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1 24 August 2004 Magnetic Random Access Memory (MRAM) Jimmy Zhu ABB Professor in Engineering Department of Electrical and Computer Engineering Carnegie Mellon University J. Zhu, 18-200 Lecture, Fall 2004 2 Computer System Computer System Disk Drive CPU SRAM TLB SRAM DRAM L1 Cache L2 Cache Main Memory Archival Memory Volatile Memory Non-Volatile Memory
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Page 1: Magnetic Random Access Memory (MRAM ... - …jzhu/class/18200/F04/Lecture05_18200... · 1 24 August 2004 Magnetic Random Access Memory (MRAM)Magnetic Random Access Memory (MRAM) Jimmy

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24 August 2004

Magnetic Random Access Memory (MRAM)Magnetic Random Access Memory (MRAM)

Jimmy ZhuABB Professor in Engineering

Department of Electrical and Computer EngineeringCarnegie Mellon University

J. Zhu, 18-200 Lecture, Fall 2004 2

Computer SystemComputer System

DRAM

SRAM

Disk Drive

CPU

SRAM

TLB

SRAM

DRAM

L1 Cache

L2 Cache

Main Memory

Archival Memory

Volatile Memory

Non-Volatile Memory

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J. Zhu, 18-200 Lecture, Fall 2004 3

Static RAM (SRAM)

6-Transistor CMOS SRAM Access time: < 1 ns

Expensive:

Fast:

Cache Memory

$100 / MByte

Low Density:

>120 F2

F -- minimum fabrication feature size

= 10-9 second

J. Zhu, 18-200 Lecture, Fall 2004 4

Field Effect Transistor (FET)

symbol

D

S

G Source

Gate

Drain n+n+ p

n-channel FET

Conducting metal plate

Insulating oxide layer

Semiconductor

Conducting ground

MOSFET: Metal-Oxide-semiconductor-FET

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J. Zhu, 18-200 Lecture, Fall 2004 5

electron with charge –e

http://www.pbs.org/transistor/science/info/transmodern.html

TGG VV >

Source

Gate

Drain

n+n+

++ + + + + + +

DI

p

DDV

GGV

n-channel FET

S D

G

Active condition:

TGS VV >i.e.

S

D

GDR

DDV

Drain current will be a function of gate voltage.

Di

How a FET Works: Transistor On

J. Zhu, 18-200 Lecture, Fall 2004 6

How a FET Works: Transistor Off

Source

Gate

Drain n+n+ p

electron with charge –e

No current

S

DG

DDD VV =

DR

DDV

TGS VV <

S

D

Gthreshold voltage TV

Cutoff condition:

Zero Drain current.

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J. Zhu, 18-200 Lecture, Fall 2004 7

A Modern CMOS ProcessA Modern CMOS Process

p-well n-well

p+

p-epi

SiO2

AlCu

poly

n+

SiO2

p+

gate-oxide

Tungsten

TiSi2

DualDual--Well TrenchWell Trench--Isolated CMOS ProcessIsolated CMOS Process

VDD

Vin Vout

M1

M2

J. Zhu, 18-200 Lecture, Fall 2004 8

Dynamic RAM Dynamic RAM

Individual access time 60 ns+++ + ++ +

−−−−−−−

CQV =

0=V

State “1”

State “0”

Main Computer Memory

All “1”s need to be refreshed every 1 ms.

$4 /MByte

10 F2

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J. Zhu, 18-200 Lecture, Fall 2004 9

Rotational Latency

7,500 – 15,000 rpm

sector

track

• Average latency: 3 – 6 ms

• Wait until desired sector passes under head

Rotational Latency

• Worst case: a complete rotation 7,500 rpm = 8 ms

15,000 rpm = 4 ms

Inexpensive: $0.001/1MByte

J. Zhu, 18-200 Lecture, Fall 2004 10

Hard Disk Drives

Magnetic Force Microscopy Image of A Disk Surface

18-316 Introduction to Data Storage

18-517 Data Storage Systems Design

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J. Zhu, 18-200 Lecture, Fall 2004 11

1E-9 1E-8 1E-7 1E-6 1E-5 1E-4 1E-3

1E-3

0.01

0.1

1

10

100

HDD

DRAMPr

ice

Per M

Byte

($)

Access Time (second)

SRAM

Price vs. Speed Price vs. Speed

J. Zhu, 18-200 Lecture, Fall 2004 12

Computer System on a Chip?Computer System on a Chip?

