IEAE CRP F1.20.16. Ion Beam Modification of Insulators3rd RCM, Chiang Mai, Thailand, 10-14 Dec 2007

Ion Beam Modification of Sputtered Metal-Nitride Thin Films -a Study of the Induced Microstructural Changes

VINČA Institute of Nuclear Sciences, Belgrade, Serbia

- project started in May 2006 -

researchers:

Momir Milosavljević (Dr)Davor Peruško (PhD student)Maja Popović (MSc student)Mirjana Novaković (MSc student)

other co-workers in the group:

Velimir Milinović (Dr – Goett)Bane Timotijević (Dr-Surrey)

Investigations on this Project- started in May 2006 -

• Ion beam modification of Cr-N and TiN thin films on Si reactively sputtered, ~ 250 nm, implanted with 120 keV Ar

• Deposition of TiN coatings on pre-implanted stainless steel, 40 KeV nitrogen, 1.3 m TiN coatings subsequently deposited

• Ion beam modification of Al/Ti and AlN/TiN multilayers on Si, with 200 keV Ar or N2 ions

VINČA Institute ofNuclear Sciences

Lab for Atomic Physics

- research facilities used for this Project -

Balzers SPUTTRON II thin film deposition systemd.c. and r.f. sputtering, four target, rective deposition

Ion implanter – HV terminal 500 kV, Nielsen or RF ion sources for gases and solids, beam current 1-100 A,

scanned target area up to 5 cm diameter

2MV Van de Graaff ion acceleratorRBS – beam line in preparation

TEM – Philips EM400T 120 keV

Multimode NanoScope 3D, STM, AFM, MFM…

VEECO NANOINDENTER

Results to be presented- from the start of this project -

• Ion beam modification of Cr-N and TiN thin films on Si reactively sputtered, ~ 250 nm, RT or 150oC, different N2 pressure, implanted with argon at 120 keV, to 1x1015 and 1x1016 ions/cm2

• Deposition of TiN coatings on pre-implanted stainless steel

– AISI C1045 steel substrates implanted with 40 KeV nitrogen, to 5x1016 – 5x1017 ions/cm2, 1.3 mm TiN coatings subsequently deposited

• Ion beam modification of Al/Ti and AlN/TiN multilayers on Si, with 200 keV Ar or N2 ions, to 5x1016 – 2x1017 /cm2

100 200 3000

2000

4000

6000

8000

10000

12000

Si

NAr

Cr

Cr-N a.d. ~ 28% N

~ 38% N

~ 50% N

2e-4 3.5e-4 5e-4

Cou

nts

Channel

RBS spectra of as-deposited films as a function of N2 pressure (Goettingen)

Ion beam modification of Cr-N films on Si

100 200 3000

2000

4000

6000

8000 a.d. PN

2

5x10-5 mbar

Ar

Cr

N

Si

data fit

Cou

nts

Channel

RBS analysis of as-deposited and implanted Cr-N/Si

200 400 6000

2000

4000

Ba

cksc

att

eri

ng

yie

ldChannel

as deposited

1x1016 ions/cm2p

N2=2x10-4 mbar

Ar

30 40 50 60 700

50

100

150

200

250

(220)CrN

(311)Si

as depositedp

N2=5x10

-4 mbar, RT

CrN

(200)

CrN(111)

Inte

nsity

(a.

u.)

2 (degree)

30 40 50 60 700

50

100

150

200

250

CrN(220)

doseAr

+=1x1015

ions/cm2

pN2

=5x10-4

mbar, RT

(111)CrN

CrN(200)

Si(311)

Inte

nsity

(a.

u.)

2 (degree)

30 40 50 60 700

50

100

150

200

250

(311)Si

(111)

(200)

(220)CrN

CrN

CrN

doseAr

+=1x1016

ions/cm2

pN2

=5x10-4

mbar, RT

Inte

nsity

(a.

u.)

