Interface integration defect of copper and low-K materials beyond nano-scale copper damascene process

This paper discusses the first evidence about the low pattern density causing abnormally high VIA resistance, which is at least more than two times the normal level. The low pattern density also induces the exposure-like shape formed in VIA bottom, where high concentration of sulfur element is detected in the copper film after electric- and thermal-torture testing. These effects, due to the low pattern density, Lire significantly important for nano-scale feature filling and the quality of VIA superfilling. This paper also proposes a mechanism to explain the observed results by inferring from the local resistance and chemical polarity difference with different numbers of VIA serially connected. The experiment with high accelerator concentration also supports the proposed mechanism by locating abnormal voids in the region with low VIA pattern density. (c) 2007 Elsevier Ltd. All rights reserved

Preparation of clay/epoxy nanocomposites by layered-double-hydroxide initiated self-polymerization

An anionic clay, magnesium-aluminum layered double hydroxide (Mg(2)Al-NO(3)-LDH), was prepared by a co-precipitation method and intercalated with poly(oxypropylene)-amindocarboxylic acid (POP-amido acid). Depending on the POP-intercalating agents with molecular weight at 2000 or 400 g/mol, the intercalated LDHs were analyzed to have d spacing of 6.8 or 2.7 nm and organic incorporation of 80 and 55 wt%, respectively. Two comparative POP/LDH hybrids were allowed to initiate the self-polymerization of the epoxy resin, diglycidyl ether of bisphenol-A (DGEBA). The curing rate was significantly increased by using the hybrids as initiators for epoxy curing, demonstrated by DSC thermal analysis that the exothermic peak shifted from 182 to 152 degrees C by increasing organoclay addition. The resultant nanocomposites prepared from the anionic LDH initiated epoxy self-polymerization have the improved thermal and physical properties, evidenced by TGA, XRD, TEM, and SEM analyses. (C) 2008 Elsevier Ltd. All rights reserved

Sequential self-repetitive reaction toward wholly aromatic polyimides with highly stable optical nonlinearity

A sequential self-repetitive reaction (SSRR) based on carbodiimide (CDI) chemistry was utilized for preparing a high-yield wholly aromatic polyimide. The polyimide was synthesized with 4,4'-methylene-diphenylisocyanate (MDI) and a di(acid-ester) compound which was derived from the ring-opening reaction of 3,3',4,4'-oxydiphthalic dianhydride (ODPA) at room temperature by the addition of equimolar methanol. Poly-CDI was first synthesized from MDI. The di(acid-ester) compound was then reacted with poly-CDI to form poly(N-acylurea). After curing process, N-acylurea moiety was converted to di(ester-amide) structure via SSRR and further subjected to a ring-closure reaction to form the wholly aromatic polyimide with a T-g of 247 degrees C. This approach was further taken to prepare thermally stable nonlinear optical (NLO) materials. Similarly a diimide-diacid containing chromophore was reacted with poly-CDI to obtain an intermediate, poly(N-acylurea). The poly(N-acylurea) with the ester side groups would exhibit excellent organosolubility, which enabled the fabrication of high quality optical thin films. After in situ poling and curing processes, N-acylurea moiety was converted to di(ester-amide) structure via SSRR and further subjected to a ring-closure reaction to form the wholly aromatic NLO polyimide with an electro-optical coefficient, r(33) of 25 pm/V (830 nm). Excellent temporal stability at elevated temperatures (200 degrees C) and a waveguide optical loss of 2.5 dB cm(-1) at 1310 nm were also obtained

Poly(urethane/malonamide) dendritic structures featuring blocked/deblocked isocyanate units

We have used 4-isocyanato-4'-(3,3-dimethyl-2,4-dioxoazetidino)diphenylmethane and diethylenetriamine as building blocks to synthesize novel poly(urethane/malonamide) dendrons possessing terminal methyl ethyl ketoxime (MEKO) units (blocked isocyanate groups). Heating the MEKO-containing dendrons regenerated the terminal isocyanate groups. Subsequently, the regenerated isocyanate groups would react with any compound with active hydrogens. In one example, the dendrons with the deblocked isocyanates further reacted with stearyl alcohol (C18-OH) to form the corresponding dendrons presenting C18 moieties. This deblocking strategy allows replacement of reactive exterior groups with desired functionality for the construction of dendritic macromolecules

Using a breath-figure method to self-organize honeycomb-like polymeric films from dendritic side-chain polymers