Can one change the disk drive into a high speed memory chip?

DRAM

SRAM

Disk Drive

CPU

SRAM

TLB

SRAM

DRAM

If one can, one can put the entire computer system on a single chip:

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J. Zhu, 18-200 Lecture, Fall 2004 13

Control Data Corp. 1Kbits Ferrite Core Memory

1965

Motorola4Mbits MRAM Chip

Magnetic tunnel junction 2003

Magnetic RAM: Historical Perspective

Honeywell 16Kbits MRAM ChipAMR Technology 1994

J. Zhu, 18-200 Lecture, Fall 2004 14

Remember Magnet !Remember Magnet !

Magnetic moment can maintain its direction without power !

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J. Zhu, 18-200 Lecture, Fall 2004 15

Tunnel barrier

CoFe/Al2O3 (7-20Å) /Co

Magnetic electrode

m1

m2

Magnetic electrode

Magnetic Tunnel Junction (MTJ)

Memory Element

0 20 40 60 80 1000.0

0.5

1.0

1.5

2.0

2.5

Res

ista

nce

(kΩ

)

Data Bits

State “0” State “1”

J. Zhu, 18-200 Lecture, Fall 2004 16

Memory ArrayMemory Array

“L” “L” “L” “L”

“L”

“H”

“H”

“L”

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J. Zhu, 18-200 Lecture, Fall 2004 17

Detailed Structure

Magnetic moments are fixed.

State “0” State “1”

Only the magnetic moment of a storage layer is switched back and forth.

J. Zhu, 18-200 Lecture, Fall 2004 18

Writing Bits Writing Bits

I

Hr

I IState “0” State “1”

H

M

Mr

Mr

State “0”

State “1”

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J. Zhu, 18-200 Lecture, Fall 2004 19

X-Point Addressing X-Point Addressing

I

half-select elements

x

y

I

-1.0 -0.5 0.0 0.5 1.0

-1.0

-0.5

0.0

0.5

1.0

Y-C

ompo

nent

Fie

ld (H

k)X-Compone Field (Hk)

3/23/23/2yxk HHH +=

J. Zhu, 18-200 Lecture, Fall 2004 20

MRAM Cell

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J. Zhu, 18-200 Lecture, Fall 2004 21

4 Mbits MRAM Chip4 Mbits MRAM Chip

Freescale 4Mbits MRAM Chip

J. Zhu, 18-200 Lecture, Fall 2004 22

MRAM: Dream Memory?MRAM: Dream Memory?

Advantages of MRAM:

Nonvolatile (No power needed to maintain memory states)

SRAM Speed (~ 1 nanosecond )

DRAM Density (~ 20 F2 )

Endurance (Infinitely rewritable)

MRAM has the potential to be an universal memory to replace SRAM, DRAM, FLASH, and disk drives in some applications to become the

Universal Solid-State Memory!

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J. Zhu, 18-200 Lecture, Fall 2004 23

A Potential Game ChangerA Potential Game Changer

If MRAM replaces SRAM, DRAM or even disk drives:

Instant on systems: No booting from disk drive

Minimum stand-by power (Turn it off!)

Enable computer system to be integrated on a single chip!

J. Zhu, 18-200 Lecture, Fall 2004 24

Applications

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J. Zhu, 18-200 Lecture, Fall 2004 25

System on Chip (SoC)System on Chip (SoC)

Function Module

Computing (processing)

Memory

NV Memory

Example:

RF Module

Data Processing

Memory

SoC

J. Zhu, 18-200 Lecture, Fall 2004 26

MRAM: Dream Memory?MRAM: Dream Memory?

Present MRAM Technology Shortfalls:

Relatively high power dissipation (high current)

Down-size scaling not clear (thermal magnetic stability)

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J. Zhu, 18-200 Lecture, Fall 2004 27

X-Point Addressing X-Point Addressing

I

half-select elements

x

y

I

-1.0 -0.5 0.0 0.5 1.0

-1.0

-0.5

0.0

0.5

1.0

Y-C

ompo

nent

Fie

ld (H

k)X-Compone Field (Hk)

3/23/23/2yxk HHH +=

99.999% of power is dissipated as I2R on the write lines!

J. Zhu, 18-200 Lecture, Fall 2004 28

Digital Line with cladding

Word Line with Cladding

Read Transistor

Magnetic Cladding (18-303 Electromagnetics)

x 5

The main power consumption arises from the ohmic dissipation, I2R, in word/digital lines.

