P l a sma Enhanced A tom i c Laye r Depos i t i on o f Mo lybdenum N i t r i de

A.Bertuch1,B.Keller2,N.Ferralis2,J.C.Grossman2andG.Sundaram11Ultratech-CambridgeNanoTechInc.,Waltham,MA,abertuch@ultratech.com2DepartmentofMaterialScienceandEngineering,MassachuseJsInsKtuteofTechnology,Cambridge,MA

IntroducKon

q  LowtemperaturetechniquesfordeposiKnghighqualitymolybdenumnitridefilmsusingplasmaenhancedatomiclayerdeposiKon(PE-ALD)wereinvesKgatedandcharacterized.

q  UniquematerialproperKes:includingelectrical,mechanical,chemical,andcatalyKcbehavior.§  MoNisanextremelyhardmaterial§  SuperconducKve§  ExcellentcatalyKcproperKes§  LowsolubilitytoCuwithgoodelectrical

conducKvity(200-500µΩ-cm)§  DiffusionbarrierforCuinterconnects

2

ImagefromSouthernIllinoisUniversity

DiffusionBarrierforCuinterconnects

MoNxAtomicLayerDeposi9onq  MoCl5andNH3at350–500°C,ResisKvity1500–100µΩ-cm

§  PetraAlen,“AtomicLayerDeposi5onofTaN,NbNandMoN,AcademicDisserta5on,UniversityofHelsinki,DepartmentofChemistry,June2005.

q  (tBuN=)2(NMe2)2MoandNH3at260–300°C§  V.Miikkulainen,M.Suvanto,andT.A.Pakkanen,“AtomicLayerDeposiKonofMolybdenumNitride

fromBis(tert-butylimido)-bis(dimethylamido)molybdenumandAmmoniaontoSeveralTypesofSubstrateMaterialswithEqualGrowthperCycle,”ChemistryOfMaterials,vol.19,no.2,pp.263-269,Jan.2007.

q  Mo(CO)6andNH3at170°Cwith400°Canneal§  DipNandi,UJamSen,DevikaChoudhury,SagarMitra,andShaibalSarkar,“AtomicLayerDeposited

MolybdenumNitrideThinFilm:PromisingAnodeMaterialforLiIonBaJeries,ACSAppl.Mater.Interfaces,2014,6(9),pp6606–6615,DOI:10.1021/am500285d

q  Mo(NtBu)2(StBu)2,andH2plasmaat300°C,ResisKvity350µΩ-cm§  YujinJang,JunBeomKim,TaeEunHong,andSoo-HyunKim,“Highly-conformalnanocrystalline

molybdenumnitridethinfilmsbyALDasadiffusionbarrier”,JournalofAlloysandCompounds663·November2015,DOI:10.1016/j.jallcom.2015.12.148

PriorWorkMoNX

3

Bis(tert-butylimido)bis(dimethylamido)Molybdenum

4

(tBuN=)2(NMe2)2Mo Vapour Pressure Curve

0.1

1

10

50 60 70 80 90 100 110

Temp (C)

VP

(tor

r)

EquaKon:LOG10P(Torr)=9.8–3447/T(K)

VaporPressureofMo(NtBu)2(NMe2)2

t-Bu-N=Mo=N-t-Bu

PriorOxideWorkq  Vosetal.,“AtomiclayerdeposiKonofmolybdenumoxidefrom(NtBu)2(NMe2)2Mo

andO2plasma“,J.Vac.Sci.Technol.A34,01A103,2016;DOI:10.1116/1.4930161q  Bertuchetal.,“AtomiclayerdeposiKonofmolybdenumoxideusing

bis(tertbutylimido)bis(dimethylamido)molybdenum”J.Vac.Sci.Technol.A32,01A119,2014;DOI:10.1116/1.4843595

