Al₂O₃/InGaAs Metal-Oxide-Semiconductor Interface Properties: Impact of Gd₂O₃and Sc₂O₃Interfacial Layers by Atomic Layer Deposition

Abstract

The use of InGaAs as a high carrier mobility CMOS-channel material requires a proper electrical passivation of its interface with the gate dielectric. We investigate InGaAs passivation by Atomic Layer Deposition (ALD) of Al2O3, Gd2O3, and Sc2O3 using tri-methylaluminum (TMA), (iPrCp)3Gd, (MeCp)3Sc, and H2O as precursors. We discuss the impact of the starting precursor and TMA exposure during the initial cycles of Al2O3 on the interface trap density (Dit), frequency dispersion, leakage current, and breakdown field. Increasing the TMA pulse time to five seconds during the first five cycles reduce the Dit to 1.8 × 1012 eV−1 cm−2, while frequency dispersion, leakage current and breakdown field generally improve. Gd2O3 and Sc2O3 interfacial layers between InGaAs and Al2O3 are examined. The initial growth study of Gd2O3 ALD on InGaAs indicates growth inhibition as compared to the hydrophilic SiO2/Si substrate. Gd2O3 and Sc2O3 improve the interface in terms of Dit and border traps. The improvement depends on the initial precursor pulse lengths, and on the Gd- or Sc-content. The lowest Dit values, 2.5 × 1012 eV−1 cm−2 and 1.8 × 1012 eV−1 cm−2, are obtained for four cycles of Sc2O3 and Gd2O3, respectively. Interfacial self-cleaning by TMA, (iPrCp)3Gd, and (MeCp)3Sc is demonstrated by X-ray Photo-electron Spectroscopy and Time-of-flight secondary ion mass Spectroscopy.

Characterization of High-k Nanolayers by Grazing Incidence X-ray Spectrometry

“…Note, however, that this assumption needs to be verified by a more systematic study utilizing a larger number of samples. For more details about the growth mechanisms and layer properties we refer to [ 33 ]. Our results clearly demonstrate the flexibility of our method in view of material systems and compositions.…”

Selective Growth of Interface Layers from Reactions of Sc(MeCp)2(Me2pz) with Oxide Substrates

“…Previously, the ALD of a Sc 2 O 3 interfacial layer was examined on an InGaAs substrate with a native oxide layer using Sc­(MeCp) 3 /water at 300 °C . Interestingly, increasing the Sc­(MeCp) 3 pulse time from 4 to 10 s during the first ALD cycle resulted in higher scandium content; no indium, gallium, or arsenic oxides were detected after the application of one Sc 2 O 3 ALD cycle, suggesting efficient interfacial self-cleaning .…”

“…The thicker films measured on the Si(111)−SiO 2 −OH substrates result from the direct reaction of 1 with SiO 2 at ≥225 °C, in addition to this gas-phase contribution. Because Sc 2 O 3 is not hygroscopic, 43 adsorbed water is not expected to be present on the ScSi x O y surface; consequently, gas-phase reactions are likely facilitated by water desorbed from the chamber walls.…”

“…Previously, the ALD of a Sc 2 O 3 interfacial layer was examined on an InGaAs substrate with a native oxide layer using Sc(MeCp) 3 /water at 300 °C. 43 Interestingly, increasing the Sc(MeCp) 3 pulse time from 4 to 10 s during the first ALD cycle resulted in higher scandium content; no indium, gallium, or arsenic oxides were detected after the application of one Sc 2 O 3 ALD cycle, suggesting efficient interfacial self-cleaning. 43 Consistent with our theory for the selective reactivity of 1, electrochemical potentials for the In(III)/In(0) and Ga(III)/ Ga(0) redox couples are −0.338 and −0.549 V, which are significantly more positive than the potential for the Sc(III)/ Sc(0) redox couple (E 0 = −2.09 V).…”

“…Numerous cyclopentadienyl (Cp) precursors of the rare earth elements have high thermal stabilities, are easily hydrolyzed, , and have been used to achieve impressive deposition rates for metal oxide ALD processes with water as a coreactant, e.g., Sc 2 O 3 , − Y 2 O 3 , − La 2 O 3 , − CeO 2 , , Pr 2 O 3 , Gd 2 O 3 , ,,, Dy 2 O 3 , Er 2 O 3 , , Yb 2 O 3 , and Lu 2 O 3 . For scandium-containing films, Sc­(Cp) 3 , and Sc­(MeCp) 3 − have been used with water for the ALD of Sc 2 O 3 and ScM x O y (M = Al, Y, or Gd), while Sc­( i PrCp) 3 has been used with ozone for the ALD of Sc 2 O 3 . All processes for Sc 2 O 3 ALD from Cp-based precursors are characterized by growth rates of 0.6–1.0 Å/cycle; however, the underlying mechanisms have been largely unexplored.…”