Plugging Leaks
Size is taking a toll on more than just contact points and wiring. The transistor's gate-its on-off switch-relies on a thin insulating layer of silicon dioxide to work. As transistors have gotten smaller, so too has this layer, which now measures just 3 or 4 atoms thick.
"The downside of getting so thin is that you tend to leak current," says David. So instead of the transistor being on or off, it's on or leaky off, wasting power. The result: Transistors are getting smaller, but their power requirements are increasing.
"It's the price we pay for faster processors," laments IBM's Shahidi. "You'll turn the transistor off, but you can't stop the current from leaking. A Pentium chip used to burn at 10 to 15 watts with less than 1 watt leakage. Today you'll need 100 watts of energy to operate, losing half of that to leakage." And that means bigger heat sinks, too. The problem is particularly acute for mobile computing. "You can't use a 100-watt chip in a laptop," says Shahidi. "30 to 40 watts is the limit."
Not surprisingly, there's a big push to solve the problem-without a solution, Moore's Law becomes Moore's History. "A lot of research is going on," says Shahidi. "Everyone is looking at new materials to use instead of silicon oxide." Continued...