In this study, we investigated various generations of waxy dendrons, dendritic side-chain polymers (varying the structure and polarity of the polymer backbone), and physical blends of dendrons with polymers for their ability to form honeycomb-like structures. Each waxy dendron comprises a focal part (possessing many hydrogen bonding sites) and a peripheral part (rich in units that undergo van der Waals interactions). Using a breath-figure process, we readily incorporated high-generation dendrons within polymer matrixes to form porous surfaces. When the high-generation waxy dendrons were grafted onto amino group - functionalized polystyrene or copolymerized with diisocyanates to form polyurethanes, the multiple long alkyl chains behaved as bristles of hydrophobic brooms, due to the presence of strong van der Waals forces. The formation of honeycomb-like patterns in the polymer films resulted from strong hydrogen bonding of the polymers to water droplets on the surfaces of substrates, with subsequent self-organization and phase separation. (C) 2011 Elsevier B.V. All rights reserved

Synthesis and montmorillonite-intercalated behavior of dendritic surfactants

A series of novel dendrons serving as surfactants for surface modification of montmorillonite (MMT) have been synthesised via a convergent approach. The most distinguishing characteristic of the prepared dendrons is the long alkyl chain at the periphery. This would certainly bring about good solubility, high yield and easy purification. By simple acidification of the "head group'' upon the dendron and then ion-exchange with Na+-MMT, the interlayer distance could be enlarged significantly between the layered silicates. The organic/inorganic ratio determined by thermogravimetric analysis (TGA) is in the range of 60% - 91%. This also confirms the occurrence of dendron ion-exchange with Na+-MMT. Transmission electronic microscopy (TEM) reveals the intercalated and exfoliated morphology of the dendron-modified MMTs. Modification using the generation 2 dendritic surfactant (G2) with molecular weight (M-w) = 2887.5 has achieved the exfoliated morphology in this work

Nonlinear optical, poly(amide-imide)-clay nanocomposites comprising an azobenzene moiety synthesised via sequential self-repetitive reaction

Poly(N-acylurea)-clay nanocomposites consisting of a modified montmorillonite and poly(N-acylurea) were prepared from which poly(amide-imide)-clay nanocomposites were subsequently obtained via the sequential self-repetitive reaction of poly(N-acylurea). The moderate T(g) of poly(N-acylurea) allows the nonlinear optically active polymer to exhibit high poling efficiency; in situ poling and curing increased the T(g)s of poly(amide-imide)-clay nanocomposites. Electro-optical coefficients, r(33) of similar to 17-20 pm/V (830 nm), were achieved; high temporal stability (120 degrees C) and waveguide optical losses of 3.4-3.9 dB/cm at 1310 nm were also obtained for poly(amide-imide)-clay nanocomposites. (c) 2008 Elsevier Ltd. All rights reserved

Orderly Arranged NLO Materials Based on Chromophore-Containing Dendrons on Exfoliated Layered Templates

Three chromophore-containing dendrons were intercalated into montmorillonite layered silicates via an ion-exchange process Enlarged d spacings ranging from 50 to 126 angstrom were achieved for these novel organoclays After the organoclays were blended with a polyimide, the steric bulkiness of the dendrons and the interaction between dendron and polyimide resulted in an ordered morphology. The orderly arranged nanocomposites were characterized by a UV-visible spectrophotometer, a variable-temperature infrared spectrometer, and electro-optical modulation The dendrons in layered silicates were capable of undergoing a critical conformational change into an ordered structure, indicated by the drastic changes of interlayer distances at certain packing densities Electro-optical coefficients increased sharply from 0 to 6 pm/V while the conformational change occurred Furthermore,, the addition of a polyimide capable of interaction-induced orientation was found to exert an enhancing effect on the degree of the noncentrosymmetric alignmen

Organo-clay hybrids based on dendritic molecules: preparation and characterization

Three generations of dendrons ( G1, G2 and G3) with phenyl end-groups were intercalated into montmorillonite ( MMT) layered silicates in dimethylformamide/water cosolvent. These dendrons synthesized via the convergent route were different in size and shape with molecular weights ranging from 930 to 5975 g mol(-1). X-ray diffraction ( XRD) and high resolution transmission electron microscopy ( HRTEM) indicate that the respective intercalations of MMT with G1, G2 and G3 dendrons exhibited organized characteristics, and the interlayer spacings were 38, 77 and 115 angstrom for G1/MMT, G2/MMT and G3/MMT, respectively. Furthermore, the modified dendron/ MMT hybrids could be well dispersed into organic solvents, such as DMF, due to the presence of hydrophobic dendritic molecules. Our results indicate that organic/inorganic hybrids resulting from the association of dendrons and inorganic layered silicate can be obtained not only by ionic exchange reaction, but possibly by a direct organized route as well. Moreover, the preparation of dendron/MMT hybrids was investigated at different dendron/MMT molar ratios regarding the changes of interlayer distance. When the molar ratio is within the range of 0.25-1.0 cationic exchange capacity ( CEC) equivalents, the d spacings increase from 19 to 38 angstrom for G1/MMT, 15 to 77 angstrom for G2/MMT and 14 to 115 angstrom for G3/MMT, revealing a conformation change of the intercalating dendrons