MoO3ALDandPE-ALD

MolecularStructure

Experimental

q  Equipment:Ultratech/CNTFiji§  ReactorturbopumpandLoadLock§  300W,13.56MHzinducKvelycoupledplasma(ICP)§  N2andH2plasmacomposiKons(2–25%N2inH2)

q  Precursor:(tBuN)2(NMe2)2Mo§  Pvapor(60⁰C)=~0.29Torr§  N2boosteddeliverytechnique1

q  ProcessTemperature:80–300°C

q  FilmCharacterizaKon§  ALDFilmproperKes(SpectroscopicEllipsometry)§  OpKcalandelectrical(SpectroscopicEllipsometryandFourPointProbe)§  FilmComposiKon(XPS)§  Crystallography(XRD)

5

1G.Liu,A.Bertuch,G.Sundaram,“PrecursorBoostforLow-Vapor-PressureALDPrecursors”,Presentedat2010ALDSeoul,Korea

0.30

0.35

0.40

0.45

0.50

0.55

0.60

0.65

0 10 20 30 40 50

GrowthPerCycle(A/Cycle)

Plasmatime(sec)

150°CMolybdenumNitride1:8N2:H2

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0

1000

2000

3000

4000

5000

6000

7000

0 10 20 30 40 50

nank(633nm)

Rho(µohm-cm)

Plasmatime(sec)

150°CMolybdenumNitride1:8N2:H2

Rhonk

PlasmaTimeDependence

ImpactofPlasmaKme,11%N2inH2150⁰C-GrowthperCycle

q  ICP Plasma )me §  15 sec plasma has a reduced process capability

§  GPC is reduced by < approximately 10% §  n and k values are reduced §  Rho is elevated

§  Plasma: 300 WaEs, 40 sec is need to complete the reac)on.

§  40 sec plasma )mes yield improved electrical and op)cal proper)es.

6

Resis9vityandop9calproper9es

0.200.250.300.350.400.450.500.550.600.650.70

50 75 100 125 150 175 200 225 250 275 300 325

GPC(A/cycle))

Temperature(C)

MolybdenumNitride1:16N2:H2

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0200400600800100012001400160018002000

50 75 100 125 150 175 200 225 250 275 300 325

nank(633nm)

Rho(µohm-cm)

Temperature(C)

MolybdenumNitride1:16N2:H2

Rhonk

TemperatureDependence

Temperaturedependence(6%N2inH2)q  Process §  (NtBu)2(NMe2)2Mo precursor

§  Plasma 1:16 N2:H2, 40 sec, 300 W

§  Film thickness = 17 - 25 nm

§  200mm uniformity < 3.5% (1-σ)

§  GPC 0.4 to 0.65 Å/cycle

q  Tunable Op)cal and Electrical Proper)es §  n (633nm) and k (633 nm) values

§  Rho (1400 – 200 µohm-cm)

q  T > 250 °C Transi)on §  Onset of changes in op)cal and

electrical proper)es

7

Resis9vityandgrowthpercycle(GPC)

Resis9vityandop9calproper9es

PlasmaN2:H2gas,T=150⁰C

N2concentraKoninH2plasmagasq  150 °C MoNX Process

§  (NtBu)2(NMe2)2Mo precursor

§  Plasma: 300 WaEs, 40 sec

§  Variable N2:H2 concentra)on

q  Tunable Op)cal and Electrical Proper)es §  Increasing n & k (633 nm) values

with increasing H2 concentra)on §  Rho (800 – 180 µohm-cm)

q  Growth Per Cycle §  Decreases with increasing H2

concentra)on (0.55 – 0.37 Å/cycle)

§ 

8

0.280.320.360.400.440.480.520.560.60

0% 4% 8% 12% 16% 20%

GPC(A/cycle))

N2 inH2 plasmagas(%)

150°CMoNwith40secplasma

GPC

0.000.501.001.502.002.503.003.504.00

02004006008001000120014001600

0% 4% 8% 12% 16% 20%

nandk(633nm)

Rho(µohm-cm)

N2 inH2 plasmagas(%)

150°CMoNwith40secplasma

Rhonk

Resis9vityandgrowthpercycle(GPC)

Resis9vityandop9calproper9es

XPS DATA MolybdenumNitride

9

XPS-SurveyScan

Intensity

(a.u.)

