Piezoresistive sensors are among the earliest micromachined silicon devices. The need for smaller, less expensive, higher performance sensors helped drive early micromachining technology, a precursor to microsystems or microelectromechanical systems (MEMS). The effect of stress on doped silicon and germanium has been known since the work of Smith at Bell Laboratories in 1954. Since then, researchers have extensively reported on microscale, piezoresistive strain gauges, pressure sensors, accelerometers, and cantilever force/displacement sensors, including many commercially successful devices. In this paper, we review the history of piezoresistance, its physics and related fabrication techniques. We also discuss electrical noise in piezoresistors, device examples and design considerations, and alternative materials. This paper provides a comprehensive overview of integrated piezoresistor technology with an introduction to the physics of piezoresistivity, process and material selection and design guidance useful to researchers and device engineers.

/pdf/review-semiconductor-piezoresistance-for-microsystems-2i2jehwa4g.pdf

Review: Semiconductor Piezoresistance for Microsystems

Photopolymers broadly comprise monomers, oligomers, polymers, or mixtures of the aforementioned materials that upon exposure to light undergo photochemical reactions that result in deep-seated changes in their structures which substantially modify their chemical and mechanical properties. Photopolymers may possess chromophores that provide for their intrinsic photosensitivity. Alternatively, other photosensitive molecules may be added that directly or indirectly interact with the photopolymer upon exposure to light to produce the desired property changes. Examples of various types of photopolymers will be presented in this article along with examples of their use in representative applications.

Photopolymer Materials and Processes for Advanced Technologies

In this review, we discuss the merits of solution-processed metal oxide semiconductors and consider their application in thin-film transistors for large-area electronics.

Solution-processable metal oxide semiconductors for thin-film transistor applications

A gate-insulated vacuum channel transistor was fabricated using standard silicon semiconductor processing. Advantages of the vacuum tube and transistor are combined here by nanofabrication. A photoresist ashing technique enabled the nanogap separation of the emitter and the collector, thus allowing operation at less than 10 V. A cut-off frequency fT of 0.46 THz has been obtained. The nanoscale vacuum tubes can provide high frequency/power output while satisfying the metrics of lightness, cost, lifetime, and stability at harsh conditions, and the operation voltage can be decreased comparable to the modern semiconductor devices.

Vacuum nanoelectronics: Back to the future?—Gate insulated nanoscale vacuum channel transistor

A discussion on transistors and electronic computing including some history introduces semiconductor devices and the motivation for miniaturization of transistors. The changing physics of field-effect transistors and ways to mitigate the deterioration in performance caused by the changes follows. The limits of transistors are tied to the requirements of the chips that carry them and the difficulties of fabricating very small structures. Some concluding remarks about transistors and limits are presented.

/pdf/physical-limits-of-silicon-transistors-and-circuits-1l6cpmahwi.pdf

Physical limits of silicon transistors and circuits

Fifty years ago, in November 1947, John Bardeen and Walter Brattain discovered the transistor on the fourth floor of Building 1 at Bell Labs in Murray Hill, NJ. Fifty years later, the authors are still working with silicon but it is a very different silicon effort. Currently with the silicon optical bench they are trying to integrate optical components the way transistors have been over the last 50 years. So, silicon technology is still progressing. When considering the invention of the transistor, the authors note that the work of Bardeen and Brattain was really a discovery not an invention. At the time they discovered transistor action, they were investigating the nature of surface states and ways to reduce their presence. It was only later that things really became clear as to what was going on. Fifty years later that discovery is celebrated, and the authors present a brief history of the major events and the key people involved.

http://rahman90.persiangig.com/electronic/transistorhistory.pdf

A history of the invention of the transistor and where it will lead us

Several techniques to reduce the ground bounce effect in CMOS chips are described. The effective width of the predrive and final driver of a CMOS output buffer is automatically adjusted to compensate for process, voltage, and temperature (PVT) variations. The slew rate of the predrive nodes is controlled by introducing a digitally weighted capacitance. Finally, a compensated active resistance is inserted into both the power and ground leads to further dampen the oscillations. These techniques allow the buffer to behave uniformly over the entire PVT range. Measurements of a 0.5-/spl mu/m CMOS test chip have demonstrated that these new buffers generate 2.5/spl times/ less ground bounce when compared to conventional buffers. An external resistance is required to set a reference current.

W.W. Troutman

Papers

A history of the invention of the transistor and where it will lead us

Forming damped LRC parasitic circuits in simultaneously switched CMOS output buffers