SREC04 Section IV Radiation activities in a project flow : Total Ionizing Dose (TID) effects

SREC04 - June 18, 2004

SREC04 Section IVRadiation activities in a project flow :

Total Ionizing Dose (TID) effects

SREC04 - June 18, 2004

Radiation : why do we care?

customer

Program manager

customerRadiationexpert

Program manager

SREC04 - June 18, 2004

Short Course Out line

Introduction

Basic concepts

Constraint linked to space radiation environment

Total ionising Dose Level (TDL) calculation

TID degradation mechanisms

Device Total ionising Dose Sensitivity (TDS) determination

TID and Radiation Hardness Assurance (RHA)

Conclusion

SREC04 - June 18, 2004

Introduction

Underestimation of radiation induced degradation may endanger any space mission– Among all radiation induced degradations, Total Ionising

Dose (TID) has to be considered

TID may degrade electronics and materials performances

TID Radiation Hardness Assurance (RHA) process has to be implemented

SREC04 - June 18, 2004

Introduction

RHA consists of all activities undertaken to ensure that the electronics and materials of a space system perform to their design specifications after exposure to the space radiation environment

TID Radiation Hardness Assurance (RHA) process is based on the comparison between – calculated in flight TID level (TDL) and,

– TID sensitivity (TDS) of the element under study.

Radiation Hardness Assurance goes beyond the piece part level

SREC04 - June 18, 2004


Introduction

Basic concepts






Conclusion

SREC04 - June 18, 2004

Basic concepts

Definition and units– TID is the measure for the quantity of radiation deposited

through ionisation mechanism at a specific location, in a specific material

– "Standard" unit is the rad(material) regardless that SI unit is the Gray(material)

· Rad = Radiation Absorbed Dose

· Gray (Gy) = J/ kg (S.I.), 1 Gy = 100 Rad

– The dose rate is the amount of TID deposited per unit of time example : rad(Si)/s or rad(Si)/hour

SREC04 - June 18, 2004


Introduction

Basic concepts






Conclusion

SREC04 - June 18, 2004

Space radiation environment

Space radiation environment of concern has to be defined in the earliest phase of the program

Particles of concern for TID are protons and electrons

They may transit through the solar system or be trapped by the Earth magnetic field

– These create the radiation belts

SREC04 - June 18, 2004

Radiation environment : mission related requirements

Different types of space mission in terms of orbit and duration– Major risks not associated to the same constituent of the

radiation environment, then, not to the same effect

– Required confidence level may vary with the mission type

Identification of the different mission– Launcher : no concern related to TID

– Telecommunication

– Earth observation / Constellation / Space station

– Scientific mission (interplanetary)

SREC04 - June 18, 2004

Radiation environment : system related requirements

Different elements of a space system may be radiation sensitive– Electronics

· Ionising and Non Ionising Dose (displacement damage), Single Event Effects (SEE)

– Materials, optics · Ionising and Non Ionising Dose

– Solar generator · mainly Non Ionising Dose

– Detectors· Ionising and Non Ionising Dose (displacement damage),

Single Event Effects

SREC04 - June 18, 2004


Introduction

Basic concepts






Conclusion

SREC04 - June 18, 2004


Robustness of a device/subsystem/system evidenced thanks to comparison between expectedin flight level (TDL) and TID Sensitivity (TDS) of the concerned device– TDL may be estimated

· by Monte Carlo technique (NOVICE, GEANT4…)

- Accurate but time consuming

· by Ray Tracing technique (NOVICE, SYSTEMA/DOSRAD…)

- Less accurate but more "industrial"

– Ray tracing technique needs as inputs

· spacecraft/equipment/device geometry

· TID dose-depth curve

SREC04 - June 18, 2004


Dose-depth curve definition– Should be preferentially usable by any sub-contractor

(e.g. compatible with their tools)

– Should be adapted to orbit type

· Electron rich orbit vs proton rich orbit

– Should be provided as a standard for Silicon target with Aluminium shielding shape for electronics

– May be provided for particular cases with

· Other target/shielding shape materials

· Specific thickness range

SREC04 - June 18, 2004


LEO solid sphere Dose-depth Curve

1,E-01

1,E+00

1,E+01

1,E+02

1,E+03

1,E+04

1,E+05

0 5 10 15 20Solid sphere Al. thickness (mm)

Do

se

[k

rad

(Si)

