Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/.

Nonvolatile Memory Technology for Space Applications

Timothy R. Oldham1, Mark Friendlich2, Hak Kim2, Melanie Berg2, Jonathan A.

Pellish3 and Kenneth A. LaBel31. Dell-Perot Systems, Inc./NASA GSFC; 2. MEI,

Inc./NASA GSFC; 3. NASA

1

National Aeronautics and Space Administration

Sept 20, 2010

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/.

Acknowledgements

• NASA Electronic Parts and Packaging Program (Ken LaBel)

• DTRA Radiation Hardened Microelectronics Program (Bruce Wilson)

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/.

IntroductionNonvolatile Memories

• Flash (NAND, NOR)• Charge Trap• Nanocrystal Flash• Magnetic Memory (MRAM)• Phase Change--Chalcogenide, (CRAM)• Ferroelectric (FRAM)• CNT• Resistive RAM

3

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/. 4

Expected Impact to Community

• NVM has always been critical in some applications, e.g., critical flight data, and flight control software

• Solid state NVM starting to be used in SSR (Solid State Recorders), replacing volatile memories

• Solid state NVM has speed advantage over hard disk drives

• NAND flash has advantage over most alternatives in cost per bit—dominant commercial technology

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/.

5

Flash Background–Disadvantages• Slow programming• Wear out• Scaling/retention—running out of electrons–Advantages• Cost per bit• Low power

–Bottom Line: Heavily used in hand-held, battery-powered consumer electronics (cell phones, iPods, digital cameras, MP3)Low weight, low cost, low power are advantagesin space, too

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/.

Floating Gate Transistor

6

Control Gate

–p - body

–Source –Drain

–n+ –n+

Write (Program) operation—Fowler-Nordheim (FN)injection of electrons into FG (for NAND)

Erase operation—FN injection of electrons from FG to substrate

Repeated P/E operations cause damage to tunnel oxide

FG

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/.

7

Flash Architectures

–NAND –NOR

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/.

Flash Radiation Response

8

TID response frequently very good for NAND NOR TID not so good SEU bit error rate very good compared to most

volatile memories Control logic errors (SEFIs) are biggest problem,

mitigation strategies very important

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/. SEE

9

Calculated Avionics SER

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/.

–Floating Gate– SONOS–(oxide/nitride/oxide)

–Nanocrystal

–Thin Film Storage–Nonvolatile–Memories

Source Drain

Substrate

50 - 100Å Oxide

50 - 100Å Oxide

SiNanocrystal

"Immobile"Charges

Silicon NanocrystalCharge Storage Medium

(Isolated Conductors)

GatePoly

Source Drain

FloatingGate

ControlGate

Leakagepath dueto SILC,

etc.

Substrate

~ 100ÅTunnelOxide

Charges are mobile

Polysilicon ChargeStorage Medium

(Conductor)

ONOInterpolyDielectric

Substrate

Nitride

50 - 90Å Oxide

18 - 70Å Oxide

Immobile Charges

Source Drain

Nitride ChargeStorage Medium

(Insulator)

GatePoly

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/.

FG Post Radiation Annealing

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/.

NC Post Radiation Annealing

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/. 13

Evaluation of Non-Volatile Memory Goals

Utilize flash memories as test vehicles for radiation effects understanding of scaled CMOS

Characterize advanced hardened and unhardened nonvolatile memories. This includes:

New materials New technologies and

architectures Current flash operate at

3.3V, 40 MHz Increase speed with new

45 nm (16G SLC) Identify new failure modes—

including combined effects Develop new test methods

and identify mitigating strategies

New failure modes

1E-10

1E-09

1E-08

1E-07

1E-06

1E-05

0.0001

0.001

0.01

0.1

1

0 50 100

Cro

ss s

ectio

n (c

m2 /d

evic

e)

Effective LET (MeVcm2/mg)

SEFI X-Sec 840 TransientDestructive 840 Static843 Transient 843 Static846 Transient 846 Static901 Transient 901 Static907 Transient

1.00E-10

1.00E-09

1.00E-08

1.00E-07

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

0 10 20 30 40 50 60

Cro

ss s

ectio

n (c

m2 /d

evic

e)

Effective LET (MeVcm2/mg)

SEFI X-Sec

Static Bit Error X-Sec

Destructive

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/.

