ultra-high resolution nano-electrical measurements for … · 2014-12-04 · ultra-high resolution...

Ultra-High Resolution Nano-ElectricalMeasurements for Semiconductors(Part 1)Peter De Wolf Dec. 3, 2014

AFM-based Nano-Electrical Modes

12/03/2014 Bruker Confidential 2

C-AFM, TUNA, Peakforce-TUNA, SSRMConductivity / Resistivity

EFMElectric Field

EFM, SCMCharge

KPFM, Peakforce-KPFMSurface Potential /

Workfunction

SCM, SSRMCarrier Density

PFMPiezoelectric Properties

Scanning Gate, Pyro-electric AFM,Photoconductive-AFM, 4-Point Probe,

Non-linear Dielectric Microscopy…Specialty Modes

AFM-based Nano-Electrical ModesSome examples

12/03/2014 3Bruker Confidential

Current

Height

Peakforce-TUNA on PP/EPDM polymer blend3x3 µm scanTunneling-AFM (TUNA) on carbon nanotubes

4x2 µm scan, 4pA scale

SSRM on cross-sectioned MOS transistors1.2x0.6 µm scan, log scale

AFM-based Nano-Electrical ModesSome examples


n+

p

n--

KPFM, 2x1 µm scan, potential map on InP nanowire with 3V electrical bias between contacts

SCM, 4x2 µm scan, carrier diffusion of cross-sectioned double-diffused SiC MOSFET

Topography dC/dV Phase dc/dV Amplitude

Practical Aspects:The Electrical AFM Probe

Solid Diamond (doped)


• The electrical AFM tip should be: Conductive, Hard, Wear-resistant& Sharp. Good materials are Diamond, Pt, PtIr, Pt-Silicide

Solid Metal (Pt)PtSicovered

CVD CoatedDiamond (doped)

Practical Aspects:Environment

• Many samples alter properties when exposed to Oxygen or Water

• At ambient conditions, a thin water layer on the sample candegrade the spatial resolution & influence electrical properties

• When applying voltages on some samples (metals,semiconductors,..), local anodic oxidation can take place andstrongly influence the measurements


SSRM on ITO layer, 10x10 µm scan

Practical Aspects:Environment - Glovebox


Dimension Icon AFM inside Glovebox

O2 ~ 0.1ppmH2O ~ 0.1ppm

Practical Aspects:Environment - Glovebox

• Under ambient conditions, theconductivity map cannotobserve the oxide layer.

• Under a controlledenvironment of < 1 ppm O2 &H2O the layer can clearly beobserved


SSRM on thin oxide layer

Nano-Electrical Characterization ofSemiconductor Devices

• Lateral dimension of transistors continue toshrink

• New architectures (SOI, FinFET, TFETS,..)and materials (SiGe, Ge, III-V,…) areintroduced

• ‘Classic’ 1D dopant profiling methods (SRP,SIMS,…) reach their limits


ITRS 2016

Spatialresolution

1 nm

Concentrationprecision

2%

Dynamicrange

1014 – 10 21

at/cm3

AFM-based 2D & 3D techniques with nm-resolution are needed

© Copyright Bruker Corporation. All rights reserved.

www.bruker.com

Ultra-high resolution nanoelectricalmeasurements for semiconductor applications.(Part 2)

P. Eyben, K. Paredis, A. Schulze, A. Nazir, U. Celano,R. Chintala, T. Hantschel and W. Vandervorst

2

© IMEC 2014 / CONFIDENTIAL

IMEC AT A GLANCE

300mmpilot line

450mmready

200mmpilot line

Nanobiolabs

NERFlab

Organicsolar cell

line

Siliconsolar cell

line

Established by state government of Flanders in 1984 withinitial staff: ~70

Imec’s staff has grown to 2,086 people in 2013. Of these,383 are residents - visiting researchers from partnercompanies & institutes and 289 are PhD researchers.

3


OUR MISSION

World-leading research in nanoelectronics

Scientific knowledge with innovative power of global partnerships in ICT, healthcare andenergy

Industry-relevant technology solutions

International top talent in a unique high-tech environment committed to provide buildingblocks for a better life in a sustainable society

4


RESEARCH PROGRAMS

HETEROGENEOUSINTEGRATION

ELECTRONICS FORHEALTHCARE& LIFE STYLE

WIRELESSCOMMUNICATION

IMAGE SENSORS &VISION SYSTEMS

ENERGY SENSORSYSTEMS

FLEXIBLEELECTRONICS

AP

PL

ICA

TIO

ND

RIV

ENR

ESEA

RC

H

TE

CH

NO

LO

GY

DR

IVEN

RES

EAR

CH MEMS SENSOR PHOTONICS

CORE CMOS

LITHOGRAPHY DEVICES INTERCONNECTS

5


CAMS

Materials & ComponentsAnalysis department

MCA: ~50 peopleResearchers: ~15 R&D support: ~20PhD students: ~10 MSc students: ~5

MCA-CASIMSRBS/ERDAPT

MCA-SPMSSRMKPFMC-AFMSTM

MCA-CSA

TOFSIMSXPS

MCA-NPNanoprober, Raman,Conductive diamond MCA-SA

TEMFIB

MCA DEPARTMENT AT A GLANCE

6


RESEARCH INTHE SPMTEAM

TCAD CALIBRATION(SSRM)

ANALYSIS OF CBRAM(C-AFM)

DEVELOPMENT OFNEW AFM MODES

(FFT-SSRM,...)

