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Study on void reduction in direct wafer bonding using Al <sub/>2</sub> O <sub/>3</sub> /HfO <sub/>2</sub> bonding interface for high-performance Si high- <i>k</i> MOS optical modulators
摘要： We have investigated the direct wafer bonding (DWB) method with a thin bonding dielectric interface to fabricate Si high-k MOS optical modulators with a thin equivalent oxide thickness (EOT). To suppress void generation on the bonded wafer during high-temperature annealing, we examined the high-k dielectric bonding interfacial layers, such as Al2O3 and HfO2. We found that the Al2O3/HfO2 bilayer enables void-less wafer bonding in conjunction with pre-bonding annealing at 700 °C. By using the 0.5-nm Al2O3/2.0-nm HfO2 bonding interface, the density of voids is reduced by three orders of magnitude as compared with that in the case of using the Al2O3 bonding interface. We achieved a density of voids of approximately 2 ' 10%3 cm%2 even when the bonded wafer is annealed at 700 °C. By thermal desorption spectroscopy (TDS), we found that degassing from the bonding interface is successfully suppressed by the introduction of the HfO2 layer and the pre-bonding annealing at 700 °C, which are considered to suppress void generation. Wafer bonding with thin Al2O3/HfO2 high-k bonding interface is promising for Si high-k MOS optical modulators.
关键词： Al2O3,void reduction,MOS optical modulators,high-k dielectric,HfO2,direct wafer bonding
更新于2025-09-23 15:21:01
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Towards a comprehensive understanding of the Si(100)-2×1 surface termination through hydrogen passivation using methylamine and methanol: a theoretical approach
摘要： Using density functional theory, we explored the termination process of Si (100)-2 × 1 reconstructed surface mechanistically through the dehydrogenation of small molecules, considering methyl amine and methanol as terminating reagents. At first, both the terminating reagents form two types of adduct through adsorption on the Si (100)-2 × 1 surface, one in chemisorption mode and the other via physisorption, from which the dehydrogenation process is initiated. By analyzing the activation barriers, it was observed that termination of the Si-surface through the dehydrogenation is kinetically almost equally feasible using either reagent. We further examined in detail the mechanism for each termination process by analyzing geometrical parameters and natural population analysis charges. From bonding evaluation, it is evident that hydrogen abstraction from adsorbates on the Si-surface is asymmetric in nature, where one hydrogen is abstracted as hydride by the electrophilic surface Si and the other hydrogen is abstracted as proton by the neucleophilic surface Si. Moreover, it was also observed that hydride transfer from adsorbate to the Si-surface occurs first followed by proton transfer. Overall, our theoretical interpretation provides a mechanistic understanding of the Si (100)-2 × 1 reconstructed surface termination by amine and alcohol that will further motivate researchers to design different types of decorated semiconductor devices.
关键词： Bonding evaluation,Si(100)-2 × 1 reconstructed surface,Dehydrogenation,Potential energy surface,Surface termination
更新于2025-09-23 15:21:01
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Synthesis of “lotus root”-like mesoporous titanium dioxide and its effects on UV response to aconitine release
摘要： Mesoporous titanium dioxide with a “lotus root”-like structure was synthesized for the first time using an improved template-free method. The structure has a BET (Brunauer Emmett Teller) surface area of 688.11 m2/g, a pore volume of 0.743 cm3/g, and a pore size of 3.59 nm. Aconitine, a botanical insecticide, could be loaded onto the mesoporous titanium dioxide via simply soaking the structure and had a maximum loading of 17.6 %. UV spectroscopy was utilized to explore the drug release behaviors, and the results showed that aconitine-loaded mesoporous titanium dioxide particles UV irradiated could successfully release aconitine with a release rate of 46.24%, which was significantly higher than the samples lacking UV irradiation (36.80%). Meanwhile, the release rate of aconitine (48.94 %) for pH 5.5 was significantly higher than that for pH 7.0 (42.09 %). The results of microcalorimetry revealed that both the enthalpy change (?H) and entropy change (?S) were negative (?H < 0, ?S < 0) for the whole process of aconitine loading onto the “lotus root”-like mesoporous titanium dioxide support. Hydrogen bonding was the driving force for drug loading, and this was also verified using Monte Carlo simulations. These results show that the “lotus root”-like mesoporous titanium dioxide material has some potential applications such as the storage and use of plant pesticides.
