Download - Recent Developments in Electrical Metrology
-
8/4/2019 Recent Developments in Electrical Metrology
1/25
Recent Developments in Electrical Metrology
for MOS Fabrication
Gate Engineering
Channel Engineering
Source-Drain Extension Engineering
George A. Brown
SEMATECH
Mark C. Benjamin
Solid State Measurements,Inc.
-
8/4/2019 Recent Developments in Electrical Metrology
2/25
Gate EngineeringGeorge A. Brown
SEMATECH
-
8/4/2019 Recent Developments in Electrical Metrology
3/25
3Slide 050309002
Introduction Gate Dielectrics
Brief Roadmap Review Traditional Gate Dielectric Electrical Metrology
Measurements, analysis, and limi tations
Improved Methods and Recent Developments
Critical C-V measurement parameters High frequency
Low series resistance test structures
Adequate area resolution
UHFCAP structure Multi-frequency C-V, D- characteristics Interface State (Dit) Measurement: charge pumping
In-line C-V Measurements
Summary
-
8/4/2019 Recent Developments in Electrical Metrology
4/254Slide 050309002
ITRS Roadmap for High Performance Gate Dielectrics (2004 update)
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
2003 2005 2007 2009 2011 2013 2015 2017
Calendar Year
Jg(A/cm2)
01
2
3
45
6
7
89
10
11
1213
14
EOT(A)
Jg,simulated
(oxynitride)
Jg,limit
EOT
Beyond this point of cross over,
oxynitride is incapable of meeting the
limit (Jg,limit) on gate leakage current
density
Scaling beyond 1 nm, 103A/cm2 is almost upon us!
-
8/4/2019 Recent Developments in Electrical Metrology
5/25
5Slide 050309002
Evolution of gate dielectric electrical metrology
ParameterTraditional
MeasurementTechnique
TraditionalAnalysis
Technique
Shortcomings forAdvanced Devices
ImprovedMeasurement
Technique
Improved AnalysisTechnique
Oxidethickness, CET
100 kHz/1 MHzMOS C-V
ClassicalPoisson's Law
Models
C-V distortion from highgate leakage
Low-Rs teststructures, UHF
C-V
Multi-elementequivalent circuits
Oxidethickness, EOT
100 kHz/1 MHzMOS C-V
ClassicalPoisson's Law
Models
Failure to account forquantum confinement,
poly depletion
Schrodinger solversfor EOT
Interface StateDensity, Dit
Quasi-static C-VClassical
Poisson's LawModels
Gate leakagedominates quasi-static
data
Charge pumpingBrew's Dit
Pulse level, rise timeto separate bulktrapping from Dit
Oxide Charge
Tgrapping
MOS C-V
HysteresisVfb
inaccurate, poorly
defined for high-k
Pulsed transient
Id-Vg
Pulse rise time
analysis
New methodologies must be developed to deal with the characteristics of
radically scaled gate dielectric stacks.
-
8/4/2019 Recent Developments in Electrical Metrology
6/25
6Slide 050309002
Measurement of 0.5 nm EOT Gate Stacks with High Leakage
High leakage gate stacks are modeled as parallel
RC equivalent circuits.
To resolve the capacitance, use of higherfrequencies will reduce the capacit ive impedance,
making that element dominate the parallel
resistance/conductance. But this only works if there is negligible parasitic
series resistance in the test structure. Use of
higher frequencies if series resistance is presentonly makes the capacitive impedance of interest
negligible in comparison with Rs.
Gp Cp
Q = Cp/Gp
Gp Cp
Rs
Requirements for EOT Measurement of High Leakage
-
8/4/2019 Recent Developments in Electrical Metrology
7/25
7Slide 050309002
Requirements for EOT Measurement of High LeakageGate Stacks
1. Capacitor test structure design with minimum seriesresistance.
Topside electrical contact to the capacitor substrate is
required to eliminate the wafer chuck from themeasurement circuit.
2. Use of measurement frequencies high enough to reduce the
effect of the parallel conductance of the gate stack.Dissipation factor must be reduced sufficiently to permit
accurate measurements.
