Effect of Post Plasma Oxidation on Ge Gate Stacks Interface Formation

Abstract

This work investigates the application of slot plane antenna plasma oxidation (SPAO) during dielectric depositionto processTiN/AlO/ZrO2/Ge MOS capacitors. The impact of SPAO exposure on effective oxide thickness (EOT), leakage current, interface state density (D it), C-V hysteresis, oxide breakdown characteristics have been studied. Considerable degradation of electrical properties has been observed with SPAO being performed before AlO/ZrO2 gate stack deposition. When SPAO is performed in between AlO/ZrO2deposition, moderate increase in EOT and significant decrease in D it was observed, which can be attributed to the formation of a thicker GeOX layer. On the other hand, when SPAO is performed after the deposition of both the high-k layers, higher D it was observed suggesting that a thinner GeOX layer formation. Time zero dielectric breakdown (TZDB) characteristics indicate that plasma exposure after and in between AlO/ZrO2 deposition enhances the dielectric quality by film densification due to plasma exposure. It was demonstrated that improved dielectric and interface quality can be achieved when ALD-AlO/ZrO2 gate stacks were exposed to SPAO.

Post Plasma Oxidation Processed ALD Al2O3/Hf1-xZrxO2Thin Films on Ge Substrates: Reliability

“…It can be noted that although the Hf 1-x Zr x O 2 layer was approximately identical in thickness (∼3.5 nm) in all devices, after the SPAO process, a thicker GeO 2 interfacial layer formation is assumed for ZrO 2 . 15 This observation further supports the observed CV characteristics (Fig. 2) and corresponding EOT shown in Fig.…”

“…5a). 7,15 Furthermore, the C-V characteristics show a typical partial inversion at 100 KHz ( Fig. 2a) and a complete inversion at 100 Hz ( Fig.…”

“…On the other hand, in case of ZrO 2 (100% Zr), the absence of Hf enhances the formation of rather thick GeO 2 -type interfacial layer at the Ge/high-k interface which was previously observed from the XPS study. 15 This reduces the accumulation capacitance ( Fig. 2) which is translated to higher EOT for devices with 100% Zr (Fig.…”

“…Parameters like C-V hysteresis, flat-band voltage shift ( V FB ), equivalent oxide thickness (EOT), interface state density (D it ) and leakage current have been estimated accurately after quantum mechanical and series resistance corrections. 15,17 To obtain the statistical information of TDDB, 10 devices with 100 μm × 100 μm area were measured at each stress condition. The charge to breakdown value (Q BD ) is extrapolated by three stress points to evaluate the quality of oxide.…”

“…15 It is known that ALD Hf based high-k dielectrics contain many oxygen vacancies. 26 Therefore, when ALD Hf 1-x Zr x O 2 is subjected to SPAO oxidation, the oxygens from SPAO source mostly fill the oxygen vacancies and the formation of GeO X growth at the interface is reduced.…”