]

electrons

trapped protons

flare protons

total

Solid Sphere dose-depth curve, GEO orbit

1,0E+01

1,0E+02

1,0E+03

1,0E+041,0E+05

1,0E+06

1,0E+07

1,0E+08

1,0E+09

0 2 4 6 8 10 12

Solid sphere Al. thickness (g/cm2)

Do

se [

rad

(Si)

] protons

bremsstrahlung

électrons

total

SREC04 - June 18, 2004


Shielding shape used as a standard is a sphere– Solid sphere or shell sphere

Such shielding shape as to be used in conjunction with the adapted ray tracing method– So called NORM or SLANT methodr

r

rr

SREC04 - June 18, 2004


Ray tracing vs reverse Monte Carlo calculation ["Comparaison des méthodologies de détermination de dose déposée sur HOTBIRD", T. Carrière, EADS ASTRIUM internal report, 1995. ]["Impact of material properties and shielding structures on dose level calculation", R. Mangeret, CNES funded study, internal ASTRIUM SAS report, 2001.]

– Total ionising dose calculation on electronics dies

· Inside different packages

· For given equipment/satellite geometries

· For various radiation environment

SREC04 - June 18, 2004


SC-N SP-SL Monte Carlo

Pack. ratio

(SC-N) / (MC)

TID

[krad(Si)]

ratio

(SP-SL) / (MC)

TID

[krad(Si)]

TID

[krad(Si)]

GEO ORBIT P1

P2

P3

1,549

1,251

1,231

26,1

15,1

28,5

1,263

0,965

0,811

21,5

11,6

18,6

16,7

11,9

24,0

P4 1,514 3,5 1,470 3,4 2,3

GTO ORBIT

P1

P2

P3

1,435

1,172

1,334

163,0

100,0

168,0

1,180

0,986

0,955

135

84,0

122,0

112,0

84,9

128,0

P4 0,937 30,4 0,937 30,4 32,5

-100

-80

-60

-40

-20

0

20

40

60

80

100

Parts

TID

Ray

Tra

cing

/ M

onte

Car

lo

[%].

Solid Sphere (slant) Shell Sphere (norm)

Shell Sphere (slant)

GEO orbit, device package +Equipment, satellite is a box

Device package + equipt

+ satellite

SREC04 - June 18, 2004


No problem for proton rich orbits (LEO, scientific)– Solid sphere to be used for ray tracing

For electron rich orbit (ex : GEO, GALILEO)– comparison with NOVICE Monte carlo calculation

· Solid Sphere + SLANT , slight underestimation possible

· Shell Sphere + NORM, overestimates generally the total dose

level as calculated by MC technique

Both give a realistic estimation of received TID

– Shell Sphere + SLANT : catastrophic underestimation

SREC04 - June 18, 2004


Impact of the tool on dose-depth curve

GEOSYNCHRONOUS ORBIT, SOLID SPHERE

1,E+03

1,E+04

1,E+05

1,E+06

5 10 15 20 25

SP Al (mm)

TID

[ra

d(S

i)]

Shieldose

NOVICE 1D

NOVICE 3D

Shieldose2

SREC04 - June 18, 2004

Short course Out line

Introduction

Basic concepts






Conclusion

SREC04 - June 18, 2004


TID effects on electronic devices– TID response on bipolar microcircuits

· Main effect at transistor level : reduction of gain

(1/)=K.DN with N#1at a low level of dose.

· Degradations of PNP transistors are generally more

serious (low initial gain), "lateral" PNP being the most

critical case.

· Integrated circuit degradation may be complex due to

interaction between individual transistors degradation

(increase of bias & offset currents, increase of offset

voltages…)

SREC04 - June 18, 2004


– TID response of bipolar devices

· Enhanced Low Dose Rate

Sensitivity (ELDRS)

· Enhanced degradation at

a given TID level when

device irradiated at low dose

rate

· Evidenced on bipolar based

integrated circuit, strongly

suggested for discrete

transistors

SREC04 - June 18, 2004


0,0E+00

2,0E-03

4,0E-03

6,0E-03

8,0E-03

1,0E-02

1,2E-02

0 20 40 60 80 100

Dose [Krad(Si)]

De

lta

(1

/hfe

)

HDR

LDR

linear (LDR)

linear (HDR)

Device type is 2N5551 transistor (STM), single lot

SREC04 - June 18, 2004


– TID response of MOS microcircuits

· charges trapped in the oxide (oxide traps)

· Charges trapped on the interface (interface traps)

Vth = Vot + Vit

- Positive charges: Vth < 0

- Negative charges: Vth > 0

· At transistor level : VGSth drift

· At integrated circuit level, increased operating and stand

by currents, degradation of input logic level…

- Rebound effect to be considered

SREC04 - June 18, 2004


– Dose rate effects in MOS devices

· High dose rate generally worst case for MOS devices

Time (Log scale)

Irradiation at Room temperature under bias condition BC. Annealing at Room temperature under bias condition BC. Annealing at High temperature under bias condition BC.

