Direct Wafer Bonding Technology employing vacuum-cavity pre-bonding

A novel low temperature direct wafer bonding technology employing vacuum-cavity pre-bonding is proposed and applied in bonding of InGaAs/Si couple wafers under 300 degrees C and InP/GaAs couple wafers under 350 degrees C. Aligning accuracy of 0.5 mu m is achieved. During wafer bonding process the pressure on the couple wafers is 10MPa. The interface energy is sufficiently high to allow thinning of the wafers down from 350um to about 100um. And the tensile strength test indicates the bonding energy of bonded samples is about equal to the bonded samples at 550 degrees C.

Small-signal and large-signal performance test of high-speed optoelectronics devices

This paper presents measurement methods for determining the reflection coefficients and frequency responses of semiconductor laser diodes, photodiodes, and EA modulator chips. A novel method for determining the intrinsic frequency responses of laser diodes is also proposed, and applications of the developed measurement methods are discussed. We demonstrate the compensation of bonding wire on the capacitances of both the submount and the laser diode, and present a method for estimating the potential modulation bandwidth of TO packaging technique. Initial study on removing the effects of test fixture on large-signal performances of optoelectronic devices at high data rate is also given.

A Selective-Area Metal Bonding InGaAsP-Si Laser

A 1.55-mu m hybrid InGaAsP-Si laser was fabricated by the selective-area metal bonding method. Two Si blocking stripes, each with an excess-metals accommodated space, were used to separate the optical coupling area and the metal bonding areas. In such a structure, the air gap between the InGaAsP structure and Si waveguide has been reduced to be negligible. The laser operates with a threshold current density of 1.7 kA/cm(2) and a slope efficiency of 0.05 W/A under pulsed-wave operation. Room-temperature continuous lasing with a maximum output power of 0.45 mW is realized.

Structure and properties of microporous titanosilicate determined by first-principles calculations

The structure of EST-10, a member of synthetic microporous titanosilicates, was recently determined by an ingenious combination of experimental and simulational techniques. However, the locations of the alkali atoms in the framework remain elusive and its electronic structure is totally unknown. Based on first-principles local density calculations, the possible locations of the alkali atoms are identified and its electronic structure and bonding fully elucidated. ETS-10 is a semiconductor with a direct band gap of 2.33 eV. The Na atoms are likely to locate inside the seven-member ring pore adjacent to the one-dimensional Ti-O-Ti-O- chain.

PHOTOINDUCED CHANGES OF HYDROGEN-BONDING IN SEMIINSULATING IRON-DOPED INDIUM-PHOSPHIDE

After illumination with 1-1.3 eV photons during cooling-down, metastable PH modes are observed by IR absorption at 5 K in semi-insulating InP:Fe. They correlate with the photo-injection of holes, but not with a change of the charge state of the K-related centres present at equilibrium. They are explained by a change of the bonding of H, induced by hole trapping, from IR-inactive centres to PH-containing centres, stable only below 80 K. One metastable centre has well-defined geometrical parameters and the other one could be located in a region near from the interface with (Fe,P) precipitates.

PHOTOEMISSION-STUDIES OF K-PROMOTED NITRIDATION AND OXIDATION OF THE INP(100) SURFACE USING SYNCHROTRON-RADIATION

The effect of a potassium overlayer on nitridation and oxidation of the InP(100) surface is investigated by core-level and valence-band photoemission spectroscopy using synchrotron radiation. In comparison with the K-promoted nitridation of the InP(110) surface obtained by cleavage in situ, we found that the promotive effect for the InP(100) surface cleaned by ions bombardment is much stronger and that the nitridation products consist of two kinds of complexes: InPNx and InPNx+y. The results confirmed that surface defects play an important part in the promotive effect. Furthermore, in contrast with K-promoted oxidation of InP(100) where bonding is observed between indium and oxygen, indium atoms did not react directly with nitrogen atoms during the K-promoted nitridation of InP(100). (C) 1995 American Vacuum Society.

Analysis of Si/GaAs Bonding Stresses with the Finite Element Method

In conjunction with ANSYS, we use the finite element method to analyze the bonding stresses of Si/GaAs. We also apply a numerical model to investigate a contour map and the distribution of normal stress,shearing stress,and peeling stress,taking into full consideration the thermal expansion coefficient as a function of temperature. Novel bonding structures are proposed for reducing the effect of thermal stress as compared with conventional structures. Calculations show the validity of this new structure.

