Defect cluster recognition system for fabricated semiconductor wafers

The International Technology Roadmap for Semiconductors (ITRS) identifies production test data as an essential element in improving design and technology in the manufacturing process feedback loop. One of the observations made from the high-volume production test data is that dies that fail due to a systematic failure have a tendency to form certain unique patterns that manifest as defect clusters at the wafer level. Identifying and categorising such clusters is a crucial step towards manufacturing yield improvement and implementation of real-time statistical process control. Addressing the semiconductor industry’s needs, this research proposes an automatic defect cluster recognition system for semiconductor wafers that achieves up to 95% accuracy (depending on the product type).     

Compact EBG in-phase hybrid-ring equal power divider

A novel electromagnetic-bandgap (EBG) in-phase hybrid-ring equal power divider is described. Coupled with the closed-form analytical expressions for the EBG structure, a systematic technique of design is presented for the first time. Compared to the conventional hybrid-ring equal power divider, based on the 15-dB return-loss criteria, an increase in both the input and output impedance bandwidth of approximately 10% from a starting frequency of 2.5 GHz, and a phase error of 0.006/spl deg/ within the passband have been achieved for the proposed structure. The proposed in-phase hybrid-ring equal power divider, besides providing a much broader bandwidth and occupying a smaller estate area, also possesses good harmonic suppression characteristic.     

Thermal unfolding of three acclimation temperature-associated isoforms of carp light meromyosin expressed by recombinant DNAs

Differential scanning calorimetry (DSC) was performed to investigate thermodynamic properties of three carp fast skeletal light meromyosin (LMM) isoforms expressed in Escherichia coli by recombinant DNAs. Three isoforms were the 10 degreesC-, intermediate-, and 30 degreesC-type LMM predominantly expressed in carp acclimated to 10, 20, and 30 degreesC. The isoforms expressed in E. coli by recombinant DNAs exhibited a typical pattern of alpha-helix in CD spectroscopy with two minima at 222 and 208 nm. Moreover, the three isoforms formed paracrystals typical of LMM, suggesting that expressed proteins retained intact structural properties. When the LMM isoforms were subjected to DSC analysis, the 10 degreesC and 30 degreesC types showed endotherms having transition temperatures (Tm) at 35.1 and 39.5 degreesC, respectively, which are responsible for thermal unfolding of alpha-helix. The intermediate type exhibited two comparable endotherms with Tm values at 34.9 and 40.6 degreesC, implying that it has intermediate thermodynamic properties between those of 10 degreesC and 30 degreesC types. However, a chimeric LMM having the 10 degreesC and 30 degreesC type as N- and C-terminal halves, respectively, showed the DSC pattern typical of the whole 30 degreesC-type molecule. On the other hand, another chimeric LMM composed of the N-terminal 30 degreesC type and C-terminal 10 degreesC type gave the pattern of the full 10 degreesC type. These results suggest that thermodynamic properties of the C-terminal half largely account for thermal unfolding of the whole molecule.     

Study of x/spl alpha/-Fe/sub 2/O/sub 3/-(1-x)ZrO/sub 2/ solid solution for low-temperature resistive oxygen gas sensors

A noble type of oxygen-sensitive and electrical-conductive material, ZrO/sub 2/-based with /spl alpha/-Fe/sub 2/O/sub 3/ thick-film gas sensor, was investigated for low operating temperature. Amorphous-like solid solutions of x/spl alpha/-Fe/sub 2/O/sub 3/-(1-x)ZrO/sub 2/ powders were derived using the high-energy ball milling technique, and their physical and microstructural properties were characterized from DTA, XRD, TEM, and XPS. The oxygen gas-sensing properties of the screen-printed thick-film gas sensors fabricated from such mechanically-alloyed materials were characterized systematically. Very good sensing properties were obtained with a relative resistance value of 82 in 20% oxygen, and at a low operating temperature of 320/spl deg/C. AC impedance spectra and thermally stimulated current were characterized to investigate the conduction properties of the solid solution, 0.2/spl alpha/-Fe/sub 2/O/sub 3/-0.8ZrO/sub 2/, in air and nitrogen (carrier gas), respectively. It was found that the Arrhenius plots of /spl sigma/T versus 1000/T have two distinct gradients corresponding to two activation energies in the high and low temperature regions. The transition temperature occurs at about 320/spl deg/C that corresponds to an optimal operating temperature of the gas sensor. It is believed that the high oxygen vacancy concentration present in the solid solution, 0.2/spl alpha/-Fe/sub 2/O/sub 3/-0.8ZrO/sub 2/, and the dissociation of the associated oxygen vacancy defect complexes at 320/spl deg/C are the critical factors for the high relative resistance to oxygen gas at low operating temperature.     