3. Geometric resolution of the test structure effective area must
be adequate to assure accurate and precise definition of EOT.
-
8/4/2019 Recent Developments in Electrical Metrology
8/25
8Slide 050309002
1-Port Philips UHF MOSCAP Design
Designed for low series resistance
Uses 3-point (G-S-G) UHF probe head
720 - 1.0x2.6 m capacitor elements Right and left ground pads connect p-well to
S/D.
active poly
-
8/4/2019 Recent Developments in Electrical Metrology
9/25
9Slide 050309002
Multi-Frequency MIS C-V Measurements on the Philips UHF MOSCAP
UHF Capacitor Test Structure: High Frequency C-V Performance
0.0E+00
5.0E-12
1.0E-11
1.5E-11
2.0E-11
2.5E-11
3.0E-11
3.5E-11
-2 -1.5 -1 -0.5 0 0.5 1 1.5 2
Gate Voltage [V]
Capac
itance
[F]
f = 100 kHzf = 1 MHz
f = 2 MHz
f = 5 MHz
f = 10 MHz
f = 20 MHz
f = 50 MHz
f = 100 MHz
CVC model
Lot-wafer 3052109-18: 40 cycles HfO2; HF-NH3 preclean
CVC Model ParametersEOT = 7.35
Nsurf = 9.7E17 /ccVfb = -0.252 V
RMS fit error = +/-0.8%
A(eff) for EOT fit = 8.74x10-6 cm2
0.0E+00
5.0E-12
1.0E-11
1.5E-11
2.0E-11
-2 -1 0 1 2
Voltage [V]
Capac
itan
ce
[F] 100KHz
1MHz
4MHz10MHz20MHz50MHz100MHz
3090511-01
2 nm SiO2 TiN gate electrode 0.7 nm EOT HfO2 poly gate
Effective Area = 8.7x10-6 cm2
Measurement: Agilent 4294A Precision Impedance Analyzer IV Probe mode
Frequency-invariant C-V data can be obtained in wafer form on 2 nm SiO2films with properly designed test structures.
Some frequency dispersion is seen on more highly scaled high-k devices.
Three element Equivalent Circuit Parameter Analysis from Dissipation
-
8/4/2019 Recent Developments in Electrical Metrology
10/25
10Slide 050309002
Three-element Equivalent Circuit Parameter Analysis from Dissipation
Factor-Frequency Characteristics
Dissipation Factor vs. Frequency PlotLot-wafer 3073102-07: STI HfSiO
0.01
0.1
1
10
1.0E+05 1.0E+06 1.0E+07 1.0E+08
Frequency [Hz]
Dissipation
Factorat-2V
D-f dataRo = 1.4E4 ohms
Rs = 18.4 ohms
D = 1/RoCo D = RsCo
ooo
s
ooo
oso
CRR
R
CRC
GRGD
1)1(
1)1(+=
+=
For low frequencies, D ~ 1/f:
In the high frequency limit, D ~ f:
osCRD =
Extraction of Ro, Rs from
D- PlotsEOT = 17.2
Go= 1/Ro Co
Rs
-
8/4/2019 Recent Developments in Electrical Metrology
11/25
11Slide 050309002
Dit: Comparison of Charge Pumping Techniques
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.510
9
1010
1011
1012 nFET W/L=10/1mTH75-2072317 #08
Vpeak
= 1.2V
Vbase = 1.0V Vbase
= -1.0V
Nit
[#/cycle*cm
2]
Vbase
[V] or Vpeak
[V]
1MHz Nit
100kHz Nit10kHz Nit
Fixed Amplitude,
Variable Base ChargePumping
Fixed Base, Variable Amplitude Charge
Pumping (into accumulation) Fixed Base, VariableAmplitude Charge Pumping
(into inversion)
These techniques provide
alternative ways to
characterize traps and
trapping processes in
high-k films.
Information on energyand depth distribution of
the traps may be obtainedfrom these curves.
