and the Trees: XRD and AFM for Compound … · XRD and AFM for Compound Semiconductors and Solar...

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See the Forest and the Trees: XRD and AFM for Compound Semiconductors and Solar Cells

Transcript of and the Trees: XRD and AFM for Compound … · XRD and AFM for Compound Semiconductors and Solar...

See the Forest and the Trees:

XRD and AFM forCompound Semiconductors

and Solar Cells

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Welcome

Assunta ViglianteHead of Business Development,Semiconductor Industry

Today’s Topics:Overview on X-ray diffraction (XRD) solutions for compound semiconductorsX-ray characterization and metrology for solar cellsAtomic Force Microscopy (AFM) applicationsBruker Nano AFMsQ&A

David SampsonProduct Manager, AFM

First, See the Forest…

XRD – Bulk material properties• thickness• orientation• roughness• epitaxy• composition• phase

AFM – Surface material properties• surface roughness• grain size• uniformity• surface potential• electrical fields• capacitance• work function• spreading resistance

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Compound Semiconductor Industries

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Material Systems Devices Applications InP

InGaAs InAlAs

InGaAlAs InGaAsP InGaAsN

1.3/1.55um Lasers LEDs

VCSELs Detectors

HBTs

Optical fibre communications Sensors

IR cameras Wireless communications

GaAs AlGaAs InGaAs

InGaAlAs InGaAsP

Solar Cells Detectors VCSELs HEMTs FETs

Fibre amplifiers Medicine

Solid state laser pumps CD, Minidisc

Gigabit Ethernet GPS, Automotive

Satellite

InGaP InAlP

InGaAlP GaN

InGaN InGaAlN

Visible Lasers UHB LEDs

Visible VCSELs InGaP HBTs

Doudle Junction Solar Cells White LEDs

Display illumination Solid-state lighting

DVD lasers Pointers, bar code

Wireless communications Satellite Medicine

Si SiGe

MOSFETs Solar Cells

HEMTs Virtual Substrates

Wireless communications Solar power

Inexpensive starting material for III-V´s Computers

Data Processing

ZnSe White LEDs Display illumination Solid-state lighting

Please use your mouse to answer the question on the right of your screen:

What types of materials do you currently analyze? (Check all that apply.)

Thin film solarCrystalline or polycrystalline SiDye sensitized solarLEDsLasersCIGS/CdTe

Audience Poll

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Band Gap vs. Lattice Constant

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Pseudomorphic Layers Compression and Tension

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Substrate Substrate Substrate

Layer underCompression

Layer without Strain

Layer underTension

D8 DISCOVER

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Sample 1460: XRR and HRXRD Measurement Consistent Data Analysis with LEPTOS

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GaN(000) GaN(002) GaN(004)

One sample-model

Multiple measurements

Sample 1460: Fast Reciprocal Space Mapping Using the LynxEye 1D-Detector

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Δt = 3.84s / point T = 418 min Δt = 1.92s / point T = 39 min

GaN(104+)GaN(002)

Conversion to reciprocal

space units using LEPTOS

Sample 1460: Fast Reciprocal Space Mapping Using the LynxEye 1D-Detector

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Δt = 3.84s / point T = 418 min Δt = 1.92s / point T = 39 min

GaN(104+)GaN(002)

Conversion to reciprocal

space units using LEPTOS

• RSM with the LynxEye are collected by looping 2theta-scans. The data are converted afterwards to RSU using the Leptos software.•Instead measuring the (105+) reflection, the (104+) reflection was chosen because of the smaller beam footprint and resulting in a better resolution.•A further reduction of the measurement time may be achieved by reducing the measurement time per point and reducing mapped area.

Changing to the In-Plane Geometry

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Quick and easy change of the setup:

• Rotate the tube by 90°• Remove the PBO• Mount the soller-slits

(0.23°) on the primaryand secondary side

• Ready to measure

What is IP-GID ?

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• Scattering geometry combining Bragg condition with total external reflection from crystal surface (non coplanar geometry)

• Penetration depth of x-rays reduced by 3 orders of magnitude (from 1-10 μm in standard Bragg condition to 1-10 nm at critical angle and below)

⇒ Surface sensitive technique

Sample 1504: Depth-Dependent Determination of the In-Plane Lattice Parameter of the Surface-Near AlInN Layer Using In-Plane Diffraction

0,40 0,45 0,50 0,55 0,60 0,65 0,700

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inte

nsity

[c

ps]]

incidence angle [deg]

Peak @ 115,4° Peak @ 113,7°

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2 peak positions at the AlxIn1-xN(300) reflection :

115,05° ± 0,2° a = 3,162Å113,66° ± 0,1° a = 3,188Å

Lateral mismatch: Δa/a = -0.0082 h - position at (104+) reflection : 1.0082l - position : 4.082αi = 0.4°

αi = 0.7°

Cu-Kα1

Cu-Kα2

surface

bottom

Thickness and Composition

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HRXRD SimulationExample: Si1-xGex - Si Structure

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Fit results

Concentration cx = 39.67 %

Thickness SiGe layer = 2.5 nm

Thickness Si layer = 80.83 nm

Sample courtesy of Uni Duisburg / IPAG

Si

Si1-xGex

Si

D8 DISCOVER with 2D HI-STAR Detector

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ω scan

2D detector used in fixed position

ω scanned for one frame for half of the 2θ range of the detector

HI-STAR

Cu LFF2.2 kW

Laser Video Scope

Homogeneity maps with µXRD

D8 DISCOVER for Material Research µ-HRXRD - Homogeneity Mapping

(In0.12Ga)N(100nm)/GaN(2000nm)/Al2O3

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Time: 2 sec.2θ (d-spacing)

χ (mosaic)

InGaNGaN

Measured areaGaN InGaN

D8 DISCOVER for Material Research µ-HRXRD - Homogeneity Mapping(In0.12Ga)N(100nm)/GaN(2000nm)/Al2O3

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Solar CellsHigh Efficiency

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Satellites and Space Explorations Applications

Epitaxial layers

GaAs, Ge, InP substrate

Efficiency 40.7%

XRD Requirements:

HRXRD on 6“ wafers

Sample ID: MI446 (002) and (004) Reflection

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(002) (004)

Solar Cells for Commercial Applications

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• Bulk Si (90%of the solar cells market)

• CdTe thin film on glass• CuInSe2 CIS and CuInxGa(1-x)Se2 thin film on glass

• New materials in R&D Organic films, films on flexible tapes, nanocrystals...

