Precursors and Inhibitors Design for Selective ALD/CVD · Halogen Alkyl Alkoxide Alkylamido Acac b-diketonato Pyrrole-imine SiR 3 Alkylsilyl NR Imide CO PR 3 Phosphine Diene Guanidinato

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THIS DOCUMENT IS ••PUBLICOwner: Jean-Marc GIRARD- ALAM Chief Technology Officer

DISTRIBUTION LIST : PUBLIC

Precursors and Inhibitors Design for Selective ALD/CVD

IITC 2018 WORKSHOP

Jean-Marc GIRARD, Ph.D.

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Presentation Outline

• Safety Moments: 3 examples

• Introduction / forewords (no details on defects, metrol…)

• Selective deposition in the industry

• The title forgets half the story: the surface

• Selective deposition processes overview

• DOD / DOM / MOM / MOD

• Metrology

• Defects

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1. Safety Moment- Pyrophoric vs Air reactive

- To dip or not to dip

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Safety Tip #1: Water Reactive Materials

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Safety Tip #2 : To dip or not to dip

• Some canisters have « IN / OUT » marking

VERY CONFUSING depending on the usage

• BUBBLER IN = DIP TUBE

• DLI IN = HEADSPACE

Canister should be marked « HEADSPACE » / « DIP »or Something else UNAMBIGUOUS

Think twice whether you can use a Vapor Draw(= no dip tube)

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Selective CVD/ALD is NOT NEW (even in the fabs)

• Epitaxy (80’s)

• Selective W (90’s)

• Co Selective Cu Cap

• « Induction time » in metal CVD…

• What is new is that selective CVD/ALD could enable or considerably simplifyadvanced process flows

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Exmple: Self Aligned Via w/o Cu Recess « DoD » ALD

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Selective Deposition in Epitaxy

• Typically to grow Epi films selectively(i.e. not on dielectic surface)

• Amorphous (p-crystalline) etched fasterthan epi films

• Used for Si, SiGe selective deposition

• Dep/Etch ratio controlled by Cl:Si and Si:H in the gas mixture

• From precursors (SiHxCly, GeClx/GeH4…)

• From additives (HCl, Cl2, SnCl4…)

crystalline Amorphous

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Selective ALD / CVD for Metal Deposition

• Metallic films generally grow preferentially on conductive films rather than on dielectric films, or Si-H, -CH3 terminated surfaces

• Lots of examples and counter examples

• Multiple parameters affect the nucleation, the growth and selectivity

• Precursor (ligands family, oxidation state, element)

• Surface & surface treatment (TiN or TiON ? Cu or Cu-H or ?...) – effect of surface energy/wettability

• Co-reactant & reaction type (combustion, reduction, homolytic decomposition, disproportionation, intra-molecular re-arrangement…)

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A vast choice of ligands for metal CVD/ALD (not exhaustive)

AmidinateDAD

Diazadiene Allyl

Carbonyl

AcNac(Ketiminato)

Arene, CHD

Cyclopentadienyl

NacNac(Diketiminato)

X R OR NR2

AlkylamidoAlkoxideAlkylHalogen

Acacb-diketonato

Pyrrole-imine

SiR3

Alkylsilyl

NR

Imide

CO PR3

Phosphine

Diene Guanidinato

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Typical Growth behaviour in Metal CVD/ALD

• Leveraging nucleation delays

No of ALD Cycles

CVD time

Th

ickn

ess

Nucleation

delay

Selective

Growth

Linear

Growth

Active Surface Inactive Surface

Nuclei

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Ligand & Surfaces: Ru unwanted nucleation on « TMS-SiO2 »

- « Combustion » ALD process

- CO-free molecule

Ru Precursor A Ru Precursor B

- Homolytic ligand removal

- CVD with H2 (no oxidizer)

- CO-containing molecule

Courtesy of imec Different defect reduction strategy

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Ligand & Surfaces & Co-reactant: Adsorption Competition

Babar, ECS SST (2014); Kumar, PhD thesis, U. Illinois (2009)

• Ligands (from precursor or intentionally added) mayadsorb with the surface and « block it » John Abelson review presentation at ASD 2017

• Ligands (or additives) may selectively adsorb with one surface and create/enhance nucleation delay / slower growth

baseline

With ligand

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Selective ALD / CVD for Dielectric Deposition

• Reaction of the precursor with the surface is usually fast & spontaneous withthe right chemical function / surface group combination

• Surface –OH terminated (oxide) or –NH2 terminated (nitride)

• Selective Dielectric deposition (ALD) relies mostly on INERTING one the surface, i.e. block the reactive sites to prevent reaction with the precursors

• DoD Block metal surface

• DoM Block dielectric surface

• In many cases, classical oxide/nitride precursors can be used if the process conditions are compatible with the blocking agent

•

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Simplified / ideal View (Dielectric on Dielectric)

Precursor exposurePrecursor should not reactwith the metal surface

MOx

Chemisorbed precursorshould react with theco-reactant to re-forma reactive surface

Reactantexposure

co-reactant shouldnot form reactive siteby reaction with the metal

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Simplified / ideal View (Dielectric on Dielectric)

Precursor exposure- Precursor should not reactwith the blocking agent- Blocking agent should bestable on the surface at reaction T

MOx

- Chemisorbed precursorshould react with theco-reactant to re-forma reactive surface

Reactantexposure

- Co-reactant shouldnot react with the blockingagent at the deposition T.

