Upload
others
View
6
Download
0
Embed Size (px)
Citation preview
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
12/03/2014 4Bruker Confidential
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)
12/03/2014 Bruker Confidential 5
• 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
12/03/2014 Bruker Confidential 6
SSRM on ITO layer, 10x10 µm scan
Practical Aspects:Environment - Glovebox
12/03/2014 7Bruker Confidential
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
12/03/2014 8Bruker Confidential
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
12/03/2014 9Bruker Confidential
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
© IMEC 2014 / CONFIDENTIAL
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
© IMEC 2014 / CONFIDENTIAL
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
© IMEC 2014 / CONFIDENTIAL
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
© IMEC 2014 / CONFIDENTIAL
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
© IMEC 2014 / CONFIDENTIAL
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
© IMEC 2014 / CONFIDENTIAL
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
© IMEC 2014 / CONFIDENTIAL
SSRM NANOCONTACT
PIERRE EYBEN
4 5 6 7 8
Ref. : K. Mylvaganam et al.@ Nanotechnology 20 (30) p. 305705 (2009)
10
© IMEC 2014 / CONFIDENTIAL
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
11
© IMEC 2014 / CONFIDENTIAL
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)
12
© IMEC 2014 / CONFIDENTIAL
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
13
© IMEC 2014 / CONFIDENTIAL
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
© IMEC 2014 / CONFIDENTIAL
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
© IMEC 2014 / CONFIDENTIAL
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
16
© IMEC 2014 / CONFIDENTIAL
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
© IMEC 2014 / CONFIDENTIAL
APPLICATION : DRAMTRENCHES
SSRM image with courtesy of
www.imec.be/cams
Implant out-diffusion at the top andbottom of the DRAM trenches.
SEM image courtesy of chipworks
18
© IMEC 2014 / CONFIDENTIAL
APPLICATION : POWER MOSFET
SSRM image with courtesy of
www.imec.be/cams
Dopant concentrations insidean integrated Schottky diode ina power MOSFET device.
metal
n-polyn+ n+
SEM image courtesy of chipworks
19
© IMEC 2014 / CONFIDENTIAL
APPLICATION : InP/InGaAs FINFET
A large in-diffusion of P into the Sisubstrate is measured.
InP(Mg)/InGaAs(Si) inV-STI trenches
20
© IMEC 2014 / CONFIDENTIAL
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
© IMEC 2014 / CONFIDENTIAL
APPLICATION : Vertical heteroTFET
22
© IMEC 2014 / CONFIDENTIAL
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
© IMEC 2014 / CONFIDENTIAL
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
© IMEC 2014 / CONFIDENTIAL
3D-SSM ON CNT-BASED INTERCONNECTS :Tomogram of individual CNTs in contact hole
Ref: A. Schulze et al.,Nanotechnology 23 (2012) 305707
25
© IMEC 2014 / CONFIDENTIAL
3D-SSRM ON FINFET
Possible short between gateand plug due to poor aligment
Possible leakyjunction ofthe drain
S DG
26
© IMEC 2014 / CONFIDENTIAL
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
© IMEC 2014 / CONFIDENTIAL
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
© IMEC 2014 / CONFIDENTIAL
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 ?