关键词： “Lotus root”-like mesoporous titanium dioxide,Monte Carlo simulations,hydrogen bonding,UV-responsed drug release
更新于2025-09-23 15:21:01
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Laser polymerized photonic wire bonds approach 1a??Tbit/s data rates
摘要： Microelectronics has solved the challenge of packaging different functional elements with integrated chips (ICs) in modern computing and communication by wire bonding. Miniaturization was a trend guided by the requirements for faster, more portable and less expensive (smaller amount of materials) solutions, where wire bonding evolved to accommodate increasingly more complex 3D architectures of chips and printed circuit boards. Even faster and more robust computing and communication can be provided by using photons rather than electrons. This was one of the underlying reasons for the fast growth of optical fiber communication, which is especially efficient over large ~1000 km distances. Data transfer in microelectronics also increasingly benefits from optical interconnects, which, however, have scaling challenges at small IC dimensions. The overall trend of optical fibers prevailing over copper wire for long-distance data transfer follows the miniaturization trend, and now, a new capability has been demonstrated on the microscale. Photonic wire bonding solves the same problem as wire bonding in microelectronics, but for optical communication on the level of chip-to-chip interconnects. In a recent study, a new milestone for data transfer over a 75 km channel at a rate of ~0.8 Tbit/s was demonstrated for Si photonic transmitters co-packaged with 1.5 μm InGaAsP lasers using photonic wire bonding. Several breakthroughs were combined to achieve the record high speed of data transfer. Optical insertion losses of only 0.7 dB were demonstrated. In addition, the required photonic wire tapering for single mode fiber operation/filtering was seamlessly achieved by direct laser writing. Most importantly, photonic wire bonding solves the stringent requirements for optical alignment between components and opens the possibility for automated packaging solutions. Si photonic platforms based on well-established complementary metal-oxide-semiconductor technologies can now be combined with other light sources and nonlinear optical components based on other platforms using photonic wire bonding. This makes hybrid photonic chip modules possible. It can be seen as a manifestation of the evolving trend in modern technology where complexity develops along with miniaturization, which has been the guiding principle established in previous decades of microelectronics.
关键词： optical communication,direct laser writing,miniaturization,photonic wire bonding,optical interconnects
更新于2025-09-23 15:21:01
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Impact of electronically excited state hydrogen bonding on luminescent covalent organic framework: a TD-DFT investigation
摘要： The investigation of intermolecular hydrogen bonding between the luminescent polypyrene covalent organic framework and formaldehyde (PPy-COF-HCHO) was carried out with the density functional theory and time-dependent density functional theory. The strengthening of the photoexcited hydrogen bond C = O—H–C was verified via geometric structures, electronic transition energies, binding energies, UV-Vis and infrared spectra comparison in both ground state and excited state of the PPy-COF’s truncated representative fragment. From the frontier molecular orbitals examination, natural population analysis, and plotted electron density difference map demonstrated that the strengthened hydrogen bond facilitated the rearrangement of electron density between H-donor and H-acceptor moieties which should account for charge transfer and ultimate fluorescence quenching. Interestingly, the energy gap between excited state and triplet state of the hydrogen-bonded complex showed the possibility of the intersystem crossing. The MOMAP programme further confirmed the quenching process because there was a lower fluorescent rate constant for the donor–acceptor PPy-COF-HCHO complex compared to free PPy-COF fragment. Results above significantly highlighted the high sensitivity of the PPy-COF towards organic analyte, i.e. the formaldehyde and can be employed as a sensor.
