reliability qualification of new technologies for space environments alexander teverovsky qss group,...

Reliability Qualification of New Technologies for Space

Environments

Alexander Teverovsky

QSS Group, Inc./GSFC

[email protected]

1/31/2007 2007 NEPP Workshop 2

Outline

Definitions and classification of new technologies.

Reliability qualification of new technologies and risk mitigation.

Stress-based and knowledge-based approaches to reliability testing.

Example of reliability qualification at cryogenic temperatures.

Conclusion.


Definitions of New Technology

Definition per TOR-2006 (8583)-5236, Technical Requirements for Electronic Parts…:a) has never been previously characterized;b) has limited space heritage; c) commercial (COTS) technology, …;

Common problem – how to qualify? NT: any technology for which existing

qualification system is not applicable.NT as a concept and NT as a device.

Mfrs. are qualifying NT (concept) early duringdevelopment.

Same NT => different quality for different part types?PE task is to qualify a product for use.


Classification of New TechnologiesBased on the level of information and control,

NTs can be divided in three groups:I. Internally grown (information/control

is available).Unique NT developed by NASA (e.g. MSA). Different approaches and metrics based on knowledge of

process/design details (TRL, DMI-development maturity index, KEPP-key engineering performance parameters, etc.)

Cooperation with small business/academia. These NTs are out of scope of the mainstream PE activities.

II. Externally grown. (Commercial NT, inf. might be limited).III. Any technology in extreme space environments without

proven methodology of qualification.Radiation.Cryogenic temperatures.Vacuum (Often underestimated).…….

Sub-mm wave doubler


Externally Grown NTMajority of NTs are growing in the market economy, so we

have to learn how to qualify them.Commercial NTs are currently used in most of the space

projects and their proportion is increasing.Examples: AD/DA converters, PBGAs, FPGA, stacked

memories, advanced passive components, etc. Commercial NTs are optimized for major target applications. Reliability of commercial technologies

and confidence level are growing with maturity.

A critical analysis of currently used approaches to qualification of NT is necessary. NEPP monitor: work closely with projects during planning and implementation periods, then LL.

Commercial technology life span

0

0.2

0.4

0.6

0.8

1

1 2 3 4 5 6 7

timeus

e of

tec

hnol

ogy Mature technology

Newtechnology

t exp~


Purpose of Reliability Qualification

Demonstrate fitness for use (reliability requirements have been met). In particular: Estimate ; Assure that no wear-out failures

would occur during the mission.Provide system manager with information necessary for risk

assessment and mitigation. Definition for components:

risk = P C = (probability of failure) (consequences),where P = f(application, environments).

Risk is not a characteristic of a component, but reliability is.Reverse system is used for “known technologies”: MAR

sets the risk levels and PEs are choosing components. The risk-level system classifies components depending on

how close they are to the relevant MIL standard.

IM random failures wear-out

time

cr

tm


A Major Risk Mitigation Method

Additional screening of revealed defects or anomalies can mitigate the risk related to NT (reduction of IM failures).

Currently derating is mostly a rule-based process. Derating as a trading-off of performance for reliability. Insertion of NTs is driven by performance. For trading you need to know what you are buying. The rule-based derating does not allow estimation of the

reliability gain. Knowledge of AF is critical for risk mitigation of NT.

AFnom

op

AF = F(T, V, W, f)


Why to Look Outside the Box for Reliability Qualification?

What is in the box?

Qualification: ensuring that the part meets the requirements. Requirements: the part should be manufactured,

sample-selected, tested, and documented per MIL-XXX (or portions of it).

Only a few types of parts are ER components ( < 10 FIT).

Major reliability tests for ICs: BI, TC, HTOL. Is any part capable of passing these tests qualified for space?Classes M, N, Q, V, B, S, T per MIL-PRF-38535G.

