BTI Characterization of MBE Si-Capped Ge Gate Stack and Defect Reduction via Forming Gas Annealing

Wan, Hsien-Wen; Hong, Yan; Cheng, Yi-Ting; Hong, M.

doi:10.1109/irps.2019.8720567

Cited by 4 publications

(10 citation statements)

References 15 publications

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“…Consequently, the charge environment becomes similar to that of the down-dimer atom. The present experimental results provide direct evidence that the unpassivated down-dimer atoms might account for the reliability issue that is related to Ge MOS devices [39,40].…”

Section: Introductionmentioning

confidence: 73%

Microscopic Views of Atomic and Molecular Oxygen Bonding with epi Ge(001)-2 × 1 Studied by High-Resolution Synchrotron Radiation Photoemission

et al. 2019

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In this paper, we investigate the embryonic stage of oxidation of an epi Ge(001)-2 × 1 by atomic oxygen and molecular O2 via synchrotron radiation photoemission. The topmost buckled surface with the up- and down-dimer atoms, and the first subsurface layer behaves distinctly from the bulk by exhibiting surface core-level shifts in the Ge 3d core-level spectrum. The O2 molecules become dissociated upon reaching the epi Ge(001)-2 × 1 surface. One of the O atoms removes the up-dimer atom and the other bonds with the underneath Ge atom in the subsurface layer. Atomic oxygen preferentially adsorbed on the epi Ge(001)-2 ×1 in between the up-dimer atoms and the underneath subsurface atoms, without affecting the down-dimer atoms. The electronic environment of the O-affiliated Ge up-dimer atoms becomes similar to that of the down-dimer atoms. They both exhibit an enrichment in charge, where the subsurface of the Ge layer is maintained in a charge-deficient state. The dipole moment that was originally generated in the buckled reconstruction no longer exists, thereby resulting in a decrease in the ionization potential. The down-dimer Ge atoms and the back-bonded subsurface atoms remain inert to atomic O and molecular O2, which might account for the low reliability in the Ge-related metal-oxide-semiconductor (MOS) devices.

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Section: Introductionmentioning

confidence: 73%

Microscopic Views of Atomic and Molecular Oxygen Bonding with epi Ge(001)-2 × 1 Studied by High-Resolution Synchrotron Radiation Photoemission

et al. 2019

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“…Using molecular beam epitaxy (MBE), a physical vapor deposition method, to grow 1 nm thick single-crystal Si on epi- Ge, followed by direct deposition of HfO 2 and Al 2 O 3 , Wan et al attained a low D it of (1–3) × 10 11 eV –1 cm –2 with conventional postmetallization annealing (PMA) in forming gas that did not require high pressure of hydrogen. Studies of the capacitance–voltage ( C–V) hysteresis under negative stress voltages yielded an effective charge sheet density (Δ N eff ) that was <3 × 10 10 cm –2 (the targeted value required of sufficient reliability) in an equivalent oxide field ( E ox ) of ∼10 MV/cm, which was larger than those at the operating conditions.…”

Section: Introductionmentioning

confidence: 99%

“…Compared with our earlier efforts, in this work, we used MBE to grow a thinner single-crystal Si of 0.79 nm thickness (six MLs) epitaxially on epi -Ge in the (001) orientation under ultra-high vacuum (UHV). At growth temperatures below 300 °C, MBE enables epi- Si growth on Ge.…”

Section: Introductionmentioning

confidence: 99%

Low-Temperature-Grown Single-Crystal Si Epitaxially on Ge, Followed by Direct Deposition of High-κ Dielectrics–Attainment of Low Interfacial Traps and Highly Reliable Ge MOS

Wan

Hong

Cheng

et al. 2021

ACS Appl. Electron. Mater.

