MURITotal Ionizing Dose Effects in Bulk

Technologies and Devices

Hugh Barnaby, Jie Chen, Ivan SanchezDepartment of Electrical EngineeringIra A. Fulton School of Engineering

Arizona State University

Outline

Overview of ASU tasks

Total ionizing dose defect models

Device TID responseo Drain-to-source leakage

o Inter-device leakage

Analysis of defect buildup across oxide structure and between technologies

Other work

ASU task

• Characterize and model TID effects in modern devices, primarily CMOS transistors

• Technologies: deep sub-micron bulk CMOS, and silicon on insulator, general isolations

ASU task

• Characterize and model TID effects in modern devices, primarily CMOS transistors

• Technologies: deep sub-micron bulk CMOS, and silicon on insulator, general isolations

In Year 1, we have primarily focused ondeep-sub-micron bulk CMOS and generalisolation technologies.

Primary TID Threat

TID defect build-up in the “thick” shallow trench isolation (STI)

Defects

• Not - oxide trapped charge (E’ )• Nit – interface traps (Pb)

Both Nit and Not are related to holesgenerated and/or hydrogen present inoxide

Not, Nit tox

first orderassumption

STI

Gate oxide

halo implants

n+ source n+ drain

p-body

STI

> 300 nm < 3 nm

Trapped charge buildup in STI

oxotygot tεfεfDkΔN

After Fleetwood et al. TNS 1994

Model Parameters

Model for Not buildup

D - total dose [rad]

kg - 8.1 x 1012 [ehp/radcm3]

fy - field dependent hole yield [hole/ehp]

fot - trapping efficiency [trapped hole/hole]

tox - oxide thickness [cm]

Hole trapping processes

+

+ - surviving hole (p)

- hole trap (NT)

- trapped hole (Not)

fp- hole flux

area =

Si-SiO2

interface

-+

-

+

-

+ +

-

+ +fp,i

tox

Ionizing radiation Si-SiO2

interface

-+

-

+

-

+ +

-

+ +fp,i

tox

Ionizing radiation

ip,T

otpotT

ot

σfN

(t)Nσf(t)NN

t

N

After Rashkeev et al. TNS 2002

Simple analytical model (Not)

yg

ygp

fkD

t

pfkD

x

f

oxygip, tfkDf (steady state) (fp > 0 for all x)

oxygTot tftkDσNN

fot D(No saturation or annealingand traps at interface)

oxitDHygit tffεfDkΔN

After Rashkeev et al. TNS 2002

Model Parameters

Model for Nit buildup

D - total dose [rad]

kg - 8.1 x 1012 [ehp/radcm3]

fy - field dependent hole yield [hole/ehp]

fDH - hole, D’H reaction efficiency [H+/hole]

fit - H+, SiH de-passivation efficiency [interface trap/H+]

tox - oxide thickness [cm]

De-passivation processes

- protons

- Si-H (NSiH)

- dangling bond (Nit)

area = it

H

H+

fH - proton flux

- hydrogen defect (D’H)

Si-SiO2

interface

-+

-

+

-

+

H

-

+fH

tox

Ionizing radiation

H

xd

H

D’H volume

fp

H+

H+

HitSiH

it

itHititSiH

it

fσN

(t)Nfσ(t)NN

t

N

After Rashkeev et al. TNS 2002

De-passivation processes

pDHDH

pDHDHH

fNt

HfN

x

f

doxDHygH xtffkDf

oxyDHgSiHit tfftkDσNN

fitD

(fH > 0 for all x)(steady state)

(No saturation or annealingand traps at interface)

Leakage paths

1 2

3

1

2

3

NMOS Drain-to-Source

NMOS D/S to NMOS S/D

NMOS D/S to NWELL

Defect build-up in STI creates leakage paths in CMOS ICs.

