Millipede memory

Millipede is an IBM-developed memory technology and is something of a mix of flash memory and (micro ) disk. It is based on the atomic force microscope technology, developed by Nobel laureate Gerd Binnig.

Basic principle

The basic principle is similar to that of the previous hole card, but it is applied to structure sizes in the range of nanometers. Another crucial difference is that in using the technology used to delete the bits and allow overwrite. Tiny levers simultaneously (English Cantilever) with a fine tip made ​​of silicon melt as tiny holes in a polymer medium to write bits. These same peaks are also used to detect these holes, thus to read out the bits again. To bringing the tip into the vicinity of the polymer film and heating it. Immerse the tip into a bit Crater, increases the heat exchange between her and the storage medium, whereby the electrical resistance of the Hebelchens decreases. To override a bit, you create with the tip on the crater rim new wells whose edges overlap the old well, and so force the polymer material in the direction of the crater.

Because the holes are very small, they can be set very close to each other and thus achieve high data densities. With this technology it is IBM scientists in laboratory Rüschlikon managed to enter in the nanometer range. Thus, when storage of data has a recording density of a terabit per square inch are achieved, which corresponds approximately to the content of the DVD 25 on the face of a stamp. This density was achieved with a single silicon tip that produces pits with a diameter of about ten nanometers. To the data rate, thus increasing the write and read speed, is not only a bit used, but a whole array of levers simultaneously, working in parallel. A prototype has more than 4000 of such peaks, are arranged in a small square of 6.4 mm side length. These dimensions allow you to pack a complete storage system with high capacity in the smallest standardized format for flash memory.

A lever arm in the Millipede writes and reads from an assigned about 100 microns x 100 microns small cell. While moving, for example, a hard drive, the read and write head and the storage media, is only the medium is moving in the Millipede memory. Two coils are placed between magnets, drive the movement of the plate: The micro- scanner can be positioned with an accuracy of up to two nanometers. From the overlapping area of ​​the strip-shaped sensors can determine the position, however, these sensors consume relatively large amount of energy.

Construction of Millipede

Hebelarmfeld

Core of the Millipede technology is a two-dimensional array of v - shaped silicon spring tongues ( lever arms ), 70 micrometers ( thousandths of a millimeter ) long. At the end of each lever arm is a sensor for reading and a resistance above the top are for writing. The tip is just one micrometer in length, and the radius is only a few nanometers. Lever arms are arranged in arrays on an integrated circuit ( IC chip). The chip is 7 × 14 mm in size. In the center is located an array of for example 4096 ( 64 × 64) of lever arms which are etched out of the silicon. The actual disk consists of a few nanometer thin polymer film on a silicon substrate. About multiplexer controlled individually read, write or erase heads the desired bit. Up to 100,000 write-and- write cycles to have been previously tested successfully. And while in the construction mechanism is used, a transmission rate of up to 20 to 30 megabits per second can be achieved.

Microscanner

The movement of the storage medium relative to the cantilever - array is realized by means of siiliziumbasierten x / y - microscanner. The scanner is composed of an approximately (6.8 x 6.8 ) mm ² scan table, which supports the polymer medium, and two electromagnetic release. The imager chip is mounted on the silicon plate, which serves as a mechanical base of the system. The distance between its surface and the surface of the moving parts of the scanner is about 20 microns. The scan table can be moved by shutter in the x -and y- directions to 120 microns. Each trigger is made of two permanent magnets which are incorporated in the silicon plate, and a small coil, which is located between the magnets. To delete the vibrations from outside is a so-called pivot used, coupled with the triggers.

Location

The information on positioning are provided by four thermal sensors. These sensors are located directly on the scan table, on the cantilever array. The sensors have thermally insulated heater. Each sensor is placed over an edge of the scan table in position and is heated by electricity. Some of this heat is directed through the air to the scan table, which now acts as cooler. A displacement of the scanning table will cause a change in the efficiency of this cooling system, resulting in the change of the temperature of the electrical resistance of the heater.

A sophisticated design ensures accurate leveling of the tips over the storage medium and dampens vibration and shock from outside. Time- multiplexing electronics, such as is used in a similar manner in the memory chips (DRAM), the addressing of each tip allows operating in parallel. Electromagnetic actuation moves the substrate with the storage medium on the surface very precisely in the x- and y- direction, so that each tip can read and write in their memory box of 100 micrometers on a side. The short distances contribute significantly to a low energy consumption.

For the functions of the device, ie reading, writing, deleting and overwriting, the tips are brought into contact with the polymer film on the silicon substrate.

Writing technology

The Bits are written by heating the integrated in the cantilever resistance to typically 400 ° C. The thus also heated tip deviates the polymer decreases and leaves an indentation of a few nanometers. To read the read sensor of the cantilever is heated without soften the polymer film. " If " is now the top in a depression, the read sensor cools due to the larger contact area between the substrate and tip, and thus a higher heat dissipation from slightly, but this leads to a measurable change in the resistance. To overwrite data sets the peak depressions in the surface. Their outer edges overlap the old wells and so delete the old data. More than 100,000 write and overwrite cycles have demonstrated that the concept is suitable for a rewritable memory type.

To get the data faster into memory and back out, worked a complete matrix arrangement of levers simultaneously the medium simultaneously. However, it turned out that it is extremely difficult to manufacture mechanics and electronics in one piece on a chip. The researchers therefore decided to realize the building into two pieces:

The prototypes shown recently the technical feasibility of the product was demonstrated for instance with regard storage density, performance and reliability. While the storage technologies used today gradually come up against fundamental limits, the nanomechanical approach has enormous development potential for a thousand-fold higher storage density. This nanomechanical media developed almost no heat, takes up very little electricity and is shock resistant.

Currently, IBM is looking once on the SD memory card manufacturers who have interest in the use of technology and to their licensing. In conversations IBM is already, but wanted no potential counterparties. To reach the market should - provided they find partners - no more than takes two to three years.