Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
3 results
Search Results
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. © 2020Item A comprehensive study to understand removal efficiency for Cr6+ using magnetic and activated biochar through response surface methodology(Springer Science and Business Media Deutschland GmbH, 2024) Narzari, R.; Poddar, M.K.; Bordoloi, N.; Sarmah, A.K.; Kataki, R.This study highlights the advantageous effect of magnetic biochar (MLC) over conventional activated biochar (ALC) used for chromium adsorption from the aqueous solution. The synthesis of MLC was done using an invasive noxious weed “Lantana camara” with impregnation of iron chloride (FeCl3) on biochar surface at 25 °C. The optimum process parameters such as pH (3.01), adsorbent concentration (1.82 g/L), and adsorbate amount (161.23 mg/L) for the maximum chromium adsorption have been calculated using response surface methodology coupled with central composite design. Successful impregnation of iron on biochar with pre and post adsorption analysis has been confirmed using various characterization techniques viz. vibrating sample magnetometry (VSM), field emission scanning electron microscope (FESEM-EDX), Fourier transform infrared (FTIR), and X-ray diffraction (XRD). Among various adsorption isotherms studied, Langmuir isotherm best fits the pseudo-second-order kinetic model for analysis of actual adsorption behavior of Cr6+ ions on ALC and MLC surfaces. Biochar MLC exhibited the maximum chromium adsorption capacity of 102.03 mg/g as compared to low chromium adsorption of 94.69 mg/g using conventional ALC biochar. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2021.