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This study investigated the effect of oxidation on the chemical bonding structures of silicon nitride thin films synthesized by a low-temperature plasma-enhanced chemical vapor deposition (PECVD) method. These films were heat treated to different temperatures up to 1373 K. The bonding structures were studied by means of x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. It was found that the amorphous PECVD SiNx films were subjected to oxidation in air at elevated temperatures. The oxidation caused the formation of crystalline silicon dioxide within the matrix of amorphous silicon nitride, conforming to the “random mixing” model. The crystalline silicon dioxide formed is believed to be stoichiometric SiO2, whereas the remaining matrix is believed to be a nonstoichiometric silicon oxynitride with a structure conforming to the “random bonding” model. [ABSTRACT FROM AUTHOR]

Highlights • Bonding and de-bonding of thin Si layer was processed at low temperature (<250 °C). • Unlike conventional wafer bonding such as smart-cut based SOI or similar substrate, wafer flip-up/down is not needed. • Hydrophilic surface was formed via plasma treatment instead of high temperature bonding annealing. Abstract We studied low temperature (<250 °C) transfer of 8 in. full sized thin Si wafer layer on the SiO 2 /Si substrate without any wafer flip up/down and subsequent high temperature process. This method includes temporary bonding of carrier wafer with bonding material at 200 °C, grinding or etching substrate, and transfer layer at 250 °C. Thickness values of transferred thin Si layer using bulk Si and silicon-on-insulator (SOI) wafer substrates are 87 μm and 216 nm on the SiO 2 /Si substrate, respectively. Plasma treatment under N 2 and O 2 mixture ambient assisting to form hydrophilic surface was carried out during bonding process and enhanced bonding strength was confirmed by contact angle measurement. Our wafer bonding process can be feasible to form various monolithic 3D devices due to thin Si layer transfer and low temperature process. [ABSTRACT FROM AUTHOR]

Room temperature GaN-Si direct wafer bonding was done by surface activated bonding (SAB). At first, a feasibility study using GaN template has been done. Then, crystal-face dependence of the bonding results for freestanding GaN substrate has been investigated between Ga-face and N-face. The results of Ga-face to Si bonding are better than that of N-face to Si bonding such as higher bonding energy and larger bonded area. This difference should be caused by their different surface roughnesses after chemical-mechanical polishing (CMP). Besides, both of the structure and composition of the two kinds of interfaces were investigated to understand the bonding mechanisms. The phenomenon of Ga-enrichment during surface activation and Ga-diffusion into Si at room temperature for both Ga-face bonding and N-face bonding has been confirmed. [ABSTRACT FROM AUTHOR]

We investigate the electronic, thermodynamic and bonding properties of the ThGeO host material by means of pseudo-potential method within the framework of density functional theory. Zircon-type ThGeO is found to undergo a pressure-driven phase transition to tetragonal scheelite structure, and beyond to monoclinic fergusonite ones. Emphasis is placed on the trends of the dynamical stability and anisotropic behavior related to structural phase transition. Linear as well as cubic thermal expansion component show a different directional dependence as a function of temperature for the investigated polymorphs of the compound. The origin of the difference in the unit cell expansion is found to be related to the distortion of the ThO dodecahedra. The analysis of the non-covalent dispersion of the zircon and scheelite structures reveals a counter-balance between destabilizing interactions due to steric crowding and the current attractive and repulsive ones. [ABSTRACT FROM AUTHOR]

Based on a previously proposed model of the electronic spectrum of binary AB graphene-like compounds (GLC), adsorption theory is constructed, which allows determination of the role of the adatom level position, the adatom-substrate coupling constant, and the gap inherent to GLC in the free state with heteropolar bonds in the formation of the adatom electronic structure. The cases of free-standing and epitaxial GLCs on a metal surface are considered. In the case of free-standing GLCs, analysis shows local states mainly contribute to the adatom occupation number n at large and intermediate adatom-GLC coupling constants; as the coupling constants decrease, the contribution of the GLC valence band increases. The main feature of an epitaxial GLC on metal is the absence of a gap, hence, the contribution of adatom local states to n . Estimations show that changes in the adatom-substrate and GLC-metal coupling constants affect n in almost the same way. In this case, the dependence of n on the GLC gap is not critical from the qualitative viewpoint. Adsorption on the GLC-semiconductor structure is briefly discussed. [ABSTRACT FROM AUTHOR]