Mechanism of Wafer Bonding Process

国家自然科学基金

Orientation relationship between hexagonal inclusions and cubic GaN grown on GaAs(001) substrates

Cubic GaN/GaAs(0 0 1) epilayers and hexagonal inclusions are characterized by X-ray diffraction (XRD), Photoluminescence (PL), Raman spectroscopy, and transmission electron microscopy (TEM). The X-ray {0 0 0 2} and (1 0 (1) over bar 0) pole figures show that the orientation relationships between cubic GaN and hexagonal inclusions are (1 1 1)//(0 0 0 1), <1 1 2 >//<1 0 (1) over bar 0 >. The distribution of hexagonal inclusions mainly results from the interfacial bonding disorder in the grain boundaries parallel to hexagonal <0 0 0 1 > directions and the lattice mismatch in <0 0 0 1 > directions on {1 0 (1) over bar 0} planes. In order to reduce the energy increase in cubic epilayers, hexagonal lamellas with smaller sizes in <0 0 0 1 > directions often nucleate inside the buffer layer or near the interface between the buffer layer and the epitaxial layer, and penetrate through the whole epitaxial layer with this orientation relationship. (C) 2001 Elsevier Science B.V. All rights reserved.

Interface energy and its influence on interface fracture between metal and ceramic thin films in nanoscale

A theoretical model about the size-dependent interface energy between two thin films with different materials is developed by considering the chemical bonding contribution based on the thermodynamic expressions and the structure strain contribution based on the mechanical characteristics. The interface energy decreases with reducing thickness of thin films, and is determined by such available thermodynamic and mechanical parameters as the melting entropy, the melting enthalpy, the shear modulus of two materials, etc. The predicted interface energies of some metal/MgO and metal/Al2O3 interfaces based on the model are consistent with the results based on the molecular mechanics calculation. Furthermore, the interface fracture properties of Ag/MgO and Ni/Al2O3 based on the atomistic simulation are further compared with each other. The fracture strength and the toughness of the interface with the smaller structure interface energy are both found to be lower. The intrinsic relations among the interface energy, the interface strength, and the fracture toughness are discussed by introducing the related interface potential and the interface stress. The microscopic interface fracture toughness is found to equal the structure interface energy in nanoscale, and the microscopic fracture strength is proportional to the fracture toughness. (C) 2010 American Institute of Physics. [doi:10.1063/1.3501090]

Chiral synthesis on catalysts immobilized in microporous and mesoporous materials

This paper reviews the recent progress made in the asymmetric synthesis on chiral catalysts in porous materials and discusses the effects of surface and pores on enantio-selectivity (confinement effect). This paper also summarizes various approaches of immobilization of the chiral catalysts onto surfaces and into pores of solid inorganic supports such as microporous and mesoporous materials. The most important reactions surveyed for the chiral synthesis in porous materials include epoxidation. hydrogenation, hydroformylation, Aldol and Diels-Alder reactions, etc. The confinement effect originated from the surfaces and the pores turns out to be a general phenomenon. which may make the enantioselectivity increase (positive effect) or decrease (negative effect). The confinement effect becomes more pronounced particularly when the bonding between the catalyst and the surface is more rigid and the pore size is tuned to a suitable range. It is proposed that the confinement in chiral synthesis is essentially a consequence of subtle change in transition states induced by weak-interaction in pores or on surfaces. It is also anticipated that the enantioselectivity could be improved by tuning the confinement effect based on the molecular designing of the pore/surface and the immobilized catalysts according to the requirements of chiral reactions.

Carbon monoxide adsorption on molybdenum phosphides: Fourier transform infrared spectroscopic and density functional theory studies

