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Polishing Parameter Dependencies and Surface Oxidation of Chemical Mechanical Polishing of Al Thin Films
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1999
Year
EngineeringPolyurethane PadOxidation ResistanceMechanical EngineeringAlumina ParticlesMineral ProcessingAl Thin FilmsAnodizingChemical EngineeringCorrosionParameter DependenciesSurface PolishingThin Film ProcessingMaterials ScienceMaterials EngineeringSurface TreatmentChemical Mechanical PolishingSurface ScienceMaterials CharacterizationSurface EngineeringThin FilmsSurface Processing
We describe chemical mechanical polishing (CMP) of blanket and patterned aluminum films employing a polyurethane pad and a slurry based on alumina particles as the abrasive and hydrogen peroxide as the oxidizer. The experiments were conducted at pressures from 19 to 47 kPa and at linear velocities from 26 to 48 m/min, and yielded Al removal rates from 80 to 250 nm/min. The oxidant concentration has a weak effect on the removal rate of Al. Polishing selectivities of Al to silicon dioxide as high as 130:1 were obtained with the maximum selectivities being observed at regions of low pressures and low velocities. The Preston equation fails to describe the dependence of the removal rate on pressure and velocity, and a power function is proposed instead. X‐ray photoelectron spectroscopy was used to examine the surface of Al before and immediately after CMP. These experiments provided information on the thickness of the oxidized Al layer. We found that larger removal rates correlated with a smaller Al‐oxide thickness. We conclude from this that Al CMP proceeds by oxidation of the Al and subsequent Al‐oxide removal. © 1999 The Electrochemical Society. All rights reserved.