Natural products containing N-N bonds exhibit important biological activity. Current methods for constructing N−N bonds have limited scope. An advanced understanding of the fundamental N−N bond formation/cleavage processes occurring at the transition-metal center would facilitate the development of catalytic reactions. Herein we present an N−N bond-forming reductive elimination, which proceeds via a mixed-valent NiII-NiIII intermediate with a Ni-Ni bond order of zero. The discrete NiII-NiIII oxidation states contrast with the cationic dimeric Ni analogue, in which both Ni centers are equivalent with an oxidation state of 2.5. The electronic structures of these mixed-valent complexes have implications for the fundamental understanding of metal-metal bonding interactions. [ABSTRACT FROM AUTHOR]

We study covalent bonds between p-doped Si wafers (resistivity ∼10 Ω cm) fabricated on a recently developed 200 mm high-vacuum system. Oxide- and void free interfaces were obtained by argon (Ar) or neon (Ne) sputtering prior to wafer bonding at room temperature. The influence of the sputter induced amorphous Si layer at the bonding interface on the electrical behavior is accessed with temperature-dependent current-voltage measurements. In as-bonded structures, charge transport is impeded by a potential barrier of 0.7 V at the interface with thermionic emission being the dominant charge transport mechanism. Current-voltage characteristics are found to be asymmetric which can tentatively be attributed to electric dipole formation at the interface as a result of the time delay between the surface preparation of the two bonding partners. Electron beam induced current measurements confirm the corresponding asymmetric double Schottky barrier like band-alignment. Moreover, we demonstrate that defect annihilation at a low temperature of 400 °C increases the electrical conductivity by up to three orders of magnitude despite the lack of recrystallization of the amorphous layer. This effect is found to be more pronounced for Ne sputtered surfaces which is attributed to the lighter atomic mass compared to Ar, inducing weaker lattice distortions during the sputtering. [ABSTRACT FROM AUTHOR]

The article offers information on the wafer bonding use for microelectromechanical systems (MEMS) devices and technology. Topics discussed include the importance of sodium (Na) in anodic bonding use to combine complementary metal-oxide semiconductor (CMOS) and MEMS devices, the advantage of aluminium (Al)- aluminium (Al) thermo-compression wafer bonding process, and the significant effects of process temperature on the bonding process.

We present a method for low temperature plasma-activated direct wafer bonding of III-V materials to Si using a transparent, conductive indium zinc oxide interlayer. The transparent, conductive oxide (TCO) layer provides excellent optical transmission as well as electrical conduction, suggesting suitability for Si/III-V hybrid devices including Si-based tandem solar cells. For bonding temperatures ranging from 100 °C to °C, Ohmic behavior is observed in the sample stacks, with specific contact resistivity below 1 X cm² for samples bonded at 200 °C. Optical absorption measurements show minimal parasitic light absorption, which is limited by the III-V interlayers necessary for Ohmic contact formation to TCOs. These results are promising for Ga0.5In0.5P/Si tandem solar cells operating at 1 sun or low concentration conditions. [ABSTRACT FROM AUTHOR]

In situ sensors can measure wire bond reliability nondestructively during thermal aging. Conventional thermal aging of ball bonds requires ovens heating the entire microchip along with the wire bonds, also affecting interconnects for in situ sensors. To protect the interconnects and on-chip logic components of in situ sensor chips, conventional thermal aging is kept below a safe temperature limit of 200°C. At higher temperatures, the doped Si components change their characteristics and transistors stop working. Localized onchip heating is introduced to circumvent these drawbacks using a new microheater to increase the safe temperature limit for nondestructive reliability assessment with in situ sensors. The effect of temperature on surrounding components is reduced. The microheater is a rectangular design resistive heater made from N+ silicon. In addition, a pad resistance measurement is introduced that indicates bond aging more conveniently than previously reported bond resistance measurements. [ABSTRACT FROM AUTHOR]

