Integrated circuits performance improvement

Chapter 10- The continuous improvement of integrated circuit performance is achieved by reducing the dimensions of the key component of these circuits the MOSFET (metal-oxide-semiconductor field effect transistor). One of the key elements that allowed the successful scaling of silicon based MOSFET is certainly the excellent material and electrical properties of the gate dielectric so far used in these devices Si02. However, further scaling of... 

The arrival of integrated circuits with very good performance/price ratios and relatively low-cost microprocessors and memories has had a profound influence on many areas of technical endeavour. Also in the measurement and control field, modem electronic circuits were introduced on a large scale leading to very sophisticated systems and novel solutions. However, in these measurement and control systems, quite often sensors and actuators were applied that were conceived many decades ago. Consequently, it became necessary to improve these devices in such a way that their performance/price ratios would approach that of modem electronic circuits. 

Dielectric constant is directly proportional to the capacitance of a material. Present computer operations are limited by the coupling capacitance between circuit paths and integrated circuits on multilayer boards since the computing speed between integrated circuits is reduced by this capacitance and the power required to operate is increased.11 If the dielectric constant is reduced a thinner dielectric provides equivalent capacitance, and the ground plane can be moved closer to the line, so that additional lines can be accommodated for the same cross-talk. Thus, the effect of a low dielectric constant will be to increase the speed ofthe signal and improve the density of the packaging, and this will result in improved system performance.2... 

Wafer-Scale Integration. One of the most well-publicized and widely debated approaches to increase system performance is wafer-scale integration (WSI), in which an entire system or a large functional block of circuits is integrated on a large chip approaching the size of a silicon wafer (168-171). WSI can greatly increase circuit density, improve reliability because of fewer interconnections, and increase speed and reduce power be-... 

There is no doubt that everyone is familiar with Moore s law, the doubling of data density per integrated circuit every 2 years. The performance of integrated circuit devices, historically limited by the characteristics of the transistors, is today limited by the electrical characteristics of the interconnect. The needed improvements in the interconnect performance are achieved with copper and a reduction in the insulator dielectric4 constant due to the associated reduction in the interconnect capacitance, the cross-talk, and the power consumption. 

Improvements in the performance of integrated circuits and the trend towards VLSI-technology require the replacement of polycrystalline silicon by materials with a lower resistivity for use as gate electrodes. Transition metal silicides appear to be valuable possibilities for these applications. Timgsten-silicon compounds could be suitable precursors for the precipitation of tungsten-silicide thin films. Moreover tungsten-silicon compounds are nearly unknown and of scientific interest. 

A HE FABRICATION OF INTEGRATED CIRCUITS involves a series of steps that defines insulator, conductor, and semiconductor structures in and on single crystals of silicon or gallium arsenide (I). As practiced today, the circuit elements are as small as 1 micrometer (1 xm) in dimension. Reproducible device performance and yield issues require control of both the dimension and placement of these 1-pm structures to tolerances of fractions of 1 xm. The number of such circuit elements per chip has steadily increased during the past three decades, mainly through a decrease in the size of the elements. This reduction in the feature size and the increase in circuit complexity and integration that it allows is largely responsible for the dramatic improvement in the performance and cost-performance ratio that has occurred and is expected to continue to occur. 

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