TOMOGRAPHY(SSRM, C-AFM,...)

ELECTRICAL PROPERTIESOF ORGANIC SC(C-AFM, KPFM)

DEFECTS IN III-V SC(NC-AFM, STM, KPFM)

7


SSRM CONCEPT

TUNA

10-9 10-6 10-3

force (N)

resi

stan

ce(a

.u.)

SSRMTUNA

10-9 10-6 10-3

force (N)

resi

stan

ce(a

.u.)

SSRM

୫ ୟୣୱ ୮୰୭ୠୣ+ ୱ୮୰ୣ ୟୢ ୧୬ ୱୟ୫ ୮୪ୣ ୠୡ

ୱ୮୰ୣ ୟୢ ୧୬

୬ ୮

8


DEDICATED DIAMONDTIPS FOR SSRM

Ref: T. Hantschel et al., physicastatus solidi (a) 206 (2009) 2077.

Two tip technologies available :- Coated diamond tips (CDT)- Full (molded) diamond tips (FDT)

Nano-protrusions at the tip apex : Reduced contact size Possible multiple nano-contacts

Tips made of (boron) dopeddiamond in order to withstand thelarge pressures (and shear stresses)involved during SSRM

FDT present a lower aspect ratio vs. CDT no tip breakage

FDT are sharper and present smaller diamond grains at their outersurface vs. CDT leading to better resolution

9


SSRM NANOCONTACT

PIERRE EYBEN

4 5 6 7 8

Ref. : K. Mylvaganam et al.@ Nanotechnology 20 (30) p. 305705 (2009)

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LIMITATIONS OF SSRM IN AIR

• Commercial Coated DiamondTips (CDT) can not be used forhigh resolution SSRM

• Percentage of working home-made Full DiamondTips (FDT) thatcan be used for high resolutionSSRM is too low

• Signal to noise ratio is too low

• Repeatability and reproducibilityare too low (Sample and tipdamaged relatively quickly)

1st scan SSRM in air 8st scan SSRM in air

SSRM

Lateral/vertical steepness of dopant profile

(nm/decade)1 - 2

Lateral/depth spatial resolution for 2D dopant

profile (nm)1 - 3

Dopant profile concentration precision across

concentration range (%)5-20%

Dynamic range (at/cm3) 1015 - 1020

ITRS 2016

1.6

1

2%

1014 - 1021

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IMPACT OF HUMIDITY

In the presence of water, thevolume of transformed

silicon is higher

Lower resolution

In the presence of water,the growth of b-Si

(6 coord.) is retarded

Need to push more

Ref. : C.Y.Tang et al. @ Nanotechnology 16, p.15 (2005)

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IMPROVED SSRM PERFORMANCESSSRM HV-SSRM ITRS 2016

Lateral/vertical steepness of dopant profile

(nm/decade)1 - 2 1 - 1.5 1.6

Lateral/depth spatial resolution for 2D dopant

profile (nm)1 - 3 0.6 - 1 1

Dopant profile concentration precision across

concentration range (%)5-20% 3-5% 2%

Dynamic range (at/cm3) 1015

- 1021

1015

- 1021

1014

- 1021

Quantified SSRM profile matches with SIMS Improved resolution (0.6-1nm) Improved signal to noise level ratio (noise <10%)

0.3-0.5 nm

oxide

1.E+16

1.E+17

1.E+18

1.E+19

1.E+20

1.E+21

1.E+22

0 50 100 150 200

Depth (nm)

Do

pa

nt/

ca

rrie

rc

on

ce

ntr

ati

on

(cm

-3) SIMS P

SIMS B

SSRM

SSRM ICON-GB ITRS2016

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SAMPLE PREPARATION FOR SSRM

Most measurements performed on cross-sections (XS)

Protective SiO2 and Si/glass dummy used to protect the XS edge

Back-contact (BC) employed to collect the spreading current : Performed manually using GaIn eutectic covered with Ag-paint On shorter structures FIB used to place local BC down to 1mm from the

XS edge (= distance to avoid Ga contamination on the XS)

14


ADVANCED SAMPLE PREPARATION

Cross-section

Back-contact pad

Oxide

FIB trench + BC

FIB-lapping

angle of incidenceFIB beam (1 )º

below 1 mreference metal line

Cross-section

Back-contact

FIB trench + BC> 1 m

Metal coating

source drain

Oxide

Back-contact

Cross-section : Polishing using diamond and Al2O3 foils (RMS roughness < 0.6nm). Micro-cleavage SELA MC600. (Position XS determine with 300nm

accuracy, less defects and extrinsic SS, RMS roughness < 0.4nm). Ga FIB lapping @ low incidence angle (1deg) and energy (3-5keV).