This paper presents a new chip-on-flexible (COF) packaging structure for flip-chip (FC) light-emitting diode (LED). Two bonding methods, AuSn and Sn–Ag–Cu (SAC) soldering, were compared from thermal, mechanical, and optical performances of the packages. Compared with the package by AuSn soldering method, the package by SAC soldering method showed lower chip temperature due to the avoiding of the large unbounded area. In addition, the SAC soldering package showed a much lower residue stress than the AuSn soldering package. Thus, the possibility for the defects, such as the crack on the reflecting layer and the warping of the pads formation decreased significantly. The reflectivity of the flexible substrate showed a sharp decrease because of the high temperature of AuSn soldering process. Based on the comprehensive evaluation of the thermal properties, residue stress, and optical performances of the LED packages, SAC soldering method is suggested to be more suitable for high-power LED packaging on COF substrates. [ABSTRACT FROM AUTHOR]

We report the first demonstration of 200 mm InGaAs-on-insulator (InGaAs-o-I) fabricated by the direct wafer bonding technique with a donor wafer made of III-V heteroepitaxial structure grown on 200 mm silicon wafer. The measured threading dislocation density of the In0.53Ga0.47As (InGaAs) active layer is equal to 3.5 x 109 cm-2, and it does not degrade after the bonding and the layer transfer steps. The surface roughness of the InGaAs layer can be improved by chemical-mechanical-polishing step, reaching values as low as 0.4 nm root-mean-square. The electron Hall mobility in 450 nm thick InGaAs-o-I layer reaches values of up to 6000 cm²/Vs, and working pseudo-MOS transistors are demonstrated with an extracted electron mobility in the range of 2000-3000 cm²/Vs. Finally, the fabrication of an InGaAs-o-I substrate with the active layer as thin as 90 nm is achieved with a Buried Oxide of 50 nm. These results open the way to very large scale production of III-V-o-I advanced substrates for future CMOS technology nodes. [ABSTRACT FROM AUTHOR]

In this paper design aspects and challenging packaging solution of a monolithic 3D force sensor will be presented. The previously developed design and process flow (Vázsonyi et al. 123-124:620-626, ; Molnár et al. 90:40-43, ) were improved by an additional hybrid wafer bonding step of simultaneous anodic and metal bonding processes. This electrostatic force assisted metal bonding can ensure both the mechanical and the electrical integrity of the device. The applied novel process sequence can eliminate the need of a possible flip-chip bonding and chemical-mechanical polishing steps. The applied glass substrate improves the thermal isolation and thermo-mechanical stability of the integrated system considering the thermal expansion coefficients of the chosen glass material and the silicon (Si) only slightly differ minimizing the residual thermo-mechanical stress during the operation. [ABSTRACT FROM AUTHOR]

We demonstrate the ability of first row transition metals to form electrically conducting interconnects between semiconducting single-walled carbon nanotubes (SWNTs) by constructive rehybridization between sidewall benzene rings as a result of the formation of bis-hexahapto-metal-bonds [(η6-SWNT)M(η6-SWNT)], which bridge adjacent SWNTs. Metal deposition on SWNT films enhances the conductivity by three distinct mechanisms: physisorption of gold leads to the formation of a non-interacting gold film and a monotonic conductivity increase; ionic chemisorption of lithium strongly increases the conductivity due to charge transfer to the SWNTs; covalent chemisorption of first row transition metals leads to an abrupt change in conductivity due to formation of (η6-SWNT)M(η6-SWNT) interconnects. [ABSTRACT FROM AUTHOR]

Abstract: Using the first principles FLAPW-GGA method, comparative study of structural, electronic properties and of chemical bonding in four 1111-like chalcogenide oxides LaMChO (LaCuSO, LaCuSeO, LaAgSO, and LaAgSeO) with ZrCuSiAs-type structure was performed. Our studies showed that: (i) replacements of d metal atoms (Cu ↔ Ag) and chalcogen atoms (S ↔ Se) lead to anisotropic deformations of the crystal structure; this effect is related to strong anisotropy of inter-atomic bonds; (ii) all of the examined chalcogenide oxides are semiconducting; the band gap decreases both at S → Se and Cu → Ag substitutions; and (iii) the bonding in LaMChO phases can be classified as a high-anisotropic mixture of ionic and covalent contributions, where mixed covalent-ionic bonds take place inside [La2O2] and [M 2 Ch 2] blocks, whereas between the adjacent [La2O2]/[M 2 Ch 2] blocks, ionic bonds emerge owing to [La2O2] → [M 2 Ch 2] charge transfer. Since the near-Fermi bands of LaMChO phases originate mainly from electronic states of [M 2 Ch 2] blocks, we speculate that chemical substitutions inside these blocks can result in striking differences in electronic properties of these systems; therefore, this approach can be promising for significant enlargement of the functional properties of these materials. [Copyright &y& Elsevier]

