![Page 1: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/1.jpg)
Data retention extraction
methodology for perpendicular
STT-MRAM
Luc Tillie1,2, E. Nowak1, R. C. Sousa2, M.-C. Cyrille1, B. Delaet1,
T. Magis1,A. Persico1, J. Langer3 ,B. Ocker3 , I-L Prejbeanu2 and L. Perniola1
1CEA-LETI, Minatec Campus, Grenoble, France, email: [email protected], Univ. Grenoble Alpes / CEA / CNRS, Grenoble, France
3Singulus Technologies AG, Kahl am Main, Germany
1LMW17 - 2.3 - L.Tillie
![Page 2: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/2.jpg)
IntroductionIn Perp STT-MRAM, retention time π at a given temperature is
related to the Thermal Stability factor π« [Feng et al. JAP 95] :
Application Retention
Time πBit Error
Rate (N=1)
Thermal
Stability π« [π€ππ]
Cache 10 ms 10β9 36 @85Β°C
Soldering ~9 min 10β5 38 @260Β°C
Storage (SCM) 1 month 10β9 56 @85Β°C
Automotive 10 years 10β5 51 @150Β°C
Consumer 10 years 10β5 51 @85Β°C
π = πππππ(π«)
2LMW17 - 2.3 - L.Tillie
Each application has a different temperature and retention target
π« = π₯π¨π βπππ΅π
πππ π β π©π¬πΉ
![Page 3: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/3.jpg)
Introduction
5% error ~ factor 10 in retention time
Thermal Stability must be extracted with high precision
3LMW17 - 2.3 - L.Tillie
-5% +5%
![Page 4: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/4.jpg)
Outline
β’ Perp-STT description
β’ Direct retention time measurement
β’ Delta extraction methods
β’ Accuracy and precision
β’ Delta dependence
β’ Conclusion
4LMW17 - 2.3 - L.Tillie
![Page 5: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/5.jpg)
MAD Leti test chipStandard Foundry Wafer
CMOS 130nm + 4 Cu Metal
TiN Bottom Electrode
Definition
Perpendicular magnetic stack
deposition by Singulus
Ta/FeCoB/MgO/FeCoB/Ta/Co
/5x[Pt/Co]/Ru/Co/13x[Pt/Co]/Pt/Ta
Γ100nm Mesa Patterning
Encapsulation and CMP
M5
CMP touch (RMS ~ 2Γ ) TiN
AlCu M5
Cu M4
Fixed Layer
Oxide Layer
Free Layer
MAD Leti test chip : Multi back-end
memory platform
5LMW17 - 2.3 - L.Tillie
![Page 6: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/6.jpg)
Resistance Hysteresis Cycle
6LMW17 - 2.3 - L.Tillie
Switching by current polarity
Parallel state : Low Resistance State
Anti-Parallel state : High Resistance State
![Page 7: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/7.jpg)
Resistance Distribution
7
4kbit matrix shows fully separated distributions
LMW17 - 2.3 - L.Tillie
~π(ππΉππ + ππΉπ)
πΉπ [π] πΉππ[π]
Average 825 980
π 9.53 11.37
![Page 8: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/8.jpg)
TMR Temperature dependence
π»π΄πΉ =πΉππ β πΉπ
πΉπ
The resistance window stays stable up to 235Β°C
Good state differentiation
8LMW17 - 2.3 - L.Tillie
![Page 9: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/9.jpg)
Sharrockβs Model
Sharrockβs model [Sharrock, IEE Trans. On Magnetism, 35 ,1999] :
Two stable states, Parallel (P) and Anti-Parallel (AP), separated
by an energy barrier ππ¬
Parallel
StateAnti-Parallel
State
ππ¬π· ππ π¨π·ππ¬π¨π· ππ π·
π~ππ¬
πππ»
9LMW17 - 2.3 - L.Tillie
![Page 10: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/10.jpg)
Outline
β’ Perp-STT description
β’ Direct retention time measurement
β On single devices
β On matrices
β’ Delta extraction methods
β’ Accuracy and precision
β’ Delta dependence
β’ Conclusion
10LMW17 - 2.3 - L.Tillie
![Page 11: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/11.jpg)
Switching Time Probability (STP) on single device
11LMW17 - 2.3 - L.Tillie
Voltage pulse AP state P state
Objective : How much time before it switches thermally?
