Flash memory lasts lifetime
Flash memory chips with a potential lifetime of hundreds of years have been developed by Japanese scientists.
The new chips also work at lower voltages than conventional chips, according to the scientists from the National Institute of Advanced Industrial Science and Technology and the University of Tokyo.
Flash memory chips are widely used in products such as Apple’s iPhone, mini notebooks like the Asus Eee PC, video games consoles such as the Nintendo Wii, flash memory cards, digital cameras and Flash-based SSD hard disk drives.
Current Flash chips are estimated to have a useful lifetime of around a decade for most applications.
However, some applications that require repeated writing and rewriting of data can theoretically cause cells to wear out much faster, sometimes rendering a Flash device useless within a few years.
This can happen when a large area of Flash memory is used as a swap file or virtual memory, or to store constantly updated log files.
The continuing miniaturisation of conventional Flash memory chips also threatens to reduce their lifetime.
This and other factors make conventional high-density Flash cells unworkable at circuit sizes below 20 nanometres, the scientists claim.
The new ferroelectric Nand Flash memory cell developed by the Japanese scientists can be scaled down to at least 10 nanometres. The next generation of conventional flash cells will use a 30 nanometre circuit density.
The ferroelectric Flash memory cell can be rewritten more than 100 million times, compared to a conventional cells lifetime of around 10,000, its inventors claim.
To prolong their life Flash memory chips use a ‘wear-levelling’ process in which all cells are used equally, and worn out cells are ‘retired’ without disabling the whole chip.
The ferroelectric cells use a rewriting voltage of fewer than six volts, compared to about 20 volts for conventional chips.