3.5 nm HfSiO / polySi
-
8/4/2019 Recent Developments in Electrical Metrology
12/25
12Slide 050309002
EM-probe Description
Straycapacitancecompensatedvia software
Tip Shaft
~35 um
~300 um
InterfaceLayerassociatedwith tipcontact
~10 to 20
200um
Small contact area provides superior
performance for ultra-thin dielectrics
AFM Indicates
No SurfaceDamage
2005 Solid State Measurements, Inc. ALL RIGHTS RESERVED
-
8/4/2019 Recent Developments in Electrical Metrology
13/25
13Slide 050309002
In-line Measurement of CET/EOT with EM-probe
y = 1.388x - 3.3638
R2 = 0.9898
0
5
10
15
20
25
30
335
0 5 10 15 20
nMOS EOT (A)
EM-
ga
teCET(Ang.)
OxynitrideThermal OxideOxynitride
25
Device-correlatable CET/EOT measurements can be made in-line
for real-time process control down to ~1 nm.
-
8/4/2019 Recent Developments in Electrical Metrology
14/25
Channel Engineering
SDE Engineering
Mark C. BenjaminSolid State Measurements, Inc.
-
8/4/2019 Recent Developments in Electrical Metrology
15/25
15Slide 050309002
Relationship Between Dose and NSURF
N
W
C
V
NSURF = Average Dopant Density within WEQ
NSURF
WEQ WMAX
Equilibrium Dose = EQD = N(w)dw from the surface to WEQ
= NSURFWEQ = SQRT(2kSSL,INVNSURF/q)2005 Solid State Measurements, Inc. ALL RIGHTS RESERVED
-
8/4/2019 Recent Developments in Electrical Metrology
16/25
16Slide 050309002
EM-gate Equilibrium CV Comparison
SSM-6100 EM-probe CV versus Implant Dose
0
1
2
3
4
5
6
-3 -1 1 3 5
Vg(V)
C(
pF)
Slot 1 1E11 cm-2Slot 3 2E11 cm-2
Slot 5 5E11 cm-2
Slot 7 1E12 cm-2
Slot 9 1E13 cm-2Slot 11 5E13 cm-2
Slot 13 8E13 cm-2
Slot 15 1E14 cm-2
2005 Solid State Measurements, Inc. ALL RIGHTS RESERVED
-
8/4/2019 Recent Developments in Electrical Metrology
17/25
17Slide 050309002
Sensitivity: Nsurf versus Implant Dose
SSM-6100 Nsurf Sensitivity Comparison
1.00E+15
1.00E+16
1.00E+17
1.00E+18
1.00E+19
1.00E+11 1.00E+12 1.00E+13 1.00E+14
Implant Dose (cm-2)
Nsurf
(cm-3
)
2005 Solid State Measurements, Inc. ALL RIGHTS RESERVED
-
8/4/2019 Recent Developments in Electrical Metrology
18/25
18Slide 050309002
Major Device and Materials Issues with USJ S/D Structures
Sheet Resistance (RS)
Surface Carrier Density(N
SURF
)
Junction Depth (XJ)
Carrier Density ProfileShape
Junction Leakage Sensitive to Implant EOR Damage
Goal: Increase Electrically Active N
and Decrease W Ideal BOX Profile!!
W
N
Ideal
Actual
EORDe
fec
ts
NMAX
XJ
2005 Solid State Measurements, Inc. ALL RIGHTS RESERVED
4 C ti l EM P b
-
8/4/2019 Recent Developments in Electrical Metrology
19/25
19Slide 050309002
4pp: Conventional vs EM-Probe
Semiconductor Substrate
USL
Force
Sheet Resistance = R S = CF(V/I)
I IV
1 2 3 4
s
Conventional Four Point Probe
dSemiconductor Substrate
USL
Force
Sheet Resistance = R S
I IV
1 2 3 4
Semiconductor Substrate
USL
Force
S
I IV
1 2 3 4
s
Conventional Four Point Probe
Semiconductor Substrate
USL
Force
I IV
1 2 3 4
EM-probe Four Point Probe
s
dSemiconductor Substrate
USL
Force
I IV
1 2 3 4
EM-
s
d
= CF(V/I)Sheet Resistance = R S
2005 Solid State Measurements, Inc. ALL RIGHTS RESERVED
-
8/4/2019 Recent Developments in Electrical Metrology
20/25
20Slide 050309002
EM-probe Description
Stray
capacitancecompensatedvia software
Tip Shaft
~35 um
~300 um
InterfaceLayerassociatedwith tipcontact
~10 to 20
200um
Small contact area provides superiorperformance for ultra-thin dielectrics
AFM IndicatesNo Surface
Damage
EM Probe CV and IV: Non penetrating
-
8/4/2019 Recent Developments in Electrical Metrology
21/25
21Slide 050309002
EM-Probe CV and IV: Non-penetrating
EM-Probe CV and IV is used extensively to measure dielectricswith thicknesses less than 1 nm.
