Page 1 SREC04 - June 18, 2004
SREC04 Section IVRadiation activities in a project flow :
Total Ionizing Dose (TID) effects
Page 2 SREC04 - June 18, 2004
Radiation : why do we care?
customer
Program manager
customerRadiationexpert
Program manager
Page 3 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
Page 4 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
Page 5 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
Page 6 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
Page 7 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
Page 8 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
Page 9 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
Page 10 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)
Page 11 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
Page 12 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
Page 13 SREC04 - June 18, 2004
Total ionising Dose Level (TDL) calculation
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
Page 14 SREC04 - June 18, 2004
Total ionising Dose Level (TDL) calculation
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
Page 15 SREC04 - June 18, 2004
Total ionising Dose Level (TDL) calculation
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
Page 16 SREC04 - June 18, 2004
Total ionising Dose Level (TDL) calculation
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
Page 17 SREC04 - June 18, 2004
Total ionising Dose Level (TDL) calculation
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
Page 18 SREC04 - June 18, 2004
Total ionising Dose Level (TDL) calculation
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
Page 19 SREC04 - June 18, 2004
Total ionising Dose Level (TDL) calculation
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
Page 20 SREC04 - June 18, 2004
Total ionising Dose Level (TDL) calculation
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
Page 21 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
Page 22 SREC04 - June 18, 2004
TID degradation mechanisms
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…)
Page 23 SREC04 - June 18, 2004
TID degradation mechanisms
– 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
Page 24 SREC04 - June 18, 2004
TID degradation mechanisms
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
Page 25 SREC04 - June 18, 2004
TID degradation mechanisms
– 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
Page 26 SREC04 - June 18, 2004
TID degradation mechanisms
– 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
Page 27 SREC04 - June 18, 2004
TID degradation mechanisms
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
Page 28 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
Page 29 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
Page 30 SREC04 - June 18, 2004
Device TID Sensitivity (TDS) determination
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
Page 31 SREC04 - June 18, 2004
Device TID Sensitivity (TDS) determination
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.
Page 32 SREC04 - June 18, 2004
Device TID Sensitivity (TDS) determination
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)
Page 33 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
Page 34 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
Page 35 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
Page 36 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
· …
Page 37 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