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Leakage current density (Jg)-CET relationship for Ge-based MOS capacitors with different interfacial control layer
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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 o...
Citations
... As discussed above the QGe/GeOx is positive. The positive QSiO2 is originated from the 3-fold bonded oxygen 26 , magnitude of which is determined by the sum of GeOx/SiO2 interface fixed charge and the SiO2 bulk charge 14,24,25,27 . The QAl2O3 is reported to be related to the trapped electrons that tunnel through the SiO2 layer and contribute to the negative charge near the SiO2/Al2O3 interface 25,28 . ...
The excellent field-effect passivation provided by aluminum oxide (Al2O3) on germanium surfaces relies on the high negative fixed charge present in the film. However, in many applications, a neutral or a positive charge would be preferred. Here, we investigate the surface passivation performance and the charge polarity of plasma-enhanced atomic layer deposited (PEALD) silicon oxide (SiO2) on Ge. The results show that even a 3 nm thick PEALD SiO2 provides a positive charge density (Qtot, ∼2.6 × 1011 cm−2) and a relatively good surface passivation (maximum surface recombination velocity SRVmax ∼16 cm/s). When the SiO2 thin film is capped with an ALD Al2O3 layer, the surface passivation improves further and a low midgap interface defect density (Dit) of ∼1 × 1011 eV−1 cm−2 is achieved. By varying the SiO2 thickness under the Al2O3 capping, it is possible to control the Qtot from virtually neutral (∼2.8 × 1010 cm−2) to moderately positive (∼8.5 × 1011 cm−2) values. Consequently, an excellent SRVmax as low as 1.3 cm/s is obtained using optimized SiO2/Al2O3 layer thicknesses. Finally, the origin of the positive charge as well as the interface defects related to PEALD SiO2 are discussed.
... In Fig. 1(d), the peaks located at 17.2 and 18.9 eV come from Hf 4f 7/2 and Hf 4f 5/2 signals from the Hf-O bond with the spin-orbit splitting energy of 1.7 eV, proving the existence of the inorganic component in Hf-HQ. 36,37 The C 1s peaks at 284.6 and 288.4 eV in Fig. 1(e) are attributed to the C-C/C-O (backbone chain carbon) bond and the O-C=C bond from phenol, respectively, which indicates the organic components in the hybrid Hf-HQ film. 32 The O 1s peaks in Fig. 1 ...
In this work, we fabricated the Pt/Hf-based hydroquinone (Hf-HQ)/Al2O3/TiN/Si bilayer hybrid memory by molecular layer deposition/atomic layer deposition. The hybrid memory units exhibit electroforming-free bipolar resistive switching (RS) characteristics with tiny fluctuation of operation voltages within 0.2 V, ON/OFF ratio above 10², and good endurance/retention properties. Meanwhile, the multi-state data storage capability is confirmed in hybrid devices. The RS mechanism based on conducting filaments has been proposed. The favorable linkage and rupture of the conducting filament prefer to occur at the interface of the hybrid Hf-HQ layer and Al2O3 layer, resulting in the brilliant performances. Furthermore, flexible hybrid memory devices fabricated on bendable mica show comparable RS behaviors to the Si-based ones at the bending radius of 7.5 mm, indicative of great potential in flexible multilevel resistive random access memory applications.
... The intercept tip is considered as E v (Sm 2 O 3 + IL) which were measured 2.94 eV, 2.72 eV, 3.08 eV and 3.04 eV for oxidation/nitridation durations of 5, 10, 15 and 20 min, respectively. Meanwhile, the tailed domain appeared at low B.E position of VB spectrums has been considered as signal of substrate Ge where, E v (Ge) ∼ 0.10 eV has been used as reference point from previous report [55]. The VBO, ΔE v (Sm 2 O 3 + IL) with respect to substrate Ge for 5, 10, 15 and 20 min oxidation/nitridation durations are 2.84 eV, 2.62 eV, 2.98 eV and 2.92 eV, respectively. ...
In this study, Sm2O3/Ge stack based capacitor prepared from thermally oxidized/nitrided sputtered metallic Sm on Ge semiconductor in N2O ambient for several oxidation/nitridation durations, i.e., 5 – 20 min have been comprehensively investigated. The film crystallinity, chemical composition and interface chemical bonding states stability was characterized from X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Formation of trigonal-Sm2O3 dielectric interface together with an interfacial layer containing asymmetrically distributed (GeO, SmOGe and GeN) species has been verified. Suppression of GeO (g) volatilization was evident from the XPS analysis due to germanate (SmOGe) formation. Structural morphology characterization using high resolution transmission electron microscope (HRTEM) also validated double stack amorphous interfaces obtaining physical oxide thickness (tox) from 4.25 − 6.91 nm. Band alignment and electrical measurements revealed that oxidation/nitridation duration of 15 min exhibited highest conduction band offset (CBO), ΔEc of 2.60 eV and valence band offset (VBO) ΔEv of 2.98 eV leading to lowest leakage current density Jg ∼ 8.38 × 10⁻⁶ A cm⁻² at enhanced breakdown field, EBD of 13.31 MV cm⁻¹. The large breakdown field has been ascribed to fewest effective oxide charge (Qeff), slow trap density, (Qit) and interface traps density Dit at this duration. Additionally, a low equivalent oxide thickness, tEOT ∼ 0.75 nm with a high dielectric constant k ∼ 31.19 eV was achieved but with a price of high Dit ∼ 10¹³ eV⁻¹cm⁻². These properties render that Sm2O3 could serve as dielectric material for future high-k/Ge stack based metal oxide semiconductor technology, although requires further investigation for Dit improvement.
