+ All Categories
Home > Documents > Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of...

Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of...

Date post: 14-Mar-2018
Category:
Upload: lamhuong
View: 217 times
Download: 2 times
Share this document with a friend
31
TM Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006. September 20, 2007 Technical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon Slaughter Manager, MRAM Magnetic Materials and Process Integration
Transcript
Page 1: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TM

Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

September 20, 2007

Technical Overview of Magnetoresistive Random Access Memory (MRAM)DISKCON USA 2007 , Santa Clara, California

Jon SlaughterManager, MRAM Magnetic Materials and Process Integration

Page 2: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Outline

Overview of Toggle MRAM WritingReadingReliabilityExtended temperaturesScalingSummary

Page 3: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

MRAM Advantages

Nonvolatile

Fast

Unlimited Cycling

Modular Integration

Highly Reliable

Extended Temperatures

Data Retention - ≥ 20 years

Symmetrical Read/Write – 35ns

Unlimited Endurance - ≥ 1016

Easily Integrates in Back EndCompatible with Embedded Designs

-40 ºC < T < 150 ºC Operation Demonstrated

Intrinsic Reliability Exceeds 20 Year Lifetime at 150 ºC Continuous Use

Page 4: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

First Commercial MRAM now in Volume Production

4 Mb Toggle MRAM • 35ns symmetrical read/write• Unlimited endurance• Data retention > 20 Years• 256Kx16bit organization• 3.3V single power supply• Fast SRAM pinout• Consumer temperature range(0 °C – 70 °C)

• Extended Industrial temperature range(-40 °C – 105 °C)

Available now

Page 5: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

How MRAM Works

ON for sense OFF for

program

MTJ

iref

Write Line 2

Write Line 1

i

i

isense

Information stored as magnetic polarization

• Detected as a resistance state

Isolation transistor can be logic device, no high on/off ratio needed

Page 6: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

4 Mb MRAM bit cell

Metal 4

MTJ

MRAM module

Contact

Via 1

Metal 2

Via 2

Metal 4

Via 3

Metal 5

Metal 3

Bit cell

Metal 1

Cu

Cu

Al

Al

Al

Metal 4

Metal 5

MTJ

Page 7: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Outline

Overview of Toggle MRAM WritingReadingReliabilityExtended temperaturesScalingSummary

Page 8: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Free Layer Field Response

H=0H=0

Conventional MRAMSingle Layer

H≠0

Toggle MRAMCoupled Trilayer

H=0 H≠0

Aligns with applied field Rotates perpendicularto applied field

pinned pinnedpinned pinned

Page 9: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Toggle Write Operation

I1

I2

High-RState

Low-RState H1

I1

H1 + H2

I2

H2

I2

I1

MTJ

pinned pinned

Advantages: Eliminates disturb - Large operating window

Page 10: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Toggle-bit Array Characteristics

4Mb, March-6N Toggle Map

No switch

100% toggle

Cur

rent

1

Cur

rent

1

No switching

No

switc

hing

SwitchingRegion

Bit SaturationCurrent 2Current 2

Page 11: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Outline

Overview of Toggle MRAM WritingReadingReliabilityExtended temperaturesScalingSummary

Page 12: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Read Distribution within an Array

14 15 16 17 18 190

500

1000

1500

2000

2500

#bits

Bit Resistance [kΩ]

Low State High State

σ~0.8%

∆R/σ = 30typical

Resistance of bits in a 4Mb array

10 nm

Optimized for MRAM

Critical Factors:1. Tunnel barrier quality2. Pattern fidelity

Critical Factors:1. Tunnel barrier quality2. Pattern fidelity

V1/2~+0.7/-0.55 V

Page 13: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Outline

Overview of Toggle MRAM WritingReadingReliabilityExtended temperaturesScalingSummary

Page 14: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Tunnel Junction Reliability: Read

LowState

HighState

Necessarymargin for

spec. read- out speed

Margin beforedrift

MarginafterdriftN

umbe

r of B

its @

RBit Resistance

1 10 100 1000 10000 1000000

1000

2000

3000

4000

5000

6000

7000

0.6V

0.8V1.0VT=175 C

Res

ista

nce

[Ω]

Time [s]

Dielectric Breakdown(catastrophic)

Resistance Drift(gradual)

Page 15: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Intrinsic Reliability vs. TemperatureMTJ failure modes as a function of address cycles

1E+15

1E+16

1E+17

1E+18

1E+19

1E+20

75 85 95 105 115 125

Average Junction Temperature (C)

Max

Cyc

les

/ Add

rMagnetic Bridging

20 year Continuous operation

Res DriftTJ TDDBEMMagn Bridging

1E+15

1E+16

1E+17

1E+18

1E+19

1E+20

75 85 95 105 115 125

Average Junction Temperature (C)

Max

Cyc

les

/ Add

rMagnetic Bridging

20 year Continuous operation

Res DriftTJ TDDBEMMagn Bridging

Res DriftTJ TDDBEMMagn Bridging

• Resistance Drift = Change in resistance of the magnetic cell materials (2% resistance change criteria)• TJ TDDB = Time Dependant Dielectric Breakdown of the Tunnel Junction Oxide• EM = Time to Failure by Electromigration in the copper write lines (10% resistance change criteria)• Magn bridging = Interlayer bridging in the magnetic materials that would cause the magnetic properties to change

Page 16: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

MRAM Endurance Cycling

0%

100%

1 100 10000 1000000 1E+08 1E+10 1E+12 1E+14

Number of Read/Write Cycles

Pass

ing

%

MRAM: Unlimited Read/Write Endurance

MRAM Endurance Tested to 58 Trillion Cycles with No Change in Critical Parameters.