In this study, electrodes on a flexible printed circuit board (FPCB) and rigid PCB (RPCB) were bonded by a thermo-compression bonding. The surface finishes on the Cu electrodes of the FPCB and RPCB were organic-solderability-preservative and electroless Ni/immersion Au (ENIG), respectively. Pb-free Sn-3.0 Ag and Sn-3.0 Ag-0.5 Cu solders were used as interlayers. In order to determine the optimum bonding conditions, such as bonding force, time, and temperature, a 90° peel test of the FPCB-RPCB joint was conducted. The relationships between the bonding conditions and peel strength were investigated. We successfully accomplished the thermo-compression bonding of reliable FPCB-RPCB joints by using Sn-Ag and Sn-Ag-Cu interlayers. The thermo-compression bonding method is a stable and well-controlled process and can produce robust and reliable connections. [ABSTRACT FROM AUTHOR]

One-dimensional metal wires are valuable materials because of their optical and electronic anisotropy, and they have potential utility in devices such as photovoltaic cells and molecular sensors. However, despite more than a century of research, only a few examples exist of well-defined one-dimensional (1D) metal wires that allow for the rational variation of conductivity. Herein we describe the first examples of 1D molecular wires supported by Pd-Pd bonds, the thin-film conductive properties of which can be altered by controlled molecular changes. Wires based on Pd(III) give semiconducting films with a modifiable bandgap, whereas wires based on Pd(2.5) give films that display metallic conductivity above 200 K: a metallic state has not been reported previously for any polymer composed of 1D metal wires. The wires are infinite in the solid state and maintain 1D structures in solution with lengths of up to 750 nm. Solution stability enables thin film coating, a requisite for device fabrication using molecular wires. [ABSTRACT FROM AUTHOR]

Abstract: In this work we present an in situ investigation of the interface composition between an In0.53Ga0.47As substrate and an Al2O3 oxide grown by molecular beam deposition in ultra high vacuum conditions. In the effort to improve the chemical quality of the interface, reduction of semiconductor-oxygen bonding at the interface can be obtained by growing a few Å thick pure Al layer before starting exposure of the surface to the atomic oxygen flux. Conversely, when a Ge interface passivation layer is intercalated between the semiconductor and the oxide stack, the interface chemistry is governed by Ge reaction with other species (Al, O), leading only to a partial suppression of the interface oxides. [Copyright &y& Elsevier]

This paper investigates and reviews the effects of wafer bow in three- dimensional (3D) integration bonding schemes, including copper wafer bonding and oxide fusion wafer bonding with silicon on insulator (SOI)-based layer transfer technology. Wafer bow criteria for good bonding quality and fabrication techniques to minimize wafer bow are introduced for 3D integration technology and applications. [ABSTRACT FROM AUTHOR]

Abstract: Full-potential linearized augmented plane waves (FPLAPW) calculations have been used to determine the equilibrium properties and elastic constants of the chalcopyrite phase of AgGaSe2. The topological analysis of the electron density shows a clear polar bonding, with the integrated basin charges revealing a clear dominance of the covalent over the ionic character. The bonding analysis also provides a partition of the bulk modulus and compressibility into atomic contributions. Se is seen to dominate the global behavior (B=51.2GPa), with a local bulk modulus intermediate between the values of the other two atoms: 44.8 (Ga), 51.1 (Se), and 56.6GPa (Ag). [Copyright &y& Elsevier]

Abstract: Copper (Cu) thermo-compression bonding of wafers can be used to fabricate multi-layer three-dimensional (3-D) integrated circuits (ICs). This work examines the thermal characteristic of the Cu bonding layer and demonstrates experimentally that Cu bonding layer can act as a spreading layer that helps in heat dissipation of bonded 3-D ICs stack more efficiently compared to silicon dioxide bonding layer. The use of Cu bonding layer in a double-layer stack of ICs provides better cooling by as much as 9°C compared to oxide bonding interface. [Copyright &y& Elsevier]

