CMOS devices

Eig. 3. Cross sections of electronics devices used in ICs. (a) NMOS transistor (b) a twin-tub CMOS device on an n-ty e substrate. 

Cryoelectronics. Operation of CMOS devices at lower temperatures offers several advantages and some disadvantages (53). Operation at Hquid nitrogen temperatures (77 K) has been shown to double the performance of CMOS logic circuits (54). In part, this is the result of the increase in electron and hole mobilities with lower temperatures. The mobiHty decreases at high fields as carrier speeds approach saturation. Velocity saturation is more important for cryoelectronics because saturation velocities increase by only 25% at 77 K but saturation occurs at much lower fields. Although speedup can... 

For example, chloride and duoride ions, even in trace amounts (ppm), could cause the dissolution of aluminum metallization of complimentary metal oxide semiconductor (CMOS) devices. CMOS is likely to be the trend of VLSI technology and sodium chloride is a common contaminant. The protection of these devices from the effects of these mobile ions is an absolute requirement. The use of an ultrahigh purity encapsulant to encapsulate the passivated IC is the answer to some mobile ion contaminant problems. 

Zhang Z, Liang X, Wang S et al (2007) Doping-free fabrication of carbon nanotube based ballistic CMOS devices and circuits. Nano Lett 7 3603-3607... 

A performance evaluation, however, shows that such circuits are not likely to be a competitor for current CMOS devices [54]. A comparison with current CMOS devices (R 0.01 MO, C 2 10 16 F) shows that... 

Bryant A, Haensch W, Mii T. Characteristics of CMOS device isolation for the ULSI Age. lEDM Technical Digest Dec 1994. p 671-674. 

CMOS devices are very sensitive to damage to the silicon substrate. Therefore care must be taken to ensure that the oxide CMP process used for STT has low defect densities and stops on the Si3N4 mask layer. Li particular scratches must be kept to a minimum. Also, because the oxide CMP processes tend to have low selectivity to Si3N4, the amount of overpolishing performed must be kept to a minimum, which requires high polish rate uniformity to ensure that all of the SiOj overburden is cleared evenly. 

Figure 2.1. IBM s 4 megabit DRAM is a retrograde n-well CMOS device with 0.8- xm nUnimum features. The access time of this chip is 65 ns, and the chip...

Another possible application for high temperature superconductors is as interconnects in computer systems with semiconducting devices (31). These could be called hybrid systems, since they involve both superconductors and semiconductors. In particular CMOS devices are well-known to have enhanced performance at 77 K and are thus potentially compatible with YBaCuO. 

For relatively short lines, as might be of interest in interconnections on a microcircuit chip, a lumped circuit analysis is appropriate, and the performance can be estimated from an RC time constant. Here it is not sufficient to consider only the interconnect line resistance in the total resistance R. The effective output impedance of the CMOS device also contributes and is a key feature which limits the leverage of the superconductor. 

Fig. 14.5. Schematic illustration of a pnpn device made up by (a) a CMOS device and (b) its equivalent circuit...

Fig. 14.7. Dose and energy requirement for major implantations steps in CMOS device fabrications (modified from Rubin and Poate 2003)...

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