Patterning of noble metal electrodes and oxygen barriers by CMP

Abstract

In this study the chemical mechanical polishing (CMP) of Iridium and Iridium Oxide has been investigated. The results show that it is possible to polish this highly inert noble metal and its oxide with removal rates and selectivities that are satisfactory for damascene processes in semiconductor manufacturing. All slurries are based on commercially available abrasives and chemicals. Using blanket wafers, two slurry systems have been systematically studied. Concentration variations of abrasive as well as oxidizer and base have been investigated for Iridium and Iridium oxide, respectively. The dependence of the removal rate on polishing parameters such as time, pressure and rotational speeds have been investigated. Iridium and Iridium oxide removal rates up to 50 and 260 nm /min with selectivities to SiO2 up to 30:1 and 50:1 could be reached, respectively. The polishing processes presented here allow for the first time the implementation of noble metal damascene processes in semiconductor manufacturing.