![Page 12: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/12.jpg)
Switching Time Probability (STP) on single device
π· π = π β ππππ
πππππ π«
+ Simple Method
+ Exact value of Retention time
- Impractical for long retention time
- Extrapolation for low temperature
12LMW17 - 2.3 - L.Tillie
1000 events
![Page 13: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/13.jpg)
Switching Time Probability (STP) on matrix
13LMW17 - 2.3 - L.Tillie
+ Simple Method
+ Exact value of Retention time
- Impractical for long retention time
- Extrapolation for low temperature
![Page 14: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/14.jpg)
Outline
β’ Perp-STT description
β’ Direct retention time measurement
β’ Delta extraction methods
1. Switching Current Density
2. Switching Pulse Width
3. Switching Field Density
β’ Accuracy and precision
β’ Delta dependence
β’ Conclusion
14LMW17 - 2.3 - L.Tillie
![Page 15: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/15.jpg)
(1/3) Switching Current Density (SCD)
πΊπͺπ« π° =π«
πππ π«ππ©ππ±π© β
ππ©
π(π«)[Huai et al, JAP 98, 2005]
15LMW17 - 2.3 - L.Tillie
T Ξ [kbT] Ic [mA]
ππΒ°π
![Page 16: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/16.jpg)
(1/3) Switching Current Density (SCD)
16LMW17 - 2.3 - L.Tillie
T Ξ [kbT] Ic [mA]
ππΒ°π ππ π. π
πΊπͺπ« π° =π«
πππ π«ππ©ππ±π© β
ππ©
π(π«)[Huai et al, JAP 98, 2005]
![Page 17: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/17.jpg)
(1/3) Switching Current Density (SCD)
17LMW17 - 2.3 - L.Tillie
T Ξ [kbT] Ic [mA]
ππΒ°π ππ π. π
πππΒ°π ππ π. π
πΊπͺπ« π° =π«
πππ π«ππ©ππ±π© β
ππ©
π(π«)[Huai et al, JAP 98, 2005]
![Page 18: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/18.jpg)
(1/3) Switching Current Density (SCD)
T Ξ [kbT] Ic [mA]
ππΒ°π ππ π. π
πππΒ°π ππ π. π
πππΒ°π ππ π. π
18LMW17 - 2.3 - L.Tillie
+ Fast Method
+ Standard measurement
πΊπͺπ« π° =π«
πππ π«ππ©ππ±π© β
ππ©
π(π«)[Huai et al, JAP 98, 2005]
![Page 19: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/19.jpg)
(2/3) Switching Pulse Width (SPW)
πΊπ·πΎ ππ = π°π π βπ
π«πππ
ππ
ππ
19LMW17 - 2.3 - L.Tillie
In thermally activated regime :
[Koch et al, Phys. Rev. Lett. 92, 2004]
T Ξ [kbT] Ic [mA]
ππΒ°π
![Page 20: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/20.jpg)
(2/3) Switching Pulse Width (SPW)
20LMW17 - 2.3 - L.Tillie
[Koch et al, Phys. Rev. Lett. 92, 2004]
T Ξ [kbT] Ic [mA]
ππΒ°π ππ π. ππ
πΊπ·πΎ ππ = π°π π βπ
π«πππ
ππ
ππIn thermally activated regime :
![Page 21: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/21.jpg)
(2/3) Switching Pulse Width (SPW)
21LMW17 - 2.3 - L.Tillie
[Koch et al, Phys. Rev. Lett. 92, 2004]
T Ξ [kbT] Ic [mA]
ππΒ°π ππ π. ππ
πππΒ°π ππ π. ππ
πΊπ·πΎ ππ = π°π π βπ
π«πππ
ππ
ππIn thermally activated regime :
![Page 22: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/22.jpg)
(2/3) Switching Pulse Width (SPW)
T Ξ [kbT] Ic [mA]
ππΒ°π ππ π. ππ
πππΒ°π ππ π. ππ
πππΒ°π ππ π. ππ
22LMW17 - 2.3 - L.Tillie
+ Fast Method
+ Requires to be in thermally activated regime
- Degradation due to long pulses
[Koch et al, Phys. Rev. Lett. 92, 2004]
πΊπ·πΎ ππ = π°π π βπ
π«πππ
ππ
ππIn thermally activated regime :
![Page 23: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/23.jpg)
(3/3) Switching Field Density (SFD)
πΊππ« π― =π
πΉπ―πππππ β
π―π
ππππΉπ―
π
πππππ π π β
π―
π―ππππ βπ π β
π―
π―π
π
[Feng et al. J.A.P 95, 2004]
23LMW17 - 2.3 - L.Tillie
T Ξ [kbT] Hk [mT]
ππΒ°πͺ
![Page 24: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/24.jpg)
(3/3) Switching Field Density (SFD)
πΊππ« π― =π
πΉπ―πππππ β
π―π
ππππΉπ―
π
π«ππππ π« π β
π―
π―ππππ βπ« π β
π
ππ€
π
[Feng et al. J.A.P 95, 2004]
24LMW17 - 2.3 - L.Tillie
T Ξ [kbT] Hk [mT]
ππΒ°πͺ ππ π. ππ
![Page 25: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/25.jpg)
(3/3) Switching Field Density (SFD)
πΊππ« π― =π
πΉπ―πππππ β
π―π
ππππΉπ―
π
π«ππππ π« π β
π―
π―ππππ βπ« π β
π
ππ€
π
[Feng et al. J.A.P 95, 2004]
25LMW17 - 2.3 - L.Tillie
T Ξ [kbT] Hk [mT]
ππΒ°πͺ ππ π. ππ
ππΒ°πͺ ππ π. ππ
![Page 26: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/26.jpg)
(3/3) Switching Field Density (SFD)
πΊππ« π― =π
πΉπ―πππππ β
π―π
ππππΉπ―
π
π«ππππ π« π β
π―
π―ππππ βπ« π β
π
ππ€
π
[Feng et al. J.A.P 95, 2004]
T Ξ [kbT] Hk [mT]
ππΒ°πͺ ππ π. ππ
ππΒ°πͺ ππ π. ππ
ππΒ°πͺ ππ π. ππ
26LMW17 - 2.3 - L.Tillie
+ No degradation (only for reading)
