Chemical mechanical polishing of Al and SiO2 thin films: The role of consumables

Chemical mechanical polishing (CMP) studies of blanket aluminum, patterned aluminum, and SiO2 thin films using a commercial slurry based on Al2O3 abra sive particles are presented. Both silicon dioxide and aluminum blanket fil ms were polished with two pads of different hardness and structure. The rem oval rate and the dependence of the removal rate on pressure and linear vel ocity for both materials varies significantly with pad type. For the softer pad, the Al removal rate depends critically on the surface saturation of t he pad with Al2O3 slurry particles. Scanning electron microscopy and X-ray photoelectron spectroscopy were used to study the texture and chemical comp osition of the soft pad after different polishing conditions. We found satu ration of the pad surface with Al2O3 particles but no metallic aluminum on the pad after CMP Pad reconditioning causes the removal of the abrasive par ticles from the pad surface. Patterned aluminum samples with a TiN barrier layer were polished in alumina slurry with and without hydrogen peroxide us ing the soft pad. During CMP of microstructures, both Al and TiN must be re moved at similar rates. The removal rate of the TiN film is dramatically en hanced when H2O2 is incorporated into the slurry, whereas polishing of alum inum thin films showed that the oxidizer has no effect on the Al removal ra te. Passive soaking of TM in H2O2 slurry revealed that TiN readily dissolve s in the presence of a strong oxidizer, which increases the chemical compon ent of the CMP process. (C) 1999 The Electrochemical Society. S0013-4651(98 )10-061-7. All rights reserved.