Transcript SIM Mode - Czech Technical University in Prague

Agilent Technologies
Scanning Microwave
Microscopy (SMM Mode)
Electromagnetic materials
characterization at high spatial
resolution
Scanning Microwave Microscopy
Page 1
December 15, 2010
Overview
• SMM System – PNA with AFM
• Features and Benefits
• Microwave Network Analyzer Basics (VNA)
• System overview
•Calibrated capacitance & dopant density
• Beyond SCM, what can be done with SMM - Applications
• Biological samples
• Thin films and coatings
• Quantum dots/quantum structures
• Summary
Scanning Microwave Microscopy
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December 15, 2010
Features & Benefits
• Provides exceptionally high spatial electrical resolution
• Offers highest sensitivity and dynamic range in the industry
• SMM facilitates
– Complex impedance (resistance and reactance)
– Calibrated capacitance
– Calibrated dopant density
– Topography measurements
• Works on ALL semiconductors Si, Ge, III-V and II-VI
• Does not require and oxide layer
• Operates at multiple frequencies (variable up to 18GHz)
Scanning Microwave Microscopy
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December 15, 2010
What is a Vector Network Analyzer?
Vector network analyzers (VNAs)…
Transmission
DUT
• Are stimulus-response test systems
S21
Reflection
S11
S22
S12
• Characterize forward and reverse reflection and transmission responses
(S-parameters) of RF and microwave components
• Quantify linear magnitude and phase
• Are very fast for swept measurements
Magnitude
• Provide the highest level
of measurement accuracy
RF Source
Phase
LO
R1
A
Test port 1
R2
B
Test port 2
Scanning Microwave Microscopy
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December 15, 2010
High-Frequency Device Characterization
Incident
Transmitted
R
B
Reflected
A
TRANSMISSION
REFLECTION
Reflected
Incident
=
SWR
S-Parameters
S11, S22
Reflection
Coefficient
G, r
A
Transmitted
R
Incident
Return
Loss
Impedance,
Admittance
R+jX,
G+jB
=
B
R
Group
Delay
Gain / Loss
S-Parameters
S21, S12
Transmission
Coefficient
T,t
Insertion
Phase
Scanning Microwave Microscopy
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December 15, 2010
Scanning Microwave Microscopy (SMM)
Basic Idea
Actuator
Tip and sample
form a capacitor
Measuring C yields er
Capacitance
C = e0 er A/d
C ~ fF
Capacitance bridges too slow
Integration times of several seconds not practical for imaging
Scanning Microwave Microscopy
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December 15, 2010
System Overview
Coaxial cable
Network Analyzer
Scanning AFM in X and Y
and Z (closed loop)
• Network analyzer sends an incident RF signal to the tip through the diplexer
• RF signal is reflected from the tip and measured by the Analyzer
• Magnitude & phase of the ratio between the incident & reflected are calculated
• Apply a model to calculate the electrical properties
• AFM scans and moves tip to specific locations to do point probing
Scanning Microwave Microscopy
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December 15, 2010
Compatible with Agilent 5420 & 5600LS AFM/SPM
5420 AFM
5600LS AFM
Scanning Microwave Microscopy
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December 15, 2010
Sub 7 nm Conductive tip development
Pt/Ir Cantilever
Agilent Precision Machining and Process
Technologies to deliver RF/MW to the conductive tip
Alumina Carrier
Scanning Microwave Microscopy
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December 15, 2010
Simultaneous Imaging of Topography, Capacitance,
and dC/dV
Scanning Microwave Microscopy
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December 15, 2010
PNA Controls from PicoView
Scanning Microwave Microscopy
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December 15, 2010
Capacitance calibration
60 mm
60 mm
Calibration staircase sample
50
50mm
mm
(collaboration with National Institute of Standards
and Technology, NIST)
TOP
VIEW
TOP
VIEW
10 micron
Gold caps on SiO2 „staircase“ on Si.
AFM topography 3D view (left) and
schematic overview (right).
nm
200nm
200
METAL
METAL
SILICON
SILICON
OXIDE
OXIDE
SILICON
C2 SILICON
SIDE VIEW
C1
SIDE VIEW
1


d*

signal
Ae C 2
Transfer Function: S11 signal [dB]  capacitance [F]
Scanning Microwave Microscopy
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December 15, 2010
Capacitance Calibration
Capacitance (amplitude)
dB
16
60 mm
12
50 mm
8
4
0
10µm
TOP VIEW
Sample: „NIST2“ staircase with goldcaps
200 nm
METAL
SILICON
OXIDE
C1
C2 SILICON
SIDE VIEW
Scanning Microwave Microscopy
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December 15, 2010
Capacitance Calibration
1


