Study of Copper / Ruthenium Chemical Mechanical Polishing in alkaline hydrogen peroxide system with ammonium persulfate and nanoscale silica

The study can be separated to three parts. The first part focus on probing the electrochemical factors when copper and ruthenium film reacting in different concentration of hydrogen peroxide slurries, adjusting to pH9 by sodium hydroxide. For the second part, we mimiced the real situation when copper and ruthenium film are processed during the CMP by using different concentration of ammonium persulfate in hydrogen peroxide slurries, which is adjusting to pH9 by sodium hydroxide, and then we probe the variation of their surface patterns. For the last part, we add fixed amount of 15-20nm nanoscale silica to investigate its surface patterns. In the experiment, not only we use DC polarization technique to find out its electrochemical factors, but we also use Atomic Force Microscope and Scanning Electron Microscopy to probe its root mean square surface roughness and the surface patterns. For the results of the experiments, the first part showed that when the slurries adjusting to pH9 with sodium hydroxide, could have the best corrosion rate with 7wt% hydrogen peroxide for either copper or ruthenium film. Based on the results of the first part, we could find out that slurries with 7wt% hydrogen peroxide and 3wt% ammonium persulfate, adjusting to pH9 with sodium hydroxide, could demonstrate a better removal rate ratio, 0.926 ,of the copper/ruthenium removal rate, with the copper one was about 4.115 nm/sec and the ruthenium one was 5.805nm/sec. For the surface roughness, the copper one was declined from about 55.8nmto 9.12nm while the ruthenium one was declined from 42.5nm to 7.78nm. After adding 2wt% 15-20nm nanoscale silica, we found out that pH9 slurries with 7wt% hydrogen peroxide, 1wt% ammonium persulfate and 2wt% 15-20nm nanoscale silica, with removal rate ratio was 0.811. The copper removal rate was 3.457nm/sec and the ruthenium removal rate was 4.265nm/sec. The surface roughness was declined to 1.01nm and 6.97nm respectively. For requesting a proper result for the use of industries, the pH9 slurries with 7wt% hydrogen peroxide, 1wt% ammonium persulfate and 2wt% 15-20nm nanoscale silica would be the best choice, which removal rate ratio is 0.709, of the copper/ruthenium removal rate, with the copper one was about 4.1153nm/sec and the ruthenium one was 5.80493nm/sec. For the surface roughness, the copper one 6.54nm while the ruthenium one was 2.06nm.