关键词： luminescence,TD-DFT,MOMAP,hydrogen bonding
更新于2025-09-23 15:21:01
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Investigation of the Physical Properties of Plasma Enhanced Atomic Layer Deposited Silicon Nitride as Etch Stopper
摘要： Correlations between physical properties linking film quality with wet etch rate (WER), one of the leading figures of merit, in plasma-enhanced atomic layer deposition (PEALD) grown silicon nitride (SiNx) films remain largely unresearched. Achieving a low WER of a SiNx film is especially significant in its use as an etch stopper for technology beyond 7 nm node semiconductor processing. Herein, we explore the correlation between the hydrogen concentration, hydrogen bonding states, bulk film density, residual impurity concentration, and the WERs of PEALD SiNx using Fourier transform infrared spectrometry, X-ray reflectivity, and spectroscopic ellipsometry, etc. PEALD SiNx films for this study were deposited using hexachlorodisilane and hollow cathode plasma source under a range of process temperatures (270 °C – 360 °C) and plasma gas compositions (N2/NH3 or Ar/NH3) to understand the influence of hydrogen concentration, hydrogen bonding states, bulk film density, and residual impurity concentration on the WER. Varying hydrogen concentration and differences in the hydrogen bonding states resulted in different bulk film densities, and accordingly, a variation in WER. We observe a linear relationship between hydrogen bonding concentration and WER as well as a reciprocal relationship between bulk film density and WER. Analogous to the PECVD SiNx processes, a reduction in hydrogen bonding concentration arises from either (1) thermal activation or (2) plasma excited species. However, unlike the case with silane (SiH4)-based PECVD SiNx, PEALD SiNx WERs are affected by residual impurities of Si precursors (i.e., chlorine impurity). Thus, possible wet etching mechanisms in HF in which the WER is affected by hydrogen bonding states or residual impurities are proposed. The shifts of amine basicity in SiNx due to different hydrogen bonding states and the changes in Si electrophilicity due to Cl impurity content are suggested as the main mechanisms that influence WER in the PEALD processes.
关键词： plasma-enhanced ALD (PEALD),bulk film density,hexachlorodisilane (HCDS),wet etch rate (WER),silicon nitride,hydrogen/chlorine content,atomic layer deposition (ALD),hydrogen bonding state
更新于2025-09-23 15:21:01
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Hydrogen bonding between ethynyl aromates and triethylamine: IR spectroscopic and computational study
摘要： Ethynylpyridines (EPs) and ethynylbenzene (EB) are multifunctional systems able to participate in hydrogen-bonded complexes as both donors and acceptors of the H-atom. Their structures and stabilities are mainly a function of the hydrogen-bonding properties of the partner in the complex and the surroundings in which the complexation occurs. In this paper, IR spectroscopy and quantum chemical calculations are employed to characterize hydrogen-bonded complexes of 2- and 3-EP and EB with triethylamine (TEA) in tetrachloroethene (C2Cl4) solution. The formation of ≡C?H···N hydrogen bonds is experimentally confirmed by the appearance of TEA concentration-dependent signals in the IR spectra of the EPs and EB. Along with the signals due to unassociated ≡C?H and C≡C oscillators (2-EP: 3308 cm–1 and 2120 cm–1; 3-EP: 3308 cm–1 and 2116 cm–1; EB: 3313 cm–1 and 2113 cm–1) weak, red-shifted signals arise at ~3215 ± 5 cm–1 and ~2105 ± 5 cm–1 which are assigned to the stretching vibrations of hydrogen-bonded ≡C?H··· and C≡C··· oscillators, respectively. This result is at variance with those of previous investigations of EB and TEA in the gas phase. In the 2-EP···TEA complex these bands remain at the same position with increasing TEA concentration. However, in the 3-EP···TEA and EB···TEA complexes the ≡C?H··· stretching band demonstrates a slightly reduced red-shift as the TEA concentration increases, whereas the C≡C··· stretching band absorbs at the same wavenumber in the investigated TEA concentration range. The results of B3LYP-D3 calculations indicate that complexes with more or less linear ≡C?H···N intermolecular hydrogen bonds are more stable than other, dispersion-driven complexes. Complexes with the Cs symmetrical TEA conformer are predicted to have larger binding energy than those formed with the C3 and C1 symmetrical conformers. The predicted IR spectral shifts are slightly different for complexes with the three different TEA conformers. Association constants of hydrogen-bonded complexes at 26 °C are estimated to be ~0.1 mol–1 dm3.
