Effective reduction of fixed charge densities in germanium based metal-oxide-semiconductor devices

Deng, Shaoren; Xie, Qi; Deduytsche, Davy; Schaekers, Marc; Lin, Dennis; Caymax, Matty; Delabie, Annelies; Berghe, S. Van den; Qu, Xin-Ping; Detavernier, Christophe

doi:10.1063/1.3622649

Cited by 29 publications

(20 citation statements)

References 21 publications

(21 reference statements)

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“…The use of different oxidizing atmospheres was shown to have beneficial effects on the electrical properties of dielectric/Ge structures amending electrically active defects. Such treatments include the use of wet N 2 , 15 high pressure water treatment using supercritical fluids, 16 post metal annealing in an oxygen/nitrogen mixture, 17 and high pressure (70 atm) O 2 . 18 The observed improvements may be due to the suppression of GeO desorption and to modifications of the original dielectric layer.…”

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confidence: 99%

Oxygen transport and GeO2 stability during thermal oxidation of Ge

Silva

Rolim

Soares

et al. 2012

Applied Physics Letters

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Oxygen transport during thermal oxidation of Ge and desorption of the formed Ge oxide are investigated. Higher oxidation temperatures and lower oxygen pressures promote GeO desorption. An appreciable fraction of oxidized Ge desorbs during the growth of a GeO2 layer. The interplay between oxygen desorption and incorporation results in the exchange of O originally present in GeO2 by O from the gas phase throughout the oxide layer. This process is mediated by O vacancies generated at the GeO2/Ge interface. The formation of a substoichiometric oxide is shown to have direct relation with the GeO desorption.

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confidence: 99%

Oxygen transport and GeO2 stability during thermal oxidation of Ge

Silva

Rolim

Soares

et al. 2012

Applied Physics Letters

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“…Considering the work functions for Al (4.16 eV), NiGe (5.2 eV), Ge (4.33 eV), and SiGe (4.55 eV) and the gate oxide thickness of 3-4 nm, our experimental observations of negative Vfb suggest estimated positive fixed charge densities of ~5 × 10 11 cm −2 at interfaces of SiO2/SiGe and SiO2/Ge dot. It is interesting to note that the positive fixed charges measured for our NiGe/SiO2/SiGe and Al/SiO2/Ge-dot/SiO2/SiGe MOS capacitors are in contrast to the conventional expectation of negative fixed charges produced by the thermal oxidation of SiGe alloys (LeGoues et al, 1989;Nayak et al, 1990Nayak et al, , 1992 or at high-k dielectric/Ge interfaces generated either by chemical vapor deposition or atomic layer deposition (Bai et al, 2005;Zhang et al, 2006;Deng et al, 2011) As described in our previous reports (Kuo et al, 2012;Lai et al, 2015), the interfacial SiO2 layer between the Ge dot and the SiGe shell is formed by the thermal oxidation of Si interstitials that are released from the Si substrate. The oxide layer between the Ge dot and the deposited Al gate is formed by the thermal oxidation of Si interstitials that migrate along the surface of Ge dot to its distal end.…”

Section: Discussionmentioning

confidence: 67%

Gate-Stack Engineering for Self-Organized Ge-dot/SiO2/SiGe-Shell MOS Capacitors

et al. 2016

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We report the first-of-its-kind, self-organized gate-stack heterostructure of Ge-dot/ SiO2/SiGe-shell on Si fabricated in a single step through the selective oxidation of a SiGe-nanopatterned pillar over a Si3N4 buffer layer on a Si substrate. Process-controlled tunability of the Ge-dot size (7.5-90 nm), the SiO2 thickness (3-4 nm), and the SiGeshell thickness (2-15 nm) have been demonstrated, enabling a practically achievable core building block for Ge-based metal-oxide-semiconductor (MOS) devices. Detailed morphologies, structural, and electrical interfacial properties of the SiO2/Ge-dot and SiO2/SiGe interfaces were assessed using transmission electron microscopy, energy dispersive X-ray spectroscopy, and temperature-dependent high/low-frequency capacitance-voltage measurements. Notably, NiGe/SiO2/SiGe and Al/SiO2/Ge-dot/SiO2/SiGe MOS capacitors exhibit low interface trap densities of as low as 3-5 × 10 11 cm −2 eV −1 and fixed charge densities of 1-5 × 10 11 cm −2, suggesting good-quality SiO2/SiGe-shell and SiO2/Ge-dot interfaces. In addition, the advantage of having single-crystalline Si1−xGex shell (x > 0.5) in a compressive stress state in our self-aligned gate-stack heterostructure has great promise for possible SiGe (or Ge) MOS nanoelectronic and nanophotonic applications.

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“…It can be found that flat band voltage ( V fb ) values of HfO 2 /SiO 2 /Ge before and after PDA are 0.42 and 0.27 V, respectively. The calculated ideal V fb value is 0.55 V. The slightly negative V fb shift indicates positive fixed charges, which may be induced by the oxygen vacancies in the dielectrics [26, 27]. During the inert atmosphere annealing process, more oxygen vacancies may be induced, resulting in a slightly negative V fb shift.…”

Section: Resultsmentioning

confidence: 99%

Interfacial, Electrical, and Band Alignment Characteristics of HfO2/Ge Stacks with In Situ-Formed SiO2 Interlayer by Plasma-Enhanced Atomic Layer Deposition

Cao

et al. 2017

Nanoscale Res Lett

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In situ-formed SiO2 was introduced into HfO2 gate dielectrics on Ge substrate as interlayer by plasma-enhanced atomic layer deposition (PEALD). The interfacial, electrical, and band alignment characteristics of the HfO2/SiO2 high-k gate dielectric stacks on Ge have been well investigated. It has been demonstrated that Si-O-Ge interlayer is formed on Ge surface during the in situ PEALD SiO2 deposition process. This interlayer shows fantastic thermal stability during annealing without obvious Hf-silicates formation. In addition, it can also suppress the GeO2 degradation. The electrical measurements show that capacitance equivalent thickness of 1.53 nm and a leakage current density of 2.1 × 10−3 A/cm2 at gate bias of Vfb + 1 V was obtained for the annealed sample. The conduction (valence) band offsets at the HfO2/SiO2/Ge interface with and without PDA are found to be 2.24 (2.69) and 2.48 (2.45) eV, respectively. These results indicate that in situ PEALD SiO2 may be a promising interfacial control layer for the realization of high-quality Ge-based transistor devices. Moreover, it can be demonstrated that PEALD is a much more powerful technology for ultrathin interfacial control layer deposition than MOCVD.

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Effective reduction of fixed charge densities in germanium based metal-oxide-semiconductor devices

Cited by 29 publications

References 21 publications

Oxygen transport and GeO2 stability during thermal oxidation of Ge

Oxygen transport and GeO2 stability during thermal oxidation of Ge

Gate-Stack Engineering for Self-Organized Ge-dot/SiO2/SiGe-Shell MOS Capacitors

Interfacial, Electrical, and Band Alignment Characteristics of HfO2/Ge Stacks with In Situ-Formed SiO2 Interlayer by Plasma-Enhanced Atomic Layer Deposition

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