Magnetic RAM: The Universal
Memory
Overview
Overview
Introduction
Historical
Perspective
Technical
Description
Challenges /
Constraints
Principals
Market
Summary
•
•
•
•
•
•
•
Introduction
Historical perspective
Technical Description
Challenges
Principals
Market impacts
Summary
Introduction
Overview
Introduction
Historical
Perspective
Technical
Description
Challenges /
Constraints
Principals
Market
Summary
• 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
Introduction
Overview
Introduction
Historical
Perspective
Technical
Description
Challenges /
Constraints
Principals
Market
Summary
• 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
Historical Overview
Overview
Introduction
• Why MRAM Became an Important Research Topic
– Universal Memory (Computing & Electronics)
– “Instant-On” Computing
Historical
Perspective
– Read & Write to Memory Faster
Technical
Description
– Save Data in Case of a Power Failure
– Reduced Power Consumption
• Modern MRAM Technology Emerged from
Challenges /
Several Technologies :
Constraints
– Magnetic Core Memory
Principals
– Magnetoresistive RAM
Market
– Giant Magnetoresistance
Summary
Magnetic Core Memory
Overview
Introduction
Historical
Perspective
Technical
Description
Challenges /
Constraints
Principals
Market
Summary
• 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
Giant Magnetoresistance
Materials
Overview
• Giant Magnetoresistance Materials (GMR) were
Introduction
discovered in 1989
Historical
• By 1991 GMR technology provided a
Perspective
magnetoresistance ratio of 6% (3 times that
provided by previous technologies)
Technical
Description
• Read access time of 50 ns (9 times improvement)
Challenges / • Still not as fast as semiconductor memory
Constraints
• Large size because lines of 1micron were
Principals
required
Market
Summary
Technical Overview
Overview
• 3 MRAM Technologies are Currently Being
Introduction
Developed
Historical
Perspective
Technical
Description
– Hybrid Ferromagnet Semiconductor Structures
– Magnetic Tunnel Junctions
– All-Metal Spin Transistors & Spin Valves
• Writing Data to a Cell is Similar for all 3
Technologies
Challenges /
•
Reading
a
Cell’s
Data
Reads
the
Direction
of
Constraints
Magnetization of a Ferromagnetic Element, but
Principals
the Method Varies for Each Technology
Market
Summary
Basic Principles
Overview
• The 2 Possible
Introduction
Magnetization States
of a Ferromagnetic
Historical
Element can be
Perspective
Described by a
Technical
Hysteresis Loop
Description
• Magnetization of Film
Challenges /
vs. Magnetic Field
Constraints
Principals
Market
Summary
Diagram Courtesy: IEEE Spectrum
• A magnetic field, with magnitude greater than the
switching field, sets magnetization in direction of
applied field
Writing a Bit
• MRAM Utilizes a Wire Directly Over &
Overview
Magnetically Coupled to the Magnetic Element
Introduction • A Current Pulse Traveling Down the Wire
Creates a Magnetic Field Parallel to the Wire
Historical
Perspective • Each Cell is Inductively Coupled with a Write
Wire From a Row & a Column
Technical
Description
Challenges /
Constraints
Principals
Market
Summary
Diagram Courtesy: IBM
Hybrid Ferromagnet
Semiconductor Structures
• A Ferromagnetic Element is Placed Directly
Over a Semiconducting Channel
Introduction
• The Fringe Field has a Large Component
Historical
Perpendicular to the Plane of the Channel
Overview
Perspective
Technical
Description
Challenges /
Constraints
Principals
Market
Summary
Diagram Courtesy: IEEE Spectrum
Magnetic Tunnel
Junctions
• 2 Ferromagnetic Films Separated by a Dielectric
Overview
Tunnel Barrier
Introduction • Resistance Between Films Depends on their
Magnetic States
Historical
Perspective • Parallel Fields: Low Resistance
Technical
• Antiparallel Fields: High Resistance
Description
Challenges /
Constraints
Principals
Market
Summary
Diagram Courtesy: IEEE Spectrum
Comparison
Overview
Introduction
Historical
Perspective
Technical
Description
Challenges /
Constraints
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
Overview
Introduction
Historical
Perspective
Technical
Description
Challenges /
Constraints
Principals
Market
Summary
•
•
•
•
•
Interference
Manufacturing
Uniformity
Power efficiency
Size
Interference
Overview
Introduction
Historical
Perspective
Technical
Description
Challenges /
Constraints
Principals
Market
Summary
-Interference
between adjacent
cells
-Disturbance by
digit line current to
adjacent line current
-The effect of heat
cause bit flip
Manufacturing
Overview
Introduction
Historical
Perspective
Technical
Description
Challenges /
Constraints
Principals
Market
Summary
• 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
Uniformity
Overview
Introduction
Historical
Perspective
Technical
Description
Challenges /
Constraints
Principals
Market
Summary
-Distribution of the electromagnetic field
Power efficiency
Overview
Introduction
Historical
Perspective
Technical
Description
Challenges /
Constraints
Principals
Market
Summary
• 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
The Players
Overview
• Principal Players:
Introduction
Historical
Perspective
Technical
Description
Challenges /
Constraints
Principals
Market
Summary
• Additional Players:
–
–
–
–
Bosch
Intel
Siemens
Toshiba
- Hewlett-Packard
- NVE Corporation
- Sony
Impacts on Broader
Society
Overview
Introduction
Historical
Perspective
Technical
Description
Challenges /
Constraints
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
Overview
Introduction
Historical
Perspective
Technical
Description
Challenges /
Constraints
Principals
Market
Summary
• 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
Market analysis
Overview
Introduction
Historical
Perspective
Technical
Description
Challenges /
Constraints
Principals
Market
Summary
• IBM being the leader in the
development of MRAM is chase by:
• Motorola
• Intel
• Siemens
• Toshiba
Next 5 years
Overview
Introduction
Historical
Perspective
Technical
Description
Challenges /
Constraints
Principals
Market
Summary
• 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
I&O long term
Overview
Introduction
•
Historical
Perspective •
•
Technical
Description •
Challenges / •
Constraints
•
Principals
Market
Summary
Digital camera
Cellular phones
PDA
Palm pilot
MP3
HDTV
Quality of life impacts
Overview
Introduction
Historical
Perspective
Technical
Description
Challenges /
Constraints
Principals
Market
Summary
• 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
Summary
Overview
Introduction
Historical
Perspective
Technical
Description
Challenges /
Constraints
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
References
Overview
Introduction
Historical
Perspective
Technical
Description
Challenges /
Constraints
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_mrami
mages.shtml>.
• Johnson, Mark. “Magnetoelectronic memories last and last.”
IEEE Spectrum 37 (2000 Feb): 33-40.