关键词： triethylamine,hydrogen bonding,ethynyl aromates,IR spectroscopy,B3LYP-D3 calculations
更新于2025-09-23 15:21:01
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Strain Effect in Highly-Doped n-Type 3C-SiC-on-Glass Substrate for Mechanical Sensors and Mobility Enhancement
摘要： This work reports the strain effect on the electrical properties of highly doped n-type single crystalline cubic silicon carbide (3C-SiC) transferred onto a 6-inch glass substrate employing an anodic bonding technique. The experimental data shows high gauge factors of (cid:1)8.6 in longitudinal direction and 10.5 in transverse direction along the [100] orientation. The piezoresistive effect in the highly doped 3C-SiC film also exhibits an excellent linearity and consistent reproducibility after several bending cycles. The experimental result is in good agreement with the theoretical analysis based on the phenomenon of electron transfer between many valleys in the conduction band of n-type 3C-SiC. Our finding for the large gauge factor in n-type 3C-SiC coupled with the elimination of the current leak to the insulated substrate could pave the way for the development of single crystal SiC-on-glass based MEMS applications.
关键词： piezoresistance,wafer bonding,silicon carbide,MEMS,strain engineering
更新于2025-09-23 15:21:01
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Effects of post bonding annealing on GaAs//Si bonding interfaces and its application for sacrificial-layer-etching based multijunction solar cells
摘要： By using the sacrificial layer (SL) etching, GaAs substrates are separated from III–V epi substrate//Si substrate junctions that are made by surface activated bonding (SAB) technologies. The post-bonding low-temperature (300-?C) annealing plays an essential role in achieving a promising (～90%) bonding yield. The effects of the post-bonding annealing are investigated by hard X-ray photoemission spectroscopy and current–voltage measurements of GaAs//Si bonding interfaces. It is found that the concentration of oxygen atoms at interfaces is reduced and the resistance decreases to 1.6–2.1 m??cm2 by the low-temperature annealing. Aluminum fluoride complexes are not observed by X-ray photoelectron spectroscopy on the exposed surfaces of separated GaAs substrates. The roughness average of the surfaces is ≈0.25–0.30 nm. The characteristics of double junction cells fabricated on the GaAs//Si junctions prepared by the SL etching are almost the same as those of cells fabricated by dissolving GaAs substrates after bonding. These results indicate that multijunction cells could be fabricated in a process sequence compatible with reuse of GaAs substrates by combining the SL etching and SAB.
关键词： Sacrificial layer etching,GaAs//Si double junction cells,Surface activated bonding,Low temperature annealing,Epitaxial lift-off
更新于2025-09-23 15:19:57
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[IEEE 2018 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Sydney, Australia (2018.11.10-2018.11.17)] 2018 IEEE Nuclear Science Symposium and Medical Imaging Conference Proceedings (NSS/MIC) - A Laser-based Time Calibration System for the MEG II Timing Counter
摘要： Wireless sensor networks (WSNs) can utilize the unlicensed industrial, scientific, and medical (ISM) band to communicate the sensed data. The ISM band has been already saturated due to the overlaid deployment of WSNs. To solve this problem, WSNs have been powered up by cognitive radio (CR) capability. By using CR capability, WSNs can utilize the spectrum holes opportunistically. The sensor nodes, which need large bandwidth to transmit their sensed data from source to destination require some scheme, which should be able to provide them a wide band channel whenever required. Channel bonding (CB) is a technique through which multiple contiguous channels can be combined to form a single wide band channel. By using CB technique, CR-based WSN nodes attempt to find and combine contiguous channels to avail larger bandwidth. In this paper, we show that by increasing the number of channels, the probability of finding contiguous channels decreases. Moreover, we then propose a primary-radio (PR) user-activity-aware CB algorithm and compare it with three state-of-the-art schemes: SWA, KNOWS, and AGILE. It has been demonstrated through extensive NS-2 simulations that intelligent CB decisions can reduce harmful interference to PR nodes. We find that CB in CR sensor networks attempts to provide greater bandwidth and utilizes the spectrum effectively.
关键词： cognitive radio,dynamic spectrum access,Channel bonding,wireless sensor networks
更新于2025-09-23 15:19:57