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Agilent TechnologiesAgilent Technologies

Scanning Microwave Microscopy (SMM)Microscopy (SMM)

Expanding Impedance M h N lMeasurements to the Nanoscale: Coupling the Power of Scanning Probe Microscopy with the PNA

Presented by:

Craig Wall PhDProduct Manager – Agilent AFMProduct Manager – Agilent AFM,Nanomeasurements Division

Scanning Microwave Microscopy

12/15/2008

OutlineOutline

IntroductionIntroduction

Principle

Instrument setup

Experiments

SummarySummary

12/15/2008


IntroductionAvailable SPM-based techniques to probe materials electric properties:

Scanning near-field microwave microscopy (SNMM)Scanning capacitance microscopy (SCM)Scanning capacitance microscopy (SCM)Scanning spreading resistance microscopy (SSRM)Electrostatic force microscopy (EFM)Current-sensing (or conductive) AFM (CSAFM)Current-sensing (or conductive) AFM (CSAFM)Kelvin force microscopy (KFM)More …

Scanning Probe Microscopy, edited by S. Kalinin and A. Gruverman, Springer, New York, 2007.

Vector network analyzer + AFMimpedancecapacitance

Scanning Probe Microscopy, edited by S. Kalinin and A. Gruverman, Springer, New York, 2007.

capacitancedopant densitymore …


12/15/2008

Scanning Microwave Microscopy (SMM)

Z

AFM Basic ConfigurationAFM Basic ConfigurationZ

XY

AFM tip monitors surface Closed loop scanner (xyz) or stageS ith ti ith lScan with tip or with sampleVideo access


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AFM Imaging Modes

Contact Mode AFM (1986)Dynamic in x and yDynamic in x and yTip is in contact or near contact with the surfaceSmall vertical force, but the probe dragged over the surface exerting lateral force.Weakly bound or soft samples move easily.Lower lateral resolution.

AC Mode AFM (1993)Dynamic in x, y, and zIntermittent contact. Soft surfaces are stiffened by viscoelastic response. Impact is predominately vertical, therefore large vertical force, but no lateral force.Higher lateral resolutionHigher lateral resolution.


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PrincipleZZ

complex reflection coefficient

incident transmitted0

0

ZZZZ

L

L

+−

=Γ

REFLECTION

ReflectedIncident

REFLECTION

AR

=

Optical analogy

reflectedSWR

S P t I d

ReturnLoss

incident transmitted

Optical analogy S-ParametersS11, S22 Reflection

Coefficient

Impedance, Admittance

R+jX, G+jB Γ, ρ

incident transmitted

reflectedScanning Microwave Microscopy

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Microwave transmission

Schematic

SSource

Half wave lengthCoaxial resonator 50 Ohm

Probe


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Instrument setup

professional network analyzerAFM

For dC/dV measurements, a low-frequency modulation is added to the microwave. Demodulated signal is detected by an ac mode controller with built-in digital lock-in amplifiers.


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Agilent 5400 Based SMM


12/15/2008

Agilent 5400 Based SMM

Load DiplexerLoad Diplexer

RF to PNA

Scanner headScanner head With Conductive Tip


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Scanner assembly, cantilever

Cantilever holder

Pt/Ir cantilever

Scanner assembly Al substrate


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Agilent PerformanceVector Network Analyzer

PNA

SignalConditioning

Conductive tip

Conditioning

Agilent 5400SPM Instrument

Agilent PrecisionMachining and ProcessTechnologies to deliver


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gRF/MW to the conductive tip

PNA Controls from PicoView

Agilent General Audience

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Experiments – frequency sweep


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DRAMDRAM


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SMM image of SRAM

A – topographyB – capacitanceB capacitanceC – dC/dV

Schematic of 6-FET unit cell of SRAM


Schematic of 6 FET unit cell of SRAM

12/15/2008

0

2.50

2.5

0

2.5

Topography Phase Surface Potential

Kelvin Force Microscopy of Semiconductor Surfaces1st Eigen/10kHz

5

7.5

10

12.5

15

17.5

5

7.5

10

12.5

15

17.5

5

7.5

10

12.5

15

17.5

SiGe

µm

20

22.5

µm

20

22.5

µm

20

22.5

0

5

10

0

5

10

0

5

1010

15

20

25

30

35

10

15

20

25

30

35

10

15

20

25

30

35

SRAM

40

45

50

40

45

50

40

45

50

Surface Potential Surface Potential Surface Potential

25 μm40 μm40 μm

Agilent General Audience(70kHz/10kHz) (70kHz/425kHz) (425kHz/70kHz)

25 μm40 μm40 μm

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Images of an SDRAM

• Very high sensitivity• Can see semiconductor, insulators and conductors• Can be calibrated


• Can also get inductance and reactance

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SMM image of SRAM

Topography dC/dVTopography dC/dV

Zoomed scans of a transistor.


Line feature of 10 – 20 nm in width can be seen in the dC/dV image

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Carriers at 0V bias in SRAM


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Sample 1

Optical images of sample 1. The failed 48th transistor is marked with a blue circle.Optical images of sample 1. The failed 48 transistor is marked with a blue circle.


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Sample 1

Topography (top), dopant concentration (middle), and capacitance (bottom) images of scans across FETs 43 46 (right) and FETs 45 48 (left) Dopant density images (middle) clearly show a difference on the 48th FET– 46 (right) and FETs 45 – 48 (left). Dopant density images (middle) clearly show a difference on the 48th FET

from all others (43 – 47). The missing dark area (p dopant) indicates a problem in the channel of the 48th FET.


12/15/2008

Sample 1

Topography (top), dopant concentration (middle), and capacitance (bottom) images of scans across FETs 47 – 50 (right) and FETs 49 – 52 (left). Like the last slide, dopant concentration images also show a

ti bl diff th 48th FET f ll th C it i f th 48th FETnoticeable difference on the 48th FET from all others. Capacitance image of the 48th FET appears some difference from others as well. The result here is consistent with the observation obtained on July 10.


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SiGe device

Topography Capacitance dC/dV


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InGaP/GaAs heterojunction bipolar transistor

Topography Impedance1 4 7 1 4 7

Different regions from the emitter-side contact layer (7 and 8) to the subcollector layer (1) with different doping levels were clearly resolved in the impedance image. (Sample courtesy of T. Low)


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Biological sample

Bacteria cells of geobacter sulfurreducens

Topography Impedance

Sample courtesy of N Hansmeier T Chau R Ros and S Lindsay at Arizona State University


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Sample courtesy of N. Hansmeier, T. Chau, R. Ros, and S. Lindsay at Arizona State University.

SummaryA new technique, which integrates AFM with a professional network analyzer, has been developed.

scanning microwave microscopy— scanning microwave microscopy

Mapping impedance, capacitance, dielectric constants, etc.— SNMMSNMM

Measuring two-dimensional dopant density of semiconductors.— SCM

High sensitivity with resolution ultimately limited by the probe.

Metals, semiconductors, dielectric materials, ferroelectric materials, insulators, and even biological samples.

12/15/2008


Agilent Technologies = Innovation in Measurements

We are presenting a state of the art AFM/SMMWe are presenting a state of the art AFM/SMM microscope to enable material measurements at the Nanoscale

+ =

Coaxial cableCoaxial Resonator

Sample scanning AFM in X and YNetwork Analyzer

SampleThe MW diplexer

Ground/Shield


12/15/2008

Sample scanning AFM in X and Y and Z (closed loop)

Analyzer

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