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Single-crystal silicon (Si) of six monolayer thickness was epitaxially grown on epi-germanium (Ge) in the (001) orientation at substrate temperatures lower than 300 °C, followed by direct deposition of hafnium oxide (HfO2) and aluminum oxide (Al2O3) under ultra-high vacuum. We monitored and studied the Si growth and its epitaxy with the epi-Ge substrate using in-situ reflection high-energy electron diffraction and high-resolution synchrotron radiation X-ray diffraction. Using the gate stacks, we obtained interfacial trap densities of (1–3) × 1011 eV–1 cm–2 without the use of high-pressure hydrogen annealing and a highly reliable Ge p-type metal-oxide semiconductor with a high acceleration factor of 11.

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“…Owning to the higher bulk mobility of both hole and electron, germanium (Ge) possesses great potential to replace silicon (Si) in the channel of CMOS to enhance the carrier transport and consequently to achieve higher drive currents and switching speeds [1]. Ge MOSFETs used to suffer from the lack of a good native oxide which results in massive interface states, but significant progress has been made recently [2][3][4][5][6][7][8][9][10][11][12]. After good initial performance was achieved, attention has been paid to device reliability to pave the way for the debut of Ge CMOS.…”

Section: Introductionmentioning

confidence: 99%

“…The improvement of Ge MOSFETs was usually achieved through two routes: GeO2 directly on Ge [2,4,6,8] or using a Si capping layer [3,7]. Previous studies reveal that GeO2/Ge devices offer higher mobility for both p and n MOSFETs but suffer from poor reliability [19][20][21], while Si-capped devices exhibit a better NBTI reliability compared to Si counterpart [19].…”

Section: Introductionmentioning

confidence: 99%

A Comparative Study of AC Positive Bias Temperature Instability of Germanium nMOSFETs With GeO₂/Ge and Si-cap/Ge Gate Stack

Gao

Lin

et al. 2021

IEEE J. Electron Devices Soc.

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AC positive bias temperature instability (PBTI) of germanium nMOSFETs with GeO2/Ge and Si-cap/Ge gate stack was investigated in this brief. AC-DC-AC alternating PBTI stress tests were conducted on both types of devices, the experiment data shows the inserted DC stress phase has little impact on the following AC stress kinetics on GeO2/Ge nMOSFETs but introduce a significant "additional DC generation" on Si-cap/Ge devices. The "additional DC generation" is ascribed to the existence of energy alternating defects (EAD) according to previous studies. Energy distribution under DC and AC stress further demonstrate that EAD are significant on Si-cap/Ge but negligible on GeO2/Ge devices. Effective lifetime prediction is carried out and compared under DC stress after discharge (with a purposely introduced measurement delay) and AC stress on both GeO2/Ge and Si-cap nMOSFETs. The results show GeO2/Ge nMOSFETs' effective lifetime exhibits no difference under two stress modes, while Si-cap/Ge nMOSFETs' effective lifetime is underestimated using DC stress after discharge approximation without considering the EAD-induced "additional DC generation". An extra 0.14V 10-year Vdd design margin can be obtained for Si-cap/Ge nMOSFETs to gain higher performance by taking "additional DC generation" into account. The conclusion is beneficial for process optimization and PBTI reliability improvement of Ge nMOSFETs.

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BTI Characterization of MBE Si-Capped Ge Gate Stack and Defect Reduction via Forming Gas Annealing

Cited by 4 publications

References 15 publications

Microscopic Views of Atomic and Molecular Oxygen Bonding with epi Ge(001)-2 × 1 Studied by High-Resolution Synchrotron Radiation Photoemission

Microscopic Views of Atomic and Molecular Oxygen Bonding with epi Ge(001)-2 × 1 Studied by High-Resolution Synchrotron Radiation Photoemission

Low-Temperature-Grown Single-Crystal Si Epitaxially on Ge, Followed by Direct Deposition of High-κ Dielectrics–Attainment of Low Interfacial Traps and Highly Reliable Ge MOS

A Comparative Study of AC Positive Bias Temperature Instability of Germanium nMOSFETs With GeO₂/Ge and Si-cap/Ge Gate Stack

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