... The conventional tailed region noticed at low binding energy site of VB spectra is being considered as Ge substrate signal. The reference position of VB edge, E v (Ge) was considered at 0.10 eV, obtained from the reported literature 59 and was assumed to be constant for various oxidation/nitridation duration. The VB edge, E v of Ho 2 O 3 / IL was approximated by the linear extrapolation intercept of the maximum negative slope leading edge in VB spectra with the minimum edge of Ge substrate baseline as demonstrated in Figure 10A. ...
The influence of different thermal oxidation/nitridation durations (5, 10, 15, and 20 minutes) at 400°C for transforming metallic Ho sputtered on Ge substrate in N2O gas ambient have been systemically investigated to develop Ho2O3/Ge based on metal‐oxide‐semiconductor (MOS) device. The structural and chemical properties of the film were characterized using X‐ray diffraction spectroscopy, X‐ray photoelectron spectroscopy (XPS), and high‐resolution transmission electron microscopy. Cubic‐Ho2O3 dielectric layer has been formed along with sandwiched interfacial layer (IL) between substrate Ge and high‐k interface comprising tetragonal‐GeO2, GeOx, and cubic‐Ge3N4 compounds. Energy band alignment for Ho2O3/IL/Ge MOS stack has been determined from XPS spectrum where 10‐minute sample exhibited maximum conduction band offset, ΔEc ~ 2.47 eV and valance band offset, ΔEv ~ 4.67 eV, inducing lower leakage current density, J ~ 10−5 A cm−2 at the higher electrical breakdown, EBD ~ 8.59 MV cm−1. The electrical results of this sample also revealed higher dielectric constant k ~ 13.60, lowest effective oxide charge, slow trap density, and interface trap density which has been attributed to the confinement of Ho2O3 dielectric interface and densification Ge3N4 interfacial compound. An oxidation/nitridation model related to Ho2O3/IL/Ge stack growth is being proposed. It has been anticipated that Ho2O3 could serve as a gate dielectric oxide for Ge‐based MOS systems such as a capacitor.
... Fig. 9a illustrates the XPS valance band spectra for sample investigated at 300 • C, 400 • C and 500 • C. A typical small tail is observed in the valence band spectra which is considered as Ge signal. The valence band edge (E v ) of Ge = 0.10 eV was used as reference from literature [51,52]. The valance band edge (E v ) for sm 2 O 3 /IL was calculated by extrapolation of the maximum negative slope near the edge to the minimum horizontal Ge signal baseline as illustrated in Fig. 9a [43,51]. ...
... The valence band edge (E v ) of Ge = 0.10 eV was used as reference from literature [51,52]. The valance band edge (E v ) for sm 2 O 3 /IL was calculated by extrapolation of the maximum negative slope near the edge to the minimum horizontal Ge signal baseline as illustrated in Fig. 9a [43,51]. The valance band edge (E v ) of Sm 2 O 3 with respect to Ge substrate were estimated 3.27, 3.02 and 3.08 eV for 300 • C, 400 • C and 500 • C, respectively. ...
... This finding indicates that flatband voltage (V FB ) shifted positively, which confirms the presence of negative oxide charges or native defects in the gate stack [54][55][56]. Several reported literatures have demonstrated that oxygen vacancies generated by GeO desorption causes flatband voltage (ΔV FB ) shift by generating additional negative charges [51,56]. It is clearly visible from Fig. 14 that 400 • C sample shows an obvious negative shift in compare to other investigated samples. ...
A systematic study of chemical, structural and electrical properties of Sm2O3 gate stack has been carried out for RF sputtered Sm thin film on Ge substrate followed by thermal oxidation and nitridation at different temperatures, i.e. 300°C – 600°C in N2O ambient. The crystallinity and phase identification were investigated using X-ray diffraction (XRD) analysis. The crystallite size and micro-strain were approximated using Williamson-Hall plot. Chemical composition and interfacial bonding state have been identified by X-ray photoelectron spectroscopy analysis. High-resolution transmission electron microscopy was performed to investigate the cross-sectional morphology and thickness estimation of Sm2O3/IL/Ge. Presence of amorphous Sm2O3 film layer with an amorphous interfacial layer comprising GeO2, Ge3N4 and Sm-O-Ge were identified. Band alignment of Sm2O3 gate stack was estimated from X-ray photoelectron spectroscopy with a conduction band offset of ΔEc =2.87 eV and valance band offset ΔEv= 2.98 eV; exhibited a high electrical breakdown of 13.31 MVcm⁻¹ at leakage current density, 10⁻⁶ A/cm². Through the correlation of findings, possible growth mechanism of Sm2O3 has been suggested. This type of oxide could be served as gate dielectric in Ge MOS-based devices.
