Tsung-Eong Hsieh

Mechanical properties of clay-polyimide (BTDA-ODA) nanocomposites via ODA-modified organoclay

Clay–polyimide [3,3′, 4,4′-benzophenone tetracarboxylic dianhydride–4,4′-oxydianiline (BTDA–ODA)] nanocomposites were synthesized from ODA-modified montmorillonite (organoclay) and poly(amic acid). The layered silicates of organoclay were intercalated by polyimide (BTDA–ODA), as confirmed by X-ray diffraction and by transmission electron microscopy, and the tensile mechanical properties of the nanocomposites were measured. It was found that the modulus and the maximum stress of these organoclay/BTDA–ODA nanocomposites were much higher than those of pure BTDA–ODA: a twofold increase in the modulus and a one-half-fold increase in the maximum stress in the case of 7/93 organoclay–BTDA-ODA. In addition, the elongation-for-break of organoclay/BTDA–ODA nanocomposites is even slightly higher than that of pure BTDA–ODA, which is a sharp contrast to that of conventional inorganics-filled polymer composites.

Optical characteristics and microstructure of ZnO quantum dots-SiO2 nanocomposite films prepared by sputtering methods

ZnO quantum dots (QDs)-SiO2 nanocomposite films were prepared using the target-attached radio-frequency sputtering. The transmission electron microscopy revealed the uniform dispersion of ZnO QDs with diameters about 2–7nm in amorphous SiO2 matrix. The photoluminescence showed that small ZnO QDs are able to emit white light with luminescence spectra similar to those of the present GaN-based light emitting diode (LED). The calculated chromaticity coordinates of emitting light evidenced the feasibility of ZnO QDs-SiO2 nanocomposite films as the fluorescence material in optoelectronic devices.

The effect of composition on Ba-Nd-Sm-Ti-O microwave dielectric materials for LTCC application

Effect of composition of BaO.(R 2 O 3 )y.(TiO 2 ) z 0.06(2Bi 2 O 3 .3TiO 2 ) materials. R = Nd 1-x)Sm(x)BRT, on the materials characteristics and microwave dielectric properties of the samples was systematically examined. The Ti/Ba ratio (z value) shows the most significant effect on the microwave dielectric properties of the materials. The Q x f-value is small for z ≤ 3.82 materials, and showing maximum value for z = 4.32 samples, then decrease for z = 4.52 composition, which is possibly due to the presence of secondary phase for z = 3.82 and 4.52 materials. Diffusion couple experiments shows that the interaction diffusion zone between glass and BRT ceramic is not pronounced, so that Ba-B-Si glass and BRT could be a good low temperature co-firable ceramic system is inferable.

Highly stable precursor solution containing ZnO nanoparticles for the preparation of ZnO thin film transistors

ZnO particles with an average size of about 5 nm were prepared via a sol-gel chemical route and the silane coupling agent, (3-glycidyloxypropyl)-trimethoxysilane (GPTS), was adopted to enhance the dispersion of the ZnO nanoparticles in ethyl glycol (EG) solution. A ZnO surface potential as high as 66 mV was observed and a sedimentation test showed that the ZnO precursor solution remains transparent for six months of storage, elucidating the success of surface modification on ZnO nanoparticles. The ZnO thin films were then prepared by spin coating the precursor solution on a Si wafer and annealing treatments at temperatures up to 500 degrees C were performed for subsequent preparation of ZnO thin film transistors (TFTs). Microstructure characterization revealed that the coalescence of ZnO nanoparticles occurs at temperatures as low as 200 degrees C to result in a highly uniform, nearly pore-free layer. However, annealing at higher temperatures was required to remove organic residues in the ZnO layer for satisfactory device performance. The 500 degrees C-annealed ZnO TFT sample exhibited the best electrical properties with on/off ratio = 10(5), threshold voltage = 17.1 V and mobility (micro) = 0.104 cm(2) V(-1) s(-1).

Phase transition behaviors of Mo- and nitrogen-doped Ge2Sb2Te5 thin films investigated by in situ electrical measurements

Phase-change behaviors of Ge2Sb2Te5 (GST) thin films doped with molybdenum (Mo) or nitrogen (N) were investigated by utilizing in situ electrical property measurement, x-ray diffraction (XRD), transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy. It was found that the Mo doping mainly reduces the resistivity level of amorphous GST while the N-doping raises both the resistivity levels of amorphous and crystalline GSTs. XRD and TEM analyses revealed that the element doping stabilizes the amorphous state of GST and suppresses the grain growth in GST films. This resulted in the increase in recrystallization temperature (Tm) and activation energy (Ea) of amorphous-to-crystalline phase transition in GST layers, as revealed by the calculation in terms of Kissinger’s theory. The results of data fitting into various percolation models and Johnson–Mehl–Avrami analysis indicated the heterogeneous feature of phase transition process in GST layers that the nucleation first occurs at the atmosph...

