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 particular 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 up to 30:1 and 50:1 could be reached, respectively. Based on the results obtained on planar wafers slurries with optimized parameters were applied to structured wafers. The dishing effect is very small (<10 nm) both in small (<1 μm) and larger (10 μm width) structures. Erosion of tetraethyl orthosilicate is in the range between 20 and 40 nm, and the surface roughness (root mean square 0.5-2 nm) measured by atomic force microscopy as well as the depth of scratches (5-15 nm) were comparable to those of copper CMP. Overall, the process performance demonstrated on planar and patterned wafers fully satisfies production requirements. Therefore, these novel polishing processes allow, for the first time, the implementation of noble metal damascene processes in semiconductor manufacturing. © 2001 The Electrochemical Society. All rights reserved.
Published Version
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