Sulfur passivation for the formation of Si-terminated Al2O3/SiGe(0 0 1) interfaces

Sardashti, Kasra; Hu, Kai-Ting; Tang, Kechao; Park, Sangwook; Kim, Hyonwoong; Madisetti, Shailesh; McIntyre, Paul C.; Oktyabrsky, S.; Siddiqui, Shariq; Sahu, Bhagawan; Yoshida, N.; Kachian, Jessica S.; Kummel, Andrew C.

doi:10.1016/j.apsusc.2016.01.123

Cited by 27 publications

(25 citation statements)

References 38 publications

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“…12 The positive voltage shift could be due to the increase in fixed oxide and/or interface charge, and the shift scales linearly with the thickness of the dielectric layer. According to theory, a thicker dielectric layer will increase the absolute magnitude of the fixed oxide charge contribution to the flat band voltage.…”

Section: Discussionmentioning

confidence: 99%

“…Previous work shows that (NH 4 ) 2 S solutions deposit 0.54 ML of S, but both Si and Ge oxides remain after treatment. 12 We investigated how the addition of acid to (NH 4 ) 2 S changes the S and O coverages. To complement the chemical characterization of the surface, we fabricated metal-insulator-semiconductor capacitor (MISCAP) devices to mimic the gate stack in a transistor.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, there have been studies on controlling the growth of both Si and Ge oxides at the SiGe/high-k (Al 2 O 3 ) interface by manipulating the composition of the metal contact layer, plasma postnitridation, preatomic layer deposition (ALD) dosing, and wet chemical sulfur passivation. [12][13][14][15][16][17] with the ratio of 1:1:500 for 2 min followed by rinsing with UPW for 1 min and blown dry with N 2 . Oxides were removed by immersion in HF:HCl:H 2 O with the ratio of 1:3:300 for 5 min.…”

Section: Introductionmentioning

confidence: 99%

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Reaction of aqueous ammonium sulfide on SiGe 25%

Heslop

Peckler

Muscat

2017

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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SiGe 25% substrates were treated with aqueous solutions of ammonium sulfide with and without added acid to understand the adsorption of sulfur on the surface. X-ray photoelectron spectroscopy showed no sulfide layer was deposited from aqueous (NH 4 ) 2 S alone and instead both Si and Ge oxides formed during immersion in the sulfur solution. The addition of hydrofluoric and hydrochloric acids dropped the pH from 10 to 8 and deposited sulfides, yet increased the oxide coverage on the surface and preferentially formed Ge oxides. The sulfur coverage grew with increasing concentrations of acid in the aqueous (NH 4 ) 2 S. The simultaneous deposition of O and S is suspected to be the result of oxidized sulfur species in solution. Metal-insulator-semiconductor capacitor (MISCAP) devices were fabricated to test the electrical consequences of aqueous ammonium sulfide wet chemistries on SiGe. MISCAPs treated with acidic ammonium sulfide solutions contained fewer interface defects in the valence band region. The defect density (D it ) was on the order of 10 þ12 cm -2 eV À1. The flat band voltage shift was lower after the acidic ammonium sulfide treatment, despite the presence of surface oxides. Adsorption of S and potentially O improved the stability of the surface and made it less electrically active.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reaction of aqueous ammonium sulfide on SiGe 25%

Heslop

Peckler

Muscat

2017

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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“…Previously, several techniques such as nitride and sulfur passivation on Si 0.7 Ge 0.3 (001) were studied with Al 2 O 3 gate oxides and reduction in the interface defect density via suppression of GeO x formation was reported [10][11] . However similar low defect density interfaces could not be established with HfO 2 gate oxide.…”

Section: Introductionmentioning

confidence: 99%

“…Similar to 6×(9HfO 2 +1Al 2 O 3 ) NL gate dielectric structure, gate oxide without oxidant during Al 2 O 3 ALD is performed by only TMA dosing and D it reduction along with C max observed indicating Al 2 O 3 layer formation by oxygen scavenging. It is hypothesized that TMA exposure scavenges weakly bound oxygen from the interface either by diffusing into the interface as TMA or TMA reaction products (for example monomethyl aluminum) or it decomposes the GeO x remotely, producing suboxide species that diffuse readily through even thin Al 2 O 3 (remote gettering)10 . As TMA interacts and scavenges oxygen from the interface, it is likely that GeO x dissociates and donates oxygen to TMA due to the lower Gibbs free energy of formation of GeO x in comparison to SiO x 27.…”

