Bruce K. Furman

Field-effect transistors comprising molecular beam deposited α,ω-di-hexyl-hexathienylene and polymeric insulator

Abstract Insulated-gate field-effect transistors (IGFETs) comprising molecular beam deposited α,ω-di-hexyl-hexathienylene (DH6T) as the semiconductor layer and different polymeric gate insulators were fabricated and tested. Field-effect mobility values up to 0.13 cm 2 V −1 s −1 were obtained, which are the highest values obtained from thin-film transistors of DH6T.

A Practical Implementation of Silicon Microchannel Coolers for High Power Chips

This paper describes a practical implementation of a single-phase Si microchannel cooler designed for cooling very high power chips such as microprocessors. Through the use of multiple heat exchanger zones and optimized cooler fin designs, a unit thermal resistance 10.5 C-mm2 /W from the cooler surface to the inlet water was demonstrated with a fluid pressure drop of <35kPa. Further, cooling of a thermal test chip with a microchannel cooler bonded to it packaged in a single chip module was also demonstrated for a chip power density greater than 300W/cm2. Coolers of this design should be able to cool chips with average power densities of 400W/cm2 or more

A practical implementation of silicon microchannel coolers for high power chips

The paper describes a practical implementation of a single-phase Si microchannel cooler designed for cooling very high power chips such as microprocessors. Through the use of multiple heat exchanger zones and optimized cooler fin designs, a unit thermal resistance of 10.5 C-mm/sup 2//W from the cooler surface to the inlet water was demonstrated with a fluid pressure drop of less than 35 kPa. Further, cooling of a thermal test chip with a microchannel cooler bonded to it packaged in a single chip module was also demonstrated for a chip power density greater than 300 W/cm/sup 2/. Coolers of this design should be able to cool chips with average power densities of 400 W/cm/sup 2/ or more.

Enabling technologies for wafer-level bonding of 3D MEMS and integrated circuit structures

In this paper, we describe several critical aspects of wafer scale or die level bonding to demonstrate: (1) low temperature bonding for planar layer interconnections; (2) low temperature bonding for non-planar layer sealing; (3) alignment and transfer of process sub-assemblies such as BEOL wiring, MEMS cavity or active device structures; and (4) integration methodology for fabrication of these layer stacks into 3D circuits and MEMS. We also show examples of how layer stacking protocols using wafer bonding technology provides a capability to integrate mixed materials and technologies potentially adaptable to many other applications. In addition, we demonstrate that in order to evaluate the influence of bonding on the electrical integrity of the transferred ICs, state-of-the art circuits, such as short channel length MOSFETs or ring oscillators, should be tested as they are most sensitive to environmental/processing changes.

trans-trans-2,5-Bis-[2-5-(2,2′-bithienyl)ethenyl]thiophene: synthesis, characterization, thin film deposition and fabrication of organic field-effect transistors

Abstract trans-trans -2,5-Bis-[2-5-(2,2′-bithienyl)ethenyl]thiophene (BTET) was synthesized and then purified in a gradient sublimation system. It was characterized using IR, UV—Vis and mass spectroscopy, and elemental analysis. BTET films were deposited with molecular beam deposition (MBD) or spin-coating from solution. Insulated-gate field-effect transistor (IGFET) devices based on such films were used to study their electrical transport properties. A field-effect mobility of 0.01 cm 2 V −1 s −1 was measured from films deposited with MBD, while the mobility of the spin-coated films was slightly above 0.001 cm 2 V −1 s −1 .

High Performance and Sub-Ambient Silicon Microchannel Cooling

High performance single-phase Si microchannel coolers have been designed and characterized in single chip modules in a laboratory environment using either water at 22°C or a fluorinated fluid at temperatures between 20 and −40°C as the coolant. Compared to our previous work, key performance improvements were achieved through reduced channel pitch (from 75 to 60 microns), thinned channel bases (from 425 to 200 microns of Si), improved thermal interface materials, and a thinned thermal test chip (from 725 to 400 microns of Si). With multiple heat exchanger zones and 60 micron pitch microchannels with a water flow rate of 1.25 lpm, an average unit thermal resistance of 15.9 C-mm2 /W between the chip surface and the inlet cooling water was demonstrated for a Si microchannel cooler attached to a chip with Ag epoxy. Replacing the Ag epoxy layer with an In solder layer reduced the unit thermal resistance to 12.0 C-mm2 /W. Using a fluorinated fluid with an inlet temperature of −30°C and 60 micron pitch microchannels with an Ag epoxy thermal interface layer, the average unit thermal resistance was 25.6 C-mm2 /W. This fell to 22.6 C-mm2 /W with an In thermal interface layer. Cooling >500 W/cm2 was demonstrated with water. Using a fluorinated fluid with an inlet temperature of −30°C, a chip with a power density of 270 W/cm2 was cooled to an average chip surface temperature of 35°C. Results using both water and a fluorinated fluid are presented for a range of Si microchannel designs with a channel pitch from 60 to 100 microns.Copyright