BindingEnergy1200 900 600 300 0.0

2

10

8

12

6

4

O1sMo3s

N1sMo3p1/2Mo3p3/2

Mo3p

Mo3d3/2Mo3d5/2

Mo3dC1s Si2s

Si2p1/2Si2p

Si2p3Mo4s

CONSi

Mo

1min Ar spuEer was used for surface prepara)on.

Peaks associated with Mo, N, O, and C are observed and analyzed from the survey scan.

The MoNX doublet (Mo 3d3/2 and Mo 3d5/2 peaks)

was used for evalua)on

Analysis of film composi)on

0

10

20

30

40

50

60

70

0% 4% 8% 12% 16% 20%

Composition(%)

N2 inH2 plasmagas(%)

XPSCompositon

MoNCO

MoNx Film Composi)on

q  Temperature (80 – 250 ⁰C)

§  Reduc)on in O and N concentra)on with increasing temperature.

§  Less than 8% O2 from 75 - 250 ⁰C, with a Minima at 250 ⁰C at 3% O2

§  Increasing C concentra)on to 250 ⁰C, then sharp decline at 300 ⁰C

§  10% at 300 ⁰C may explain reduced op)cal and electrical performance at 300 ⁰C

q  H2:N2 Ra)o §  Reduc)on in N has propor)onal to N2 gas

concentra)on

§  Carbon concentra)on increases as the H2 content approaches 100%

§  Corresponding improvements are observed in the op)cal and electrical proper)es with reduced N2.

0

10

20

30

40

50

60

50 100 150 200 250 300 350

Composition(%)

TemperatureC

XPSCompositon

MoNCO

XPSDataComposiKon

ComposiKon(%)TemperatureDependence,6%N2inH2

150⁰Cplasmagasdependence(H2andN2)

0.00.20.40.60.81.01.21.41.6

0% 4% 8% 12% 16% 20% 24%

MoNRatio(N/Mo)

N2inH2 plasmagas(%)

150°CMoNxComposition

XPSMoNXStoichiometry

N/MoComposiKon-MoNX

00.10.20.30.40.50.60.70.80.91

50 100 150 200 250 300 350

MoNRatio(N/Mo)

Temperature(°C)

MoNxCompositionTemperatureDependence,6%N2plasma

150⁰CplasmagasDependenceH2andN2

q  MoNx Composi)on is dependent upon §  H2:N2 composi)on in plasma step

§  Deposi)on Temperature (75 – 250 ⁰C)

q  The MoNX composi)on

§  By changing the process condi)ons the composi)on of the MoNX can be adjusted.

§  Higher Mo content with increasing H2 concentra)on in the plasma gas

§  Increasing electrical conduc)vity.

q  300 ⁰C data point shows a dis)nct increase in MoN ra)o MoN0.64 §  Thermal transi)on?

§  Precursor Decomposi)on?

§  MoNX crystallinity?

§  Equipment? Single data point

Morichfilm(MoN0.4)

Nrichfilm(MoN1.4)

Morichfilm(MoN0.4)

Nrichfilm(MoN1.4)

XRD DATA MolybdenumNitride

13

0

50

100

150

200

250

300

25 35 45 55 65 75 85

NormalizedScattering

Intensity(a.u.)

2? ( )

80°C 100°C150°C 200°C250°C 300°C

q  What is the structure of the MoN? §  Amorphous §  MoN0.5 (cubic)

§  β-Mo2N phase (body centered tetragonal)

§  γ-Mo2N phase (face centered cubic)

q  XRD data indicates γ-Mo2N phase (face centered cubic) for all inves)gated temperatures

XRDSurveyScan

2thetaplot–TemperatureDependence

γM

o 2N(1

11)

γM

o 2N(2

00)

γM

o 2N(2

20)

γMo 2N(3

11)

Sirefl

ec9o

ns

(113)

14

Peak Intensity were normalized to the 111 peak

0.0

0.5

1.0

1.5

2.0

2.5

35.6

35.8

36

36.2

36.4

36.6

50 100 150 200 250 300

111FWHM

111Position(2θ°)

Temperature(°C)

111position- MoNprocess

0.0

0.5

1.0

1.5

2.0

2.5

35.6

35.8

36.0

36.2

36.4

36.6

0% 4% 8% 12% 16% 20%

111FWHM

111Position(2θ°)

N2 inH2 plasmagas(%)

111position- 150CMoNprocess

0

50

100

150

200

250

300

32 34 36 38 40 42 44 46

NormalizedScattering

Intensity(a.u.)

