How Many Nanometers in a Micron?
It's hard to overhear any discussion of chip manufacturing for more than a few minutes without hearing about microns or nanometers. (Okay, it's hard to listen to any discussion of chip manufacturing at all, but that's not the issue here.) These two terms describe exactly how small the transistors and metal wires on a chip are. For clean room workers and manufacturing technicians, microns and nanometers are everything.
Both terms are simply measurements. In fact, they're measurements of the same thing. One micron is exactly one one-millionth of a meter (0.000001 meter). For fans of English measurement, that's about 25,000 microns to the inch (see Figure 4.10). For comparison, a human hair is about 50 microns thick, so we're talking about very small measurements here.
Figure 4.10. Silicon transistors can be made as big as you wish, but smaller transistors are usually the goal. A 90-nanometer transistor is barely three one-millionths of an inch across. That's about twice the size of a virus but smaller than a bacteria, smoke particle, human hair, or grain of sand. Single atoms measure about a quarter nanometer across, so today's transistors are only about 400 atoms thick.
Yet a micron is a vast distance to a chip manufacturer. Individual transistors are smaller than a single micron across, and have been since the early 1990s. Starting around 2001, manufacturers started producing the first transistors that were smaller than one-tenth of a micron (0.1 micron), leading to some tongue-twisting dimensions, even for engineers. So rather than continue to speak in fractions of a micron, silicon engineers began using the next smallest unit of measure, the nanometer.
A nanometer is one one-billionth of a meter (0.00000001 meter), or 1,000 times smaller than a micron. For comparison, a single hydrogen atom is only about 0.25 nanometers across (assuming one can measure these things). Amazing as it seems, we are rapidly approaching a time when the thickness of these materials will be measured by counting their atoms.