Copper Indium diselenide thin films have been deposited on to well cleaned glass substrates in a vacuum of 10-5 Torr. The thicknesses of the films have been determined by micro balanced method and confirmed by multiple beam interferometric method. The EDAX results of the deposited CuInSe2 films show that the composition of the films is almost the same as that of the source material. The resistivity is found to decrease with increase in temperature confirming the semiconducting nature of the deposited CuInSe2 films. Two types of conduction mechanism namely variable range hopping and thermally activated process is found to be operative in the deposited CuInSe2 films. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes the fabrication process and device performance of complimentary metal oxide field effect transistor (CMOSFET) with direct silicon bonded (DSB) substrate. This works offers the first comprehensive evaluation of source/drain engineering for DSB devices. Scanning spreading resistance microscopy (SSRM) technique reveals specific dopant profile by lateral diffusion of boron along the bonding interface, in addition to the highly activated dopant at bonding interface in pMOSFET with DSB substrate. Key process condition, such as DSB thickness, hybrid formation process, source/drain engineering and optimization method are described. [Copyright &y& Elsevier]

The direct bonding of macroscopically patterned silicon wafers is studied with a cohesive zone model (CZM), the form and key parameters of which are obtained from molecular dynamics simulations. The CZM is implemented in a spectral scheme. For the case of ideally flat wafer surfaces investigated here, the results are consistent with previous work in which the CZM was derived from an assumption of a continuum water film. This multiscale approach has the potential to model directly the effects of surface roughness, nanotopography and small-scale patterning on the efficacy of direct wafer bonding. [Copyright &y& Elsevier]

Abstract: Plasma immersion ion implantation with hydrocarbon gases (HC-PIII) leads to both carbon implantation and carbon thin film deposition. The films are diamond-like carbon (DLC), mostly amorphous carbon with hydrogen (a-C:H). In the present review, examples from the literature on the deposition of HC-PIII DLC films are discussed. The process parameters of HC-PIII, including bias voltage, plasma-forming gas, and experimental setup, are correlated with the properties of the DLC film, such as bonding characteristics, hardness, stress state, and the resulting tribological performance, as shown in friction and wear tests. [Copyright &y& Elsevier]

Abstract: Using wafer bonding (WB) and wet oxidation (WO) techniques, GaInP microdisks having an asymmetric waveguide (diameters ) with embedded InP quantum dots (size/density ∼100 nm/) have been fabricated on Si and GaAs substrates, respectively. The (, ) and (, ) whispering gallery modes with quality factors have been identified in photoluminescence spectra of these microdisks (MDs) in the spectral range 720–770 nm. Lasing thresholds of 6 (30) μW and mode coupling constants 0.9 (0.7) have been demonstrated for WO (WB) MDs. [Copyright &y& Elsevier]

Abstract: This paper presents design, fabrication and evaluation of a wafer level MEMS (Micro Electro Mechanical System) encapsulation using an Au to Au direct bonding with wrinkle patterned layer. For the effective encapsulation, the optimal bonding condition, the bonding temperature 350°C, the bonding pressure 58MPa and the duration time 30min, was developed and used in this paper. We briefly evaluated the bonding strength of test wafers after the bonding test. For RF (Radio Frequency) device packaging, we effectively interconnected Au CPW (Coplanar Waveguide) lines to feedthroughs and measured the RF characteristics. Measured insertion loss of the packaged CPW line was −0.11dB at 2GHz. The glass wafer having patterned Au sealing lines was also bonded and has been dipped in the acetone solution for 24h to examine the leakage of bonding wafer. After 24h dipping, any leakage point has not been observed at the sealing line and inside the cavity. These results showed that our Au to Au direct bonding method is very reliable and suitable for RF device packaging. [Copyright &y& Elsevier]

The wear resistance of high chromium iron is well recorded. However, the same is not the case as regards the use of manganese at higher percentages in high chromium irons and its influence on wear behaviour. Hence, this work highlights the slurry wear characteristics of chromium (◻ 16-19%) iron following the introduction of manganese at two levels i.e. 5 and 10%. It is known that the wear properties are dictated by the microstructural features. To alter the structure, the cooling rate of casting has been varied by adopting two different types of moulds (i.e. sand and metal) and subsequently subjecting to thermal treatment. The as-cast and heat treated samples are examined for microstructure and then evaluated for hardness and slurry erosion properties. As the manganese content is increased from 5 to 10%, the hardness showed a decrease in value both in the as-cast and heat treated conditions. The slurry erosion loss, expectedly, showed an increase irrespective of the sample condition (i.e. mould type/heat treatment adopted). The findings are corroborated with the microstructural features obtained through optical and scanning electron microscopy. [ABSTRACT FROM AUTHOR]