-1.8 -1.6 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2
Gate Voltage (V)
0
10
20
30
40
C(pF)
EM-gate Short Term Repeatability Test8 Angstrom SiON Wafer
Mean = 9.83 Ang.Sigma = 0.051 Ang.
-12 -10 -8 -6 -4 -2 0
Vg(V)
10-14
10-13
10-12
10-11
10-10
10-9
10-8
10-7
10-6
10-5
10-4
10-3
I(A)
EM-gate IV: Thin OxidesStepped Voltage IV, Step Delay = 1000 msec
90 Ang. (Slot 7)30 Ang. (Slot 24)10 Ang. (Slot 25)
TOX = 90 Ang.
TOX=30Ang.
TOX=10Ang.~ 4 to 5 Orders of Magnitude Difference
2005 Solid State Measurements, Inc. ALL RIGHTS RESERVED
Basic Principle of Four Point Probe (4pp) Method for R
-
8/4/2019 Recent Developments in Electrical Metrology
22/25
22Slide 050309002
Basic Principle of Four Point Probe (4pp) Method for RS
IA
VM
Voltmeter: Requires High ZIN, low
Input Offset Current
+ + - -
t
Resistivity = = [qp]-1 = RArea/lRArea/l P-type
Resistance = VM/IA
Sheet Resistance = /t = CF(VM/IA); = [q N(x)dx]-1
For Probes located far from Edge of Circular Sample, CF = 4.532
Semi-Infinite Slab
Defined StructureL
W RS = (V/I)/(L/W) , Units /Square
xJ
To eliminate Contact Resistance, Kelvin or Transmission Line(TLM)Structures are Used
Irvins Curves
1
2
2005 Solid State Measurements, Inc. ALL RIGHTS RESERVED
C ti l EM P b 4 R C 1 P USJ St t
-
8/4/2019 Recent Developments in Electrical Metrology
23/25
23Slide 050309002
Conventional versus EM-Probe 4pp RS Case 1: P+ USJ Structures
10
100
1000
10000
100000
#1-1 #1-2 #1-3 #1-4 #1-5 #1-6
Rs
(Ohms
/square
)
Conventional 4pp
EM-gate 4pp
16 nm
45 nm
15 nm
45 nm45 nm
28 nm
Rs vs xj Comparison
0
0.2
0.4
0.6
0.8
11.2
0 200 400 600xj (Ang.)
Ratio(Method/EM-Probe)
Conventional 4pp
VPS
Hg Probe 4pp
2005 Solid State Measurements, Inc. ALL RIGHTS RESERVED
R N Correlation: General Considerations
-
8/4/2019 Recent Developments in Electrical Metrology
24/25
24Slide 050309002
RS NSURF Correlation: General Considerations
Correlation Depends on Activation and xJ
N
W W
N
Xj ~ Constant,Diffusionless
Nsurf Increasing;Higher Activation Nsurf ~ Constant
Xj increasing
Good Rs Nsurf Correlation Poor Rs Nsurf Correlation
2005 Solid State Measurements, Inc. ALL RIGHTS RESERVED
Summary
-
8/4/2019 Recent Developments in Electrical Metrology
25/25
25Slide 050309002
Summary
Gate Engineering requires new measurement and analysistechniques
Channel engineering requires new measurement techniques for in-
line metrology Equilibrium Nsurf extends usefulness
Source-Drain Extensions (USJ) require new measurement
techniques Junction leakage requires thought -> Nsurf ?
2005 Solid State Measurements, Inc. ALL RIGHTS RESERVED