(<10nm accuracy)

FIB can also be used to mark area(s) of interest and/or to generatelocal BC pads.

15


APPLICATION : PROCESS CALIBRATION (DRAM)

0.1 1 10

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

0.30

|Vth

_sa

t@

Vd

=-1

V|(

V)

Lg (m)

experimentaldefault_simucalibrated

0.1 1 10

0

50

100

150

200

250

300

350

DIB

L(m

V/V

)

Lg (m)

experimentaldefault_simucalibrated

Processing :implantation

(dose, energy,...),annealing(diffusion,

activation,...)

SSRM :measurement

andquantification

Devicesimulations

Predict the deviceperformance andcompare them to

measuredelectrical data

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APPLICATION : CMOS IMAGE SENSOR

Individual Pixels of Image Sensors

SSRM image with courtesy of

www.imec.be/cams

SSRM provides high resolution 2Dcarrier distributions inside the individualpixels of a CMOS image sensor.

photocathode

SEM image courtesy of chipworks

17


APPLICATION : DRAMTRENCHES


www.imec.be/cams

Implant out-diffusion at the top andbottom of the DRAM trenches.


18


APPLICATION : POWER MOSFET


www.imec.be/cams

Dopant concentrations insidean integrated Schottky diode ina power MOSFET device.

metal

n-polyn+ n+


19


APPLICATION : InP/InGaAs FINFET

A large in-diffusion of P into the Sisubstrate is measured.

InP(Mg)/InGaAs(Si) inV-STI trenches

20


APPLICATION : Ge FINFET

SiGe / strained Ge in STI trenches

P-doping level in SiGe and P diffusion into strained Ge Higher P concentration noticed in Ge

21


APPLICATION : Vertical heteroTFET

22


Use of slice and viewconcept (implemented on

CNT interconnects)

100nm

0nm

Tomography : How to realize 3D-SSRM ?

Use of dedicated staggeredtest-structures

(implemented on FinFETs)

COMPARATIVE STUDY Staggering Digging

Resolution in 3rd direction 2-3nm 3-5nm

Dedicated test-structure needed YES NO

Versatility (different materials present,...) YES More limited

23


3D-SSRM ON NW-TFET

23

100nm 100nm100nm

0

100

200

300

400

500

600

100nm 100nm 100nm

0

100

200

300

400

500

600

100nm

(1) (2) (3) (4) (5) (6) (7)

24


3D-SSM ON CNT-BASED INTERCONNECTS :Tomogram of individual CNTs in contact hole

Ref: A. Schulze et al.,Nanotechnology 23 (2012) 305707

25


3D-SSRM ON FINFET

Possible short between gateand plug due to poor aligment

Possible leakyjunction ofthe drain

S DG

26


3D C-AFM ON CBRAMFilament evolution from top to bottom electrode

20 nm

(~ 2nm)

(Rem. Rate 0.7 nm/scan)

[Schindler ,et al.. APL 2009, 94, 072109]

Anode

Cathode

Conductive (filament) Bridging Device

U. Celano et al.,Nanoletters, 2014, 14, 5, 2401

27


C-AFM ON ORGANIC SOLAR CELLS

Cross sectionview of spray

coatedP3HT:PCBM (1:1)

BHJ solar cell

ITO

PEDOT:PSS

P3HT:PCBM

P3HT:PC[60]BM

P3HT:PCBM 1:1 ratio 200 nm active layer η~4%

Operation principlehv

PCBM

P3HT

Craters with varying depth weremade using Ar cluster beam

Depth profile using SPM techniquesbased on electrical properties ofP3HT and PCBM

28


Red P3HT Blue PCBM

C-AFM-BASED DEPTH PROFILING :Vertical phase segregation &efficiency of exciton dissociation

On degraded sample, no more P3HTplateau poorer efficiency

Hypothesis : 100% optical

absorption Equal absorption for

P3HT and PCBM 10 nm exciton

diffusion length

ηfresh = (87 ± 3)%

ηdegraded= (65 ± 5)%

Ultra-high resolution nanoelectricalmeasurements for semiconductor applications.

P. EYBEN, J. MODY, A. NAZIR, K. PAREDIS, A.SCHULZE,T. HANTSCHEL AND W. VANDERVORST

QUESTIONS ?

ultra-high resolution nano-electrical measurements for … · 2014-12-04 · ultra-high resolution...

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