- Involves magnetic field (Setup compatibility)
![Page 27: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/27.jpg)
Outline
β’ Perp-STT description
β’ Direct retention time measurement
β’ Delta extraction methods
β’ Accuracy and precision
β’ Delta dependence
β’ Conclusion
27LMW17 - 2.3 - L.Tillie
![Page 28: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/28.jpg)
Precision Measurement
SCD
28LMW17 - 2.3 - L.Tillie
Low cycle number induces optimistic π« extraction
and high variability
High number of cycles needed
![Page 29: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/29.jpg)
Measurement parameters
LMW17 - 2.3 - L.Tillie 29
Two main measurement conditions :
- Number of significant points for curve fitting
- Number of events measured
![Page 30: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/30.jpg)
Delta β accuracy and precision
Delta extraction requires :
At least 5 points over the distribution
A high number of events measured
30LMW17 - 2.3 - L.Tillie
![Page 31: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/31.jpg)
Summary Table
Switching
Mechanism
Significant
points #Events #
Step
speedComments
Accuracy Precision
5% 1% 5% 1%
STPRetention
(thermal)- - β₯10 β₯20
1s β
1 yr
+ Simple method
+ Most precise
- Impractical for long retention time
SCD
Current
pulse
(amplitude)β₯3 β₯6 β₯200 β₯ πππ ns
+ Fast method
+ Typically no degradation
SPW
Current
pulse width
(length)
β₯3
(per
pts)
β₯5
(per
pts)
β₯10 β₯100ns β
ms
+ Fast method
- Requires to be in thermally
activated regime
- Degradation due to long pulses
SFDMagnetic
Fieldβ₯6 - β₯300 β₯ πππ
Β΅s β
ms
+ No degredation
- Involves magnetic field
31LMW17 - 2.3 - L.Tillie
![Page 32: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/32.jpg)
Outline
β’ Perp-STT description
β’ Direct retention time measurement
β’ Delta extraction methods
β’ Accuracy and precision
β’ Delta dependence
β Diameter dependence
β Temperature dependence
β’ Conclusion
32LMW17 - 2.3 - L.Tillie
![Page 33: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/33.jpg)
Stability dependence with diameter
60Β°C 150Β°C 210Β°C
SCD
SPW
Non-quadratic behavior
Coherent with a constant sub-volume nucleation.
[Sun et al, Phys. Rev. B 84β]
33LMW17 - 2.3 - L.Tillie
![Page 34: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/34.jpg)
Stability dependence with temperature
34LMW17 - 2.3 - L.Tillie
STP at high temperature : Reference values
![Page 35: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/35.jpg)
Stability dependence with temperature
35LMW17 - 2.3 - L.Tillie
SCD on all range : Coherent with reference values
![Page 36: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/36.jpg)
Stability dependence with temperature
36LMW17 - 2.3 - L.Tillie
SPW Measurements : Coherent at high temperature,
deviates from SCD below 100Β°C
![Page 37: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/37.jpg)
Stability dependence with temperature
37LMW17 - 2.3 - L.Tillie
SFD at low temperature : noisy but coherent with SCD
Stability dependence with temperature
![Page 38: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/38.jpg)
Thermal stability modeling
38LMW17 - 2.3 - L.Tillie
- MacroSpin and Domain-Wall models coherent at high temperature
- MacroSpin deviates below 100Β°C
- Domain-Wall close to SCD on all range
Up
Down
Uniform Magnetic Reversal
Β« MacroSpin Β»
Domain-Wall Propagation
![Page 39: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/39.jpg)
LMW17 - 2.3 - L.Tillie 39
Application Retention
Time πBit Error
Rate (N=1)
Thermal Stability π«[π€ππ]
Cache 10 ms 10β9 36 @85Β°C
Soldering ~9 min 10β5 38 @260Β°C
Storage (SCM) 1 month 10β9 56 @85Β°C
Automotive 10 years 10β5 51 @150Β°C
Consumer 10 years 10β5 51 @85Β°C
Stability dependence with temperature
![Page 40: Data retention extraction methodology for perpendicular](https://reader030.vdocuments.us/reader030/viewer/2022012801/61bd0b5561276e740b0ec8a2/html5/thumbnails/40.jpg)
Conclusion
β’ 4 retention time methods have been compared in
diameter and temperature
β’ Accuracy and precision study showed the need of
measuring enough events with a minimum number of
significant points
β’ The 4 extractions gave similar results except the SPW
which deviates significantly below 100Β°C
β’ Extrapolating from high temperature to a certain value
has to be done with care
40LMW17 - 2.3 - L.Tillie