2 (degree)

XRD analysis => for PN2 = 2 and 3.5x10-4 mbar, Cr2N is formed for PN2 = 5x10-4 mbar, CrN phase forms

as-deposited 1x1015 Ar/cm2 1x1016 Ar/cm2

analysis of samples deposited at 150oC, PN2 = 5x10-4 mbar,implanted to 1x1015 and 1x1016 Ar/cm2

X-TEM analysis of Cr-N deposited at 150oC, PN2 = 5x10-4 mbar

as-deposited 1x1015 Ar/cm2 1x1016 Ar/cm2

0 2 4 6 8 10100

150

800

850

3.5x10-4mbar

2x10-4mbar

Ion fluence (x1015 ions/cm2)

5x10-4 mbar

Re

sist

ivity

(cm

)

Sheet resistance measurements of Cr-N films

RT

1500C

Samples deposited at 150oC

100 200 3000

2000

4000

6000

Ar

Ti

N

Si

data fit

Co

unt

s

Channel

RBS analysis of as-deposited films (Goettingen)

0 2000 40000

20

40

60

80

100

Con

cent

ratio

n (

at %

)

Depth (x1015

at/cm2)

Ti N Ar Si

(b)

Ion beam modification of TiN films on Si

TEM analysis of TiN deposited at RT

as-deposited

implanted1x1016Ar/cm2

0

50

100

150

200

0

50

100

150

30 40 50 60 70 800

50

100

150

TiN

TiNTiN

TiN

Inte

nsity

(a.

u)

(111)

(200)(220)

(311)

Si(311)

(a)

2(degrees)

TiN

TiNTiN

TiN(311)

(220)(200)

(111)

(311)(b)Si

(c)

(111) (200) (220)

(311)

TiN TiN TiN

TiN

Si(311) 0 2 4 6 8 10

50

60

70

80

90

Re

sist

ivity

(c

m)

Ion fluence (x1015ions/cm2)

RT 150oC

Sheet resistance measurements

XRD analysis of TiNdeposited at 150o C

Conclusions for Cr-N and TiN films

• Ion irradiation induces local rearrangements in the layer structure, the polycrystalline structure being retained

• Original columns become disconnected, nano-particles of the same phase are formed

• The resulting structures contain more crystalline defects (point defects in larger grains, nano-particles) which induce higher electrical resistivity

• No measurable changes in surface roughness were found• Sheet resistance measurements can be useful to interpret the

results of structural analysis

20 30 40 50 60 70 80 90 100 110

0

10000

Fe2N

Fe2N

Fe2N

Fe2N

Fe2N

2 (degree)

(c)

(110)

(200)(211)

(220)

Fe2N

(210)

(002)

(211)

(212)

(400)

(213)

0

10000

Fe2NFe

2N

Fe2N

Fe2N

FeFe

Fe

Fe

Fe

Fe

FeFe

(b) Fe2N

(210)

(002)

(211)

(212) (400)

0

10000

(220)(211)

(200)

(110)

FeFe

(a)

Fe(110)

(200)(211) Fe

(220)

Nitrogen pre-implantation of steel substrates shallow implants at 40 keV

standard XRD of TiN coating

GXRD of implanted substrate

unimplanted

2x1017

5x1017

30 40 50 60 70 80 900

100

200

300

400

Fe

FeTiN

TiN

TiN

TiN

Re

lativ

e In

ten

sity

2 (degree)

TiN(111)

(200)

Fe(110)

(220)(200)

(311)

(222)(211)

0 1x1017 2x1017 3x1017 4x1017 5x1017

500

1000

1500

2000

2500

3000 substrate substrate with coating

Mic

roha

rdne

ss (

MP

a)

Ion Fluence (ions/cm2)

Microhardness measurements

Conclusions for substrate pre-implantation

• Low energy, high fluence nitrogen implants induce formation of Fe-nitrides in the near surface region of the substrates

• Substrate pre-implantation influences preferred orientation of the grown TiN crystal grains

• The layers deposited on pre-implanted substrate exhibit a higher microhardness

• Total increase of the substrate microhardness after nitrogen pre-implantation and TiN deposition is up to more than eight times

Ion beam modification of multilayered thin film structures

nano-scaled multilayered structures TiN/Ti, TiN/AlN, etc, offer numerous advantages over single layer components

higher performance at much lower thickness, higher strength and hardness due to multiple interfaces, can form super lattices, graded structures, etc

ion beams can be useful for preparation and modification in the processes such as IBAD, plasma immersion, or ion implantation – homogenization, more dense and less porous structures

High fluence nitrogen implantation in Al/Ti multilayers on Si

10 alternative Al and Ti layers, deposited by ion sputtering in a single vacuum run, total thickness ~ 270 nm

200 keV N2+ ions, to 1x1017 and 2x1017 at/cm2, Rp ~ mid depth

aim – to study interface mixing and formation of metal-nitrides

N2+ ions

Al/Timultilayers

Si

Experimental work

Thin film deposition, ion implantation and TEM analysis – Vinča Inst

RBS analysis, 1.5 MeV He+ beam, two detectors, 148.2o scatt in ibm and172.8o in cornel geometry, Data Furnace – University of Surrey

