Microelectronics semiconductors

The basic active devices which are used in preamplifiers in chronological sequence are tubes, transistors, field-effect transistors (FET s), and chips. Chips are self-contained microelectronic semiconductor circuits which are now available in numerous configurations. Thus one can buy certain basic amplifiers and other circuits as chips for incorporation into electronic systems. Much instrument design is now being done using these ready-to-use modular units. Many chips are comparable in size to transistors and have low power requirements. 

Undeniably, one of the most important teclmological achievements in the last half of this century is the microelectronics industry, the computer being one of its outstanding products. Essential to current and fiiture advances is the quality of the semiconductor materials used to construct vital electronic components. For example, ultra-clean silicon wafers are needed. Raman spectroscopy contributes to this task as a monitor, in real time, of the composition of the standard SC-1 cleaning solution (a mixture of water, H2O2 and NH OH) [175] that is essential to preparing the ultra-clean wafers. 

CVD gaseous reactants (precursors) delivered to a heated substrate in a flow reactor undergo tliennal reaction to deposit solid films at atmospheric or reduced pressure, and volatile side products are pumped away. CVD is used for conductors, insulators and dielectrics, elemental semiconductors and compound semiconductors and is a workliorse in tire silicon microelectronics industry. 

The advantages of miniaturization are now being exploited in areas beyond microelectronics. Adaptation of materials and processes originally devised for semiconductor manufacture has allowed fabrication of sensors (for example, pressure meters and accelerometers used in the automotive industry) (6,7), complex optical (8) and micromechanical (6,7,9) assembHes, and devices for medical diagnostics (6,7,10) using Hthographic resists. 

Deposition of Thin Films. Laser photochemical deposition has been extensively studied, especially with respect to fabrication of microelectronic stmctures (see Integrated circuits). This procedure could be used in integrated circuit fabrication for the direct generation of patterns. Laser-aided chemical vapor deposition, which can be used to deposit layers of semiconductors, metals, and insulators, could define the circuit features. The deposits can have dimensions in the micrometer regime and they can be produced in specific patterns. Laser chemical vapor deposition can use either of two approaches. 

Because of the high functional values that polyimides can provide, a small-scale custom synthesis by users or toU producers is often economically viable despite high cost, especially for aerospace and microelectronic appHcations. For the majority of iudustrial appHcations, the yellow color generally associated with polyimides is quite acceptable. However, transparency or low absorbance is an essential requirement iu some appHcations such as multilayer thermal iusulation blankets for satellites and protective coatings for solar cells and other space components (93). For iutedayer dielectric appHcations iu semiconductor devices, polyimides having low and controlled thermal expansion coefficients are required to match those of substrate materials such as metals, ceramics, and semiconductors usediu those devices (94). 

Berylha ceramic parts ate frequendy used in electronic and microelectronic apphcations requiting thermal dissipation (see Ceramics as ELECTRICAL materials). Berylha substrates are commonly metallized using refractory metallizations such as molybdenum—manganese or using evaporated films of chromium, titanium, and nickel—chromium alloys. Semiconductor devices and integrated circuits (qv) can be bonded by such metallization for removal of heat. 

OGG Microelectronic Materials, Olin/CIBA-GEIGY venture photosensitive polyimides, high performance semiconductors... 

The development of microelectronics cannot be envisaged without a comprehensive modeling of the devices. The modeling of OFETs is currently hampered by several features. First, charge transport in organic semiconductors is still not completely understood. The situation is clear at both ends of the scale. In high mobility materials (//>IOcnr V-1 s l), transport occurs within delocalized levels when temperature... 

Metallo-organic CVD (MOCVD) and plasma CVD are developing rapidly, not only in the semiconductor-microelectronic area but also in hard coatingsfor erosion andwearapplicationssincethelower deposition temperature now permits the use of a broader spectrum of substrates. Special emphasis hasbeen given to these two areas in this second edition of the CVD Handbook (see Ch. 4 and 5). 

A semiconductor microcircuit is a series of electrically intercoimected films that are laid down by chemical reactions. The successful growth and manipulation of these films depend heavily on proper design of the chemical reactors in which they are laid down, the choice of chemical reagents, separation and purification steps, and the design and operation of sophisticated control systems. Microelectronics based on microcircuits are commonly used in such consumer items as calculators, digital watches, personal computers, and microwave ovens and in information processing units that are used in communication, defense, space exploration, medicine, and education. 

The acoustic microscopy s primary application to date has been for failure analysis in the multibillion-dollar microelectronics industry. The technique is especially sensitive to variations in the elastic properties of semiconductor materials, such as air gaps. SAM enables nondestructive internal inspection of plastic integrated-circuit (IC) packages, and, more recently, it has provided a tool for characterizing packaging processes such as die attachment and encapsulation. Even as ICs continue to shrink, their die size becomes larger because of added functionality in fact, devices measuring as much as 1 cm across are now common. And as die sizes increase, cracks and delaminations become more likely at the various interfaces. 

Silicon wafer has been extensively used in the semiconductor industry. CMP of silicon is one of the key technologies to obtain a smooth, defect-free, and high reflecting silicon surfaces in microelectronic device patterning. Silicon surface qualities have a direct effect on physical properties, such as breakdown point, interface state, and minority carrier lifetime, etc. Cook et al. [54] considered the chemical processes involved in the polishing of glass and extended it to the polishing of silicon wafer. They presented the chemical process which occurs by the interaction of the silicon layer and the... 

Ronald A. Powell and Stephen Rossnagel, PVD for Microelectronics Sputter Deposition Applied to Semiconductor Manufacturing, Volume 26, 1998. 

In the field of microelectronics, there is continuing research in developing new materials to be used in semiconductor fabrication. They must be formed as thin films in a controlled, reproducible and uniform manner to be useful in semiconductor manufacturing applications. Depth profiling by AES is used to assess the properties of such films. The samples are sputtered with an argon ion beam and analysis performed using standard sensitivity factors, and it is possible to demonstrate that such films are uniform throughout a depth of, say, 250 nm. 

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