Space dose rate irradiation Lab dose rate irradiation + RT anneal

Lab dose rate irradiation + High Temp anneal

0

t irr ( 1 ) D

DR 1 t irr ( 2 ) D

DR 2

t RTanneal t irr ( 2 ) t irr ( 1 )

t HT _ anneal

SREC04 - June 18, 2004


TID effects in materials– Organic materials : chemical reactions initiated

· Cross-linking, chain scission, formation of gaseous by-

products…

– Transparent materials (optics)

· Darkening (colour centres)

· Index of refraction changes

· Mechanical and structural changes

For external materials, UV degradation (surface) has to be taken into account

SREC04 - June 18, 2004


Introduction

Basic concepts






Conclusion

SREC04 - June 18, 2004

Device TID Sensitivity (TDS) determination

TID Device Sensitivity (TDS) is determined thanks to :– Manufacturer guarantee (TID hardened devices)

– Technological assessment

– TID ground testing

TDS validity is ensured by complying to TID Radiation Hardness Assurance (RHA) rules– Manufacturer guarantee should rely on data set relevant for

space application (ELDRS issue)

– Technological assessment to be based on degradation mechanisms already presented

– TID ground testing should be adapted to space issues

SREC04 - June 18, 2004


TID testing issue

– Objective is to forecast the behaviour of devices regarding TID flight constraint

– In most cases, simulating space radiation environment at ground level is not possible

· Testing should mimic or bound the flight usage

· TID testing likely to be implemented with 60Co source

SREC04 - June 18, 2004


TID testing issue

– Existing specifications for electronics are

· ESA SCC 22900 issue 2

· MIL STD 883D TM 1019.6

– Both specification are (off course) significantly different

· Specification provides with guidelines to insure test

conditions reproducibility and test results comparison

· Insure test adequacy regarding flight conditions, based

on the technical state of the art.

– Material TID testing is particularly tough and is in most of the cases performed on case by case bases.

SREC04 - June 18, 2004


Two approaches may be used for TDS determination

– "worst case" approach : TID level at which the worst case device of the worst case tested lot exceeds its parametric or functional limits

– "Statistical" approach : "K factor" / 3-sigma

– Then, TDS may corresponds to the first parametric "out of specification" level or to application related Worst Case Analysis (WCA)

SREC04 - June 18, 2004


Introduction

Basic concepts






Conclusion

SREC04 - June 18, 2004

TID and RHA

RHA methodologies for TID & electronics– Main used method is to categorise devices regarding

TID constraint

– Radiation Design Margin (RDM) is defined as being the ratio between TDS and TDL

· Several empirical methods exists for RDM determination

- Design Margin Breakpoint

- Part categorisation Criteria

SREC04 - June 18, 2004

TID and RHA

Examples of industrial RHA approaches regarding TID

– EADS ASTRIUM : DMBP related approach

· A major point is that for RDM value to be valid, both TDL and TDS have to be valid

– ALCATEL SPACE : "RADLAT" approach

SREC04 - June 18, 2004

TID and RHA

TID mitigation– Some countermeasure may have to be implemented

in the course of a space program

– Several possibilities exist for TID mitigation

· Shielding at device or equipment level

· To refine TDL with more accurate calculation (MC)

· Equipment / system re-design

· Replacement of concerned device by a radiation

hardened product

· Cold redundancies

· …

SREC04 - June 18, 2004

Conclusion

From ESA upcoming ECSS-E-10-12 specification

– "There is no space system in which radiation effects can be neglected"

TID is one of these radiation effects, then

– Degradation mechanisms at sensitive element level should be understood

– TDL has to be determined with an adequate degree of precision

– TDS has to be evaluated in accordance with state of the art radiation knowledge

Risks have to be lowered as much as possible, in conformance with mission requirements, by help of a RHA process

SREC04 Section IV Radiation activities in a project flow : Total Ionizing Dose (TID) effects

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