The rule-based qualification system is not applicable to new technologies by definition.

tNAF

n

11

2

)22,(2


The Significance of Reliability Qualification

Reliability: the probability that a device can perform its intended function for a specified interval under stated conditions.

Historically, for high-reliability applications screening (burn-in) was considered as more essential than long-term reliability testing.

For many commercial NTs wear-out failures are becoming more important than infant mortality failures.

Physics-of-failure (or K-B) approach allows for estimation of AFs for wear-out failures (characterization of a concept).

old IC: no mechanical parts => no wear-out

time

Screening is the major QA element Long-term reliability estimations are more important

t1 t2

New IC AF = t1/t2

time

1/31/2007 2007 NEPP Workshop 10

Stress-based and Knowledge-Based Reliability Qualification Testing

S-B methodology (MIL-STD-883) is an essential part of the rule-based system: used for many generations of devices and created substantial statistical data;a significant improvement of reliability has been achieved;provided consistency and standards for testing.

The foundation of the K-B methodology is understanding failure mechanisms. Key components are:Knowledge of each failure mode and mechanism.Mathematical models, distributions, and AFs.Knowledge of the application conditions.

K-B qualification is used extensively in the industry and models for many degradation mechanisms (TDDB, HCI, NBTI, electromigration) have been developed allowing calculation of AFs and worst-case analysis.

K-B approach is described in multiple papers and industry guidelines: JEDEC, SEMATECH, SSB, RAC, TOR. ( EEE-INST?)

1/31/2007 2007 NEPP Workshop 11

Reliability Qualification of HVD at 30 K

Device. CMOS LV serial-to-HV parallel output driver,redesign of commercial SUPERTEX device.

Package.Bare die on a silicon substrate, Au/1 mil wirebonds. For testing the die is mounted onto a Si substrate and the assembly was installed and interconnected into a ceramic 18X18 PGA.

Application conditions. Steady-state operating temperature 32K, storage temperatures +50 oC to 22 K, Vout = 25 V, 5 years min, 105 MSA reconfigurations.

Standard life test.For thermally activated degradation mechanisms even with low Ea ~0.3 eV, Arrhenius equation shows that a life test of less than 10-35 hrs would be equivalent to a 10-year operation at 30 K.

substrate

die

1/31/2007 2007 NEPP Workshop 12

Analysis of Operation

Reduced tsw and Rsd result in significant increase of the current and voltage spices, especially when all outputs are switched simultaneously, Isp = CV/t, Vsp = LI/t.

Noise reduction measures for life testing.Electrical conditions should simulate the worst case real

application conditions regarding the level of voltages and loads.

Schematic of the part Transient at 20 oC Transient at -196 oCRT, VPP=40, no output load, Cvpp=15 uF

-10

0

10

20

30

40

50

60

70

300 350 400 450 500

time, nsV

ou

t, V

Vout_1Vout_3Vout_10Vout_30Vout_128

LN, VPP=40, no output load, Cvpp=15 uF

-10

0

10

20

30

40

50

60

70

300 350 400 450 500

time, ns

Vo

ut,

V

Vout_1Vout_3Vout_10Vout_30Vout_128

1/31/2007 2007 NEPP Workshop 13

Possible Reliability Hazards

Multiple exposures to cryogenic temperatures during ground-phase testing and integration period.

Degradation due to Hot Carrier Instability.Current and voltage spiking during

output switching.Mechanical stresses in die.Stresses in wire bonds.Reliability of accessory components

and assemblies.

1/31/2007 2007 NEPP Workshop 14

Reliability Hazards: Cryo Cycling

q

oT

TAF

Coffin-Manson model can be applied for brittle materials. For these materials q varies from 6 to 9.

LN cycles equivalent to 30 cycles to 22 K

q = 6 q = 7 q = 8 q = 9

115 144 181 227

Cycling to 22K is a slow process, ~1 cycle per day.

RT - LN cycling might provide an easy-to-perform alternative to cycling down to 22K.

