Transcript Total ionising Dose Level (TDL) calculation

SREC04 Section IV
Radiation activities in a project flow :
Total Ionizing Dose (TID) effects
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Radiation : why do we care?
customer
Radiation
customer
expert
Program manager
Program manager
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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
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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
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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
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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
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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
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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
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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
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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)
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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
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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
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Total ionising Dose Level (TDL) calculation
 Robustness of a device/subsystem/system
evidenced thanks to comparison between expected
in 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
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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
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Total ionising Dose Level (TDL) calculation
Solid Sphere dose-depth curve, GEO orbit
Dose [rad(Si)]
1,0E+09
1,0E+08
solid sphere Dose-depth Curve
LEO1,0E+07
1,0E+06
1,0E+05
1,0E+04
1,0E+03
1,0E+02
1,0E+01
1,E+05
Dose [krad(Si)]
1,E+04
1,E+03
1,E+02
1,E+01
0
2
protons
bremsstrahlung
électrons
total
electrons
trapped protons
flare protons
total
4
6
8
Solid sphere Al. thickness (g/cm2)
1,E+00
1,E-01
0
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15
10
5
Solid sphere Al. thickness (mm)
SREC04 - June 18, 2004
20
10
12
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 method
r
r
r
r
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
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
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Total ionising Dose Level (TDL) calculation
Solid Sphere (slant)
TID Ray Tracing / MonteCarlo
[%].
100
Device package + equipt
+ satellite
Shell Sphere (norm)
Shell Sphere (slant)
80
60
SC-N
SP-SL
Monte
Carlo
40
20
Pack.
0
-20
ratio
TID
ratio
TID
TID
(SC-N) / [krad(Si)] (SP-SL) / [krad(Si)] [krad(Si)]
(MC)
(MC)
-40
-60
P1
P2
P3
P4
-80
-100
Parts
1,549
1,251
1,231
1,514
GEO ORBIT
1,263
26,1
0,965
15,1
0,811
28,5
1,470
3,5
21,5
11,6
18,6
3,4
16,7
11,9
24,0
2,3
135
84,0
122,0
30,4
112,0
84,9
128,0
32,5
GTO ORBIT
GEO orbit, device package +
Equipment, satellite is a box
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P1
P2
P3
P4
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1,435
1,172
1,334
0,937
163,0
100,0
168,0
30,4
1,180
0,986
0,955
0,937
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
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Total ionising Dose Level (TDL) calculation
 Impact of the tool on dose-depth curve
GEOSYNCHRONOUS ORBIT, SOLID SPHERE
1,E+06
Shieldose
TID [rad(Si)]
NOVICE 1D
1,E+05
NOVICE 3D
Shieldose2
1,E+04
1,E+03
5
10
15
SP Al (mm)
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25
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
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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…)
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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
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TID degradation mechanisms
Device type is 2N5551 transistor (STM), single lot
1,2E-02
Delta (1/hfe)
1,0E-02
8,0E-03
6,0E-03
HDR
LDR
linear (LDR)
linear (HDR)
4,0E-03
2,0E-03
0,0E+00
0
20
40
60
80
Dose [Krad(Si)]
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100
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
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TID degradation mechanisms
– Dose rate effects in MOS devices
Time (Log
scale)
0
t RTanneal  tirr ( 2 )  tirr (1)
D
tirr (1) 
DR1
tirr (2 ) 
D
DR 2
Space dose rate
irradiation
Lab dose rate
+ RT
irradiation
anneal
Lab dose rate
+ High Temp
irradiation
anneal
t HT _ anneal
Irradiation at Room temperature under bias
condition
AnnealingBC.
at Room temperature under bias
condition BC.
Annealing
at High temperature under bias
condition BC.
· High dose rate generally worst case for MOS devices
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TID degradation mechanisms
 TID effects in materials
– Organic materials : chemical reactions initiated
· Cross-linking, chain scission, formation of gaseous byproducts…
– 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
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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
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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
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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
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60Co
source
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.
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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)
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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
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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
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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
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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
· …
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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
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