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Semiconductors and electronics

Semiconductors and electronics

Noise threatens Moore’s Law

18 Dec 2002 Belle Dumé

The semiconductor industry has obeyed Moore’s Law for about 40 years and some experts believe that it will be valid for another two decades. However, Laszlo Kish at Texas A&M University believes that thermal noise -- which increases as circuits become smaller -- could put an end to Moore’s Law much sooner (LB Kish 2002 Physics Letters A 305 144).

In 1965 Gordon Moore, the co-founder of Intel, predicted that the number of transistors per square inch on integrated circuits would double every year and this came to be known as “Moore’s Law”. The silicon industry has followed this law and transistors have exponentially decreased in size since the 1970s. At present they measure around 100nm.

Kish believes that any further increase in the density of computer chips means that they will reach a physical limit — due to thermal noise — relatively soon. This limit is expected to come into effect around 40nm and below – and could cause problems as early as in six years time.

These problems arise from a fundamental thermodynamical process — the increasing thermal or “Johnson-Nyquist” noise voltage. Although Kish does not set any physical limits on transistor sizes he argues that the logical threshold voltage — the supply voltage — cannot be reduced below a certain limit. Thermal noise can induce “false bit-flips” that occur randomly — making them difficult to identify and control. False bit-flips can only be avoided, says Kish, by halting any further increase in integration density.

It is possible, Kish suggests, that these effects may already be having a detrimental impact on the most advanced integrated circuits.

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