The influence of chemical treatments on tungsten films found in integratedcircuits

The influence of four different chemical solutions on the composition, morp hology, and etch rates of thin, chemically vapor deposited tungsten films h ave been investigated. These films are the standard material patterned to c reate tungsten plugs in integrated circuits through a chemical mechanical p lanarization (CMP) step. The tungsten films were treated with aqueous solut ions of KOH, KIO3 + NaOH, H2O2 + NH4OH, and H2O2 + HCl. We have evaluated t he resulting changes in the surface chemical composition of the tungsten fi lm with X-ray photoelectron spectroscopy (XPS). Changes in film morphology have been recorded with atomic force microscopy and material removal rates have been determined with calibrated four-point-probe resistivity measureme nts. Together, these measurements demonstrate the complex manner in which c hemical pretreatments in the CMP process influence thin tungsten films. (C) 2001 Elsevier Science B.V. All rights reserved.