CD Laboratory for Nonvolatile Magnetoresistive Memory and Logic

The continuous miniaturisation of semiconductor devices is accompanied by an enormous increase in power consumption, even in standby mode. This CD Laboratory is researching alternative magneto-resistive memory forms as an energy-saving approach.

The continuous miniaturisation of semiconductor devices has been one of the driving forces in increasing the speed and performance of modern electronic circuits and is known as Moore's Law. However, due to small device sizes and increasing leakage current, power consumption in standby mode is growing and becoming comparable to that in active mode, which now seems to have reached a limit of miniaturisation. Furthermore, high performance is required in large data centres not only for efficient data processing, but also for memory data transfer. All this runs counter to global efforts to reduce power consumption and new approaches are urgently needed. In terms of reducing power consumption in standby mode, non-volatility in main memory and caches, which are fast buffer memories, is a very attractive solution. Non-volatile data storage refers to various data storage devices whose stored information is retained even when the computer is not in operation or is not supplied with power. Examples include hard drives, CDs, DVDs, flash memory or magnetic-resistive memory. Devices that use such memories are ready for operation as soon as they are switched on and do not have to load the data required for operation from a read-only memory into the main memory; the associated energy requirement is eliminated.

Magnetic tunnel contacts are such magnetoresistive memories and are considered excellent candidates for the realisation of energy-saving approaches. They are manufactured using thin-film technology, whereby the individual layers are only a few atomic layers thick at around 1 nm or less. The magnetisation can be permanently poled to "0" or "1" and thus store data independently of the power supply. They have a simple structure, long retention time, high continuous power and fast operating speed and enable a high integration density. Integration density refers to the number of transistors per unit area on integrated circuits.

For the ultimate success of magnetoresistant memories, it is particularly important to integrate them into the main memory and the caches. However, high switching currents and energy-intensive write operations compromise the benefits of non-volatility. Approaches to solving the problem include vertically arranged magnetic tunnel contacts, decoupling write and read paths, controlling magnetisation by voltage and using new materials. However, there is currently no simulation software for magnetoresistant memories, as there is with TCAD (technology computer-aided design) in semiconductor simulation. The lack of models and simulators is slowing down the broad application of non-volatile technology. This CD Laboratory will now develop the simulation capabilities central to the success of the magnetoresistive memory element and will serve as a key player for future generations of electronic devices.