The survival of cemented endosseous implants can be improved by enhancing the bond between the implant and the cement. We hypothesized that the light-inducible generation of super-hydrophilicity of titanium positively affects its bone cement-philicity and bone cement–titanium bonding. Commercially pure titanium disks with machined surface and acid-etched micro roughened surfaces were prepared. Ultra-violet (UV) light treatment (0.1 mW/cm2 UVA and 0.03 mW/cm2 UVB for 48 h) created a super-hydrophilic surface for both surface types. The area of poly-methyl methacrylate (PMMA)-based bone cement spread increased by 30% and 20% on the light-treated machined titanium and acid-etched titanium surfaces, respectively, compared to the matched untreated ones. The contact angle of the bone cement decreased significantly after the light treatment, confirming the enhanced wettability of bone cement by the light treatment. Interfacial tensile stress between the bone cement material and titanium was increased 100% for the machined surface and 50% for the acid-etched surface by light treatment. Interfacial shear stress measured by a push-out test of titanium rods also revealed a 40% increase for the machined surface and 25% increase for the acid-etched surface. In conclusion, the pre-UV light treatment of titanium enhances the wettability and bonding strength of poly-methyl-methacrylate-based bone cement. [ABSTRACT FROM AUTHOR]

The paper gives an overview on the influence of point defects on electronic properties of interfaces including band alignment (barrier heights) and transport properties. As examples interfaces between metals and the II–VI semiconductors CdTe and ZnTe are presented. In addition untypical phenomena at semiconductor heterocontact formation at In2S3/ZnO and CuInSe2/CdS interfaces is described. It is suggested that the barrier heights as well as the transport properties at both interfaces are strongly affected by defects, which are either present because of non-stoichiometry of the materials or introduced by contact formation due to chemical interactions. [ABSTRACT FROM AUTHOR]

This paper reports the design, fabrication, and characterization of a two-dimensional stress-sensor array based on a stress-sensor element exploiting the transverse pseudo-Hall effect in metal-oxide-semiconductor (MOS) field effect transistors (FET). P-channel MOS (PMOS) devices were integrated in a 4 × 4 stress sensor array with a total area of 120 × 120 µm². The individual elements of the array are sensitive to the local shear stress in the chip plane. They are selected using a CMOS integrated digital decoder and transmission gates. The new array was characterized using a commercial ball-wedge wire bonding tool and was used for the in situ monitoring of the bonding process. The spatially resolved measurement of the stress distribution under- neath and close to a bond pad during the bond wire touch-down is demonstrated. The array is able to resolve variations in the touch-down position of 10 µm. The time of 1.6 ms for acquisition of a full frame is currently limited by the experimental setup. To monitor the stress distribution during the bonding process, an aluminum covered stress sensor array similar to a standard bond pad was used. The successful bond formation between a gold ball and the metal bond pad was observed. The bond formation becomes evident as a characteristic, concentrated stress profile with large peak value appearing within 20 ms. The maximum stresses underneath the successfully bonded area exceeds stress levels in unbonded sensor locations by a factor of up to 60. [ABSTRACT FROM AUTHOR]

A study of the performance of an ablative capillary discharge through a PVC capillary is reported. It is shown that the PVC capillary is capable of producing strong in-band 13.5 nm EUV radiation. This band of radiation is produced by transition arrays of multiply ionised heavy metal ions (Sn, Zn, etc.) that are constituents of various chemical additives in commercial PVC grades. A low concentration of radiating ions, good thermalisation of the capillary plasma and plasma homogeneity along the capillary axis produce well-defined bands with little line radiation outside the band of interest. Two interesting cases are discussed, both producing band radiation with a full-width at half-maximum of around 1 nm and maxima near 10, 13.5 and 15.5 nm, respectively. The plasma spectra are not very sensitive to input discharge voltage, but in some cases the amount of energy in the band of interest can be controlled by it. The most serious problem of such discharges still remains the amount of macroscopic debris produced by the capillary ablation. [Copyright &y& Elsevier]