d*

signal
Ae C 2
Scanning Microwave Microscopy
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December 15, 2010
Enhancing the Sensitivity
DPMM approach:
Use the Flatband transfer function as
AM mixer to modulate the reflected MW
signal at the rate of drive frequency
(<100 KHz).
The AM modulation amplitude is
function of the dopant density.
Scanning Microwave Microscopy
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December 15, 2010
Imaging Dopant Density
Agilent PNA
Coupler
Coupler
k
A
B
LO
LO
A/D
S11 
Waveguide
Scanner
Source
AFM
A/D
Z L  Z0
Z L  Z0
Probetip
Sample
LF
LF
Demodulator AC Bias
dC/dV Module
Agilent
DPMM
Scanning Microwave Microscopy
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December 15, 2010
Dopant Density calibration with IMEC Standard
0.001
1014
Spec sheet IMEC calibration sample
bulk
Resistivity
[Ωcm]
1
1017
4
6
3
edge
8
7
30
20
10
0
Si Wafer
Cleave or polish
from top to expose
the layers
1020
1000
5
Density (/cm³)
2
1
Deposit
Layers with
Various Doping
Levels
Depth [µm]
Scanning Microwave Microscopy
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December 15, 2010
Dopant Density calibration with IMEC Standard
bulk
dC/dV Amplitude
1 2
3 4 5
6
edge
7 8
Scanning Microwave Microscopy
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December 15, 2010
Images of an SDRAM
Topography
dC/dV
Capacitance
Images of SDRAM chip acquired with SMM Mode. The underneath n-type (bright) and p-type doped
structure clearly indentified in both capacitance and dC/dV Images (W.Han)
• Very high sensitivity
• Can see semiconductor, insulators and conductors
• Can be calibrated
• Can also get inductance and reactance
Scanning Microwave Microscopy
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December 15, 2010
SMM Images of SRAM Chip
Topography (A and C) and dC/dV (B and D) images of SRAM. C and D are zoomed scans on one
of the transistors in the n well marked in the blue square in A / B. A very fine line feature of 10 to
20 nm in width can be seen in the dC/dV image, as pointed in D, indicating high resolution
capability of the scanning microwave microscope.
Scanning Microwave Microscopy
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December 15, 2010
Simultaneous Images of SRAM Chip
Simultaneous topography (A), capacitance (B), and dC/dV (C) images of an SARM chip.
Alternating lightly doped p and n wells are clearly identified in both capacitance and dC/dV
images. Five of the six transistors in a unit cell are marked in B and C.
Scanning Microwave Microscopy
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December 15, 2010
Dopant on SiGe
Topography (left) capacitance (middle) and dC/dV (right) images of a dpoed SiGe device acquired
with Scanning Microwave Microscopy (SMM). Both capacitance and dC/dV images showed
dopant structure not seen topography.
Scanning Microwave Microscopy
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December 15, 2010
InGaP/GaAs Transistor
Topography (left) and impedance (right) images of a cross section of a InGaP/GaAs hetrrojunction
bipolar transistor. Different regions from the emitter to the subcollector with different dopant levels
were clearly resolved in the impedance image. (W. Han sample courtesy of T. Low)
Scanning Microwave Microscopy
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December 15, 2010
Semiconductor Failure Analysis
Optical image of a small section of the tested
SRAM chip. The failed bit contains an n-type FET
(the 48th on that row) with an abnormal Vt.
Four sets (A, B, C, and D) of
scanning microwave
microscopy images on the
failed SRAM chip. Each set
contains topography (top),
dC/dV (middle), and VNA
amplitude (bottom) images
acquired simultaneously. The
red squares outlined the failed
48th n-type FET, the blue
squares are normal n FETs on
the same row.
Scanning Microwave Microscopy
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December 15, 2010
Bacteria Cells
Topography (left) and impedance (right) images of dried bacteria cells.
(W. Han, Sample courtesy of N Hansmeier, T. Chau, R.Ros and S. Lindsay at ASU)
Scanning Microwave Microscopy
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December 15, 2010
Summary
• Characterization of electromagnetic materials at High spatial
resolution
• Offers highest sensitivity and dynamic range in the industry
• Complex impedance
• Sidewall diffusion
– Calibrated capacitance – unique
– Calibrated dopant density – unique
• Works on ALL semiconductors Si, Ge, III-V and II-VI
• Does not require and oxide layer
• Operates at multiple frequencies (variable up to 18GHz)
Scanning Microwave Microscopy
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December 15, 2010
Back-up Slides
Scanning Microwave Microscopy
Scanning Microwave Microscopy
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December 15, 2010
Scanning Microwave Microscopy
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December 15, 2010
• Scanning only
• qualitative
• poor sensitivity
• limited 1015-1020 Atoms/cm3
• No Conductors/Insulators
Scanning Microwave Microscopy
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December 15, 2010
Lightwave Analogy to RF Energy
Incident
Reflected
Transmitted
Lightwave
DUT
RF
Scanning Microwave Microscopy
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December 15, 2010
Standard Vector Network Analyzer
as a reflectometer
Very small capacitor
High SNR
Low Resolution
Source
A
LO
S11 
Z L  Z0
Z L  Z0
A/D
B
LO
A/D
Probe
Highly resistive load
High SNR
Low Resolution
Load close to 50
Ohms
Low SNR
High Resolution
Figure 1: reflection
coefficient vs.. impedance
Low resistive load
High SNR
Low Resolution
Scanning Microwave Microscopy
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December 15, 2010
Simplified Single Frequency Solution
Source
A
B
LO
LO
50 Ohm
Half wave length
Coaxial resonator
A/D
A/D
Probe
m2
freq=1.910GHz
dB(S(1,1))=-57.550
m1
0
dB(S(1,1))
S(1,1)
m1
freq=1.910GHz
S(1,1)=0.001 / -90.076
impedance = Z0 * (1.000 - j0.003)
-20
-40
m2
-60
0.5
1.0
1.5
2.0
2.5
3.0
freq, GHz
freq (500.0MHz to 3.000GHz)
Scanning Microwave Microscopy
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December 15, 2010