Reliability, Design Qualification,and Prognostic Opportunity

of in Die eFuse

W.R. Tonti Ph.D./MBAFIEEEIEEE Director, Future Directions

OutlineIntroduction Drive to PHM

One Time Programmablen (OTP) eFuseDesign

Programming Conditions Reliability

Applications

Conclusion

IntroductionNeed for an electronic fuse

Laser (non-PHM) versus electronic (PHM)fuse

One Time Programmable (OTP) eFuse PHM, but 1 way street by design

Leveraging a failure mode: Electromigration

Integration in a standard CMOS process flow.

Base level fuse design

A statement of reliability

Typical use of the efuse

4

E Spectrum 2004er, W. Tonti

5

E Spectrum 2004er, W. Tonti

roduction: The need for an eFuseCircuit elements at time zero are not perfect. Circuit spares are esigned, tested and available for replacement. Fuses are needed o enable the replacement. Time zero PHM

Circuit trimming for process variances is needed to optimize erformance. Fuses serve in this optimization. Custom PHM

Electronic Chip ID (ECID) is very useful throughout a products life ycle. Fuses are used to encode a chips DNA.

PHM identification.

Products require unique personalization for a given customer. For xample the identical memory chip may be available in x8 or x16. uses can be used to personalize and deliver the correct ustomization.

Custom PHM

Non volatile data is an option whenever fuses are provided. Trusted PHM

eFuse at 100,000 Feet

The eFuse advantage are: Enabled at any level of assembly. They function within the product. Do not require an external programming

stimulus Have autonomic capability They can be used to make a reliable

product more reliable

eFuse versus Laser Fuse

eFuse scales with technology critical dimension

Laser Fuse does dot scale

eFuse enables autonomic repair capability PHM

Laser Fuse cannot be used to enable autonomic repair.

eFuse relies on front end process technology, Laser fuse relies on back end process technology

eFuse is designed to not impact the back end wiring channels.

Laser fuse-boxse-box

* F T t i l IEEE 2007 IRPS R K th d C Ti

(*)

OTP eFuse

Latch Trip Point

E Fuse RIntrinsic

Rintrinsic + Rsystem

Ipgm limited

Programming Current is Established by T0 FuseResistance

Incomplete programmingresets T0 fuse resistance

Not possible to reprogram

esign for ElectromigrationInvestigate a fuse programming solution that we can electrically control

Control is governed by electromigtaion of a low resistance species

Design of a structure where

Electrically Programmable eFuse Using Electromigration in Silicides

EqZkT

TDNF

*)(=he flux of a migrating species

mic density diffusion coefficient of the migrating species (Silicide)

fective charge

cal Electric Field tromigration to initiate 0 F

n be influenced by either changing the diffusion species gradient, D , anging the thermal gradient the species sees, T electrically programmed eFuse one can easily control the thermal gradient the design of the Cathode, Link, and Anode. Electrical optimization through the f the programming delivery system, ie the programming transistor provides an al control for establishing the thermal gradient. Using the thermal insulating es of shallow trench isolation completes the loop for controlled electromigration.

This methodology leads to physical eFuse scaling

Programmed eFuse in a standard CMOS flow

SilicidePolysilicon

Controlled EM in fuse linkogram Open

Shallow Trench Isolation: Dielectric

Si Substrate

AnodeCathode

Programmed eFuse: WSi2 0.2m technology

Reliability, and Desiqn Qualification of a Sub-Micron Tungsten Silicide eFuse W Tonti J Fifield J Higgins W Guthrie W Berry C Narayan IRPS 2004 Proceedings pg 152 156 IBM

Current

Fina

l R

eFUSE Programming ControlIntact Fuse

Actual post program resistance distributions

Latch Trip Point

Fail PassActual statistics affected by long tails, andErratic programmed bits due to ruptures and EM stringers

Fuse ApplicationsECID: PHM identificationPHM Repairs: Wafer, Module, Fielde-Odometer: PHM Electronic oil changePHM Autonomic Core control

Data, Thermal

mpedance Control Using eFusesUSPA 6141245 10/31/2000 USPA 6,243,283 6/5/2001 IBM

Bertin, Fifield, Hedberg, Houghton, Sullivan, Tomashot, Tonti

Teaches: In system customization.Trimming driver for exactimpedance matching.