A novel method for calculating the band structure of the GaxAl1−xN solid-state alloys (with x=0.15; 0.52 and 0.65) was proposed. This approach consists in the orthogonalisation procedure for the plane wave basis set with respect to the core-like orbitals and the application of the Perdew–Alder exchange–correlation scheme. Experimental ellipsometric data and X-ray photoelectron spectra were used as a criterion of preferability between the different calculation techniques. The results of traditional one-electron methods of band structure calculations (e.g. self-consistent norm-conserving pseudo-potential (NCPP), linear muffin tin orbital method (LMTO), full linear augmented plane wave (FLAPW) and linear combination atomic orbital (LCAO) methods) are compared with the experimental data. We demonstrate that better agreement with experiment is achieved when the NCPP wavefunctions are orthogonalised to the 3dGa core-like states. Due to using of the mentioned procedure a better agreement with experimental X-ray photoelectron spectroscopy and ellipsometric data is achieved. Concerning the LMTO and the FLAPW all-electron methods, only appropriate application of the virtual crystal approximation to these approaches produces results that are in agreement with the proposed modified NCPP method. [Copyright &y& Elsevier]

Discusses the use of Vialux 81, an epoxy-based photo-dielectric dry film material, to fill microvia holes in semiconductors. Development of a cure kinetics model based on differential scanning calorimetry experiments; Formulation of cure shrinkage model based on thermal and chemical shrinkage experiments; Determination of the thermochemical properties of Vialux 81 dry film.

Abstract. Uniform direct or fusion wafer bonding of GaAs wafers up to 4 inch in diameter was achieved by means of two methods: (I) pre-heating, bonding at elevated temperatures and post-annealing in a H[sub 2] atmosphere (gas environmental hot bonding) and (ii) bonding inside an UHV apparatus at temperatures as low as 150 Celsius after cleaning with atomic hydrogen. Both methods yield atomically abrupt interfaces as shown by cross-sectional TEM and by imaging the screw-dislocation network formed at low angles of twist between the wafers. At large twist angles, additional "step" dislocations arising from bonding across surface steps could be clearly imaged. The problem of occasionally occurring microvoids, probably arising due to insufficient pre-cleaning or at excessive post-annealing, is addressed. Both bonding procedures neither need mechanical loading of the wafers nor channel-patterning of the surfaces. [ABSTRACT FROM AUTHOR]

A silicon direct bonding (SDB) process was developed using a special chamber for cleaning, contacting and prebonding wafers up to 100 mm. After prebonding the wafers at 200°C, annealing was carried out at temperatures ranging from 600°C to 1180°C for times between 30 minutes and 20 hours. Bare silicon and oxidized wafers were bonded. The electrical specification was done by evaluating the I-V characteristics with respect to breakdown, reverse current, ideality factor, series and parallel resistance (R[sub s], R[sub p]). A strong dependence of R[sub s] and R[sub p] on bonding temperature and time was observed. In order to prove the viability of the bonded substrate for power devices, we fabricated p-i-n diodes. The diodes exhibit breakdown voltages up to 1400V and forward current densities of 2 Amm.[sup -2] These p-i-n diodes were superior to diodes fabricated simultaneously on epitaxial material. [ABSTRACT FROM AUTHOR]

Describes a microscopic model of an isolated silicon dangling bond at interfaces of ordered and disordered semiconductors. Application of a self-consistent mean-field approximation to study the electronic structure of the dangling bond; Atomic relaxation; Calculation of thermal and optical transition energies, correlation energy, equilibrium displacements and wave function structure.

Since localized plastic deformation (as given by thermocompression bonding damage) has been shown to affect the electrical properties of GaAs a preliminary study has been undertaken of the effect of various parameters such as the material dopant, orientation, bonding tool profile and the material type, namely both epitaxial and bulk material, on the amount of induced damage. Our results suggest that of the dopants considered, i.e. Cr, Zn, Te and a combination of impurities resulting in compensated material, the Cr doped material exhibited the least amount of induced damage for given bonding conditions and the (100) seems to be preferable to the (111) orientation as is also understandable with its higher yield stress. Bulk GaAs appears to be more strongly affected by bonding than epitaxial material, and a rounded tool tip is preferable to a flat one since the former contains no sharp edges. [ABSTRACT FROM AUTHOR]

Discusses various die attach materials and methods, and reviews die attach bonding mechanisms in manufacturing semiconductors. Failure mechanisms and reliability; Testing and characterization; Future trends.