Data from >2800 bits from 900 devices 8 orders of magnitude more cycles than current Flash technologyNo known failure modes are seen or expected.

Flash Capability

Page 17: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Outline

Overview of Toggle MRAM WritingReadingReliabilityExtended temperaturesScalingSummary

Page 18: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

OperatingRegion

T = 125 ºC

Non-SwitchingRegion

Bit Line Current

Dig

it Li

ne C

urre

nt

OperatingRegion

T = 125 ºC

Non-SwitchingRegion

Bit Line Current

Dig

it Li

ne C

urre

nt

Fiel

d (O

e)

0

50

100

150

200

250

300

0 50 100 150Temp (°C)

Hsat

Hsw

Write Operating Region at 125 °C

•Hsat, Hsw decrease linearly w/Temp, reducing window

Page 19: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Read Signal vs. Temperature

0.9 1 1.1 1.2 1.3Normalized Rcell

150 °C25 °C

“0” “1”

Less read margin at 150 °C, but distributions are still well separated

0

5

10

15

20

25

30

35

-50 0 50 100 150

MR

(%)

MR decreases with temperature

T (°C)

Page 20: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Read Speed with Temperature

Read access time strobe for temperatures-40 to 125 °C

Meets specifications over industrial temperature range

26 28 30 32 3410-1

100

101

102

103

104

105

106

107

Fail

bits

Access Time Strobe (ns)

0

T = -40 C

T = 125 C

Page 21: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Outline

Overview of Toggle MRAM WritingReadingReliabilityExtended temperaturesScalingSummary

Page 22: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Historical Trend of TMRRoom temperature TMR values reported in the literature

050

100150200250300350400450500

1994 1996 1998 2000 2002 2004 2006 2008

Year

TMR

at R

T (%

)

TohokuMIT

AnelvaSonyTohokuIBMFujitsu CNRS

MPI CSIC

AIST

AIST

AnelvaAlOx

Tunnel Barriers

MgOTunnel Barriers

Freescale

Tohoku & Hitachi

Freescale

IBMAIST

IBM

Page 23: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Read Margin with MgO Tunnel Barrier

0

5000

10000

15000

20000

25000

0.8 1 1.2 1.4 1.6 1.8 2Normalized Rcell

Num

ber o

f Bits

σ~1.5%

49 σ

“0” “1” Much higher MR with MgO replacing AlOx in tunnel barrier

• MR/σ = 2X AlOx

Demonstration in 4Mb circuit

AlOx → MgO

Page 24: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

MRAM Cell Integration in 90nm BEOL

Full integration of MgO-based MRAM devices with 90nm front end CMOS.

MRAM process with clad Cu write lines.

8 kb arrays of memory cells

Cell Size 0.29 µm2 –Linear shrink from 180nm

MTJ resistance of 1kohm-µm2

Toggle write characteristics

90nm CMOS

MRAM

0.29µm 2Bit CellIEDM 2005

Page 25: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Large Operating Window at 90nm

Effective operating

region

Operating region where the bit toggles when both write currents are over their threshold values.

Scalability of the toggle MRAM concept to 90nm is demonstrated.

Page 26: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Spin-Torque MRAM

∆S

IDC

Each spin flipproduces ∆S = ħ

free magnettunnel barrier

∆S∆t

= Torquefixed magnet

Jc ≈ 107 A/cm2Isolationtransistor

Advantages: Smaller cell size, lower write current

Page 27: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Distribution Considerations

Vswitch VbVread

σbσsσr

6*(σs+σb)

6*(σs+σr)

Spin-transfer MRAM

+/- Vswitch

Iswitch

Applied Voltage

• For Small Cell – Iswitch = Vswitch/Rcell must be <<1mA• Vswitch << Vbreakdown for good Endurance• Vread << Vswitch to avoid Disturb• Vread >> transistor mismatch requirement• 10 Yr Data Retention requires Eb / kbT ≥ 50

Page 28: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

High MR at Low RA MTJ Material

0

20

40

60

80

100

120

0 1 2 3 4 5 6 7RA (Ω-µm2)

MR

(%)

2 nm

X-TEM: MgO-based MTJ Stack

Fixed

Free

Best process gives good MR down to < 2 Ω-µm2

TMR vs. RA for Optimized Lowest-RA MTJ Material

MgO

Page 29: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Batch Fabrication of MgO Tunnel Junction Nanopillars

•200 mm Si wafer• Optical lithography: • 100 nm x200 nm bits

50 nm

SiO2

Top electrode

Bottom electrode

100nm

500nm 2 nm

RA (Ω−µm2) MR (%) IcP→AP (mA)

JcP→AP: ~4.5x106 A/cm2Quasistatic

Page 30: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.

Summary

• Advances in magnetic materials and devices have enabled in the first commercial MRAM

• Toggle MRAM is the only MRAM technology shipping today• High-performance, high-endurance and highly reliable non-

volatile memory• Extendable to industrial and automotive applications

-40 °C – 105 °C operation available now

• New materials and devices show the potential for advanced scaling and further performance improvements

• High TMR from MgO enables high-speed and scaling• Spin-Torque has potential to achieve high densities

Page 31: Technical Overview of Magnetoresistive Random Access ... · PDF fileTechnical Overview of Magnetoresistive Random Access Memory (MRAM) DISKCON USA 2007 , Santa Clara, California Jon

TM


Recommended