Molybdenum phosphide (MoP) and supported molybdenum phosphide (MoP/gamma-Al2O3) have been prepared by the temperature-programmed reduction method. The surface sites of the MoP/gamma-Al2O3 catalyst were characterized by carbon monoxide (CO) adsorption with in situ Fourier transform infrared (FT-IR) spectroscopy. A characteristic IR band at 2037 cm(-1) was observed on the MoP/gamma-Al2O3 that was reduced at 973 K. This band is attributed to linearly adsorbed CO on Mo atoms of the MoP surface and is similar to IR bands at 2040-2060 cm(-1), which correspond to CO that has been adsorbed on some noble metals, such as platinum, palladium, and rhodium. Density functional calculations of the structure of molybdenum phosphides, as well as CO chemisorption on the MoP(001) surface, have also been studied on periodic surface models, using the generalized gradient approximation (GGA) for the exchange-correlation functional. The results show that the chemisorption of CO on MoP occurred mainly on top of molybdenum, because the bonding of CO requires a localized mininum potential energy. The adsorption energy obtained is DeltaH(ads) approximate to -2.18 eV, and the vibrational frequency of CO is 2047 cm-1, which is in good agreement with the IR result of CO chernisorption on MoP/gamma-Al2O3.

Molecularly imprinted monolithic stationary phases for liquid chromatographic separation of enantiomers and diastereomers

The method for preparation of molecularly imprinted monolithic stationary phase has been improved to achieve liquid chromatographic separation of enantiomers and diastereomers. By adopting low polar porogenic solvents of toluene and dodecanol and optimal polymerization conditions, the molecularly imprinted monolithic stationary phases with good flow-through properties and high resolution were prepared. Enantiomers of amino acid derivatives and diastereomers of cinchona alkaloids were completely resolved using the monolithic stationary phases. The influence of porogenic composition, monomer-template ratio and polymerization conditions on the chromatographic performance was investigated. Some chromatographic conditions such as the composition of the mobile phase and the temperature were characterized. Scanning electron microscopy showed that the molecularly imprinted monolithic stationary phase has a large through-pore structure to allow the mobile phase to flow through the column at very low backpressure. Accelerated separations of enantiomers and diastereomers were therefore achieved at elevated flow rates. Finally, the chiral recognition performance of the prepared stationary phase in aqueous media was investigated. Hydrophobic interaction, and ionic and/or hydrogen bonding interactions were proposed to be responsible for the recognition mechanism. (C) 2002 Elsevier Science B.V. All rights reserved.

Synthesis and characteristics of composite chiral stationary phases based on cellulose derivatives

Composite chiral stationary phases (CSPs) were prepared on the basis of cellulose derivatives coated or bonded onto silica. "Molecular exterior" type CSPs were prepared by mixing together two different cellulose tris-derivatives before or after being coated or bonded onto silica, and the "molecular interior" type was obtained by synthesizing non-regioselectively heterosubstituted cellulose derivatives coated or bonded onto silica. For the sake of comparison, the individual phases were also prepared with corresponding cellulose derivatives by coating or bonding approaches, respectively. All of the prepared CSPs were characterized and their chiral recognition properties were evaluated by HPLC with several test racemates. The experimental results demonstrated that the "molecular exterior" CSPs generally exhibit chiral recognition capacities intermediate between those of the two individual phases. However, in the separation of some racemates higher enantioselectivity may be achieved on the "molecular interior" phases than on individual phases, thus broadening the application range of a single cellulose-based CSP.

Theoretical studies of product polarization and state distributions of the H+HCl reaction

The angular momentum polarization and rotational state distributions of the H-2 and HCl products from the H + HCl reaction are calculated at a relative translational energy of 1.6 eV by using quasiclassical trajectories on two potential energy surfaces, one from G3 surface [T.C. Allison et al., J. Phys. Chem. 100 (1996) 13575], and the other from BW2 surface [W. Bian, H.-J. Werner, J. Chem. Phys. 112 (2000) 220]. Product rotational distributions obtained on the G3 potential energy surface (PES) are much closer to the experimental results (P.M. Aker et al., J. Chem. Phys. 90 (1989) 4795; J. Chem. Phys. 90 (1989) 4809) than the distributions calculated on the BW2 PES. The distributions of P(phi(r)) for the H-2 and HCl products obtained on the G3 PES are similar, whereas the rotational alignment effect of the H-2 product is stronger than that of the HCl product. In contrast to the polarization distributions obtained on the G3 PES, the rotational alignment effect of the two products calculated on the BW2 PES is similar. However, the abstraction reaction is dominated by out-of-plane mechanisms, while the exchange reaction is dominated by in-plane mechanisms. The significant difference of the product rotational polarization obtained on the G3 and BW2 PESs implies that the studies of the dynamical stereochemistry can provide a sensitive test for the accuracy of the PES. (C) 2002 Elsevier Science B.V. All rights reserved.