Possible Heir To Floating-Gate-Based Flash
Motorola says it’s the world’s top producer of embedded processors, but it foresees when even its engineers won’t be able to scale floating-gate-based flash devices — the workhorse of embedded nonvolatile memories — to smaller and smaller geometries. While CPUs are shrinking to 90-nanometer-process architecture, the high-voltage (9V to 12V) transistors needed to write and erase floating-gate flash hog too much of the chip area at such dimensions.
As an alternative, Motorola says, it’s demonstrated the world’s first fully functional 4-megabit memory device based on silicon nanocrystals. The latter, part of an advanced class of memory techniques called thin film storage, resemble 50-angstrom-diameter spheres mounted between two layers of oxide. The silicon spheres are engineered to hold and prevent lateral movement of charge to other isolated nanocrystals.
Researchers at Motorola’s Dan Noble Center in Austin, Texas, built the test array on 200mm wafers using a 90-nanometer process. The company says the next step is to reduce die size and tighten the technology specifications for potential shipping products, which could prove to be evolutionary successors to conventional flash memories, starting in 2004.