Investigation of Electroless Co"W,P… Thin Film as the Diffusion Barrier of Underbump Metallurgy

The plating characteristics of an electroless cobalt–tungsten–phosphorus CoW,P layer and its capability to serve as a diffusion barrier of underbump metallurgy UBM for flip-chip Cu–IC are investigated. Increasing the pH of the plating solution in a range of 7.6–9.0 decreased the rate of deposition, increased the phosphorus content, altered the structure from polycrystalline to amorphous, and decreased the surface roughness of CoW,P films. The barrier capability of CoW,P to eutectic PbSn solder was evaluated by means of liquid- and solid-state aging tests. In specimens subjected to tests of these two types, a P-rich layer presented in between solder and unreacted CoW,P, demonstrating the sacrificial barrier behavior of CoW,P. Transmission electron microscopy TEM analysis of specimens subjected to liquid-state aging indicated the supersaturated P atoms, and the Co2P consequently formed, might aggregate at grain boundaries of the P-rich layer, thus enabling the stuffed-type barrier capability of the CoW,P layer. TEM, scanning electron microscopy, and energy-dispersive spectrometer characterizations of specimens subjected to solid-state aging revealed that the reaction of solder and CoW,P implies a formation of CoSn2 and CoSn3 intermetallic compounds IMCs and a mixture of various IMCs in P-rich layer. Our experimental results demonstrated a satisfactory barrier property of electroless CoW,P, heralding promising applications in UBM structures for flip-chip Cu–IC.

Effects of composition on low temperature sinterable Ba-Nd-Sm-Ti-O microwave dielectric materials

Abstract This work investigated the effects of MgO and ZnO additives on the microwave properties of BRT 114 =[(BaO·R 2 O 3 ·4TiO 2 )·0.06(2Bi 2 O 3 ·3TiO 2 )] materials. Incorporation of small amount of ZnO (≦1 wt.%) markedly lowered the temperature coefficient of resonant frequency ( τ f ), to around τ f ≒1 ppm/°C, slightly increased the density and dielectric constant ( e r ) of the materials, but degraded the Q × f factor . Doping 2.5 mol% of MgO, in addition to ZnO, further improved the τ f -value for the BRT 114 materials. The dielectric constant and the Q×f factor of the materials degrade pronouncedly when doped with too abundant ZnO. Microstructure and EDX analyses indicated that the main factor for degrading the microwave properties is the induction on formation of secondary phases. Moreover, sol–gel and fused Ba–B–Si glass reacted with BRT 114 in quite a different way. Fused glass wets BRT 114 materials more easily than the sol–gel derived glass, resulting in composite materials with higher density and larger dielectric constant. Precalcining the glass-dielectrics mixture, greatly improved the wetting ability of the glass and markedly increased the microwave properties of the glass/dielectric composite, i.e. LTCC materials.

Stress Migration and Electromigration Improvement for Copper Dual Damascene Interconnection

Stress migration (SM) and electromigration (EM) were widely used to study the performance of interconnection process of metal/via formation in copper dual damascene of wafers. Necking and voids at the via bottom were important in causing failures in tests of stress migration and electromigration. In this report, the contamination of the bottom of via, which results in poor step coverage, the adhesion of seed layers, and poor copper grain formation are identified to be the underlying causes of the necking and void formation after the first EM and SM tests are performed. The contamination of the via formation processes included via etching, trench etching, and barrier/seed layer depositions. A well-shaped via profile can be optimized using three methods, the first involves Cu/SiN interface stress, the second involves Cu grain growth, and the third involves post via etching clean study. Eliminating the contamination of the via bottom and optimizing step coverage and adhesion of the barrier seed layers improve the EM and SM performance from time-to-fail = 13 to 59 s, in the copper-related processes for fabricating 300 mm wafers using technology that is beyond 0.13 μm technology.

Initialization Characteristics and their Effects on the Erasabilty of Phase Change Optical Disks Using Transmission Electron Microscopy

We investigated the microstructure of phase change optical disks subjected to various initialization conditions using transmission electron microscopy (TEM). The effects of initialization powers on the erase ratio of phase change optical disks and corresponding microstructure changes were also studied. It was found that the increase of initialization power enlarged the width of the recrystallization band formed in the recording media of the disk. A wide recrystallization band was effective for decreasing the residual signal level hence the erase ratio increased. Disk dynamic test and TEM study results also revealed the deterioration of carrier-to-noice ratio (CNR) characteristic and the increasing trend of erase ratio was reduced when a substantial amount of coarse grains appeared in the crystalline region. This elucidates the necessity for phase change optical disks to have good heat dissipation property in order to suppress the formation of coarse granular structures.

Dielectric confinement effect in ZnO quantum dots embedded in amorphous SiO2 matrix

The dielectric confinement effect on the blue shift ΔEg(a) of the ZnO quantum dots (QDs) embedded in the SiO2 matrix is evaluated by applying a multi-shell two-electron system model. The experimental measurement and the calculations of various dielectric structures indicate that the composite matrix structure provides a better estimation of the blue shift of the ZnO QDs–SiO2 system than the multi-shell structure. The proportionality factor x defined in this work exhibits a dependence of the dielectric confinement energy on the specific dimension ratio (the b/a ratio) and the dielectric constant ematrix of the outer matrix. The result of the calculation also shows the limit of the two-electron system in estimating the ground-state energy of samples with high dot density. However, the correlation shows the existence of the strong dielectric confinement effect in ZnO QDs–SiO2 thin films and allows a better understanding of the semiconductor QDs–dielectric systems.