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931.
Wetting interaction between Sn-Zn-Ag solders and Cu 总被引:4,自引:0,他引:4
The wetting interaction of Sn-(7.1–9)Zn-(0–3)Ag solders with Cu was investigated from 230°C to 300°C. The wetting time, wetting
forces, and activation energy of the wetting reaction were studied. The wetting time decreases with increasing temperature
and increases with Ag content. The wetting force exhibits a disproportional correlation to temperature rise, while no trend
was observed with respect to Ag content. The wetting behavior was ascribed to the interaction between Cu and Zn. The AgZn3 compound was formed at the interface when the solder contains 0.3% Ag and above, while it was formed within the bulk solder
at 2% Ag and above. 相似文献
932.
N. Y. Garces Lijun Wang N. C. Giles L. E. Halliburton D. C. Look D. C. Reynolds 《Journal of Electronic Materials》2003,32(7):766-771
Electron paramagnetic resonance (EPR) has been used to monitor the diffusion of lithium ions into single crystals of ZnO.
The in-diffusion occurs when a crystal is embedded in LiF powder and then held in air at temperatures near 750°C for periods
of time ranging up to 22 h. These added lithium ions occupy zinc sites and become singly ionized acceptors (because the material
is initially n type). A corresponding reduction in the number of neutral shallow donors is observed with EPR. To monitor the
lithium acceptors, we temporarily convert them to the EPR-active neutral acceptor state by exposure to laser light (325 nm
or 442 nm) at low temperatures. Also, after each diffusion treatment, we monitor the EPR signal of singly ionized copper acceptors
and the photo-induced EPR signal of neutral nitrogen acceptors. These nitrogen and copper impurities are initially present
in the crystal, at trace levels, and are made observable by the thermal anneals. Infrared-absorption measurements at room
temperature in the 2–10 μm region show that the concentration of free carriers decreases as lithium is added to the crystal.
After 22 h at 750°C in the LiF powder, the free-carrier absorption is no longer present, and the crystal is semi-insulating. 相似文献
933.
Low-energy electron-enhanced etching of HgCdTe 总被引:3,自引:0,他引:3
Jaehwa Kim T. S. Koga H. P. Gillis Mark S. Goorsky Gerald A. Garwood John B. Varesi David R. Rhiger Scott M. Johnson 《Journal of Electronic Materials》2003,32(7):677-685
Low-energy electron-enhanced etching (LE4) is applied to HgCdTe to eliminate ion-induced surface damage. First, LE4 results
for patterned samples are illustrated. The LE4 mechanism is understood from a mechanistic study in terms of three etch variables:
direct current (DC) bias, gas composition, and sample temperature. For this paper, the effects of DC bias (electron energy)
and gas composition (CH4 concentration) are summarized qualitatively, followed by quantitative evidence. Etch rate, the amount of polymer, surface
stoichiometry, and surface roughness have specific relations with each etch variable under competition between pure LE4 and
polymer deposition. 相似文献
934.
Alexander Usenko 《Journal of Electronic Materials》2003,32(8):872-876
We observe hydrogen platelet buildup in single-crystalline silicon caused by hydrogen-plasma processing. The platelets are
aligned along a layer of lattice defects formed in silicon before the plasma processing. The buried-defect layer is formed
by either silicon-into-silicon or argon-into-silicon implantation. We discuss the platelet nucleation, growth, and merge phenomena
and discuss applicability of the plasma hydrogenation to silicon-on-insulator (SOI) wafer fabrication by layer transfer. 相似文献
935.
Solid-state intermetallic compound layer growth between copper and 95.5Sn-3.9Ag-0.6Cu solder 总被引:4,自引:0,他引:4
Long-term, solid-state intermetallic compound (IMC) layer growth was examined in 95.5Sn-3.9Ag-0.6Cu (wt.%)/copper (Cu) couples.
Aging temperatures and times ranged from 70°C to 205°C and from 1 day to 400 days, respectively. The IMC layer thicknesses
and compositions were compared to those investigated in 96.5Sn-3.5Ag/Cu, 95.5Sn-0.5Ag-4.0Cu/Cu, and 100Sn/Cu couples. The
nominal Cu3Sn and Cu6Sn5 stoichiometries were observed. The Cu3Sn layer accounted for 0.4–0.6 of the total IMC layer thickness. The 95.5Sn-3.9Ag-0.6Cu/Cu couples exhibited porosity development
at the Cu3Sn/Cu interface and in the Cu3Sn layer as well as localized “plumes” of accelerated Cu3Sn growth into the Cu substrate when aged at 205°C and t>150 days. An excess of 3–5at.%Cu in the near-interface solder field
likely contributed to IMC layer growth. The growth kinetics of the IMC layer in 95.5Sn-3.9Ag-0.6Cu/Cu couples were described
by the equation x=xo+Atnexp [−ΔH/RT]. The time exponents, n, were 0.56±0.06, 0.54±0.07, and 0.58±0.07 for the Cu3Sn layer, the Cu6Sn5, and the total layer, respectively, indicating a diffusion-based mechanism. The apparent-activation energies (ΔH) were Cu3Sn layer: 50±6 kJ/mol; Cu6Sn5 layer: 44±4 kJ/mol; and total layer: 50±4 kJ/mol, which suggested a fast-diffusion path along grain boundaries. The kinetics
of Cu3Sn growth were sensitive to the Pb-free solder composition while those of Cu6Sn5 layer growth were not so. 相似文献
936.