1/31/2007 2007 NEPP Workshop 15

Reliability Hazards: Hot Carriers At LT carriers can easier gain enough energy to overcome the Si

– SiO2 barrier and penetrate into the oxide. Conditions for avalanche breakdown are favorable at LT. Activation energy of HCI is negative, Ea = -0.1 to -0.2 eV. In CMOS inverters, HCI degradation occurs only during

transients. High voltage transistors are more susceptible to HCI.

Lucky hot electrons Drain avalanche CMOS inverter

1/31/2007 2007 NEPP Workshop 16

Reliability Hazards: Stress-Induced Voiding

At LT Al metallization is under significant tensile stresses, which might cause a flow of metal atoms and results in a void formation.

To is the stress-free temperature;

n = 2 to 5; Ea = 0.5 to 1 eV.

The stress-induced voiding most likely will not cause failures of the part at cryogenic conditions.

Tk

ETTAT an

F exp0

Life time due to stress voiding

1.E-09

1.E-06

1.E-03

1.E+00

1.E+03

1.E+06

1.E+09

-200 -100 0 100 200 300 400

temperature, C

tim

e, a

rb.u

nit

s

n = 2 n = 3

n = 4 n = 5

n = 6 n = 7

Temperature of minimum lifetime

0

50

100

150

200

250

300

350

0 2 4 6 8

n

T,

oC

Ea =0.3 Ea=0.4Ea=0.5 Ea=0.6

1/31/2007 2007 NEPP Workshop 17

Reliability Hazards: Multiple High Current Transients

Current-spike induced overheating:

where r, c, and d are the specific resistance, heat capacity, and density of aluminum.

Damage due to thermo-mechanical fatigue.

Under pulsed current conditions strains due to TCE mismatch lead to large stresses and might result in open circuit failures.

Spikes of ~200 ns and ~4107 A/cm2 can cause open-circuit failures.

2

2

Wh

tI

cT

Microstructural evolution with time of

AC stressing (100 Hz, 10 MA/cm2)

1/31/2007 2007 NEPP Workshop 18

Suggested Approach to Reliability Qualification (life test)

Assumptions: Reliability hazards for HVD at cryogenic conditions are related

to hot carriers injection and transient current/voltage spikes. Both processes depend on the number of switching cycles

rather than on duration of the part operation at cryogenic temperatures.

During the mission only a limited number of latching cycles (Nm = 1.3107) is required.

Approach: To assure reliable operation of the part during the mission

lifespan, the life testing can be carried out by increasing tenfold the number of required cycles.

Duration of life testing: tLT =10Nm256/f . At f ~ 100 kHz tLT = 90 hrs.

1/31/2007 2007 NEPP Workshop 19

Life Test Simulation

m

s

onomop V

V

Parameters of distributions were calculated using Monte-Carlo simulations for one out of 30 samples failed after 1.3108 cycles (no failures during life testing).

At 2 < < 5:2.5 10-12 < < 3.8 10-9, and probability of failure varies from 2 10-4 to 4.7 10-8.

Derating of VPPfrom 40 to 25 Vmight decrease in 2.6 to 6.5 times.

Required number of

cycles

1E4 1E81E5 1E6 1E7

0.05

0.1

0.5

1

5

10

50

90

99

0.01

Weibull Simulations

Number of switching cycles

Cu

mu

lativ

e p

rob

ab

ility

, %

=2

=5

1/31/2007 2007 NEPP Workshop 20

Conclusion NTs can be classified based on the accessibility to

information and control over the development. Majority of NTs are coming from commercial

manufacturing. Cooperation with manufacturers is necessary to get

information on major failure mechanisms and accelerating factors, and to assess their quality management system.

Critical analysis of accumulated experience and use of knowledge-based approaches are necessary to qualify NTs for space applications.

Knowledge-based approach can be effective to assure reliable operation of components at cryogenic temperatures.

reliability qualification of new technologies for space environments alexander teverovsky qss group,...

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