Solvent, LICL, and Temperature Effects on the Morphological Structure and Electronic Properties of Polyaniline

Extensive gel permeation chromatography coupled with surface structure measurements clearly indicate that polyaniline (pani) base has a tendency to aggregate as a result of interchain hydrogen-bonding. The aggregation is present in the solid state powder; the extent of aggregation is found to be significantly dependent on the synthetic conditions. Pani base powders having a high degree of aggregation have significantly reduced solubility. The degree of aggregation of pani base in solution is found to be dependent on the solvent, concentration, and temperature. As the solvent becomes a better solvent for the base material, the less aggregated is the structure. Solvents which can strongly interact with the polymer disrupt the aggregation. In addition, salts such as LiCl which complex the polymer via a “pseudo-doping” process, also disrupt the internal pani hydrogen-bonding and deaggregate the polymer. As the polymer is deaggregated to different levels by a solvent or by LiCl, the individual chains can better be solvated and thus a conformational change also occurs. The chains adapt a more expanded coil type of conformation. The degree of expansion depends on the solvation power of the solvent. As the level of deaggregation and subsequent chain expansion increases, a significant red shift is observed in the λmaximum of the exciton absorbance and the surface structure of the polymer becomes smoother. It is found that the LiCl induced morphological changes results in increased conductivity upon doping pani base with a protonic acid.

Direct integration of dense parallel optical interconnects on a first level package for high-end servers

The direct integration of dense 48-channel parallel multiwavelength optical transmitter and receiver subassemblies directly onto a first level package using a flex lead attach has been demonstrated. Such an approach, at 10 Gb/s/channel would provide a linear edge bandwidth density of 300 Gb/s/cm. By attaching dense multichannel optical subassemblies directly onto an MCM, the performance limitations of the connectors and node card wiring can be avoided and the total bandwidth off the MCM can be increased while also enabling longer distance and higher speed signaling. This approach involves only a modest modification to the bent-flex approach commonly used for parallel optical modules intended for board mounting but enables a significant density and performance improvement for this application.

Factors Affecting Metal/Polymer Interface Durability in Microelectronics Packaging: Chemistry and Water Uptake

Durability of metal/polymer interfaces is essential for the long-term reliability of high performance microelectronics packages. Such interfaces undergo stresses during production and in service. In this work, we report on the durability of interfaces formed between reactive metals and polyimides (PI) that have been subjected to stresses simulating both types of environment. The P1 surfaces were treated by Ar RF plasmas prior to metal deposition, and durability was determined by measuring the 90 degree peel strength as a function of environmental exposure. The durability of Cr and Ti/PMDA-ODA interfaces through processing stresses (i.e., large thermal excursions) depends on the PI surface modification and the metal reactivity. For both, we observed interfacial degradation due to oxidation of the metal–the cause is water absorbed by the polyimide. These studies, coupled with water transport measurements, suggest that the physical structure of the interface is the dominant factor. To determine the durability under service environmental stresses (e.g., temperature/humidity), we correlated peel strengths with interfacial chemistry and water uptake. In this case, Ar and O 2 plasmas were used. For Ta/BPDA-PDA, the durability depends on the type of plasma treatment. Ar-treated specimens maintain strength through 500 hours T/H stressing whereas those treated by O 2 plasma alone fail at 165 hours. The differences here can be explained by the interfacial chemistry–Ta/Ar-etched surfaces form a stable TaG-like structure whereas the Ta/O 2 -etched surfaces form a metastable, sub-oxide structure that transforms to Ta 2 O 5 during stressing. Ta/PMDA-ODA interfaces fail readily under these conditions due to the increased water uptake of the PI.

Ta/polyimide adhesion durability

The adhesion durability of Ta to plasma-modified polyimide surfaces has been investigated under thermal exposure. The failure mechanism was correlated with Auger analysis. Resistance to oxidation at the Ta/polyimide interface was found necessary to obtain a durable metal/polymer adhesion strength.