CMOS inverters

2 and 3 are inter-device leakage

NMOS drain-to-source leakage

1.E-11

1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

0 0.2 0.4 0.6 0.8 1 1.2 1.4

0k

100k

500k

No

rm. d

rain

cu

rren

t [A

/m

]

gate-to-source bias [V]

VG = 1.32V20 rad/s

Polysilicongate

N+ drain

N+ Source

LeakageLeakage

Polysilicon gate

N+ drain

N+ Source

LeakageLeakage

Polysilicongate

N+ drain

N+ Source

LeakageLeakage

Polysilicon gate

N+ drain

N+ Source

LeakageLeakage

130 nm bulk CMOS

Increasingtotal dose

Parasitic leakage model

“as drawn” “edge”

Weff

tOX-eff

VTH-eff“as drawn” “edge”

Weff

tOX-eff

VTH-eff

• Parasitic “edge” device modeled as MOSFET operating in parallel with “as drawn” FET.

• “Effective” parameters for “edge” device are extracted from data.

Extracting electrical characteristics

ID“edge”(post) ≈ IDtotal(post) – IDtotal(pre)

ID“edge”(post)

IDtotal(post)

IDtotal(pre)

Two assumptions:

1. IDtotal(pre) ≈ ID“as-drawn”(pre)

2. ID“as-drawn”(post) ≈ ID“as-drawn”(pre)

“Edge” Capacitor

Prior to radiation exposure, the

MOS capacitor of the “edge” device has small dimensions, W and tox

STI

Weff tox-eff

++

++

++

“Edge” Capacitor

Upon radiation exposure, the “edge capacitor is degradedand the dimensions enlarged.

STI

Weff tox-eff

++

++

STI

Weff

tox-eff

++

+ ++

++

Increasingtotal dose

++

“Edge” Capacitor

Increased defect buildup in theSTI sidewall leads to further increases in W and tox, until inherent limitations are met.

STI

Weff tox-eff

++

++

STI

Weff

tox-eff

++

+ ++

++

Increasingtotal dose

++

STI

Weff tox-eff

++

+ ++

+++

++++

++++

+++

+

2D simulations

Not = 2×1012 cm-2 Not = 5×1012 cm-2 Not = 7×1012 cm-2

Simulations show how increased Not along sidewall increases the width of the channel and the capacitor thickness

Weff Weff

Weff

New Test Structure

Devices designed by Faccio and fabricated at STMicro enable measurements on sidewall capacitor.

•1.3 um

•90 um

overlap

Pre-rad

Parameter extraction

1.00E-16

1.00E-14

1.00E-12

1.00E-10

1.00E-08

1.00E-06

1.00E-04

-0.5 0 0.5 1 1.5

gate bias (V)

drai

n cu

rren

t (A

) 100 krad

500 krad

1 Mrad

Series1

Series2

Series3

Expon.(Series1)Expon.(Series2)Expon.(Series3)

Img (1 Mrad)

2 1

3

4

Img (500 krad)

Img (100 krad)

1. Weff increases withTID (increased strong -inv current)

2. Not and Nit increase with TID (shift in threshold voltage)

3. Nit and tox increasewith TID (reducedsubthreshold slope)

4. Not increasewith TID (shifts inmidgap voltages)

Simultaneous equations

dsF

22

-qV /kTq2φ /kTsi a ids S F eff

F

e f

a

f ε qN kT nI (φ = 2φ ) =μ e (1-

L 4φ

We )

q N

si a B OTOX-efmg FB F f

OX

2ε qN φ - qV = V + φ +

ε

Nt

ITb

OX-ef

XO f

C + qn = 1+ ( )

ε

Dt

OX dsds eff gs TH-ef

eff

OX-efds

ff

ε VI = μ (V - V ) -

tV

L 2

W

1.

2.

3.