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confidence: 99%

Engineering High-k/SiGe Interface with ALD Oxide for Selective GeO_x Reduction

Kavrik

Ercius

Cheung

et al. 2019

ACS Appl. Mater. Interfaces

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Suppression of electronic defects induced by GeO x at the high-k gate oxide/SiGe interface is critical for implementation of high mobility SiGe channels in CMOS technology. Theoretical and experimental studies have shown that a low defect density interface can be formed with an SiO xrich interlayer on SiGe. Experimental studies in literature indicates better interface formation with Al 2 O 3 in contrast to HfO 2 on SiGe however the mechanism behind this is not well understood. In this study, the mechanism of forming a low defect density interface between Al 2 O 3 /SiGe is investigated using atomic layer deposited (ALD) Al 2 O 3 insertion into or on top of ALD HfO 2 gate oxides. To elucidate the mechanism, correlations are made between the defect density determined by impedance measurements and the chemical and physical structure of the interface determined by high resolution scanning transmission electron microscopy and electron energy loss spectroscopy (STEM-EELS). Compositional analysis reveals an SiO x rich interlayer for both Al 2 O 3 /SiGe and HfO 2 /SiGe interfaces with insertion of Al 2 O 3 into or on top of the HfO 2 oxide. The data is consistent with the Al 2 O 3 insertion inducing decomposition of the GeO x from the interface to form an electrically passive, SiO x rich interface on SiGe. This mechanism shows that nanolaminate gate oxide chemistry cannot be interpreted as resulting from a simple layer by layer ideal ALD process because the precursor or its reaction products can diffuse though the oxide during growth and react at the semiconductor interface. This result shows that in scaled CMOS, remote oxide ALD (oxide ALD on top of the gate oxide) can be used to suppress electronic defects at gate-oxide semiconductor interfaces by oxygen scavenging.

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Back‐Bias Effects in a SiGe Nanosheet Transistor with Multiple Independent Gates

Beyer,

Bhattacharjee,

Mikolajick

et al. 2024

Adv Materials Technologies

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Silicon germanium presents a great opportunity to improve the performance of Schottky barrier transistors through band gap engineering. This work presents a multi‐gated reconfigurable transistor built from pure SiGe channel material for bandgap reduction. The device utilizes industrial‐grade SiGe‐on‐insulator wafers, a hysteresis‐free HfO2‐based dielectric, and alloyed NiTiGeSi contacts, leading to Fermi‐level pinning of the Schottky contact about 200 meV above the valance band. Electron and hole transport in this complex structure have been analyzed as a function of the applied back‐bias by electrical measurements and corresponding technology computer‐aided design simulation. An on/off ratio of 103 with on‐currents up to 3.15 µA can be achieved for the p‐mode. At the same bias, the n‐mode showed no influence of the top gates due to a dominant parasitic hole current path. A strong positive back‐bias induced an n‐type switching operation, resulting in similar on/off‐ratio and subthreshold slopes as achieved with the p‐type mode. Opposed to this, it is shown that a strong negative back‐bias leads to a loss of gate control over the p‐mode, inducing an always‐on behavior. The results will give guidelines for applying Schottky barrier devices in industrial SiGe technologies, e.g., for reconfigurable or cryogenic computing.

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Sulfur passivation for the formation of Si-terminated Al2O3/SiGe(0 0 1) interfaces

Cited by 27 publications

References 38 publications

Reaction of aqueous ammonium sulfide on SiGe 25%

Reaction of aqueous ammonium sulfide on SiGe 25%

Engineering High-k/SiGe Interface with ALD Oxide for Selective GeO_x Reduction

Back‐Bias Effects in a SiGe Nanosheet Transistor with Multiple Independent Gates

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Sulfur passivation for the formation of Si-terminated Al2O3/SiGe(0 0 1) interfaces

Cited by 27 publications

References 38 publications

Reaction of aqueous ammonium sulfide on SiGe 25%

Reaction of aqueous ammonium sulfide on SiGe 25%

Engineering High-k/SiGe Interface with ALD Oxide for Selective GeOx Reduction

Back‐Bias Effects in a SiGe Nanosheet Transistor with Multiple Independent Gates

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Engineering High-k/SiGe Interface with ALD Oxide for Selective GeO_x Reduction