Tungsten passivation layer (WO3) formation mechanisms during chemical mechanical planarization in the presence of oxidizers
- Authors
- Poddar, Maneesh Kumar; Jalalzai, Palwasha; Sahir, Samrina; Yerriboina, Nagendra Prasad; Kim, Tae Gon; Park, Jin-Goo
- Issue Date
- Jan-2021
- Publisher
- Elsevier BV
- Keywords
- Fe(NO3)3; H2O2; Hydroxyl radicals; Surface oxide layer; W CMP
- Citation
- Applied Surface Science, v.537, pp.1 - 8
- Indexed
- SCIE
SCOPUS
- Journal Title
- Applied Surface Science
- Volume
- 537
- Start Page
- 1
- End Page
- 8
- URI
- https://scholarworks.bwise.kr/erica/handle/2021.sw.erica/682
- DOI
- 10.1016/j.apsusc.2020.147862
- ISSN
- 0169-4332
- Abstract
- 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
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