17 June 2009—What do data archivists have in common with monarch butterflies, salmon, and most geese? They are always preparing for their next migration. From magnetic tape through hard disks, floppy disks, CDs, DVDs, and Blu-ray, digital data formats change periodically, forcing archivists to migrate their data before obsolescence or end-of-lifetime sets in. But now Tadahiro Kuroda, a research engineer and professor at Keio University, in Yokohama, Japan, and his team have come up with a device that could put an end to this recurring—not to mention costly—upheaval in data preservation by maintaining the data safely in an unchanging format that’s predicted to last 1000 years.
The device is a permanent memory system based on semiconductor technology. The prototype consists of four stacked 300-millimeter silicon wafers incorporating 2.5 terabits, (320 gigabytes), of data encoded on read-only memory and fabricated using a 45-nanometer complementary metal-oxide-semiconductor (CMOS) process, together with a separate data reader. Data is written on the chips using an electron beam, and the package is sealed with silicon-based film to prevent erosion.
On-chip inductors receive power through the silicon seal by induction from a reading device. Separate inductors transmit data to the reader. The reader can be made small enough to read one chip at a time or large enough to read the entire stack in one session, depending on a customer’s needs.
One for the Ages
Keio University's Tadahiro Kuroda and a mock-up of his 1000-year wireless archival storage system.
Kuroda worked in Toshiba Corp.’s semiconductor division for 16 years before moving to academia, and he has spent much of his recent past researching chip-to-chip wireless communications. Traditionally, wire bonding has been used for interchip communications. But given the progress made in semiconductor geometric scaling and chip-stacking schemes, Kuroda says this method has reached its limit. A popular solution that many companies are looking at, through-silicon vias (TSVs), which uses interconnects passing through an entire stack of chips, is expensive and not always reliable, he says.