advanced ion beam technology, inc. a hermes-epitek company cascadescientific global analytical...

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A Hermes-Epitek Company1Cascadescientific global analytical services

Chicane Deceleration –Chicane Deceleration –Qualifying a new technique to Qualifying a new technique to control energy contaminationcontrol energy contamination

Nick White, John Chen,

Chris Mulcahy, Sukanta Biswas,

Russ Gwilliam

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A Hermes-Epitek Company2Cascadescientific

global analytical services

IntroductionIntroduction

Implantation of high-current boron beams at 200eV for SDE with USJ

Goal: Preserve the advantages of conventional implanters while meeting productivity requirements: Use of established source materials and technologies Accurate dosimetry Precise angle control Robust charging control

Eliminate deep tails caused by energy contamination Quantify sources of variation

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• Figure shows 0.2, 0.5, 1.0 & 2.0 keV ion implants

• Energy Contamination during implantation canbe observed in most of the implants

• 400 eV O2+ was

implemented for the lower energy implants whilst 700 eV was applied for the higher energy implants

• Lowest implant energies benefit from lower energy O2

+

1E+15

1E+16

1E+17

1E+18

1E+19

1E+20

1E+21

0 100 200 300 400 500 600 700 800 900 1000

Depth / Angstroms

Con

cent

ratio

n /

Ato

ms.

cm-3

1E+22

0.2 keV B

0.2 keV B

0.5 keV B

1.0 keV B

2.0 keV B

ULE Boron and Energy ContaminationULE Boron and Energy Contamination

Historical Data

Earlier data compiled by Cascade.

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MethodMethod

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Chicane decelerationChicane deceleration

+5,800 V

6,000 eV

200 eV

-Sending ions up a potential ‘hill’ reduces their energy-Tortuous path removes particles with the wrong energy or charge

30:1 shown4:1 to 30:1 available

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ChicaneChicane

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Beam currents used in these testsBeam currents used in these tests

BF2 current: 1.0 mA at 200eV 2.0 mA at 400eV 3.5 mA at 891eV

Boron current: 2.5 mA at 200eV 4.5 mA at 1000eV

Decel ratio from 10:1 to 30:1 (4:1 is available)

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Direct measurement of angles in the beamDirect measurement of angles in the beam

Aperture plate

Beam burns 150mm beyond plate

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Beam Divergence and Angle ControlBeam Divergence and Angle Control

Insignificant change in overall angles down to 200eV,but each beamlet spreads more at low energy.

Horizontal Angular spreadBoron 5 keV

-4

-3

-2

-1

0

1

2

3

4

-30 -20 -10 0 10 20 30

Horizontal distance, mm

Hor

izon

tal a

ngle

, deg

rees

Horizontal Angular spreadBoron, 200eV

-4

-3

-2

-1

0

1

2

3

4

-30 -20 -10 0 10 20 30

Horizontal distance, mm

Ho

rizo

nta

l an

gle

, de

gre

es

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Effect of SIMS energyEffect of SIMS energy

1E+15

1E+16

1E+17

1E+18

1E+19

1E+20

1E+21

1E+22

0 50 100 150 200 250 300

Depth (angstroms)

Co

nc

en

tra

tio

n

Sample3bX_750_200_overlay.SWF

Sample 3

02/02/2006

O2 Cascade Scientific

B: O2 200 eV 45 degrees: 5.00E14 at/cm2B: O2 750 eV 45 degrees: 5.00E14 at/cm2

Background is higherwith low energy SIMS

BF2 891eV drift implant.Same sample analyzed by 2 techniques.Results normalized to 5.00e14 dose

Depth resolution is ~15A betterwith low energy SIMS

Effect of reducing SIMS beam energy

0

10

20

30

40

50

60

70

80

90

100

0 100 200 300 400 500 600 700 800

SIMS O2+ energy (at 45 degree incidence)

Mea

su

red

dep

th o

f 1E

19

For this study we used 200eV O2

+ at 45 degrees, equivalent to ~70 eV O+ at normal incidence.

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Experimental DetailsExperimental Details

Prime n-type wafers, 200mm Most wafers preamorphized

100keV Ge to 2e15 because we also investigated higher energies because if energy contamination was present, we did not want

the tails to channel and be distorted

Some coated 50% with photoresist Energy contamination from neutralization is proportional to

pressure Outgassing from resist at high current must be evaluated

Energy measured directly by voltmeter from ion source to endstation Only uncertainty is plasma potential in ion source.

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Implant Matrix and ControlsImplant Matrix and Controls

891eV BF2 has same velocity as 200eV B

Surface oxide about 1.3 nm

Energy Species Wafer # Dose Analysis PreA Mode Other Beam Current

200 B+ 20 5.00E+14 200eV O2 45deg Ge 2E15 100 keV Chicane 6keV Bare 2.08



200 B+ 25 1.00E+15 200eV O2 45deg None Chicane 6keV 50% photoresist 2.41

200 B+ 23 1.00E+15 200eV O2 45deg Ge 2E15 100 keV Chicane 6keV 50% photoresist 2.49

891 BF2+ 26 5.00E+14 200eV O2 45deg Ge 2E15 100 keV Chicane 6keV Bare 3.61

891 BF2+ 24 5.00E+14 200eV O2 45deg Ge 2E15 100 keV Drift Bare 18.33 uA


400 BF2+ 28 5.00E+14 200eV O2 45deg None Chicane 8keV Bare 2.01


200 BF2+ 30 5.00E+14 200eV O2 45deg None Chicane 6keV Bare 0.97

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ResultsResults

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Boron 200eV 2.5 mA – raw dataBoron 200eV 2.5 mA – raw data