Nonvolatile Memory Evaluation Status

• Phase Change—samples obtained from Numonyx, SEE and TID testing performed

• STT-MRAM—Avalanche to supply test structures, TID proton test conducted

• CNT—LM to supply test structures, unclear when• FeRAM—TI, compare response of hardened and

unhardened versions• Cypress NVSRAM—samples received, laser test

planned• Unity—transistor-less RAM, to supply test

structures

14

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/.

Numonyx 4G NAND SEE Test Results

15

1.00E-10

1.00E-09

1.00E-08

1.00E-07

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

0 20 40 60 80 100C

ross

sec

tion

(cm

2 /dev

ice)

Effective LET (MeVcm2/mg)

SEFI X-Sec

Dynamic R/E/W BitError X-Sec

Destructive

One destructive event after 2.3x107 Xe ions/cm2,equivalent to 2.7x109 yearsin geosynchronous orbit SEU rate manageable, especially with EDAC SEFI impact unclear, mitigation required

–Not enough data to endorse for flight programs, yet,but initial results are promising

Highlights/Accomplishments

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/. 16

Reliability/Endurance StudySamsung 8G NAND after 106 P/E Cycles

0.0001

0.001

0.01

0.1

1

10

100

1000

10000

0 20 40 60 80 100 120

Aver

age

Erro

r Cou

ntpe

r 103

cycl

es

Dose (krads (SiO2))

BestMedianWorst

No clear indication that radiation exposure reduces flash endurance

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/.

Highlights/AccomplishmentsCurrent Spikes

17

Current spikes observed in some experiments, notin others

Two joint experiments have failed to explain differences Agreed to disagree, for now

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/.

Phase Change Highlights

18

Heavy ion testing performed at TAMU Chalcogenide storage element appeared to be

“bullet proof” Unhardened commercial substrate suffered SEL TID better than 100 krads (SiO2)

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/.

Radiation Testing—Lessons Learned

19

Angular effects matter—differences observed between normal and high angle, also between tilt and roll at same angle Destructive effects in flash occur primarily in high voltage Programor Erase operations—have to emphasize, SEGR failures occur primarily atnormal incidence Try to keep flux low enough to avoid collective effects (Shindou et al.,IEEE TNS, Dec 2005) but want high fluence for good statistics—trade-offs to optimize beam time Have to estimate rate in space for effects observed in testing, e.g., flux in space at LET>60 is less than 1 ion/cm2 per hundred years

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/. 20

Can we test anything completely?

Commercial 1 Gb SDRAM68 operating modes

operates to >500 MHzVdd 1.8V external, 1.25V internal

Amount Item3 Number of Samples

68 Modes of Operation4 Test Patterns3 Frequencies of Operation3 Power Supply Voltages3 Ions3 Hours per Ion per Test Matrix Point

Sample Single Event Effect Test Matrix

full generic testing

66096 Hours2754 Days7.54 Years

and this didn’t include temperature variations!!!

Test planning requires much more thought in the modern ageas does understanding of data collected (be wary of databases).

Only so much can be done in a 12 hour beam run – application-oriented

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/. 21

Plans (FY10/11)

• Reliability study—retention after cycling and radiation exposure

• Characterize Micron stacked 128G MLC NAND (32 nm)• Compare SLC/MLC response (e.g., Samsung 8G)• Prepare draft test guideline document for NVM testing• Monitor development of new NVM technologies,

perform testing as test vehicles become available

Presented by Raymond Ladbury at the 11th European Conference on Radiation and its Effects on Components and Systems (RADECS) conference, Radiation Effects on Non Volatile Memories Thematic Workshop, 9/20/2010, Langenfeld, Austria, and on http://radhome.gsfc.nasa.gov and http://nepp.nasa.gov/.

Conclusions

• End of scaling has been predicted since before Moore’s Law—scaling will continue for a while longer

• Flash will be leading NVM technology for a while• Many new NVM technologies have promising

radiation resistance of the bit cells—hardening control logic is the main challenge

• Testing challenges will multiply as circuit complexity increases