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J. Zhu, 18-200 Lecture, Fall 2004 29

Thermally Activated Reversal

08.0 xx HH =

Hx

t2 ns

τrise= 0.3 ns

0.2 µm

0.1 µm

E

Angle

J. Zhu, 18-200 Lecture, Fall 2004 30

The Potential Universal Memory

SRAM DRAM Disk Drive FLASH

Speed

MRAM

Cost

Density

Cyclability

Non-volatility

Power consumption

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J. Zhu, 18-200 Lecture, Fall 2004 31

MRAM: The enabling technology for computer systems on a single chip!

Only Continued Innovation Will Ensure Future Competitiveness of MRAM

Conclusions

J. Zhu, 18-200 Lecture, Fall 2004 32

Data Storage Systems Track

18-220

18-30318-316

18-517

18-396

Eng. ElectromagneticsIntro. to Data Storage Tech.

Data Storage Sys. Design18-715

18-716

Signal & Sys.

Physics of Appl. Magn.

Advanced Appl. Magn.

Fundamentals of E.E.

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J. Zhu, 18-200 Lecture, Fall 2004 33

Building a Virtual Disk Drive using MATLAB/SIMULINKBuilding a Virtual Disk Drive using MATLAB/SIMULINK

Equalizer

Detector

Data to be recorded Retrieved signal

Recovered data

18-517 Data Storage Systems Design

J. Zhu, 18-200 Lecture, Fall 2004 34

18-315 Fall 2004

Introduction to Optical Communication Systems

Professor Jimmy Zhu

Course Objective:Provide a basic understanding of present optical communication systems and components, as well as future engineering challenges.

[email protected]

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J. Zhu, 18-200 Lecture, Fall 2004 35

1 8 5 0 1 9 0 0 1 9 5 0 2 0 0 0 2 0 5 011 01 0 01 k1 0 k1 0 0 k1 M1 0 M1 0 0 M

1 G1 0 G1 0 0 G1 T1 0 T1 0 0 T1 P

Bandwidth Explosion

Dat

a R

ate

Cap

acity

(bi

ts/s

econ

d)

Year

Voice-centric Network

Doubles every 4.7 years

Doubles every 9 months

Data-centric Network(Optical)

Fiber

WDM

DWDM

Coax

Telephone

Telegraph

Video on demand

World wide web

O.S.

Source: Agilent Technologies

J. Zhu, 18-200 Lecture, Fall 2004 36

FactsA single optical fiber is capable of transmiting 2x1012 bits of data per second, which is equivalent to

simultaneously carry more than 30,000,000 phone conversations, or

200,000 users download (upload) information at 10 Mbits/second data rate at same time, or

download all 380 CDs (each with 1 hour long music) in 1 second , or

download 30 DVD movies in 1 second .

Present dense wavelength division multiplexing (DWDM) technology is realizing the full potential of a single optical fiber !

A optical fiber cable may contain up to 200 fibers.

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J. Zhu, 18-200 Lecture, Fall 2004 37

Fiber-Optical Long-Haul Routes Source: KMI

J. Zhu, 18-200 Lecture, Fall 2004 38

Metro Optical NetworkSource: Nortel Networks e.g. 10 Gbits Ethernet

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J. Zhu, 18-200 Lecture, Fall 2004 39

Course Coverage

How light carries information Generation of lightLight traveling in a fiber Amplification of Light

FiberLEDSemiconductor lasersFiber AmplifiersOptical receiversOptical modulatorsOptical couplers and switches

Time Division Multiplexing (TDM)Wavelength Division Multiplexing (WDM)Optical networks

Light

Systems

Devices and Components

18-315 Introduction to Optical Communication Systems

Encoder Laser driver Amp. Decoder

Fiber receiverlaser

J. Zhu, 18-200 Lecture, Fall 2004 40

prepare students with up-to-date education ready for the optical communication and network industry.

Provide students sufficient background knowledge for further career development in optical communication systems and networks.

Stimulate students’ ability for innovation.

Train students’ problem analyzing and problem solving abilities.

This course is designed to:

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J. Zhu, 18-200 Lecture, Fall 2004 41

“A road to a world with no borders, no boundaries, no flags, no countries, where the heart is the only passport you carry.”

Carlos Santana

Future Optical Internet…


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