report
1.8.7 ICT: Application Profile: Data Storage

Short application description

Data storage technologies include ‘solid-state' storage such as DRAM and Flash, and storage technologies with a mechanical component, including hard disk drives. Data storage applications include:

Computers(which would commonly contain both RAM and a hard disk drive)
Mobile Devices (in which the memory media is more likely to be a memory card, commonly Secure Digital (SD) format)
Portable media players (the first generation iPods used a hard disk drive produced by Toshiba, but later versions has switched to flash memory storage.)

There are a number of nanotechnology-based approaches to the development of data storage which are described in the technology sector report and which are briefly summarised here:

Magnetoresistive Random Access Memory (MRAM), in which each memory cell consists of two ferroelectric plates, sandwiching an insulating layer
Ferroelectric RAM (FeRAM), similar to DRAM but for the fact that a ferroelectric layer is substituted for the dielectric layer.
Resistive RAM (RRAM), in which a conduction path is created in a dielectric material
NRAM (Nanotube RAM), a trademark of Nantero, using the positing of carbon nanotubes to determine memory states.

Functional requirements

Functional requirements of data storage include the following:

Capacity

Capacity is a measure of the amount of data (in MB, megabytes) that can be stored on a given memory type. To give an example of a product currently on the market, Seagate currently sells hard disk drives with a memory capacity of 1 500 000 MB, or 1.5 terabytes (TB). SanDisk sells Flash memory with capacities of up to 16 GB for imaging and mobile applications, and sells solid state drives with up to 240 GB as hard disk drive replacements[1].

Memory Density

Memory density is a function of capacity and size, and is typically driven by the size of individual memory cells (and the amount of data that each cell can store). Multi-level cells enable the storage of multiple data bits per cell - Fujitsu reported Flash memory with 4 bits per cell in 2007[2].

Lifetime

The target lifetime of a data storage application is measured in read/write cycles (lifetimes expressed in years are sometimes used, but these are an average of the expected read/write cycles per day). Flash memory will degrade over time. Memory manufacturer Kingston Technology claims that it's Flash Multi-Level Cells last for 10,000 read/write cycles, and it's Single Level Cells for 100,000 cycles[3]. Alternative nanotechnology-based approaches, such as MRAM, should demonstrate improved endurance.

Read/Write Speed

As an electromechanical device, hard disk drives have a time lag between receiving an instruction to access memory and actually being able to read or write it (as the disk has to be rotated to the correct location, and the read/write head has to be moved). These delay times are usually measured in milliseconds. Solid state memory has much quicker access times.

Cost

As with many of the applications described in this report, cost is a function of the manufacturing efficiency and defect rate. The production of Flash memory is now a highly optimised process, which has demonstrated dramatic scaling improvements.

Volatility

Data storage is non-volatile if it maintains the contents of memory without power. The primary volatile memories currently in use are SRAM and DRAM. A ‘universal memory' would combine the speed of SRAM and DRAM with non-volatility.

Boundary conditions

Whilst CMOS compatibility is not per se a boundary condition for all data storage applications, it is an important factor in ensuring ease of integration and cost effectiveness of manufacturing.

Product examples

Everspin MRAM

Freescale Semiconductor released a 4Mb MRAM product in 2006, which is believed to be the first commercially available MRAM product, and which won a number of awards at that time. At the beginning of 2008, an MRAM module was included in a magnetometer subsystem on a Japanese satellite. The selection of MRAM seems to have been influenced by its greater endurance and extended temperature operation[4]. Subsequently, Freescale's MRAM business was spun out to form a new company, Everspin[5].

Economic Information and Analysis

A 2005 study by NanoMarkets projected that nanotechnology-enabled storage devices would be a $65,7bn market by 2012[6]; accounting for 40% of the total memory market.

Relatively few nanotechnology enabled storage technologies are know to be available at this time.

Selected Key Companies Profiles

Ramtron

Ramtron (http://www.ramtron.com/) sells FeRAM products and integrated solutions for a number of applications areas, including automotive, computing, and metering.

Nantero

Nantero (http://www.nantero.com) develops NRAM, a registered trademark of the company. NRAM was developed by Thomas Rueckes, who is currently the CTO of the company. Nantero has developed a number of prototype devices, including one with an array of 10 million nanotube junctions. The company has priorities compatibility with existing semiconductor manufacturing processes.

Crocus Technology

Crocus (http://www.crocus-technology.com) claims to have addresses a number of the problems associated with MRAM, including thermal sensitivity. The company is currently moving from a development to early commercialisation stage. Crocus has locations in Silicon Valley and Grenoble.

[1] http://www.sandisk.com

[2] http://www.fujitsu.com/downloads/EDG/binary/pdf/find/25-1e/3.pdf

[3] http://www.kingston.com/products/pdf_files/FlashMemGuide.pdf

[4] http://media.freescale.com/phoenix.zhtml?c=196520&p=irol-newsArticle&ID=1111857&highlight=

[5] http://www.eetasia.com/ART_8800528389_499486_NT_49445c1e.HTM

[6] NanoTechWire, http://nanotechwire.com/news.asp?nid=1059&ntid=123&pg=11