Density-functional theory molecular dynamics simulations of a-HfO2/a-SiO2/SiGe and a-HfO2/a-SiO2/Ge with a-SiO2 and a-SiO suboxide interfacial layers

Chagarov, Evgueni; Kavrik, Mahmut Sami; Ziwei, Fang; Tsai, W.; Kummel, Andrew C.

doi:10.1016/j.apsusc.2018.02.041

Cited by 11 publications

(10 citation statements)

References 33 publications

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“…Once the Al 2 O 3 gate oxide reaches a critical thickness, an additional 25% increase in oxide thickness results in a 4× reduction in D it and nearly complete elimination of the SiGeO x interfacial layer. For HfO 2 , the selective scavenging process benefits from the difference in formation enthalpy of SiO x in comparison to GeO x and reduces the interface trapped charge density by forming Si-rich SiO x at the interface, consistent with the predictions of the DFT models 16 . This is also consistent with the known ability of TMA to reduce low enthalpy of formation oxides on substrates at the start of ALD, a process known as ALD cleanup [19][20] .…”

Section: Introductionsupporting

confidence: 79%

“…For HfO 2 , the selective scavenging process benefits from the difference in the formation enthalpy of SiO x in comparison to GeO x and reduces the interface-trapped charge density by forming Si rich SiO x at the interface, consistent with the predictions of the DFT models. 15 This is also consistent with the known ability of TMA to reduce low enthalpy of formation oxides on substrates at the start of ALD, a process known as ALD cleanup.…”

Section: ■ Introductionsupporting

confidence: 78%

“…The main challenge for implementing SiGe FETs is the binary atom termination (Si-Ge) of the surface which results in formation of SiGeO x mixed oxides and dangling bonds on both Si and Ge atoms [6][7][8] . GeO x and associated dangling bonds are the main sources of defects producing interface trapped charge (D it ), while SiO x is a stable oxide that forms a nearly defect-free interface according to theoretical calculations 9 .…”

Section: Introductionmentioning

confidence: 99%

“…6−8 GeO x and associated dangling bonds are the main sources of defects producing interface-trapped charge (D it ), whereas SiO x is a stable oxide that forms a nearly defectfree interface according to theoretical calculations. 9 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 a 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%

“…14 Theoretical density functional theory (DFT) models of the amorphous HfO 2 /Si 0.5 Ge 0.5 (001) interface have shown that low defect interfaces may be formed even before hydrogen passivation with short anneals (<10 ps) when the interface is comprised solely of silicon monoxide (SiO). 15 Experimental studies have shown a 10× D it reduction at the Al 2 O 3 /SiGe and HfO 2 /SiGe interfaces via selective oxygen scavenging by using an oxygen scavenging, metallic Al gate; 16 the selectivity is due to the difference in the formation enthalpy of GeO x compared to SiO x facilitating transfer of oxygen from GeO x to Al. 6,16 However, this process induced thicker gate oxides and reduced the maximum capacitance density (C max ) resulting from Al oxidation on top of ALD-grown gate oxide.…”

Section: ■ Introductionmentioning

confidence: 99%

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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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Section: Introductionsupporting

confidence: 79%

Section: ■ Introductionsupporting

confidence: 78%