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 ( OH) was solely responsible for WO3 layer formation. Quantitative evaluation of OH generation was estimated using a UV–visible spectrophotometer and confirmed that in-situ generation of hydroxyl radicals ( 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 OH radicals during the W CMP process.

中文翻译：

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存在氧化剂的化学机械平坦化过程中钨钝化层 (WO3) 的形成机制

摘要 研究了含Fe(NO3)3 和H2O2 酸性二氧化硅浆料的单一和混合氧化剂的影响，以研究钨(W) 化学机械平坦化(CMP) 的机理。从 CMP 测试获得的 W 抛光速率表明，与 H2O2 或 Fe(NO3)3 的单一氧化剂相比，在 Fe(NO3)3 和 H2O2 的混合氧化剂存在下，W 抛光速率较高。XPS 证实，氧化钨 (WO3) 钝化层的形成和 W 溶解可能是这些结果的原因。进一步的研究表明，产生更强的羟基自由基 (OH) 氧化剂是 WO3 层形成的唯一原因。使用紫外-可见分光光度计对 OH 生成进行了定量评估，并确认通过将硬 W 膜转化为软钝化膜，羟基自由基 (OH) 的原位生成可能是高 W 抛光速率的主要驱动力。 WO3。使用动电位极化研究进一步证实了 WO3 膜的形成，与单独观察到的大 Icorr 值相比，Fe(NO3)3 和 H2O2 的混合氧化剂中的腐蚀电流密度 (Icorr) 值较小。该研究表明，Fe(NO3)3 或 H2O2 的单一氧化剂无法实现高 W 去除率。相反，只有 Fe(NO3)3 和 H2O2 的混合氧化剂才能导致高 W 抛光速率，因为在 W CMP 过程中原位生成了过多的 OH 自由基。