Single-Wafer Wet Chemical Oxide Formation for Pre-ALD High-k Deposition on 300 mm Wafer

摘要

This study demonstrated that single-wafer wet chemical oxidation could be applied for surface preparation for pre-high-k deposition. Interface oxide thickness could be controlled by process time. It showed better uniformity than the batch system. After XPS correction of the ellipsometric oxide layer thicknesses, it was found that HTO_2 deposition both on Si<110> and Si<110> showed at similar dependency on XPS corrected thickness. Therefore, actual thin oxide thickness must be considered. C-V measurements on the capacitor lot showed 0.5 and 0.6-nm interfacial oxide were insufficient to keep the capacitances. It implied entire surface -OH coverage was completed from 0.7-nm. On the other hand, TEM measurement revealed non-covered areas by thin oxide at the 0.7-nm interface oxide. Around 0.7～0.8-nm ellipsometric thickness was concluded as the minimum interfacial oxide needed. The EOT values including various interfacial oxide thicknesses were affected by post-annealing, and the difference was smaller than expected. From the EOT comparison between 0.7 nm and 1.2-nm, it was certainly improved. In conclusion, in order to create minimum interfacial oxide, single-wafer treatment can provide sufficient and uniform thin oxide.