Fabrication

About: Fabrication is a research topic. Over the lifetime, 20475 publications have been published within this topic receiving 235676 citations.

Laser micro-fabrication of concave, low-roughness features in silica

Abstract: We describe a micro-fabrication method to create concave features with ultra-low surface roughness in silica, either on the end facets of optical fibers or on flat substrates. The machining uses a single focused CO2 laser pulse. Parameters are chosen such that material is removed by thermal evaporation while simultaneously producing excellent surface quality by surface tension-induced movement in a low-viscosity melt layer. A surface roughness {\sigma}~0.2nm is regularly obtained. The concave depressions are near-spherical close to the center with radii of curvature between 20 and 2000{\mu}m. The method allows the fabrication of low-scatter micro-optical devices such as mirror substrates for high-finesse cavities or negative lenses on the tip of optical fibers, extending the range of micro-optical components.

Microfabricated structures and processes for manufacturing same

Abstract: Various techniques for the fabrication of highly accurate master molds with precisely defined microstructures for use in plastic replication using injection molding, hot embossing, or casting techniques are disclosed herein. Three different fabrication processes used for master mold fabrication are disclosed wherein one of the processes is a combination of the other two processes. In an embodiment of the first process, a two-step electroplating approach is used wherein one of the metals forms the microstructures and the second metal is used as a sacrificial support layer. Following electroplating, the exact height of the microstructures is defined using a chemical mechanical polishing process. In an embodiment of the second process, a modified electroforming process is used for master mold fabrication. The specific modifications include the use of Nickel-Iron (80:20) as a structural component of the master mold, and the use of a higher saccharin concentration in the electroplating bath to reduce tensile stress during plating and electroforming on the top as well as sides of the dummy substrate to prevent peel off of the electroform. The electroforming process is also well suited towards the fabrication of microstructures with non-rectangular cross sectional profiles. Also disclosed is an embodiment of a simple fabrication process using direct deposition of a curable liquid molding material combined with the electroforming process. Finally, an embodiment of a third fabrication process combines the meritorious features of the first two approaches and is used to fabricate a master mold using a combination of the two-step electroplating plus chemical mechanical polishing approach and the electroforming approach to fabricate highly accurate master molds with precisely defined microstructures. The microstructures are an integral part of the master mold and hence the master mold is more robust and well suited for high volume production of plastic MEMS devices through replication techniques such as injection molding.

Methods for selective and conformal epitaxy of highly doped si-containing materials for three dimensional structures

Abstract: The present invention addresses the key challenges in FinFET fabrication, that is, the fabrications of thin, uniform fins and also reducing the source/drain series resistance. More particularly, this application relates to FinFET fabrication techniques utilizing tetrasilane to enable conformal deposition with high doping using phosphate, arsenic and boron as dopants thereby creating thin fins having uniform thickness (uniformity across devices) as well as smooth, vertical sidewalls, while simultaneously reducing the parasitic series resistance.

Thermal‐Sensing Fiber Devices by Multimaterial Codrawing

Abstract: Thermal sensing and thermography yield important information about the dynamics of many physical, chemical, and biological phenomena. Spatially resolved thermal sensing enables failure detection in technological systems when the failure mechanism is correlated with localized changes in temperature. Indeed, IR-imaging systems have become ubiquitous for applications where line-of-sight contact can be made between the measured object and the camera lens. Nevertheless, many critical applications do not lend themselves to radiative IR imaging because of the subterraneous nature of the monitored surface, spatial constraints, or cost considerations. The recent challenge of monitoring the skin temperature beneath the thermal tiles on the space shuttle represents a good example in which high-spatial-resolution information is required on very large surface areas but which cannot be obtained using traditional thermal-imaging systems. Thus, the problem of continuously monitoring and detecting a thermal excitation on very large areas (100 m) with high resolution (1 cm) is one that has remained largely unsolved. We present a new methodology for measuring spatially resolved temperature information on large areas with high spatial resolution and low cost. Underlying our approach is a new fiber material that senses heat along its entire length and generates an electrical signal. This is in contrast to all previous work on thermal sensing using fibers, which require the use of optical probing signals. Although the fibers are produced by thermal drawing, they contain a set of materials that have not been traditionally associated with this process. The use of thermal drawing guarantees the production of extremely long fibers, while the innovation in preparation of the preform and choice of materials allows the incorporation of novel functionalities. Specifically, both thermal and electrical functionalities are obtained in the fibers studied in this communication, while optical and optoelectronic functionalities in alternative designs have been obtained previously and are reported elsewhere. The fibers are produced by a novel fabrication technique that enables the incorporation of materials with widely disparate electrical and thermal properties in a single, macroscopic, cylindrical preform rod, which subsequently undergoes thermal drawing to give solid-state microstructured fibers with high uniformity. The main requirements in the materials used in this preform-to-fiber approach are as follows: 1) the component which supports the draw stress should be glassy, so as to be drawn at reasonable speeds in a furnace, with self-maintaining structural regularity; 2) the materials must be above their respective softening or melting points at the draw temerature to enable fiber codrawing; and 3) the materials should exhibit good adhesion/wetting in the viscous and solid states without delamination, even when subjected to thermal quenching. According to these requirements, we identified suitable semiconducting, insulating, and metallic materials. The insulating material is a 75 lm thick polymer film: polysulfone (Ajedium, USA), having a glass-transition temperature, Tg = 190 °C. The chosen semiconducting glass, Ge17As23Se14Te46 (GAST), was arrived at by optimizing the composition formula GexAs40–xSeyTe60–y (10 < x < 20 and 10 < y < 15) under constraints of compatibility of Tg and viscosity with the codrawn polymer. Metallic electrodes are made of the alloy 96 %Sn–4 %Ag, which has a low meltingtemperature range (TM = 221–229 °C) below the fiber-drawing temperature of 270 °C. The chemical composition of the glass is chosen such that the electronic mobility gap of the amorphous semiconductor is small, yielding high electrical responsivity to small changes in temperature. The fabrication process (see Fig. 1A) begins with preparing cylindrical rods of the glass (see “Amorphous Semiconductor Synthesis” in the Experimental section). A cylindrical shell of polymer having an inner diameter equal to that of the glass rod is prepared with four slits removed from the walls. Four thin rods of the metal alloy are then placed in these slits. The glass rod is inserted into the polymer shell (Fig. 1A(a)), and a polymer sheet is then rolled around the resulting cylinder to provide a protective cladding (Fig. 1A(b)). Finally, the cylinder is thermally consolidated (Fig. 1A(c)) and subsequently is drawn in a fiber-draw tower producing hundreds of meters of C O M M U N IC A IO N S