AES primary electron energy 3 keV, two Ar ion guns for sputtering off 5x5 mm2 of the sample area – Jožef Stefan Inst, Ljubljana

100 150 200 2500

2000

4000

6000

8000

10000

12000

14000

O

N

Si

Al

Ti

as-dep 1e17 N 2e17 N

Cou

nts

Channel

RBS experimental spectra (Surrey)

100 150 200 2500

2000

4000

6000

8000

10000

12000

data A fit A data B fit B

Cou

nts

Channel

100 150 200 2500

2000

4000

6000

8000

10000

12000

ArO

data B fit B Al Ti Si

Cou

nts

Channel

as-deposited sample

100 150 200 2500

2000

4000

6000

8000

10000

12000

14000

data A fit A data B fit B

Cou

nts

Channel

100 150 200 2500

2000

4000

6000

8000

10000

12000

14000

ArON

data fit Al Ti Si

Cou

nts

Channel

sample implanted to 2x1017 N/cm2

0 200 400 600 800 1000 1200 1400 1600 1800 20000

10

20

30

40

50

60

70

80

90

100

Al Ti Si Ar O NC

once

ntra

tion

(at%

)

Depth (1015

at/cm2)

0 200 400 600 800 1000 1200 1400 1600 1800 20000

20

40

60

80

100

Al Ti Si Ar O N

Con

cent

ratio

n (a

t%)

Depth (1015

at/cm2)

0 200 400 600 800 1000 1200 1400 1600 1800 20000

20

40

60

80

100

Al Ti Si Ar O

Con

cent

ratio

n (a

t%)

Depth (1015

at/cm2)

RBS depth profiles

as deposited

1x1017 N/cm2

2x1017 N/cm2

0 20 40 60 80 100 1200

20

40

60

80

100

Al Ti N O C SiC

once

ntra

tion

(at%

)

Sputtring time (min)

0 20 40 60 80 1000

20

40

60

80

100

Al Ti N O C Si

Con

cent

ratio

n (a

t%)

Sputtring time (min)

AES depth profilesJS Institute

as deposited

1x1017 N/cm2

2x1017 N/cm2

0 20 40 60 800

20

40

60

80

100

Al Ti O C Si

Con

cent

ratio

n (a

t%)

Sputtring time (min)

x-TEM analysis as-deposited samples

implanted to 2x1017 N/cm2

Conclusions for high fluence N implantation in Al/Ti multilayers

Nitrogen implantation can be used to form (Al,Ti)N multilayered structures from Al/Ti layers

The layers are intermixed => tightly bound at the interfaces, have graded composition, but the multilayered structure is preserved

Ion irradiation induces larger grains and formation of lamellar grains stretching over a number of layers

XPS studies are in progress to analyze chemical composition

Microhardness results – shown below

Comparative analysis of ion irradiation stability of Al/Ti versus AlN/TiN multilayers

Similar structures as described before, total thickness ~ 270 nm irradiated with 200 keV Ar+, from 5x1015 to 4x1016 ions/cm2

deposition of AlN/TiN done by reactive sputtering

700 800 900 1000 11000

2500

5000

7500

10000

as-deposited

1x1016

Ar/cm2

4x1016

Ar/cm2

Bac

ksca

tter

ing

yiel

d

Energy (keV)

RBS spectra of Al/Ti structures on Si (Surrey)as a function of Ar+ fluence

RBS analysis of Al/Ti sample irradiated with 200 keV Ar+, to 1x1016 ions/cm2

600 800 1000 12000

2500

5000

7500

10000

AlO Ar

TiSi

data fit

Bac

ksca

tter

ing

yiel

d

Energy (keV)

400 600 800 1000 12000

2000

4000

6000

8000

Si

Al

Ti

N

as-deposited

2x1016

Ar/cm2

B

acks

catt

erin

g yi

eld

Energy (keV)

RBS analysis of AlN/TiN structures on Si (Surrey)

as-deposited sample

100 200 3000

2000

4000

6000

8000

10000

12000

14000

data fit N Ti Si Al

Cou

nts

Channel

Titanium point by point depth profiles

0 250 500 750 1000 1250 1500 17500

20

40

60

80

100

as deposited

1 x 1016

Ar/cm2

2 x 1016

Ar/cm2

Con

cent

ratio

n (a

t.%

)

Depth (1015

at/cm2)

