Magnetic RAM: The Universal Memory

Magnetic RAM: The Universal Memory

Overview

• Introduction

• Historical perspective

• Technical Description

• Challenges

• Principals

• Market impacts

• Summary

Overview

Introduction

Historical Perspective

Technical Description

Challenges / Constraints

Principals

Market

Summary

Introduction

• Non-volatile– Information is saved even when there is

no power• Immediate boot up

– No need to wait for your computer to boot up

• MRAM, SRAM and DRAM– MRAM is potentially capable of replacing

both DRAM, SRAM and many advantages over technology currently used in electronic devices

Overview

Introduction




Principals

Market

Summary

Introduction • DRAM

– Advantages: cheap– Disadvantages: Comparatively slow

and loses data when power is off• SRAM

– Advantages: fast – Disadvantages: cost up to 4 times as

much as DRAM loses data when power is off

• Flash memory– Advantages: save data when power is

off– Disadvantages: saving data is slow and

use lot of power

Overview

Introduction




Principals

Market

Summary

Historical Overview• Why MRAM Became an Important Research Topic

– Universal Memory (Computing & Electronics)

– “Instant-On” Computing

– Read & Write to Memory Faster

– Reduced Power Consumption

– Save Data in Case of a Power Failure

• Modern MRAM Technology Emerged from Several Technologies :– Magnetic Core Memory

– Magnetoresistive RAM

– Giant Magnetoresistance

Overview

Introduction




Principals

Market

Summary

Magnetic Core Memory• In 1953 a team at MIT called Whirlwind

introduced the magnetic core memory

• Magnetic core memory utilized arrays of thousands of small ring magnets threaded with wires

• Data bits were stored and manipulated by sending electric current pulses through the magnets

• Magnetic cores were the most reliable and inexpensive memories for almost twenty years

Photo Courtesy: Magnetism Group, Trinity College, Dublin

Overview

Introduction




Principals

Market

Summary

Giant Magnetoresistance Materials

Overview

Introduction




Principals

Market

Summary

• Giant Magnetoresistance Materials (GMR) were discovered in 1989

• By 1991 GMR technology provided a magnetoresistance ratio of 6% (3 times that provided by previous technologies)

• Read access time of 50 ns (9 times improvement)

• Still not as fast as semiconductor memory

• Large size because lines of 1micron were required

Technical Overview

Overview

Introduction




Principals

Market

Summary

• 3 MRAM Technologies are Currently Being Developed– Hybrid Ferromagnet Semiconductor Structures

– Magnetic Tunnel Junctions

– All-Metal Spin Transistors & Spin Valves

• Writing Data to a Cell is Similar for all 3 Technologies

• Reading a Cell’s Data Reads the Direction of Magnetization of a Ferromagnetic Element, but the Method Varies for Each Technology

Basic Principles

Overview

Introduction




Principals

Market

Summary

• The 2 Possible Magnetization States of a Ferromagnetic Element can be Described by a Hysteresis Loop

• Magnetization of Film vs. Magnetic Field

Diagram Courtesy: IEEE Spectrum

• A magnetic field, with magnitude greater than the switching field, sets magnetization in direction of applied field

Writing a Bit

Overview

Introduction




Principals

Market

Summary

• MRAM Utilizes a Wire Directly Over & Magnetically Coupled to the Magnetic Element

• A Current Pulse Traveling Down the Wire Creates a Magnetic Field Parallel to the Wire

• Each Cell is Inductively Coupled with a Write Wire From a Row & a Column

Diagram Courtesy: IBM

Hybrid Ferromagnet Semiconductor Structures

Overview

Introduction




Principals

Market

Summary

• A Ferromagnetic Element is Placed Directly Over a Semiconducting Channel

• The Fringe Field has a Large Component Perpendicular to the Plane of the Channel


