Faculty Publications
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Item Nanocatalyst-induced hydroxyl radical (·OH) slurry for tungsten CMP for next-generation semiconductor processing(Springer, 2020) Poddar, M.K.; Ryu, H.-Y.; Yerriboina, N.P.; Jeong, Y.-A.; Lee, J.-H.; Kim, T.-G.; Kim, J.-H.; Park, J.-D.; Lee, M.-G.; Park, C.-Y.; Han, S.-J.; Choi, J.-G.; Park, J.-G.Chemical mechanical polishing (CMP) is one of the important steps that involves during fabrication of semiconductor devices. This research highlights the importance of tungsten (W) polishing slurries consisting of a novel nonionic, heat-activated FeSi nanocatalyst on the performance of W chemical mechanical polishing. The results obtained from the polishing data showed a higher W removal rate of 5910 Å/min with a slurry consisting of FeSi nanocatalyst at a polishing temperature of 80 °C. The increase in W polishing rate using FeSi slurry was explained on the basis of formation of a thicker oxide layer (WO3) due to the interaction between the W surface and hydroxyl radicals (·OH) generated via the reaction between FeSi and hydrogen peroxide at 80 °C. Higher ·OH generation and increase in oxygen depth profile of W film were confirmed by UV–Vis spectrometer and AES analysis, respectively. Compared to Fe(NO3)3 catalyst, the slurry with FeSi showed a higher static etch rate at 80 °C. Potentiodynamic polarization results obtained using FeSi slurry showed thicker WO3 passivation layer as compared to the slurry with Fe(NO3)3. The increase in the polishing rate of W CMP using slurry with FeSi nanocatalyst can be essentially attributed to the generation of much stronger oxidant ·OH due to its increased catalytic effect at a high polishing temperature of 80 °C. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.Item Tungsten passivation layer (WO3) formation mechanisms during chemical mechanical planarization in the presence of oxidizers(Elsevier B.V., 2021) Poddar, M.K.; Jalalzai, P.; Sahir, S.; Yerriboina, N.P.; Kim, T.-G.; Park, J.-G.Effects of single and mixed oxidants of Fe(NO3)3 and H2O2 containing acidic silica slurries were studied to investigate the mechanism of tungsten (W) chemical mechanical planarization (CMP). The W polishing rate obtained from the CMP test depicted high W polishing rate in the presence of mixed oxidants of Fe(NO3)3 and H2O2 as compared to a single oxidant of either H2O2 or Fe(NO3)3. The formation of a passive layer of tungsten oxide (WO3) and W dissolution could be the reason for these results as confirmed by XPS. Further investigation revealed that the generation of much stronger oxidants of hydroxyl radicals ([rad]OH) was solely responsible for WO3 layer formation. Quantitative evaluation of [rad]OH generation was estimated using a UV–visible spectrophotometer and confirmed that in-situ generation of hydroxyl radicals ([rad]OH) could be a main driving force for the high W polishing rate by converting a hard W film into a soft passive film of WO3. WO3 film formation was further confirmed using potentiodynamic polarization studies, which showed a smaller value of corrosion current density (Icorr) in mixed oxidants of Fe(NO3)3 and H2O2 as compared to the large values of Icorr observed for H2O2 alone. This study revealed that a single oxidizer of either Fe(NO3)3 or H2O2 was not capable of achieving a high W removal rate. Rather, only mixed oxidants of Fe(NO3)3 and H2O2 could cause a high W polishing rate due to excessive in-situ generation of [rad]OH radicals during the W CMP process. © 2020