Contact Engineering by Implant - Applied Materials

Applied Materials ConfidentialSILICON SYSTEMS GROUP

Contact Engineering by Implant

Baonian Guo, PhD

Global Process Engineering

SSG/VSE

Taiwan AMAT symposium, Tainan

March 2014

Applied Materials ConfidentialSILICON SYSTEMS GROUPSILICON SYSTEMS GROUP

Agenda

Contact Engineering Challenges & Trends

Implant PME Applications for Contact Engineering - Logic

Summary

2


Contact Area & Rext Trends

3

Rc increasing for each node Solutions needed for Rc reduction

Rc Challenges & Opportunities

Contact area decreasing with each node Rc increasing

14nm contact resistivity (ρc) required: < 3E-9 ohm-cm2

Reduction of ρc from1E-8 to 3E-9 Ω•cm2

20% increase in Id gain 1 tech node !

I. Young, IEDM 2011 Short CourseH. Wong et al., IEEE Trans Electron Dev, 2009

Contact AreaDecreasing

Required ρc vs. Tech Node Segmentation of Rext

I. Young, IEDM 2011 Short Course

Impact of RSDon Id


Silicide Trend

4

N- (past) N0 (present) N+ (future)

Logic CoSi2 NiSiNiSiTiSi

DRAM TiSi2 CoSi2 CoSi2

Flash TiSi2CoSi2

NiSi (NOR)TiSi2

Sheet resistance trend

Next generation silicides criteria

1. Low SBH (to achieve low contact resistivity)

2. Thermal stability

3. Scaling challenges (3-D conformal)


Common Issues of Silicides

5

TiSi2

Difficult lateralscaling

(line widthdependent Rs)

CoSi2

Difficult verticalscaling

(too much Siconsumption)

NiSi

Thermalstability

• Roughinterface

• Interfacedopingconcentration

• SBH

AMAT PMESolutions


Agenda



Summary

6


Pre-Silicide Amorphization

NMOS

Improve Contact Quality Enhance thermal stability

Improve Silicide/Siinterface

Better Silicide thicknessuniformity across wafer

Prevent metal piping anddefects

VSE PME Solutions for Contact Engineering

Electrical Modification SBH

Reduce SBH

• hole or electron barrier

height reduction

• Reduce Rc

• Improve Ion/Ioff

Dopant SegregatedSchottky (DSS)

NMOSDopant Segregation

Improve Rc

• Reduce Parasiticresistance

• Reduce Si / Dopant loss

• Better Silicide thickness

uniformity across wafer

• Prevent metal piping


Incomplete Amorphization Increased Amorphization

Surface Defects High ContactResistance (Rc) Silicide yieldloss (NiSi pipes)

EOR Defects Leakage TED

After anneal

PTC II Implant

Clean SurfaceBetter RcHigherActivationNo SilicideYield Loss

No EOR Defects No leakage

(Ioff, Iboff,GIDL, DIBL)

Improve Xj/Rs

Normal Implant

Cryo Implant Improves Device Performance

8

SurfaceDefects

EORDamage

8

Cryogenic enables device performance boost and scalability


PSA to Process Integration

NMOS

1) Target NiSi Thickness Optimized with SDE/SD profile Lowest Rcontact-under and Rcontact-side

2) Amorphous layer fully consumed by salicide process Amrohous thickness = Target NiSi thickness

Rc-under

Rc-side

3) EOR defects Leakage source Need completely amorphized layer with PTC II

4) Implant damage curing needs msec anneal

Option A-1

Implant

SD Implant

Spike Anneal

NiSi – RTA 1

NiPt Dep

Ni Wet Etch

Milli-Sec Anneal

9

PSA Scheme


Carbon PSA w/ PTC II for NiSi Formation

Ge Ni

ATOM PROBE RESULTS

Ge diffuses into NiSi athigh concentrations and

agglomerates; result:lowers melting point

and stability

Ge agglomerationresults in rough NiSiinterface and high

Rc

No Pre-silicide

Cold Carbon Presilicide

No Ge agglomeration Smooth NiSi

Pre-Nickel Dep Carbon PSA ImproveNiSi Quality (Physical and chemicaleffects)

1. Lower NiSi Rs and lower NiSiformation Temperature

2. Wide thermally stable NiSi

3. Delayed NiSi phase change andagglomeration

A. Renau, IWJT 2010S. Deshpande et al., IWJT2010


Carbon PSA w/ PTC II for NiSi Formation –Strain Retention

HXRD results of ISBD SiGe30% samples

Operations: Import

File: L004 67SOH1 500c.raw - Type: General Scan - Start: 3.8 - End: 4.0 - Step: 0.0 - Step time: 10. s - Temp.: 25 °C (Room) - Time Started: 6 s - 2-Theta: 66.160 ° - Theta: 32.980 ° - Chi: -0.68 ° - Phi: 0.0

Operations: Import

File: L004 67SOH1 as dep.raw - Type: General Scan - Start: 3.8 - End: 4.0 - Step: 0.0 - Step time: 10. s - Temp.: 25 °C (Room) - Time Started: 6 s - 2-Theta: 66.163 ° - Theta: 32.984 ° - Chi: -0.68 ° - Phi: 0.

Lo

g(C

ounts

)

1

2

10

3

4

56

100

1000

1e4

Aux1 - Scale

3.85 3.9 4.0

File: L004 69SOA7 500c.raw - Type: General Scan - Start: 3.8 - End: 4.0 - Step: 0.0 - Step time: 10. s - Temp.: 25 °C (Room) - Time Started: 6 s - 2-Theta: 66.160 ° - Theta: 32.955 ° - Chi: -0.73 ° - Phi: 0.0

Operations: Import

File: L004 69SOA7 as dep.raw - Type: General Scan - Start: 3.8 - End: 4.0 - Step: 0.0 - Step time: 10. s - Temp.: 25 °C (Room) - Time Started: 6 s - 2-Theta: 66.176 ° - Theta: 32.958 ° - Chi: -0.83 ° - Phi: 0.