4.Solving simultaneouslyenables extraction ofparameters and defectlevels at each TID value

Parameters and sidewall defects

VTH-eff (V) tOX-eff (nm) Weff (nm)

pre N/A N/A N/A

100 krad 0.194 17.9 43.7

500 krad 0.180 17.9 99.9

1 Mrad 0.169 20.0 128.1

Parameters

Defects

Not (cm-2) NIit (cm-2)

100 krad – 500 krad 8.5×1010 6.4×1010

100 krad – 1 Mrad 1.0×1011

1.2×1011

Inter-device leakage

Aluminum line Polygate

Polygate

p+ p+n+n+

Aluminum gate

+++ + + + + + + + + + + + +

++

n+ p+n+

Leakage path

n+

p+ n+

n-well

n-well

VDD0V

Aluminum line Polygate

Polygate

n+ n+n+n+

Aluminum gate

+++ + + + + + + + + + + + +

++

n+ n+ n+n+

Aluminum line Polygate

Polygate

n+ n+n+n+

Aluminum gate

+++ + + + + + + + + + + + +

++

n+ n+ n+n+

Leakage path

VDD0V

n+ D/S to n-well n+ D/S to n+ D/S

Charge build-upin STI base

Field oxide transistors

1.E-11

1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

0 10 20 30 40

gate-to-source bias [V]

dra

in c

urr

en

t [A

]

50k

100k

500k

130 nm bulk CMOS

noisefloor

p-well

STIn+ n+

n-well

-n+ D/S

n+ D/S n-well

n-well

Metal 1

Metal 1

++++

Field oxide capacitors

1500 Single Cell FOXCAPs in parallel

gate area of individual cell ~ 7.4 μm x 11.4 μm

Single cell

0.97

0.98

0.99

1

-40 -30 -20 -10 0 10 20 30

Gate Voltage [V]

Nor

mal

ized

Cap

actia

nce

Pre-rad

Rad-inducedshift

After 1-weekanneal

0.97

0.98

0.99

1

-40 -30 -20 -10 0 10 20 30

Gate Voltage [V]

Nor

mal

ized

Cap

actia

nce

Pre-rad

Rad-inducedshift

After 1-weekanneal

130 nm data

Defect build-up in STI base

Total Dose [krd(Si)]

Def

ect

s [c

m-2

]

Defect build-up is:

1. Greater for higher oxidefields (consistent w/ fy)

2. Linear with dose(no saturation … yet)

Comparison to other isolation technologies (Not)

Device tox (nm) Type Area (cm2) ∆Vot (V) K (x 103)

FOXCAP 320 p 0.0023 6.5 63.5

RF25 600 p 0.0012 4.175 11.6

XFCB 600 p 0.0070 6.12 17

E4403/W21* 1080 n 0.030 7.7 33.01

SIMOX 370 n 0.022 2.2 16.07

*data taken after 20 krad(SiO2) exposures

**radiation bias is 0V for all devices

yotox

g

2ox

ot ffε

qk

Dt

ΔVK

Sidewall vs. Base Comparison (Not)

01E+162E+163E+164E+165E+166E+167E+168E+16

100 400 700 1000Total Ionizing Dose (krad)

No

rmal

ized

No

t

STI sidewall

STI base

Indicates saturation in defect buildup

500 k 1000k

STI sidewall .0147 .0068

STI base .0109 .0094

otyff

Sidewall vs. Base Comparison (Nit)

0

1E+16

2E+16

3E+16

4E+16

5E+16

6E+16

7E+16

100 400 700 1000

TID (krad)

NIT

(n

orm

. to

ox

ide

thic

kn

ess

)STI sidewall

STI base

Other Work

• Separation of switch state defects in thick isolationoxides using frequency dependent charge pumping

• Packaging issues

Gate sweep data

12 umbase

collector

gate

emitter

12 umbase

collector

gate

emitter

Nss

Nss

Increased current is caused by switching state buildup (Nss) whichis composed of both interface and border traps

Separation of Switching States

Indicates border traps

Packaging IssuesGate Sweep (Crane)

1.E-09

1.E-08

1.E-07

1.E-06

-100 -80 -60 -40 -20 0

Vg (V)

Ib (

A)

sealed @ 30krad

unsealed @ 30Krad after 8 days• Recent testing showed

3x increase in Nit in GLPNP devices packaged with sealed gold plated kovar lids than packages with taped-on lids.