1E+17

1E+18

1E+19

1E+20

1E+21

1E+22

1E+23

0 2 4 6 8 10 12 14 16

Depth, nm

Co

nc

entr

atio

n /c

c

High vacuum, PAI, 8e14High vacuum, PAI, 1.4e15High vacuum, PAI, 1.9e1550% Photoresist, PAI, 1.3e1550% Photoresist, channeled, 1.4e15Drift BF2 891 eV 5.8e14

All implants 200eV B+ using chicane decelerationSIMS O2+ 200eV 45 degrees(effective O+ energy is 71 eV)

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Profile changes with doseProfile changes with doseEffect of Dose on Profile Peak

0.00

0.05

0.10

0.15

0.20

0.25

0.0E+00 5.0E+14 1.0E+15 1.5E+15 2.0E+15

Dose, atoms/sq.cm

Dep

th o

f pe

ak,

nm

0.0E+00

1.0E+21

2.0E+21

3.0E+21

4.0E+21

5.0E+21

Con

cent

ratio

n at

Pea

k, a

tom

s/cc

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Saturation at 200eV?Saturation at 200eV?

0

5E+14

1E+15

1.5E+15

2E+15

2.5E+15

0 2E+14 4E+14 6E+14 8E+14 1E+15 1.2E+15 1.4E+15 1.6E+15

Ret

aine

d do

se b

y S

IMS

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Boron 200eV 2.5mA SIMS ProfilesBoron 200eV 2.5mA SIMS Profiles

1E+17

1E+18

1E+19

1E+20

1E+21

1E+22

0 2 4 6 8 10 12 14 16

Depth, nm

Co

nc

entr

atio

n /c

c

High vacuum, PAI, 8e14High vacuum, PAI, 1.4e15High vacuum, PAI, 1.9e1550% Photoresist, PAI, 1.3e1550% Photoresist, channeled, 1.4e15Drift 891eV BF2 5.8e14

All profiles normalized to 8.00e14 total dose200eV B+ using chicane deceleration891eV BF2 drift for referenceRolling average to reduce noise, width varies from 0.01 to 0.1 nm with depth(or the differences cannot be discerned)SIMS O2+ 200eV 45 degrees(effective O+ energy is 71 eV)

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Discussion of 200eV dataDiscussion of 200eV data

First 0.5 nm: Surface is clean. Minimal oxide effects. Concentration as % of dose falls with dose

0.5-2.0 nm Concentration is slightly higher with higher dose Ion beam mixing during implant

>3 nm Effect of increased pressure is resolved Profile becomes ~0.23nm deeper

>4 nm Channeling is distinct; level is approx 1.23% Range of channeled ions is ~4nm deeper for 0.1% of dose

>10 nm No effect of pressure can be resolved Why does BF2 have a lower background?

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DiscussionDiscussion

Possible Sources of profile shifts and deep tails: Channeling

We used RBS to look for channeling Pilot experiments eliminated channeling as source of

background variation Our amorphization was complete

SIMS system background and SIMS knock-on BF2 has a much lower background

Does the fluorine inhibit SIMS knock-on?

Higher energy beam components Neutralization close to exit of chicane

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What contaminants get past the chicane?What contaminants get past the chicane?

Zone of possibleEnergy contamination

Ions can be neutralized within the chicane

This process must occur within the exit zone if the contaminant is to reach the wafer

The electric potentials limit the maximum energy contamination to a fraction of final energy Proportional to pressure

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-0.5

0

0.5

1

0 5 10 15

Depth, nanometers

Shi

ft in

dep

th d

ue t

o P

R, n

anom

eter

s

Noisy due to backgroundbelow 1e18

Highly resolved dopant shiftHighly resolved dopant shiftdue to PR outgassingdue to PR outgassing

-Obtained by subtracting SIMS from PR wafer from SIMS from bare wafer after re-normalizing-Dose on PR wafer was 5% lower due to beam neutralization and loss

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USJ Implants using BFUSJ Implants using BF22

1.0E+16

1.0E+17

1.0E+18

1.0E+19

1.0E+20

1.0E+21

1.0E+22

0 1 2 3 4 5 6 7 8 9 10

Depth, nanometers

24 - BF2 891eV drift

29 - BF2 200eV PAI chicane

30 - BF2 200eV channeled chicane

24

29

30

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USJ Implants using BFUSJ Implants using BF22, smoothed, smoothed

1.0E+16

1.0E+17

1.0E+18

1.0E+19

1.0E+20

1.0E+21

1.0E+22

0 2 4 6 8 10 12

Depth, nanometers

24 - BF2 891eV PAI drift

26 - BF2 891eV PAI Chicane

27 - BF2 400eV PAI chicane

28 - BF2 400eV Channeled chicane

29 - BF2 200eV PAI Chicane

30 - BF2 200eV Channeled Chicane

24

29

30

Normalized to 5E14Smoothed using moving averageof increasing width from 0.01 to 0.1 nm

26

27

28

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Conclusions:Conclusions:

Chicane technique can deliver ~70 wph at 200eV B 5e14 with Xj (unannealed) of < 7 nm Magnitude of energy contamination is ~22eV, or < 0.3 nm

Channeling can modify the as-implanted profile by ~ 3nm Metrology must resolve 3nm! PAI required

Chicane technique can deliver ~100 wph of 891eV BF2 5e14 May have tighter profile and less diffusion PAI required

Chicane technique can deliver ~33 wph for 200eV BF2 5e14 with Xj (unannealed) of < 5 nm

Does not require PAI

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Acknowledgements:Acknowledgements:

Implants and beam measurements: Ed Petersen Yap Han Chang

SIMS analysis Neil Montgomery Paul Ebblewhite

RBS analysis Chris Jeynes

advanced ion beam technology, inc. a hermes-epitek company cascadescientific global analytical...

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