Simulates wire deformation processes during thermocompression bonding of integrated circuits without ultrasonic vibration using a numerical model based on the finite-element technique. Growth process of interfacial contact between wire surface and lead frame; Expansion of lateral wire surface; Link between wire reduction and interfacial contact area.

A novel micro-printing process, using anodic bonding to deposit patterned diamond-like carbon (DLC) coatings on glass, is investigated. Various patterns such as squares, triangles and letters are successfully fabricated. The coatings are characterised by Raman spectroscopy, atomic force microscope (AFM) and ultraviolet spectrophotometer. A G-band shift of approximately 1614 cm-1 indicates that the DLC coatings have a relatively high content of sp³ bonds (>20%). The result of the AFM topography shows that the surface roughness of DLC coatings is 1.21 nm. The transmittance of DLC-coated glass wafer is above 85% ranging from 760 to 1100 nm, indicating that the patterned DLC coatings have high optical transparency in the infrared radiation spectral range. [ABSTRACT FROM AUTHOR]

The article offers the author's insights on the role of fusion bonding in boosting scaling for logic device performance. He says that based from the International Roadmap for Devices and Systems (IRDS), parasitic scaling is expected to be driving the logic device performance which requires new transistor architectures like gate all around (GAA) transistors. He explains how fusion and hybrid wafer bonding can cater three-dimensional System-on-Chip (3D SoC) applications, saving cost and power.

Wafer-level 3-D integration using Cu through-silicon vias (TSVs) and fine-pitch Cu/Sn–BCB hybrid bonding is investigated with electrical leakage current. With the well-fabricated Cu TSVs and Cu/Sn bond structures, the leakage current path in this scheme due to backside process was found, and the corresponding mechanism is discussed. The leakage current can be solved by the modified backside process. The improved 3-D integration scheme shows extremely low leakage current and no visible defects inside Cu TSV. [ABSTRACT FROM AUTHOR]

The article explores the advantages of Wafer Support System (WSS) and its significance in supporting ultra-thin semiconductor wafers during backgrinding and subsequent post-thinning processes. It discusses factors illustrating the process flow of the system including process flow bonding, backgrinding process and laser debonding. It offers information on how the thermal stability of WSS can be determined and the role of liquid ultraviolet (UV)-curable acrylic adhesives in WSS.

Ge-on-insulator structures have been fabricated by wafer bonding and layer transfer techniques. Ultralow bonding temperatures of 150–300 °C are employed in order to suppress hydrogen outdiffusion and to produce a low defect density, in an attempt to produce high photocurrent and photoresponse. Thus reducing the hydrogen outdiffusion results in decreased surface roughness. A low defect density is suggested by a low inversion-current leakage of the tunnel diodes. The photoresponse of the Ge-on-insulator detector is also found to increase with decreasing bonding temperature, indicating that defects caused by hydrogen implantation are passivated more effectively. [ABSTRACT FROM AUTHOR]

A direct wafer bonding process has been developed to accurately control both the bonding interface twist and tilt angles between a monocrystalline layer and a bare monocrystalline wafer. This process is based on the bonding of twin surfaces produced by splitting a single wafer, using for instance the Smart Cut® process. A targeted control of ±0.005° is obtained for the twist angle without any crystallographic measurement. Moreover, pure twist-bonded interfaces have been artificially made between two (001) bonded silicon surfaces. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents the method of fabricating ferroelectric-semiconductor heterostructures using direct wafer bonding. Process used to deposit polycrystalline Bi[sub 4]Ti[sub 3]O[sub 12] films on silicon wafers; Increase of bonding energy after thermal annealing; Measurement of the surface energy.

Investigates the silicon hydride (SiH) bond-bending modes of the hydrogen-Si-(oxygen-Si)[sub 3] group in a-Si dioxide:hydrogen alloys using infrared absorption methods. Double degenerate frequency of the SiH bond-bending mode in C[sub 3] symmetry; Split off and additional feature in the spectrum caused by asymmetry.

Examines the electric current operation of indium gallium arsenic photodetectors on silicon and gallium arsenide substrates using a wafer bonding technique. Fabrication of the photodetectors; Current measurement of the substrates under 5 volts reverse bias; Resistance measured across the bonded interface.

Examines the lateral bonding speed in silicon wafer bonding. Mechanism used to determine the lateral bonding speed; Equilibrium between gas molecules in wafer surfaces; Correlation between lateral bonding speed and ambient pressure; Application of silicon wafer bonding to power devices.