IBM stores 125 GB in one square inch

IBM stores 125 GB in one square inch

With the use of new technologies, IBM has succeeded in storing 125 GBytes on 625 mm². Compared to today's hard drives, this corresponds to a storage density that is twenty times higher. Not counting, 25 million book pages or the content of 25 DVDs can be stored on the surface of a postage stamp.

This was achieved as part of the “Millipede” project at the IBM research laboratory in Zurich. In this development, nanomechanics plays a central role instead of conventional magnetic or electronic storage technology: With thousands of extremely fine tips, Millipede 'writes' tiny depressions that represent individual bits in a thin plastic film. The result is comparable to a traditional punch card, but on the nanometer scale (millionths of a millimeter). The bits can also be deleted and overwritten.

The terabit density was achieved with a single silicon tip, created the pits just 10 nanometers in diameter - 50,000 times smaller than the period at the end of this sentence. The team at the IBM research laboratory in Zurich tested the functionality of the concept with an experimental memory chip with more than a thousand tips. They are currently working on the prototype of a complete storage system, which will be ready for operation next year and which will demonstrate that the promising new technology can meet the practical requirements of a marketable product. This prototype will have more than 4,000 tips arranged in a small square with a side length of 7 millimeters. The dimensions would make it possible to pack a complete high-capacity storage system into the smallest standardized format for flash memory.

The capacity of flash memory is not expected to exceed 1-2 GB in the near future. With Millipede technology, you couldon the other hand, there is space for 10-15 GB on the same area without using more energy.

Technical background The core of Millipede technology is a two-dimensional arrangement of V-shaped silicon spring tongues (Cantilever) that are 0.5 micrometers (thousandths of a millimeter) thick and 70 micrometers long. At the end of each 'tongue', a point less than 2 micrometers high protrudes from one side. The current experimental setup contains a total of 1024 (32 x 32) 'tongues' in a square 3 mm long, which are etched out of the silicon. A sophisticated design ensures the exact leveling of the tips above the storage medium and dampens external vibrations and shocks.

For the Functions of the device, i.e. reading, writing, erasing and overwriting, the tips are brought into contact with the polymer film on the silicon substrate, which is only a few nanometers thick. Bits are written by heating the resistor integrated in the cantilever to typically 400 degrees Celsius. The tip, which is also heated as a result, softens the polymer, sinks in and leaves a depression. For reading, the temperature of the resistor is reduced to typically 300 degrees Celsius. The polymer does not soften at this temperature. If the tip “falls” into a depression, the resistor cools down slightly because of the better heat transfer, which leads to a measurable change in the resistance. To overwrite data, the tip etches offset recesses in the surface. Their outer edges overlap the old wells and thus erase the old data. More than 100,000 write and overwrite cycles have proven that the concept is suitable for a rewritable memory type.

The energy consumption depends heavily on the data rate at which the device is operated. At a few megabits per second, Millipede is likelydo not require more than 100 milliwatts, which corresponds roughly to the energy requirements of a flash memory and is well below that of magnetic storage.

With the experimental chip with 1024 points on a 3 mm square, a Storage density of 200 gigabits per square inch and a potential capacity of about 0.5 gigabytes is achieved. The next Millipede generation will have four times as many points - 4096 or 64 x 64 in a 7 mm square.