Lo

g(C

ounts

)

1

2

10

3

4

56

100

1000

1e4

Aux1 - Scale

3.85 3.9 4.0

As-dep NiPtFully strained.ISBD SiGe30%

(w/o C)

ISBD SiGe30%(w/o C)

ISBD SiGe30%(w/o C)

NiSi formation(480C)

~7% relaxed

ISBD SiGe30%(w/o C)

As-dep NiPtFully strained.

NiSi formation(480C)

Fully strained.4 keV C PAI at -100CVarian tool at ANT

No implant control

Cold Carbon

A. Renau, IWJT 2010


Pre-Silicide Amorphization for Logic Device

Key Questions Benchmark Learning

Species C, N, Si, Ge, Xe

Amorphous

thickness

Less than 1.8 x Ni film thickness

Close to target NiSi thickness

DoseHigher than amorphization threshold

dose

Thermal

treatmentRe-optimization for recrystallization

PSA prior to Ni deposition

Silicidation Implant

SD Implant

Spike Anneal

NiSi – RTA 1

NiPt Dep

High qualityamorphization

3% Ion/Ioff Improvement

Log

Ioff

(A/u

m)

Ion (mA/um)

2xnm logic Si PSA implant

12

Yield improvement with PSA through defect reduction

Applied Materials ConfidentialSILICON SYSTEMS GROUPSILICON SYSTEMS GROUP 13


NMOS







Reduce SBH


height reduction

• Reduce Rc




Improve Rc







Pre-Silicide Implant & Post-Silicide Implant

Dopant Segregated Schottky (DSS)

– Increased dopant concentration at interface

– Reduced Schottky barrier height due to image-force induced barrier lowering

Reduction of specific contact resistivity

Pre-silicide implant: Silicidation Induced Dopant Segregation (SIDS)

– Dopant rejection from silicide: snowplow effect

Through-silicide implant: Silicide as Diffusion Source (SADS)

– Dopant pile-up at silicide/silicon interface during thermal annealing(diffusivity in silicide = 5 – 6 orders of magnitude higher than diffusivity insilicon)

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Through-Silicide Implant

Low implant energy case

– as-implanted profile within silicide

– relatively higher temperatureannealing

Points of consideration:degradation of silicide sheetresistance due to high temperatureanneal

15

High implant energy case

– as-implanted profile Rp atsilicide/silicon interface

– relatively lower temperatureannealing

Points of consideration: residualimplant damage and SCEdegradation

NMOS

Rc-under

Rc-side


DSS Implant to Process Integration

1) Choice of species As+ or P+ (nMOS)

2) Ion placement within silicide or Rp at silicide/Si interface

3) Ion Dose Maximize dose to reduce Rc but no degradation DIBL

4) Implant Step Implant to silicide

NiSi – RTA 1

Implant

SD Implant

Spike Anneal

NiPt Dep

Ni Wet Etch

Milli-Sec Anneal

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NMOS

Rc-under

Rc-side

NiSi – RTA 1

Implant

NiSi – RTA 2/msec

SD Implant

Spike Anneal

NiPt Dep

Ni Wet Etch

Milli-Sec Anneal

Scheme #1 Scheme #2


NiPt Silicide on nSD with P+ Implant

17

Process flow (Scheme #2)

KV Rao et al., eMRS2013

DSS (B) applicable to PFETas well

Dopant segregation (P) at NiPtSi/Siinterface can decrease NFET specificcontact resistivity by ~40 %



NMOS







Reduce SBH


height reduction

• Reduce Rc




Improve Rc







TCAD Modeling of SBH Effect on Ion

TCAD Model predicts up to 12% Ion improvement potential for HP 32nmplanar bulk Si nMOS devices (upside for 20nm and beyond)

Device Characteristics:NSD = 4.3E20cm-3

Vth,lin = -326mVIoff = 96 nA/umIdsat = 1.71 mA/um

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Source: Hans Gossmann


SBH Modulation Species

S, Se:– prevent Fermi level pinning at mid-gap

Al:– work function reduction (n-type: Al inside

silicide)

– dipole formation (p-type: Al at silicide/siliconinterface)

N:– interface passivation

– band gap narrowing

– drawback: silicide sheet resistanceincrease

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Ideal

Se/S: valence mending adsorbate Fermi level de-pinning

NiSi, CoSi2, TiSi2Bn ~ 0.6eV for n-doped Si


NiPt Silicide on nSD with Se+ Implant

Se+ implant into NiPt silicide candecrease specific contactresistivity by ~25 %.

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Process flow

Se confined within silicide nojunction leakage degradation

(Scheme #1)KV Rao et al., IIT 2010


Agenda



Summary

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Summary

CMOS Contacts: HVP

Rc increasing for each node

ρc reduction requires material selection & interfacial engineering

AMAT Implant Solutions for Contact Engineering

Cryogenic implants for SD & pre-silicide amorphization (PSA)

Dopant segregated Schottky (DSS) implants

SBH-modifying implants

Lesson Learns and Future for Implant PME contact engineering

Process Integration scheme determined the best implant solution - DSAkey enabler

AMAT developed process know-how, tools (Crion, Exotic, Trident)

Extend next contact engineering learning cycle to new materials (SiC,SiGe, Ge, GeSn, InGaAs)

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Contact Engineering by Implant - Applied Materials

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