Curvature and Bending Moments from Inclinometer Data

Bending moments in excavation support walls and deep foundations are frequently estimated using curvature derived from inclinometer surveys. The basic idea involves fitting a curve or a series of curves to the inclinometer data. The curvature is then estimated as the second difference of the displacement profile. Although many methods are available to estimate curvature, there is a lack of a consistent standard in deducing curvature from inclinometer readings. Twelve methods for estimating curvature that lend themselves well to spreadsheet or programmable calculations are reviewed. They are then applied to 60 sets of inclinometer readings obtained from a variety of walls and drilled shafts. Included are six laterally load tested drilled shafts which were monitored using both inclinometers and strain gauges. A direct comparison of curvatures from inclinometers with those from strain gauges was performed. The comparisons show that a piecewise cubic polynomial curve fitting a moving window of five successive inclinometer data points provide curvature values that are in good agreement with those from strain gauges, and is proposed as a reasonable method for estimating bending moments from inclinometer data.     

Synthesis of civetone from palm oil products

Metathesis of ethyl oleate, catalyzed by WCl₆ and SnMe₄, provided diethyl 9-octadecenedioate (the desired starting material for the synthesis of civetone) in 99% yield. Dieckmann condensation of diethyl 9-octadecenedioate gave 2-ethoxycarbonyl-9-cycloheptadecenone (63% yield), the hydrolysis-decarboxylation reaction of which yielded civetone (93%). Identification of all products was by¹H nuclear magnetic resonance, infrared and mass spectroscopic data. This is the first report of the synthesis of civetone from palm oil-derived products.     

Electroosmotic flow in irregular shape microchannels

The electrokinetic flow through star-point family microchannels is studied. Mathematical solutions using a semi-analytical approach are employed to model the steady, fully developed electroosmotic flow in the closed-end star point family microchannels. The model can be extended to other irregular shape channels. The effects of sharp corners, electrolyte concentration and packed capillary radius, R₀ are analyzed. Comparisons of the flow characteristics and induced pressure gradient inside and outside of the packed capillaries are presented.     

Dehydrogenative polycondensation of telechelically bis(dimethylsilyl)functionalized oligo(dimethylsiloxane)s or aromatics and 1,3,3,5,5,7,7,7-octamethyltetrasiloxane

Telechelically bis(hydrodimethylsilyl)-functionalized oligo(dimethylsiloxane)s or aromatics were found to give polymers constituting of alternating disilylene and oligodimethylsiloxane or 4,4′-diylaromatics as repeating units by dehydrogenative coupling reaction in the presence of palladium dibenzylideneacetone complex. The same catalyst gave polysilylenes with trisiloxane pendant from 1,1-dihydro-1,3,3,5,5,7,7,7-octamethyltetrasiloxane. Received: 18 October 1996/Accepted: 31 October 1996     

Thermal properties and aging characteristics of chemically modified oil palm ash-filled natural rubber composites

The chemically modified oil palm ash (OPA) with the cetyltrimethylammonium bromide (CTAB) solution was prepared prior to compounding with the natural rubber and other curing ingredients. The aging resistance and thermal stability of CTAB-modified OPA-filled natural rubber composites were evaluated in the same manner as non-modified OPA samples. The retention tensile properties after thermal aging was measured and based on the result shown, the CTAB-modified OPA-filled natural rubber composites imparted insignificant effect to aging resistance as compared to the non-modified OPA-filled natural rubber composites at very low OPA loading; however, the effect became apparent beyond 3 phr OPA loading where the CTAB-modified OPA-filled natural rubber composites provided better aging resistance than the corresponding non-modified OPA-filled natural rubber composites. The thermogravimetric analysis indicated that the CTAB-modified OPA-filled natural rubber composites exhibited lower thermal stability which showed lower temperature at their respective weight loss and lesser char residue than that of non-modified OPA-filled natural rubber composites. This was attributed to the CTAB which started to decompose at the temperature of 210 °C. However, for the range from ambient temperature to 210 °C, the CTAB-modified OPA-filled natural rubber composites produce better thermal stability than those of non-modified OPA-filled natural rubber composites.     

A bond model for DEM simulation of cementitious materials and deformable structures

There is an increasing use of the discrete element method (DEM) to study cemented (e.g. concrete and rocks) and sintered particulate materials. The chief advantage of the DEM over continuum based techniques is that it does not make assumptions about how cracking and fragmentation initiate and propagate, since the DEM system is naturally discontinuous. The ability for the DEM to produce a realistic representation of a cemented granular material depends largely on the implementation of an inter-particle bonded contact model. This paper presents a new bonded contact model based on the Timoshenko beam theory which considers axial, shear and bending behaviour of the bond. The bond model was first verified by simulating both the bending and dynamic response of a simply supported beam. The loading response of a concrete cylinder was then investigated and compared with the Eurocode equation prediction. The results show significant potential for the new model to produce satisfactory predictions for cementitious materials. A unique feature of this model is that it can also be used to accurately represent many deformable structures such as frames and shells, so that both particles and structures or deformable boundaries can be described in the same DEM framework.