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Usual blocking agents

Blocking agent Surface

blocked/passivated

Reactive site Knobs

(X)nSi(R)4-n

« silylating agents »

X = hydrolysable group

-OH terminated surfaces

(SiO2, MOx...). Can be

an oxidized metal (W, Al)

-OH n: number of OH-reactive groups

X: halide, or alkylamino typically

R: length of the chain + function

R-SH

« Thiols »

Cu, Co -Cu(O)

-Co(O)

R: length of the chain + function

R-P(=O)(OH)

Phosphonic acids

Cu -Cu(O) R: length of the chain + function

R-SiH3 c-Si Si R: length of the chain + function

R3Si-CH=CH2

Alkene

H-terminated Si, Ti, Au Si-H

(hydrosilylation)

Ri: length of the chain + function

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Let’s look at Silicon: Step 1 / reaction with the surface

Surface

PrecursorSi-OH Si-H Si-CH3

Si-NH2

(NH3 T ou P)

Si:-N:

(N2 plasma)

Si-H plasma

Si-NR1R2 plasma

Si-OH

Si-OR

Si-CH3

Si-Cl / Br / INeeds H or Si-Si

or HT or catalyst

Alkylamino compounds will react with Si-OH surface and NOT Si-Me path for selective SiO2 ?

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Step 2: Choosing the co-reactant

Co-react

SurfaceO2 O3 O2-Plasma H2O NH3 N2-P

Si-H

Si-NR1R2

Si-OH

Si-OR

Si-C

Si- Cl / Br / I Needs HT > 450°C

Burn « R » containingligands

Too high Tor condenses

Too high T(or poorfilm)

Burn « R » containingligands

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What works* / what doesn’t

1- No good solution for SiO2 selective ALD owing to lack of O2, H2O-based SiO2 ALD films

Usual co-reactants either oxidize the no-growth surface or burn the blocking agents

2- Metal oxide / metal nitrides: examples

Film Precursor / co-reactant /

temperature

No deposition on

(substrate / SAM)

Deposition on application

HfN (imec) TDMAH / NH3 / 150°C Cu / Thiols Low-k OSG Self aligned via

TiN (imec) - a-C SiO2 Tone inversion

Y2O3 (AL) ARYA™ / O2 or H2O /

300°C

SiO2 / Si-SAM W confidential

ZrO2 (AL) CpZr(NMe2)3 « ZyALD™ /

H2O / 300°C

SiO2 / Si-SAM W confidential

* No yield & defectivity consideration

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Precursor Chemistry for Selective ALD (DoD / DoM)

1- Oxides:

• Usual ALD precursor requirements

• + reactive to O2 or H2O

• + high GPC (high GPC = less cycles = less nucleation on inhibited area)

2- Nitride: NH3 (or Hydrazine) reactive materials at T < ~ max T of the SAM on the passivated surface

Si-SAM ~ 350-450°C (DoM) Low T SiN (slow!), alkylamino metals,…

Thiols ~ 150-200°C (DoD) No Si!

Phosphonic acid ~ 200°-250°C (DoD) No Si

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Turning the knobs: Si-SAMs / « n »

- Nb of attachment legs (1/2/3) & chemical function

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Molecular Design Consideration for SAMs (DoM)

O OH

OH

O OH

OH

O OH

OH density ~ 5 / nm²

Si Si Si

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Molecular Design Consideration for SAMs (DoM)

O O OH

OH O O O O

OH density ~ 5 / nm²

Si Si SiX X

~3Å

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The Contact Angle « Proxy » for SAM screening

SAM coverage

selectivity (A vs B)

SAM coverage

density

High

Low

Low High

+ evaluate this at target process T

AB

vs

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Evaluation of SAMs

●Take into account:

• Surface A vs Surface B

• The cleaning & pretreatment steps

• The exposure protocol (dip vs gas, time, PP, …)

• The post-treatement (after SAM)

• The deposition temperature(precursor dependent)

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Best in class Si-SAM for oxide vs W

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Effect of R on Contact Angle with Thiols on Cu & Co

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Thermal Stability of SAM coverage: Phosphonic Acids

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SAMs tradeoffs and design consideration

Parameter Benefit Drawback

Si SAMs: n=1 Good steric coverage of the surface Partial –OH suppression

Lowest T resistance of the SAM

Si SAMs: n=3 Good suppression of surface OH

High T resistance

Remaining reactive group on the SAM can

induce parasitic ALD. Requires long chains

Large R groups

(Si SAMs / Thiols)

Good protection of the surface /

prevents access to the surface

- May no be volatile enough for gas phase

exposure (> ~ C8-C10)

- SAM alignement takes hours

- Accute edge effects

- Lower coverage of liquid phase exposure

Phosphonic acids Not volatile enough to be used for gas

phase exposure

Small R are « dual usage » materials

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Dealing with Parasitic Growth: Etch back

Active Surface Inactive Surface Time, cycles

Etch-back

Thickness

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Etch Back Chemistries: Example of Mox films

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Conclusion on Chemistry for Selective Deposition

● Be safe, especially with new products. Read SDS, consult suppliers, PAY ATTENTION to exhaust, abatement

● Very limited need for specific precursor designs

– amplification of induction time (etch back, additives, surface treatment) for metals

– selective surface blocking for dielectrics

● AS deposition goes hand in hand with etch (ALE, …) & multi-color contrast films development

● Key challenges

– Defectivity management / HVM manufacturability

– Metrology (SAM surface coverage, defect growth, edges… TEM is not the solution)

– Chemistry efforts needed on Si (X low T SiN, O3 or P-O2 free oxide)

Documents

Precursors and Inhibitors Design for Selective ALD/CVD · Halogen Alkyl Alkoxide Alkylamido Acac b-diketonato Pyrrole-imine SiR 3 Alkylsilyl NR Imide CO PR 3 Phosphine Diene Guanidinato