... The present report suggests that the study of the SiO 2 /SiGe interface is practically an investigation of the SiO 2 /Ge interface. Recently, Cao et al. have used XPS to study the HfO 2 /SiO 2 /Ge stack, 38) where the interfacial bonding is claimed to be in a Si-O-Ge fashion. Our recent publication regarding growth of thin single-crystal Si 0.7 nm thick on epi Ge(001)-2 × 1 and its oxidation reveals that SiO x (x = 1-4) readily formed on the Si surface upon annealing without involving the Si/Ge(001) interface. ...
By using synchrotron radiation photoemission, this study investigates the room-temperature surface electronic structure of Si1−xGex(001)-2 × 1 grown by molecular-beam epitaxy on an epi Ge(001) substrate. The electronic structure of the Ge content, which ranges from 10% to 90%, shows similar surface behaviors. The Ge 3d core-level spectra of Si1−xGex(001)-2 × 1 are essentially the same as that of epi Ge(001)-2 × 1, terminating with tilted Ge–Ge dimers and Ge atoms in the subsurface layer. The strain effect is manifest only for the Si atoms, for which three types are revealed, namely two near the surface region and one in the bulk.
... The Ge 3d XP spectrum showed peaks at 29.5 and 32.1 eV attributed to Ge and Ge-O bonding in the bulk, respectively. The doublet splitting energy of Ge was 2.8 eV, which confirms the oxidation of Ge [28]. After the PMA, the Ge-O peak was shifted to a lower binding energy, indicating that the SiO 2 IL restrained the GeO 2 layer and effectively blocked the outdiffusion of Ge atoms (to form a defective Hf-silicate layer) during the PMA. ...
... In addition, a reduction in the interface defect density near the bottom of the conduction band of Ge was observed in the G-V plots. The extracted D it values were quite low compared with those in the earlier report of Cao et al [28]. ...
... This indicates a reduction in the large trapped oxide charge in the gate dielectric film after the PMA in the NH 3 ambient at 400°C for 30 min. The obtained gate leakage current densities are better than those in the earlier report [28]. Figure 6(b) shows the current density as a function of the electric field. ...
Abstract
The effects of post-metallisation annealing (PMA) at 400 °C for 30 min in an NH3 ambient on the interfacial and electrical properties of a structure consisting of a Ge substrate coated with HfO2 by atomic layer deposition with a 3-nm-thick SiO2 interfacial layer formed in situ by a sputtering technique were evaluated. X-ray diffraction and X-ray photoelectron spectroscopy analyses confirmed the crystallinity of HfO2 and chemical bonding of the HfO2/SiO2/Ge interface before and after the annealing. Clear stretch-free distinct capacitance–voltage curves were observed for the sample after the PMA. According to the electrical measurements, the sample after the PMA exhibited a large dielectric constant (k ~ 17), low interface trap density (Dit = 1.8 × 1012 cm2 eV−1), and small oxide charge (Qeff = 2.54 × 1012 cm2 eV−1). The gate leakage current of the PMA device determined using the current–voltage curve was approximately 0.1 × 10−4 A cm−2 at Vg+ = +1 V. These results suggest that the SiO2 interfacial layer formed in situ and NH3−PMA significantly improved the structural, interfacial, and electrical characteristics of the HfO2/Ge stacks for future Ge-based complementary metal–oxide–semiconductor device applications.
Ge-based MOS capacitor with HfTiON/(LaON/Si) gate stacks and fluorine-plasma treatment (FPT) has been well investigated by transmission electron microscopy (TEM), electrical measurements and X-ray photoemission spectroscopy (XPS) in this work. Electrical measurements have shown that fluorine-plasma treated Ge MOS capacitor exhibits negligible hysteresis (15 mV), small gate leakage current (3.66 × 10⁻⁶ A/cm² at Vfb + 1 V), and low interface-state density at midgap (3.2 × 10¹¹ cm⁻² eV⁻¹). TEM results indicate that high quality LaSiON/Ge interfaces. XPS results further reveal the presence of fluorine incorporation and the less content of the Ge oxides at the LaSiON/Ge interface. These improvements should be attributed to the LaSiON passivation layer and FPT can suppress the formation of volatile and unstable Ge oxides. In addition, LaSiON passivation layer can further block inter-diffusion of elements between HfTiON and Ge substrate, and FPT can occupy the oxygen vacancies and reduce interface traps in the HfTiON dielectric and LaSiON/Ge interface. These greatly improve the performance of the Ge MOS device.