0 500 1000 1500 2000 25000

10

20

30

40

50

60

70

Titanium depth profiles

as deposited

1 x 1016

Ar/cm2

2 x 1016

Ar/cm2

Co

nce

ntr

atio

n (

at.%

)

Depth ( x 1015

at/cm2)

Al/Ti structureAlN/TiN structure

Interface mixing in Al/Ti system

200 400 600 800 1000 1200 1400 16000

10

20

30

40

50

60

Mix

ed t

hick

ness

(10

15 a

t/cm

2 )

Depth (1015

at/cm2)

1x1016

Ar/cm2

2x1016

Ar/cm2

Projected ion range

TEM analysis of Al/Ti multilayers

as-deposited implanted to 2x1016 ions/cm2

TEM analysis of AlN/TiN multilayersas-deposited

implanted to 2x1016 ions/cm2

implanted to 4x1016 ions/cm2

Other TEM images of AlN/TiN multilayers

as-deposited

implanted to 2x1016 ions/cm2

implanted to 4x1016 ions/cm2

2

0

1

3D d

balld

F Rk

NE

Ion Beam Mixing models fo diffusio profiles:

- Ballistic mixing:

k = Δσ2 /Φ

- Global spike mixing:

coh

r

coh

Dgb H

Hk

H

FNkk 2

2

3/51 1

- Local spike mixing:

1.5' '1 24/3 5/3

5(1 )

6t r

ls Dcoh coh

Z Hk k k F

N H H

ξ = [4mM/(mM)2]1/2 – kinematic factorm, M – masses of the ion and target atomΓo = 0.608 – dimensionless constant

N – atomic density of the targetRd 1nm – minimum separation

distance for the production of a stable Frenkel pairFD – deposited energy per ion per unit

length

k1=0.35 nm; k2=27.4 – constants

ΔHr – reaction enthalpy

ΔHcoh – cohesive energy of

the reaction products

k1’ and k2

’ – constants

Zt – atomic number of the target

Microhardness measurementsindentation depth ~ 200 nm

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

2x1017 ions/cm2

Mic

roh

ard

ne

ss (

N/m

m2)

TiN (9594 N/mm2)

as deposited

1x1017 ions/cm2

0,0 1x1016 2x1016 3x1016 4x1016

5000

6000

7000

8000

9000

10000

Mic

roh

ard

ne

ss (

N/m

m2 )

Ion fluence (ions/cm2)

Al/Ti AlN/TiN

TiN

Al/Ti Implanted with NAlN/TiN and Al/Ti implantedwith Ar

A.Misra, M.J.Demkowicz, X.Zhang, and R.G.Hoagland, JOM, Sep 2007, 62-65T. Höchbauer, A. Misra,a K. Hattar, and R. G. Hoagland, JAP, 98, (2005) 123516Los Alamos National Laboratory

(33-150 keV helium, 1 × 10^17/cm^2)

Cu/Nb irradiatedwith high fluence He+,

Effects of swift heavy ion irradiation and thermal annealing on nearlyimmiscible W/Ni multilayer structureSharmistha Bagchi , Satish Potdar, F. Singh, N. P. Lallaa (India)JAP, 102, (2007) 074310

W/Ni with 120 MeV Au9+,

as-deposited

and 5x1013 ions/cm 2

Conclusions for ion irradiation stability of Al/Ti versus AlN/TiN multilayers

Both systems preserve multilayered structure

Al and Ti are chemically reactive => the layers become progressively intermixed with increasing the ion fluence, formation of Al-Ti phases is detected; ion irradiation induces larger grains and formation of lamellar columns stretching over a number of layers

In AlN/TiN system the components are immiscible => no detectable intermixing is observed, it is lower compared even to ballistic mixing, only a small increase of the mean grain size in individual layers can be seen

Non-mixing, or de-mixing published so far only for immiscible metal layers Cu/Nb with He+, W/Ni with Au9+,

Presentations and publications:

two at IBMM-2006, five at YUKOMAT 2006 and 2007, two at ECAART-9 2007, one at IBA 2007

three journal papers and three accepted for NIM B

two papers submitted

2 Msci and 1 PhD thesis

Joint UniS – Vinča Workshop on Ion Beam Applications for MaterialsModification and Analysis – held in Vinča, Belgrade, 2nd September 2006, with 6 lecturers from Surrey, 2 from Germany, 1 from Hungary and 3 from Serbia, and a wide audience of local potential users

Further work will be on investigations of multilayered structuresprepared AlN/Al, TiN/Ti and Ta/Ti for further studies