Integrated Circuits
Integrated circuits (ICs) started to become a reality in the early 1960s with the advent of small-scale integration of bipolar transistors NAND gates. The baton was quickly passed the CMOS technology, which provided simpler processes, lower costs and grea
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17.1 Introduction Integrated circuits (ICs) started to become a reality in the early 1960s with the advent of small-scale integration of bipolar transistors NAND gates. The baton was quickly passed the CMOS technology, which provided simpler processes, lower costs and greater expectations in terms of integration capabilities. The time spent on and the cost of design were rather low owing to the low complexity of the functions, a situation that has completely changed today. The applications of silicon need to be understood in terms of market demand, but their market success is so dependent on other parameters that we have to describe those parameters before addressing the products and their market.
17.2 A Jump into the Past A key transition period in the history of silicon was the years 1960 to 1970, when small-scale bipolar products (10 to 20 gates) were on the market and the CMOS, complementary MOS process was in its early design phase. The engineers were facing a difficult challenge in their designs: to move from devices with physics-defined parameters (the input diode of the bipolar transistor) to devices with technology-dependent parameters (the drifting oxide threshold of the CMOS device). Design methodologies using CMOS devices were felt easier to implement owing to simpler layout constraints than for bipolar devices. An example of a product with its layout methodology is given Fig. 17.1 [1]. Following the start of production the process improved steadily, and a new product era started with the challenge, from the beginning, of making more complex products at lower cost with this new technology. Since those early times, this driving force for CMOS has remained the same. The result has been an incredible shrinking of critical dimensions of the devices versus time (as forecasted in the ITRS, international technology roadmap for semiconductors), together with an increase in the area of silicon wafers, as shown in Fig. 17.2.
P. Siffert et al. (eds.), Silicon © Springer-Verlag Berlin Heidelberg 2004
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J. Borel
Automatic Layout Synthesis Example (I'EspaJier 1975)
Date 2002 ; Paris, March 4- 8
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Fig. 17.1. Example of a product and its layout methodology
From 1 incb
to
B ________ (IOOflll1 0 ) From 20 microns
12 inches
SOC
lS.l()6 Gates
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Date 2002 : Paris, Mardi 4-8
Fig. 17.2. Shrinking of critical dimensions and increase of wafer area
The expectations in terms of a decrease in final product cost have been met well beyond the early forecasts . As a rule of thumb, for memories, we can say that the cost of a square millimeter of processed silicon has been kept nearly constant over time and that the cost decrease per bit is equal to the corresponding density increase factor (six decades in 30 years).
17.3 Importance Gained by ICs in the Global Economy Integrated circuits have been the fuel of the global economy in the sense that their pervasiveness has been seen successively in all their sectors of application (Fig. 17.3):
17 Integrated Circuits
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New Market driving forces
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