PHM

hanging Machine function with eFuse

USPA 7,268,577 9/11/2007 IBM

Teaches: In system customization.Tamper proof, ability to lock out a hacker

PHM

V Memory ElementA 6,208549 3/27/2001 Xilinix

Rao, Voogel

ches: Trusted Dataelements.

PHM

Odometer Field Repair and replacement

USPA 7,287,177 10/23/2007 IBM

B i L t T ti V t

Teaches: Autonomic Repair using standard Product Rel model to anticipate failure and replacement.

PHM

Conclusions

eFuses are the electronic gateway to PHM

eFuse programming requires precise thermal control of the migrating species flux

eFuse use and application is limitless

Design and programming conditions of the eFuse ultimately determine long term reliability of the element

As the MOSFET evolves so will the eFuse

This element has enabled autonomic computing

AcknowledgementsClaude Bertin IBM (retired)Wayne Berry IBM (retired)J. Fifield IBMJ. Higgins IBM (retired)R. Kothadaraman IBMP. Farrar IBMS. Iyer IBMC. Narayan IBMW. Guthrie IBMR. Mohler IBMN. Robson IBMP. Spinney U. Maine OronoC. Tian IBM

This work was performed at the IBM Microelectronics,Division Semiconductor Research & Development Center Hopewell Junction NY 12533, and in Essex Junction VT 05452

Backups

Programming Conditions and Reliability

ramming Conditions Establish the Basis for ability

Vdd

Vgs

eFuse

Programming Transistor

Bookkeeping:

3 banks of fuses, 960 fuses/bank- 128 Bits for ECID- Fuse Read: latch trip point 5K

nm Programming Study: oltage and Temperature Variation

Initial Fuse Resistance Summary

0

1000

2000

3000

4000

5000

6000

7000

150 160 170 180 190 200 210 220 230 240 250 260 270

Resistance (ohms)

Freq

uenc

y22 oC

85 oC

ment: Analyze eFuse variation over programming voltage and temperature windowD Programming: Control Cell, nominal conditions.ts= cell 1, 16 bits=cell 3, 16 bits =cell 2, 16 bits = cell 4.grouping is repeated twelve times for a total of 768 bits experimentally programmed.: This leaves 64 additional bits that are NOT programmed.

m

nom high

T=nom

T=high

Programming SummaryCellm)

3K7K

Cell 1 (Vlow=T=nom)

Mean: 10.5KMedian: 6.9K: 119Min: 1.7KMax: 1.4M

Cell 2 (V=high,T=nom)

Mean: 39KMedian: 26K: 0.7KMin: 1.8KMax: 5M

Cell 3 (V=low,T=high)

Mean: 2.4KMedian: 2.35K: 5Min: 1.2KMax: 9.4K

Cell 4 (V,T=high)

Mean: 7.4KMedian: 7.2K: 20Min: 1.6KMax: 23K

All eFuse bits shown are passing

icide Migration Length vs Program Resistance

cide migrated length measured from the cathode-link interface- Application: ballast resistor

Actual eFuse circuit

Cross Coupled latchCurrent Controlled Latch

E-Fuse Decode

Igpm Regulation

Rasied to Pgmommon to a fuse bank)

solation Device

atch Prechargetrobe Iread via 74

Rfuse affectsprogramming

J.Fifield

*

*

Programming Transistor Control

The programming transistor power and device controlgoverns the effectiveness of the eFuse and its reliability

2 integrated fuses on polysilicon for low voltage 0.18m CMOS applications,lnitsky ISaadat A Bergemont P Francis Proceedings of the 1999 IEEE IEDM pg 765-768 National Semiconductor

