Submicrometer device

NTEGRATED CIRCUIT (IC) TECHNOLOGY has moved Steadily toward increasing circuit density and improved performance during its brief history. These improvements have been achieved through the development of the microlithography process, which now permits production of devices with feature sizes of 1 fim. Submicrometer devices are actively being developed, and production is expected later in this decade. 

Surface analytical tools have increased in use as device dimensions have decreased into the near-surface realm. High spatial resolution and high analytical sensitivity are basic requirements for the characterization of impurities and defects in near and submicrometer devices. Electron, ion, and photon beam techniques are widely employed to characterize IC fabrication at each processing step and to analyze failures as they occur in processing as well as in the field. 

In both Si and GaAs, the critical electric field is on the order of 106 V/m. It is clear that in state-of-the-art submicrometer devices with fields on the order of 107 V/m, optical phonons will be generated. Although optical phonons interact with hot electrons, their group velocity is very small and hence they do not conduct any heat. So, they eventually decay into acoustic... 

Coalescing demister pads have been used in some single absorption plants instead of packed fiber beds to remove mist from the stack gas. For submicrometer particle collection, these devices are not as efficient as packed fiber beds. Nevertheless, they have been used in some plants to obtain nearly... 

Among these one of the most promising concepts is the development of single electron (SE) devices, which retain their scalability down to the molecular level. At present, due to exploitation of charging (Coulomb) effects in metallic SE devices comprising tunnel junctions with submicrometer size, individual charge carriers can be handled... 

The radii of both orifices can be either on a micrometer or a submicrometer scale. If the device is micrometer-sized, it can be characterized by optical microscopy. The purposes of electrochemical characterization of a dual pipette are to determine the effective radii and to check that each of two barrels can be independently polarized. The radius of each orifice can be evaluated from an IT voltammogram obtained at one pipette while the second one is disconnected. After the outer surface of glass is silanized, the diffusion-limiting current to each water-filled barrel follows Eq. (1). The effective radius values calculated from that equation for both halves of the d-pipette must be close to the values found from optical microscopy. 

Cloud Water and Precipitation Collectors. Several methods have been developed for collecting cloud water samples (24-26). Probably the device most commonly used in warm clouds is the slotted rod collector developed by the Atmospheric Science Research Center at the State University of New York (SUNY) at Albany. Commonly known as the ASRC collector (25), this collector consists of an array of rods constructed from Delrin (a form of nylon). Each rod is hollow and has a slot located at its forward stagnation line. The rod radius determines the collection efficiency as a function of particle size, the rods are sized to collect cloud droplets but not submicrometer aerosol particles, and the 50% cutoff is calculated to be at about 3 xm. 

Aleltblown, Spunbond, and Spurted Fibers. A variety of directly formed nonwovens exhibiting excellent filtration characteristics are made by meltblown processes, producing very fine, submicrometer filaments. A stream of high velocity hot air is directed on the molten polymer filaments as they are extruded from a spinnerette. This air attenuates, entangles, and transports die fiber to a collection device. Because the fiber cannot be separated and wound for subsequent processing, a nonwoven web is directly formed. 

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