24-01-2011, 03:07 PM
The beginning
Microprocessors are essential to many of the products we use every day such as TVs, cars, radios, home appliances and of course, computers. Transistors are the main components of microprocessors.At their most basic level, transistors may seem simple. But their development actually required many years of painstaking research. Before transistors, computers relied on slow, inefficient vacuum tubes and mechanical switches to process information. In 1958, engineers managed to put two transistors onto a Silicon crystal and create the first integrated circuit, which subsequently led to the first microprocessor.
Significant Breakthroughs
Transistor size: Intel’s research labs have recently shown the world’s smallest transistor, with a gate length of 15nm. We continue to build smaller and smaller transistors that are faster and faster. We've reduced the size from 70 nanometer to 30 nanometer to 20 nanometer, and now to 15 nanometer gates.
Manufacturing process: A new manufacturing process called 130 nanometer process technology (a nanometer is a billionth of a meter) allows Intel today to manufacture chips with circuitry so small it would take almost 1,000 of these "wires" placed side-by-side to equal the width of a human hair. This new 130-nanometer process has 60nm gate-length transistors and six layers of copper interconnect. This process is producing microprocessors today with millions of transistors and running at multi-gigahertz clock speeds.
Wafer size: Wafers, which are round polished disks made of silicon, provide the base on which chips are manufactured. Use a bigger wafer and you can reduce manufacturing costs. Intel has begun using a 300 millimeter (about 12 inches) diameter silicon wafer size, up from the previous wafer size of 200mm (about 8 inches).
Integrated Circuits
Digital logic is implemented using transistors in integrated circuits containing many gates.
small-scale integrated circuits (SSI) contain 10 gates or less
medium-scale integrated circuits (MSI) contain 10-100 gates
large-scale integrated circuits (LSI) contain up to 104 gates
very large-scale integrated circuits (VLSI) contain >104 gates
Improvements in manufacturing lead to ever smaller transistors allowing more per chip.
>107 gates/chip now possible; doubles every 18 months or so
Variety of logic families
TTL - transistor-transistor logic
CMOS - complementary metal-oxide semiconductor
ECL - emitter-coupled logic
GaAs - gallium arsenide
What are shown on previous diagrams cover only the so called front‑end
processing ‑ fabrication steps that go towards forming the devices and
inter‑connections between these devices to produce the functioning IC's. The end result are wafers each containing a regular array of the same IC chip or die. The wafer then has to be tested and the chips diced up and the good chips mounted and wire‑bonded in different types of IC package and tested again before being shipped out.
Moore’s Law
Gordon E. Moore - Chairman Emeritus of Intel Corporation
1965 - observed trends in industry - # of transistors on ICs vs. release dates:
Noticed number of transistors doubling with release of each new IC generation
release dates (separate generations) were all 18-24 months apart
Moore’s Law:
The number of transistors on an integrated circuit will double every 18 months
The level of integration of silicon technology as measured in terms of number of devices per IC
This comes about in two ways – size reduction of the individual devices and increase in the chip or dice size
As an indication of size reduction, it is interesting to note that feature size was measured in mils (1/1000 inch, 1 mil = 25 mm) up to early 1970’s, whereas now all features are measured in mm’s (1 mm = 10-6 m or 10-4 cm)
Semiconductor industry has followed this prediction with surprising accuracy
Limits of Moore’s Law?
Growth expected until 30 nm gate length (currently: 180 nm)
size halved every 18 mos. - reached in
2001 + 1.5 log2((180/30)2) = 2009
what then?
Paradigm shift needed in fabrication process
Technological Background of the Moore’s Law
To accommodate this change, the size of the silicon wafers on which the integrated circuits are fabricated have also increased by a very significant factor – from the 2 and 3 in diameter wafers to the 8 in (200 mm) and 12 in (300 mm) diameter wafers
The latest catch phrase in semiconductor technology (as well as in other material science) is nanotechnology – usually referring to GaAs devices based on quantum mechanical phenomena
These devices have feature size (such as film thickness, line width etc) measured in nanometres or 10-9 metres
VLSI
Very Large Scale Integration
design/manufacturing of extremely small, complex circuitry using modified semiconductor material integrated circuit (IC) may contain millions of transistors, each a few mm in size applications wide ranging: most electronic logic devices.
Origins of VLSI
Much development motivated by WWII need for improved electronics, especially for radar
1940 - Russell Ohl (Bell Laboratories) - first pn junction
1948 - Shockley, Bardeen, Brattain (Bell Laboratories) - first transistor
1956 Nobel Physics Prize
Late 1950s - purification of Si advances to acceptable levels for use in electronics
1958 - Seymour Cray (Control Data Corporation) - first transistorized computer - CDC 1604
1959 - Jack St. Claire Kilby (Texas Instruments) - first integrated circuit - 10 components on 9 mm2
1959 - Robert Norton Noyce (founder, Fairchild Semiconductor) - improved integrated circuit
1968 - Noyce, Gordon E. Moore found Intel
1971 - Ted Hoff (Intel) - first microprocessor (4004) - 2300 transistors on 9 mm2
Since then - continued improvement in technology has allowed for increased performance as predicted by Moore’s Law
Three Dimensional VLSI
The fabrication of a single integrated circuit whose functional parts (transistors, etc) extend in three dimensions
The vertical orientation of several bare integrated circuits in a single package
Noise - unwanted disturbances on a useful signal
reflection noise (varying impedance along interconnect)
crosstalk noise (interference between interconnects)
electromagnetic interference (EMI) (caused by current in pins)
3D chips fewer, shorter interconnect sfewer pins.
Advantages of 3D VLSI
Printed circuit board size/weight
planar size of PCB reduced with negligible IC height increase
weight reduction due to more circuitry per package/smaller PCBs
estimated 40-50 times reduction in size/weight