2? ( )

10:40 5:40

5:80 2.5:801.3:80

(200)(111)

20% N2

11.1% N2

5.9% N2

3.0% N2

1.6% N2

0

50

100

150

200

250

300

32 34 36 38 40 42 44 46

NormalizedScattering

Intensity(a.u.)

2? ( )

80°C 100°C150°C 200°C250°C 300°C

(200)(111)

80 ⁰C

100 ⁰C150 ⁰C

200 ⁰C250 ⁰C300 ⁰C

XRDTwoThetaPeaksdependenceN2inH2plasma,150⁰C Temperaturedependence5.9%N2inH2

Increasing N2 concentra)on in the plasma has less long range order in the crystal.

0

200

400

600

800

1000

1200

1400

1.1 1.3 1.5 1.7 1.9 2.1 2.3 2.5 2.7 2.9 3.1

Intensity(a.u.)

inter-atomicspacing,d(Å)

150C200C250C300C

q  XRD Survey scans converted to inter-layer spacing (d) using Braggs Law.

q  Lance constants were calculated for the major and minor XRD peaks

γ Mo2N face center cubic

XRDData

LasceSpacing–CalculatedfromXRDResults

Inter-atomicspacing,d(A)

MillerIndices

MeasuredLa`ceConstant,a(nm)

1.28 311 0.425+/-0.001

1.50 220 0.424+/-0.001

1.65 113 SireflecKons

2.125 200 0.425+/-0.002

2.47 111 0.428+/-0.001

γM

o 2N(1

11)

γM

o 2N(2

00)

γM

o 2N(2

20)

γMo 2N(3

11)

Braggs Law 2dsinθ = nλ

Lance spacing

222 lkhad

++=

Sirefl

ec9o

ns(1

13)

Measured Lance Constant

CrystalStructure

q  Lance Constants for MoNX §  MoN0.5 (cubic)

§  β-Mo2N phase (body centered tetragonal)

§  β-Mo16N7 (tetragonal)

§  γ-Mo2N phase (face centered cubic)

17

Mo-NPhase Structure La`ceConstants(nm)

MoN0.5 Cubic a=0.4162

β-Mo2N Bodycenteredtetragonal a=0.416c=0.800

γ-Mo2N Facecenteredcubic a=0.416–0.419a=0.4215–0.4303

β-Mo16N7 Tetragonal a=0.841c=0.805

MoN Hexagonal a=0.5787c=0.5404

Reference: Isabelle Jauberteau, et al., Molybdenum Nitride Films: Crystal Structures, Synthesis, Mechanical Electrical and Some Other ProperGes , CoaGngs 2015, 5, 656-687; doi: 10.3390/coaGngs5040656

Simple cubic Body centered Face centered

a aa

c

Summary

q  MoNX films were deposited at 80 – 300 ⁰C using PE-ALD techniques.

q  The Mo:NX stoichiometry was process dependant and ranged from 0.4 < X < 1.4.

q  The deposited film contained N, C and O impuri)es. The content of N and C correlate with the observed trends in film proper)es.

q  Electrical (Rho) and op)cal proper)es (n & k) are tunable as a func)on of deposi)on temperature and the N2:H2 plasma gas ra)o.

q  The electrical resis)vity at 150 ⁰C was demonstrated to be < 200 µohm-cm using a < 2.0% N2 in the H2 plasma gas. The measured stoichiometry was MoN0.4 with an elevated C content.

q  γ-Mo2N phase crystallinity was observed for all deposited films from 80 – 300 ⁰C

ULTRATECHCONFIDENTIAL 18

QandA