ΔNot (cm-2) ΔNit (cm-2)

Unsealed ~1.7x1011 ~0.8x1011

Sealed ~1.4x1011 ~2.5x1011

It’s a hydrogen problem

• As sealed lid is removed, H2 moves quickly out of the package and a concentration gradient is established for the remaining H2 in the oxide to diffuse out, thus reducing Nit generation.

100.00000.001917. Xenon

100.00000.000516. Krypton

100.00000.006415. NH3

100.00000.001314. Fluorocarbons

100.00000.003313. Tot. HC and Org.

100.00000.135212. Carbon Dioxide

100.00000.003211. Argon

100.00000.132610. Oxygen

100.00000.00009. Carbon Monoxide

100.000098.25088. Nitrogen

100.00000.00007. Neon (22)

100.00000.00146. Neon (20)

0.50000.09685. Water

100.00000.00584. Methane

100.00000.00143. Helium (4)

100.00000.00002. Helium (3)

100.00001.35931. Hydrogen

LIMIT in %

Volume % (1%=10,000ppm)

GASSES ANALYZED

100.00000.001917. Xenon

100.00000.000516. Krypton

100.00000.006415. NH3

100.00000.001314. Fluorocarbons

100.00000.003313. Tot. HC and Org.

100.00000.135212. Carbon Dioxide

100.00000.003211. Argon

100.00000.132610. Oxygen

100.00000.00009. Carbon Monoxide

100.000098.25088. Nitrogen

100.00000.00007. Neon (22)

100.00000.00146. Neon (20)

0.50000.09685. Water

100.00000.00584. Methane

100.00000.00143. Helium (4)

100.00000.00002. Helium (3)

100.00001.35931. Hydrogen

LIMIT in %

Volume % (1%=10,000ppm)

GASSES ANALYZED

H2

H2

H2

H2

H2

H2H2

H2

H2

H2

H2

H2

H2

H2H2

H2

H2

H2

H2

H2

H2

H2 H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2H2

H2H2

H2 H2H2

H

H

H

H

H

H2 ~ 1.3%

H2

H2

H2

H2

H2

H2H2

H2

H2

H2

H2

H2

H2

H2H2

H2

H2

H2

H2

H2

H2

H2 H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2H2

H2H2

H2 H2H2

H

H

H

H

H

H2 ~ 1.3%

ox

Si

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2 H2

H2

H2

H2

H2

H2

H2

H2

H2 H2

H2

H2

H2

H2<<1.3%

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2H2

H2

H2

H2

H2

H

H

H

H

H

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2 H2

H2

H2

H2

H2

H2

H2

H2

H2 H2

H2

H2

H2

H2<<1.3%

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2

H2H2

H2

H2

H2

H2

H

H

H

H

H

Another time dependent process

Results shows time dependence of Nit build-up related hydrogen out diffusion … we are working on the rate equations for this

Peak Base Current Vbe = 0.5V, 30Krad

0.0E+00

2.0E-08

4.0E-08

6.0E-08

8.0E-08

1.0E-07

1.2E-07

1.4E-07

1.6E-07

seal (30K) 1h (30K) 13h (30K) 7d (30K)

Time

Ib (

A)

lid off

taped kovar

taped ceramic

Not (cm-2) Nit (cm-2)

Sealed ~1.7x1011 ~2.4x1011

Unsealed 1hr

~1.6x1011 ~1.5x1011

Unsealed 13hrs

~1.6x1011 ~6.9x1010

Unsealed 7days

~1.6x1011 ~6.1x1010