ASET and TPA Update - NASADefense Threat Reduction Agency Schematic Flip-Chip Cross Section. Defense Threat Reduction ... Determination of TPA Parameters Defense Threat Reduction Agency

ASET and TPA Update

Dale McMorrow and Joseph S. MelingerNaval Research Laboratory, Code 6812, Washington, DC 20375

William T. LotshawConsultant, Bethesda, MD 20817

Stephen BuchnerQSS Group., Inc., Seabrook, MD 20706

Defense Threat Reduction Agency


Outline

• Two-Photon Absorption (TPA) Technique• Backside “through-wafer” carrier injection and

imaging• Determination of non-linear coefficients• ASETs in LMH6624

• Conclusions

Two-Photon Absorption Technique



Two-Photon Absorption SEE Experiment

• Because the laser pulse wavelength is sub-bandgap the material is transparent to the optical pulse

• Carriers are generated by nonlinear absorption at high pulse irradiances by the simultaneous absorption of two photons

• Carriers are highly concentrated in the high irradiance region near the focus of the beam

• Because of the lack of exponential attenuation, carriers can be injected at any depth in the semiconductor material

• This permits 3-D mapping and backside illumination

400 600 800 1000 1200 140010-1

100

101

102

103

104

105

1.06 µm

1.26 µm

800 nm

600 nm

Abs

orpt

ion

Coe

ffici

ent,

cm-1

Wavelength, nm







• This permit 3-D mapping and backside illumination

ωβ

ωα

2),(),(

),( 2

2 zrIzrIdt

zrdN +=

Carrier generation equation:

1-photon absorption

2-photon absorption








-4 -2 0 2 4

030

1020

N α I2

w(z)

1/e Contour

Position, µm

Dep

th in

Mat

eria

l, µm








-4 -2 0 2 4

030

1020

N α I2

w(z)

1/e Contour

Position, µm

Dep

th in

Mat

eria

l, µm








Overlayers

P (C1)

P+ (iso)P+ (iso)

N (base)

P (substrate)

12 µm

P (C2)

N+ (buried layer)

P


-4 -2 0 2 410

8

6

4

2

0

w(z)

1/e Contour

Position, µm

Dep

th in

Mat

eria

l, µm



-4 -2 0 2 410

8

6

4

2

0

w(z)

1/e Contour

Distance, µm

Dep

th in

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eria

l, µm



-4 -2 0 2 410

8

6

4

2

0

w(z)

1/e Contour

Distance, µm

Dep

th in

Mat

eria

l, µm

-4 -2 0 2 4

030

1020

N α I2

w(z)

1/e Contour

Position, µm

Dep

th in

Mat

eria

l, µm




COMPLEMENTARY TECHINQUE

• Not intended to replace “conventional” (above band gap) pulsed laser

• Not intended to replace heavy-ion irradiation

• WILL NOT replace these tools

• Is another “Tool” in our “SEE Toolbox”



Ti:Al2O3 OPA

Polarizer

λ/2

DUT

xyz

120 fs1.26 µm

CCDPD2

PD1

Back Side Illumination




Schematic Flip-Chip Cross Section


Backside “Through-Wafer” TPA Illumination

Surface elements opaque to optical excitation

Tightly focused two-photon excitation

source

Substrate transparent to single photon

sub-bandgap excitationCircuit Layer(s)

Region of 2 PhotonCarrier Generation


Backside “Through-Wafer” TPA IlluminationLM124 Operational Amplifier

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Photomicrograph of Q20 in LM124 Captured with IR Camera

Front Side Back Side

Evaluating two IR cameras – IR Sensors and Indigo


Backside “Through-Wafer” TPA IlluminationLM124 Operational Amplifier

0 5 10 15 20

0.0

1.0

2.0Q18

Out

put S

igna

l, V

Time, µs

0.0

0.5

1.0

1.5 Q18

Front Side Back Side


BAE SRAM “Through Wafer” Image


Backside “Through-Wafer” TPA IlluminationSEU in Flip Chip SRAM Test Structure

2D SEU Map


Backside “Through-Wafer” TPA IlluminationSEU in Flip Chip SRAM

• Issues• through-wafer imaging

• InGaAs FPA • highly-doped substrate

• linear loss from free-carrier absorption• attenuates IR beam • attenuates illumination light• wafer thinned to minimize absorption

• Results: SEUs successfully injected in SRAM by TPA at well characterized locations

Determination of TPA Parameters



Two-Photon Carrier Injection for SEE Testing

The values for linear absorption (αααα), two-photon absorption (TPA) coefficient (ββββ), and Re n2 qualitatively affect optical propagation– Rigorous functional mapping, generic test &

measurement applications to diverse semiconductor devices requires quantified nonlinear optical parameters

• for understanding of axial and transverse injected carrier distribution

– esp. effects due to free (doped) and photo-generated carriers

• evaluation of energy transfer (LET)


