3-D devices based on through-silicon-vias (TSVs) continue to generate a buzz. Infineon, Toshiba and Samsung discussed about timing for commercialization of the technology at ISSCC conference that was hold this month in San-Francisco.

Chipmakers are officially headed into the third dimension, as demonstrated at this week’s IEEE International Solid-State Circuits Conference (ISSCC), in San Francisco. For a number of years, researchers have been looking for ways to stack chips vertically to reduce communication delays through lengthy wiring. “3-D is an important topic this year,” says Infineon’s Werner Weber, a member of the ISSCC technology directions subcommittee. Of course, there has been activity in 3-D for at least the past two years. But what’s different this year is the presentation of a chip that’s actually on the market.

Chip firms this week are reporting progress in 3-D integration for all types of memory—dynamic random-access memory (DRAM), static random-access memory (SRAM), and NAND flash—as well as in image sensors and wireless pressure sensors. The star of the 3-D integration show, however, is Toshiba Corp., according to Weber, because its chip-scale camera module is already available.

Three-dimensional integration became a necessary solution when microprocessors became faster than memory. Consequently, the new limit on microprocessor speed was no longer the speed at which its transistors could switch on and off but the long wait to retrieve instructions and data from memory. The industry became aware of the problem about 15 years ago, but in the past five years, memory-access time lags have been increasing with each generation of chips. The problem is commonly referred to as the memory wall.

Infineon plans for 3-D integration in MEMS based Tire Pressure Monitoring System (TPMS):
Infineon’s tire-pressure monitor—a tire-mounted wireless node that senses pressure, inertia, and temperature—is a 3-D vertical chip stack that’s compact and robust enough to survive the rough conditions inside a tire. The stack contains a microelectromechanical sensor, a power-supply module, a microcontroller, and a transceiver. Only the transceiver and the tire-pressure sensor have TSV connections. In addition to sensing pressure, the device can also be used to monitor road conditions, tire wear, and vehicle load.

Weber, who is also a senior researcher with Infineon, says that the sensor is intended to be the second generation of a product whose first generation already populates all new U.S. cars. That device, however, has no 3-D stacking. “The second generation still has a lot of question marks, both technological and architectural,” he says. He anticipates that the device presented at ISSCC “will need much more basic research before it becomes a product.”