Concentrations of native and gold defects in HgCdTe from first principles calculations 总被引:1,自引:0,他引:1
We have studied the defect formation energies of the various native (vacancies, interstitials, and antisites) and Au defects
in Hg1−xCdxTe using density functional-based total energy calculations with ultrasoft pseudo-potentials. These studies are important
for infrared (IR) detection technology where the device performance can be severely degraded because of defects. To calculate
formation energies, we modeled the neutral and charged defects using supercells containing 64 atoms. From the formation energies,
we have determined the defect concentrations as a function of stoichiometry and temperature. We find the prevalent neutral
defects to be Au at the Hg site (AuHg
), Hg vacancies (VHg
), and Te antisites (TeHg
). We have also explicitly studied charged defects and have found Te
Hg
2+
, Au
Hg
1−
, V
Hg
1−
, V
Hg
2−
, and V
Te
2+
to have low formation energies. We have identified AuHg
to be the prevalent Au defect, having concentrations several orders of magnitude greater than the other Au defects. We find
that the charge state of VHg is primarily (1−) or (2−) depending on the electronic chemical potential. 相似文献
937.
Knowledge of phase equilibria of the Sn-Ag-Cu-Ni quaternary system at the Sn-rich corner is important for the understanding
of the interfacial reactions at the Sn-Ag-Cu/Ni contacts, which are frequently encountered in recent microelectronic products.
Various Sn-Ag-Cu-Ni alloys were prepared and equilibrated at 250°C. The alloys were then quenched and analyzed. The phases
were determined by metallography, compositional analysis, and x-ray diffraction (XRD) analysis. No quaternary phases were
found. The isoplethal sections at 60at.%Sn, 70at.%Sn, 80at.%Sn, and 90at.%Sn at 250°C are determined. The phase equilibrium
relationship was proposed based on the quaternary experimental results and the 250°C isothermal sections of the four constituent
ternary systems, Sn-Ag-Cu, Sn-Ag-Ni, Sn-Cu-Ni, and Cu-Ag-Ni. Because there are no ternary phases in all these three systems,
all the compounds are in fact binary compounds with various solubilities of the other two elements. 相似文献
938.
Sridhar Govindaraju Jason M. Reifsnider Michael M. Oye Archie L. HolmesJr. 《Journal of Electronic Materials》2004,33(8):851-860
This article describes the effects of rapid thermal annealing (RTA) on the photoluminescence (PL) emission from a series of GaIn(N)As quantum wells. Indium compositions of both 20% and 32% were examined with nominal N compositions of 1% or 2%. The N location was varied within our quantum structure, which can be divided into three regions: (1) quantum well, (2) Ga(N)As spacer layers at the barrier-to-well interface and well-to-barrier interface, and (3) barriers surrounding each quantum well. Eight combinations of samples were examined with varying In content, Ga(N)As spacer layer thickness, N content, and N location in the structure. In the best cases, the presence of these Ga(N)As spacer layers improves the PL properties, due to annealing, with a reduction in the emission wavelength blueshift by ~400 Å, a reduction of the decrease in the full-width at half-maximum (FWHM) by ~5 meV, and a threefold reduction of the increase in integrated intensity. It was also observed that relocating N from the quantum wells to the barriers produces a comparable emission wavelength both before and after annealing. Our results further show that the composition of incorporated N in the material is most influential during the stages of RTA in which relatively small amounts of thermal energy is present from our lower annealing times and temperatures. Hence, we believe a low thermal-energy anneal is responsible for the recovery of the plasma-related crystal damage that was incurred during its growth. However, the In composition in the quantum well is most influential during the latter stages of thermal annealing, at increased times and temperatures, where the wavelength blueshift was roughly independent of the amount of incorporated N. As a result, our investigations into the effects of RTA on the PL properties support other reports that suggest the wavelength blueshift is not due to N diffusion. 相似文献
939.
Ho-Young Cha Y. C. Choi R. M. Thompson V. Kaper J. R. Shealy L. F. Eastman M. G. Spencer 《Journal of Electronic Materials》2004,33(8):908-911
The SiC metal-semiconductor field-effect transistors (MESFETs) have been reported to have current instability and strong dispersion
caused by trapping phenomena at the surface and in the substrate, which degrade direct-current (DC) and radio-frequency (RF)
performance. This paper illustrates the change in electrical characteristics of SiC MESFETs after Si3N4 passivation. Because of a reduction of surface trapping effects, Si3N4 passivation can diminish current collapse under pulsed DC conditions, increasing the RF power performance. The reduction
of surface trapping effects is verified by the change in the ratio of the drain current to the gate current under pinch-off
conditions. 相似文献
940.
This paper proposes a secure encrypted-data aggregation scheme for wireless sensor networks. Our design for data aggregation
eliminates redundant sensor readings without using encryption and maintains data secrecy and privacy during transmission.
Conventional aggregation functions operate when readings are received in plaintext. If readings are encrypted, aggregation
requires decryption creating extra overhead and key management issues. In contrast to conventional schemes, our proposed scheme
provides security and privacy, and duplicate instances of original readings will be aggregated into a single packet. Our scheme
is resilient to known-plaintext attacks, chosen-plaintext attacks, ciphertext-only attacks and man-in-the-middle attacks.
Our experiments show that our proposed aggregation method significantly reduces communication overhead and can be practically
implemented in on-the-shelf sensor platforms. 相似文献