Nonlinear Optical Property Measurement: Z-scans

Laser Spectroscopy Facility

Nonlinear Property Measurement Requires– measured pulse duration– measured spot size– knowledge of laser mode quality– pulse-to-pulse stability

fs Ti:Soscillator

fs Ti:Samplifier fs OPA

Z-scan measurement

Pulse Diagnostics

VariableAttenuator


Nonlinear Optical Property Measurement: Z-scans

lensf.l.= zo sample beam splitter

aperture

detector 2

detector 1

sample translationwrt lens focal plane, zo

fs laser pulse@ 1/2 Eg

pulse energymonitor

Ultrashort laser pulse induces1. nonlinear lensing in sample:

2. nonlinear absorption in sample:

( ) ),(2 , zrIntrn •=∆

( ) ),( , zrItr •=∆ βα


Nonlinear Optical Property Measurement: Z-scans on Material with Positive n2

dete

ctor

2 s

igna

l

dete

ctor

1 s

igna

l

z = zo z = zo

lensbeam splitter

aperture

detector 2

detector 1

sample @ z < zo

For sample immediately in front of beamwaist (@ zo), focal power of sample adds to that of lens, the beam at detector 2 is more divergent and signal decreases



detector 2

dete

ctor

2 s

igna

l

dete

ctor

1 s

igna

l

z = zo z = zo

lensbeam splitter

aperture

detector 1

sample @ z = zo

At beamwaist, focal power of sample goes to zero so signal at detector 2 is due to lens only. Signal at detector 1 is a minimum because of TPA.



dete

ctor

2 s

igna

l

dete

ctor

1 s

igna

l

z = zo z = zo

lensbeam splitter

aperture

detector 2

detector 1

sample @ z > zo

For sample immediately behind beamwaist, focal power of sample decreases beam divergence, signal at detector 2 increases


Materials for Z-Scan Measurements

Si:– P-type (B) <0.02 ΩΩΩΩ-cm– P-type (B) >10-20 Ω-cm– P-type (B) >30-40 ΩΩΩΩ-cm– N-type (Sb) <0.02 Ω-cm– N-type (P) 10 ΩΩΩΩ-cm


Two-Photon Absorption Coefficient Measurement

0 5 10 15 20 25 30 35

0.4

0.6

0.8

1.0

Si(B), 30-40 Ohm-cm Z-scans @ 1250 nmN

orm

aliz

ed T

rans

mis

sion

(a.u

.)

Z (mm)

Io = 393 GW/cm2, ∆T = 0.593

I = 166 GW/cm2, ∆T = 0.391 I = 72.7 GW/cm2, ∆T = 0.206 I = 42.1 GW/cm2, ∆T = 0.113 I = 20 GW/cm2, ∆T = 0.03


Two Photon Absorption Coefficient

( )

( ) ( )( )

( )eff

Z

L

effeff

LIz

eLZZ

LIz

z

L

o

0At

2o

2o

0T22

10%)(~ valueseapproximatFor

1 ,1

122

T

fit to bemust data T theanalysis, rigorousFor

:

. thicknesssample theis

t,coefficien absorptionlinear theis

t,coefficien absorptionphoton - two theis

=∆×≅

±

−=

+=∆

∆

=

−

β

αβ

α

β

α

When Z-scan ∆∆∆∆T (at detector 1) scales ∝∝∝∝ I 2:


0 5 10 15 20 25 30 350.00

0.05

0.10

0.15

0.20

0.25

N

onlin

ear T

rans

mis

sion

Pulse Energy, nJ

Z-Scan Data Linear Fit

Open Aperture Z-Scan Measurement of TPAAntimony-Doped Silicon (0.02 Ω-cm)


Two Photon Absorption Coefficient

For I ≤≤≤≤ 166 GW/cm2, the ∆∆∆∆T for all Si z-scans are ∝∝∝∝ I 2, and

for 30 Ω-cm Si(B): ββββ ≅≅≅≅ 0.195 cm/GW; αααα ≅≅≅≅ 0

for 0.02 Ω-cm Si(B): ββββ ≅≅≅≅ 0.286 cm/GW; αααα = 30 cm-1

for 10 Ω-cm Si(P): ββββ ≅≅≅≅ 0.193 cm/GW, αααα ≅≅≅≅ 0

More highly doped sample shows enhanced ββββ.

Further experiments to acquire nonlinear refractive index dataand full curve fitting analyses in progress.

First Measurement of SETs inLMH6624



LMH6624 SET Test Results


SETs in LMH6624

-0.14

-0.12

-0.1

-0.08

-0.06

-0.04

-0.02

0

0.02

0.04

-80 -60 -40 -20 0 20 40 60 80 100

Time (ns)

Am

plitu

de (V

)

Position 1

-0.25

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-0.15

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0

0.05

0.1

-80 -60 -40 -20 0 20 40 60 80

Time (ns)

Am

plitu

de (V

)

Position 2

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

-80 -60 -40 -20 0 20 40 60 80

Time (ns)

Am

plitu

de (V

)

Position 3

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

-80 -60 -40 -20 0 20 40 60 80

Time (ns)

Am

plitu

de (V

)

Position 7


Summary

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Documents

ASET and TPA Update - NASADefense Threat Reduction Agency Schematic Flip-Chip Cross Section. Defense Threat Reduction ... Determination of TPA Parameters Defense Threat Reduction Agency