Magnetic Tunnel Junctions

Overview

Introduction




Principals

Market

Summary

• 2 Ferromagnetic Films Separated by a Dielectric Tunnel Barrier

• Resistance Between Films Depends on their Magnetic States

• Parallel Fields: Low Resistance

• Antiparallel Fields: High Resistance


Comparison

Overview

Introduction




Principals

Market

Summary

• Hybrid Ferromagnet Semiconductor:– Problems with Cross-Talk Between Cells

– Compatable with Standard CMOS Processing

• Magnetic Tunnel Junction– Fabrication Requirements Cause Problems with

Operating Margins and Yields

– Not Compatable with Standard CMOS Processing

• All-Metal Spin Valve– Low Impedance, Low Readout Voltage

– Not Compatable with Standard CMOS Processing

Current Challenges

• Interference

• Manufacturing

• Uniformity

• Power efficiency

• Size

Overview

Introduction




Principals

Market

Summary

Interference

-Interference between adjacent cells

-Disturbance by digit line current to adjacent line current

-The effect of heat cause bit flip

Overview

Introduction




Principals

Market

Summary

Manufacturing

• As chips get smaller the individual circuits hold less of the charge

• Risks of leaking current and other problems

• Hard to integrate with other silicon-based chips

• The resistance of the magnet device varies exponentially with it thickness

Overview

Introduction




Principals

Market

Summary

Uniformity

-Distribution of the electromagnetic field

Overview

Introduction




Principals

Market

Summary

Power efficiency

• High Current consumption– MRAM designs required a relatively

high current to write each single bit

• Power consumption is significantly greater than DRAM, only 99% of the total power is used in delivering electric current for writing data

• One transistor is required for each memory bit

Overview

Introduction




Principals

Market

Summary

The Players

Overview

Introduction




Principals

Market

Summary

• Principal Players:

• Additional Players:– Bosch - Hewlett-Packard

– Intel - NVE Corporation

– Siemens - Sony

– Toshiba

Impacts on Broader Society

Overview

Introduction




Principals

Market

Summary

• Engineers / Scientists– Designing MRAM

– Designing Hardware/Software that Interacts with MRAM

– New Memory Standards

• Society– Added Convenience

• Longer Battery Life on Portable Electronics

• “Instant-On” Computing

– Higher Productivity• Data not Lost in Power Failure

• Faster Read & Write

Market impacts

• Huge demand of memory– MRAM is expected to be the standard

memory

• The market size was $21 billion in 1999 when DRAM came out

• $48 billion in 2001• $72 billion within 2007 with

MRAM

Overview

Introduction




Principals

Market

Summary

Market analysis

• IBM being the leader in the development of MRAM is chase by:

• Motorola

• Intel

• Siemens

• Toshiba

Overview

Introduction




Principals

Market

Summary

Next 5 years

• IBM and Infineon are planning the mass production for 2004

• MRAM will become the standard memory for the next couple of year

• MRAM will be use in other devices

Overview

Introduction




Principals

Market

Summary

I&O long term

• Digital camera• Cellular phones• PDA• Palm pilot• MP3• HDTV

Overview

Introduction




Principals

Market

Summary

Quality of life impacts

• MRAM will eliminate the boot up time• Electronic devices will be more power

efficient• It could enable wireless video in cell

phones• More accurate speech recognition• MP3, instead of hundred on songs,

MRAM will enable thousand of songs and movies

Overview

Introduction




Principals

Market

Summary

• Importance– Potentially Substantial Impact on Society

– Potentially Central to Computers and Electronics that Engineers are Designing

• The Future of MRAM– Expected to Replace SRAM, DRAM, & FLASH

– Predicted to be the Memory Standard in both Computers & Consumer Electronics

• Indicators of a Breakthrough– Price of MRAM is Equivalent to or Only Slightly

More than DRAM & FLASH

– MRAM is More Common in New PCs than DRAM & More Common in New Electronics than FLASH

Summary

Overview

Introduction




Principals

Market

Summary

• Bonsor, Kevin. How Magnetic RAM Will Work. 9 Feb 2003. <http://computer.howstuffworks.com/mram.htm>.

• Daughton, James. Magnetoresistive Random Access Memory (MRAM). 4 Feb 2000. 1-13. 13 Feb 2003. <http://www.math.uwaterloo.ca/~m2wang/cs690b/mram.pdf>.

• Goodwins, Rupert. Magnetic Memory Set to Charge the Market. ZDNet UK. 12 Feb 2003. 16 Feb 2003. <http://techupdate.zdnet.co.uk/story/0,,t481-s2130312,00.html>.

• Guth, M., Schmerber, G., Dinia, A. “Magnetic Tunnel Junctions for Magnetic Random Access Memory Applications.” Materials Science and Engineering. Online 2 Jan 2002: 19. Science Direct. 16 Feb 2003. <http://www.sciencedirect.com>.

• IBM Magnetic RAM Images. 16 Feb 2003. <http://www.research.ibm.com/resources/news/20001207_mramimages.shtml>.

• Johnson, Mark. “Magnetoelectronic memories last and last.” IEEE Spectrum 37 (2000 Feb): 33-40.

References

Overview

Introduction




Principals

Market

Summary

Documents

Magnetic RAM: The Universal Memory