Effect of programming pulse time (Vgs)Experiment: Vdd, Temp=nom. Programming pulse varied

ramming 25S 1mS 2mS 4mS dition

lt High Z Isolation Damage Conductive Conductive

eliability of a fuse with correct programming

Conditions Equivalent Product Lifetime Rationale

SRAM-a DRAM-b

130C/2.85V/192 hr, 100% duty 1.5E6 device hours 2.4E9 years Electrical Duty-c

140C/2.85V/500 hr, 50% duty 2E6 device hours 3.1E9 years Electrical Duty-c

-55/125C/500 cycles 43 years 43 years Coffin-Manson model -d

sumes 500 ps fuse query per 1000 clock cycles at 4 ns cycle sumes 400 ns fuse query at powerup, and 2 powerups per day mperature and voltage acceleration not included sumes minimum exponent of 5.5 for e.g. thin film cracking {1}, deltaT(field) = e.g. Tj = 105C and Toff = 20C, and 2 on/off per day

EIA Bulletin SSB-1

Fuse Scaling: Additional data

LW

|Pro

gram

ed R

esis

tanc

e| @

+0.

1V (o

hms)

100

1000

10000

1e+5

1e+6

1e+7

1e+8

1e+9

1e+10

1e+11

1e+12

1e+13

1e+14

fuse_D fuse_B fuse_C fuse_A fuse_F fuse_G fuse_H fuse_I fuse_E device

0.06 0.08 0.06 0.08 0.12 fuse length (um

0.6 0.8 0.9 1.2 fuse width (um)

se L Fuse W CA La, Lc

2 0.08 8 1

8 0.08 8 1

9 0.06 8 1

6 0.06 8 1

2 0.12 8 1

2 0.08 16 1

2 0.08 8 0.5

2 0.08 8 1

SHORT NECK

Cathode/AnodeThermal gradient

e doping, link length reliability effects

0.9 0.6 0.9 f

HN halo adder only P ext/halo L

HN halo adder only P ext/halo C

0.001

0.010.0070.005

0.003

0.002

0.10.070.05

0.03

0.02

10.70.5

0.3

0.2

1075

3

2

20

0.6 0.9 0.6 0.9

HN halo adder only P ext/halo

HN halo adder only P ext/haloPPN

NPPN

NLink length (m)Link dopingTerminal doping

ost programming Resistancevariation in N doped fuseal design constraint for latch trip point

Ratio of stressed to initial programming resistance- Higher variation in N doped fuse

Si2 eFuse program mechanism and Reliability

The Authors show a programmed eFuse Reliability does not degrade (A) represents Silicide melt, (B) represents Co migration to the anode, and C represents Quenching of the the programming, and an amorphous Si region formed in the fuse link. 488 hours of Runtime stress shows 100nA of eFuse movement, which is in the noise of the ATE.

Melt-Segregate-Quench Programming of Electrical Fuse,T S ki N Ot k K Hi S F ji P di f th 2005 IRPS 347 352 TOSHIBA

0.35m Polysilicon TiSi2 eFuse Reliability

Authors show HTOL results for eFuse that is programmed at nominal, low, and high programming currents. Some drift is noticed at other than optimal programmed level, indicating initial programming criterion is key for an optimized fuse geometry.

Lifetime Study for a Poly Fuse in a 0.35m Polycide CMOS Process,

5nm NiSi Polysilicon eFuseAuthors show 65nm fuses can be reliably programmed at -400C, 250C, and +1250C. Reliability data is limited to a 1000hr 2500C bake.

NiSi Polysilicon Fuse Reliability in 65nm Logic CMOS Technology,

Effects of Metal tracks over eFuse Minimum M1 Parallel Min. M2 Comb structure M2

M1 M1M2 TSTM2AM2B GND

al effects over fuse T0 (pre), T1 (post programming)

Minimal impact to all types of Metal tracks over a fuse bay.

Metal 1 current

Metal 2 serpentine current