Investigation of Tm₂O₃ As a Gate Dielectric for Ge MOS Devices

Abstract

In this work atomic layer deposited Tm 2 O 3 has been investigated as a high-k dielectric for Ge-based gate stacks. It is shown that when Tm 2 O 3 is deposited on high-quality Ge/GeO 2 gates, the interface state density of the gate stack is degraded. A series of post-deposition anneals are studied in order to improve the interface state density of Ge/GeO x /Tm 2 O 3 gates, and it is demonstrated that a rapid thermal anneal in O 2 ambient can effectively reduce the interface state density to below 5·10 11 cm -2 eV -1 without increasing the equivalent oxide thickness. Fixed charge density in Ge/GeO x /Tm 2 O 3 gates has also been investigated, and it is shown that while O 2 post-deposition anneal improves the interface state density, the fixed charge density is degraded.

Formation and characterization of holmium oxide on germanium‐based metal‐oxide‐semiconductor capacitor

“…Since rare earth oxides (REOs) reveal high affinity to Ge atoms and so, several research groups have extensively investigated the behaviour of various REOs such as La 2 O 3 , CeO 2 , Gd 2 O 3 , Dy 2 O 3 , Y 2 O 3 , Tm 2 O 3 , and Sm 2 O 3 for improving the limitations of GeO 2 /Ge interface. [18][19][20][21][22][23][24][25][26][27] It has been reported that deposition of REOs as high-k on the GeO 2 /Ge shows better potential in improving both thermal and electrical properties than those of transitional metal oxides such as HfO 2 and Al 2 O 3 . 26,28,29 The key reason for such improvement has been pointed due to spontaneous growth of rare earth germanate (RE-O-Ge) interfacial layer (IL) caused by catalytic oxidation of Ge atoms through the vigorous reaction between REOs and Ge interface.…”

“…Fortunately, the rapid progress of high‐ k materials opened the door towards using mutual geometry of both high‐ k material and Ge simultaneously. Since rare earth oxides (REOs) reveal high affinity to Ge atoms and so, several research groups have extensively investigated the behaviour of various REOs such as La 2 O 3 , CeO 2 , Gd 2 O 3 , Dy 2 O 3 , Y 2 O 3 , Tm 2 O 3 , and Sm 2 O 3 for improving the limitations of GeO 2 /Ge interface 18‐27 . It has been reported that deposition of REOs as high‐ k on the GeO 2 /Ge shows better potential in improving both thermal and electrical properties than those of transitional metal oxides such as HfO 2 and Al 2 O 3 26,28,29 .…”

Process Conditions for Low Interface State Density in Si-passivated Ge Devices with TmSiO Interfacial Layer

“…Reference MOSCAPs with Ge/GeO x /Tm 2 O 3 /HfO 2 gate stacks were also fabricated by a similar process as in Ref. 13, with addition of ALD HfO 2 and FGA.…”

“…Thulium silicate (TmSiO) as a replacement of SiO 2 interfacial layer has been demonstrated in silicon gates with D it ∼ 10 11 eV −1 cm −2 , 12 and we have also shown GeO x /Tm 2 O 3 gate stacks with D it < 5•10 11 eV −1 cm −2 . 13 Hence, integrating TmSiO in Si-passivated Ge gates is a viable option.…”

Improvement on Ge/GeOx/Tm2O3/HfO2 Gate Performance by Forming Gas Anneal

“…Further improvement in the gate stack performance was realized by integrating HfO2 in the gate stack fabrication resulting in equivalent oxide thickness <1 nm [2]. Moreover, by using thermal oxidation by rapid thermal anneal (RTA), we have demonstrated Ge/GeOx/Tm2O3 gates with Dit < 5•10 11 eV -1 cm -2 [3].…”