Conventional fabs can make optical chips
Two MIT professors have designed optical chips that can be built using ordinary chip-manufacturing processes.
Using the same manufacturing facilities as Texas Instruments, the MIT researchers have put large numbers of working optical components and electronics on the same chip.
“I don’t see anyone else that’s doing that,” says Michael Watts, a researcher at Sandia National Laboratories who’s also working on optical chips. “If they’re successful at that, then convincing a major processor or memory manufacturer that this is a viable approach will be much, much easier.”
So far, the electronics haven’t been able to control the optics directly. That’s something that Professor Vladimir Stojanovi? hopes to show with a new batch of chips due back from TI and another major semiconductor manufacturer this winter.
So far, TI has produced two sets of prototypes for the MIT researchers, using waveguides built from polysilicon rather than silicon. One uses a 65-nanometer process and the other a 32-nanometer process. To keep light from leaking out of the polysilicon waveguides, the researchers hollowed out the spaces under them when they got the chips back — the sole manufacturing step that wasn’t possible using TI’s in-house processes. But, says Watts, “That can probably be fixed more elegantly in the fabrication house if they see that by fixing that, we get all these benefits,” Watts says. “That’s a pretty minor modification, I think.”
Stojanovi? hopes that the next batch of prototypes, which should give the chips’ electronics control over the optical components, will demonstrate that the resonators perform as well when loading data onto light beams.
At the same time, the team is looking to extend its approach to memory chips. “Memory’s a much tougher nut to crack, because it is such a cost-driven business, where every process step matters,” Stojanovi? says. “Things are a lot harder to change there, and optics really needs to be absolutely compatible with process flow.”
But if memory chips as well as processors sent data optically, Stojanovi? says, then in addition to saving power, they could make computers much faster. “If you just focus on the processor itself, you maybe get a 4x advantage with photonics,” Stojanovi? says. “But if you focus on the whole connectivity problem, we’re talking 10, 20x improvements in system performance.”