, which may minimize defects such as surface scratches, copper peeling, dishing and erosion. In order to achieve low stress polishing of copper while maintaining removal rate efficiency, the formation of chemically modified surface layer, which can be mechanically removed by small size and low hardness abrasives, is critical. Complexing agents play an important role in the formation of a removable surface layer in the presence of the oxidizer, which is responsible for oxide formation, and the inhibitor, which passivates the surface. A new removal mechanism is proposed by correlating results of surface roughness after polishing with removal and etch rates. The effects of large silica and alumina abrasives, ranging from 200-1000 nm in diameter, are also studied to compare the different removal mechanisms.

Fundamental Study of Iodate and Iodine Based Slurries for Copper CMP

ABSTRACTThe chemical mechanical polishing of copper in several slurry chemistries based on iodate and iodine oxidizers has been investigated. Benzotriazole (BTA) and potassium iodide (KI) were used for preparing the polishing slurry chemistries based iodate. As observed by the anodic electrochemical behavior of copper and the surface analyses of EDS, it was determined that CuI layer formed in the iodate and iodine based solutions. Especially, in I2 slurry in pH 4, CuI layer formed very fast and uniformly, and passivated the copper. In addition, the highest removal rate using this slurry was obtained. These results were compared to H2O2 based slurries. From these experimental results, the slurry containing 0.1M KIO3 and 0.01M KI, and 0.01N I2 give better results than H2O2 based slurry in copper CMP.

Planarization of Cu and Ta Using Silica and Alumina Abrasives - A Comparison

ABSTRACTExperimental results on chemical mechanical polishing of copper and tantalum in the presence of different chemicals, such as Fe(NO3)3, H2O2 and glycine, using both silica and alumina abrasive particles are presented. The polish rates with alumina slurries vary in accordance with the hardness of the material being polished, suggesting a dominant role for a wear mechanism. However, polish rates with silica slurries do not relate directly to the hardness of the film, indicating a more complex removal mechanism.

Stabilization of Alumina Slurry for Chemical−Mechanical Polishing of Copper

Stabilization of alumina slurries containing Fe(NO3)3 and benzotriazole (BTA) for chemical−mechanical polishing (CMP) of copper in acidic media was investigated. Slurry stability was evaluated from the initial settling rate of alumina particles in well-dispersed slurries. ζ potential and FTIR spectroscopy were employed to elucidate the observed effects. Fe3+, used as an etchant for copper, did not affect the slurry stability significantly, especially at low concentrations (<0.05 M). However, BTA worsened the stability, especially at higher concentrations, by reducing the electrostatic repulsion between alumina particles. This was confirmed by a drop in the measured ζ potential. FTIR spectra showed that BTA is chemisorbed onto alumina particle surfaces. Finally, the addition of poly(ethylene glycol) (MW = 1 000 000) improved the slurry stability significantly and a stable alumina slurry for the CMP of copper was obtained. Preliminary data on the removal rates of copper and the selectivities of removal betw...

Surface Layer Formation During the Chemical Mechanical Polishing of Copper Thin Films

ABSTRACTThree chemical processes that occur during the chemical mechanical polishing (CMP) of copper are described in terms of their effect on surface planarity, polish rate, and corrosion resistance of the polished copper. These processes are surface layer formation, dissolution of mechanically abraded copper, and chemical acceleration of the polish rate. The role of these processes is demonstrated with two slurry formulations used in the CMP of copper at Rensselaer.