X-ray Solutions:

• Basic XRD PhaseAnalysis• Texture/preferredorientation

• µXRF elemental composition

• µXRF can be in line

ARTAX Technique

CCDX-raytube

Detector

Laser

Probe

Capillary optics Ranging from 25µm to 100 µmEnergy range From few KeV to 25 KeV

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Analysis of Functional Coatings Solar Cells (1)

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Structure of the solar cell system

Coating Thickness Ranges

Layer Coating [µm]

ZnO 0.80 - 1.80CdS 0.05 - 0.10CuInGaSe 1.50 - 2.0Mo 0.30 - 0.40

Quality control of CIGS-Modules (30x30cm²)

with Micro X-ray Fluorescence

Results:Elemental distribution in the CIGS-layer; Coating thickness distribution of Mo, CIGS, CdS and ZnOInfluence of module curvature No influence on layer composition Influence to coating thickness small (approx. 3% per mm)

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Analysis of Functional Coatings Solar Cells (2)

Spectrum of a solar cell sample

µXRF Capabilities

Mo Micro-focus source and capillary optics

µXRF evaluation software (qualitative and quantitative multilayers analysis with fundamental parameters)

Automated height alignment and measurement scripts

Spot size can be chosen according to the collimator or capillary optics

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Acknowlegements

Martin Zimmerman, Bruker AXS, Karlsruhe, Germany

Wayne Lin, Bruker AXS, China

Keisuke Saito, Bruker AXS, Japan

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Now, See the Trees…

XRD – Bulk material properties• thickness• orientation• roughness• epitaxy• composition• phase

AFM – Surface material properties• surface roughness• grain size• uniformity• surface potential• electrical fields• capacitance• work function• spreading resistance

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Cantilever Detection: The Industry Norm

Laser Beam Bounce Detection

advantage:

simple setup, cheap

disadvantage:

alignment procedure,

larger head design

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The Bruker Difference

Interferometric Detection

advantage:

Compact design, accurate tip delfection infromation, No laser alignment –Easier to use

disadvantage:

Slightly more complex deflection detection system

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The Bruker Difference

The NANOS head design

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Bruker Nano Products

N8 NEOS - The Workhorse in Surface Inspection

• excellent time-to-result performance

• rigid combination of optical microscopy and AFM/SPM

• simple switching between techniques

• flexible sample handling

• resolution below 1 nm

Design ObjectiveObjective based AFM that combines a research quality optical microscope with a research quality AFM

Maintaining all AFM functionality and angstrom level noise floor

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NANOS – the Unique AFM / SPM

the most compact AFM on the market

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DIC ImageAFM Image

NANOS – the Unique AFM / SPM

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Surface Features

PbSe Thin Film

Roughness

Uniformity

Texture – Particle Size

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Surface Features

PbSe Thin Film

Roughness.Uniformity.Texture – Particle Size.

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What Does Roughness Mean?

PbSe Thin Film

Sa – Average Roughness 64.6 nmSq – RMS Roughness 78.8 nmSsk – Skewness -0.39Sku – Kurtosis 2.84..S10z- Ten Point Height 650 nm..Sdr - Surface Area Ratio

69%..Srwi - Radial Wave Index 0.09

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The Flaws of Roughness

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%SAD

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The Flaws of Roughness Measurements

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AFM as a Local Surface Probe

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Surface PotentialElectrical FieldsCapacitanceWork FunctionConductivity

Dopant ProfilingBand StructureDefect DetectionSurface Uniformity

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Electrical Measurements

Electrostatic Force Microscopy

Scanning Surface Potential Microscopy (Kelvin)

Scanning Spreading Resistance or Conductive AFM

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Electrostatic Force Microscopy

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Electrostatic Force Microscopy

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Electrostatic Force Microscopy

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Electrostatic Force Microscopy

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Electrostatic Force Microscopy

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Electrostatic Force Microscopy

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Three choices: Amplitude, Phase or Frequency

F = C (Vtip – Vsurface)2

Δφ = -arcsin[(Q/2k)(d2C/dz2)ΔV)Q = quality factor k = spring Constant

Electrostatic Force Microscopy

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Scanning Surface Potential

• AC mode• Measures the work function between the tip and the sample• Can map the band bending and doping

• AC voltage applied to tip• Nulling voltage applied to minimize oscillations• Nulling voltage is ≈ ΔWork function

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SSPM Measurements on GaN

topography

SSPM signal (Wmod component)

p-GaN

n-GaN

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Electrical Measurements

MeasurementElectronics

Conductance AFM – High Current

Tunneling AFM – Low Current

Scanning Spreading Resistance – Logarithmic Amplifier

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Electrical Measurements

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Electrical Measurements

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Electrical Measurements

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Standard AFM

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Photo Assisted AFM

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Lock InAmplifier

Signal Generator

Controller

Raw data to lock inSeparated data back to controller

Please use your mouse to answer the question on the right of your screen:

What technique do you feel would best complement AFM?

RamanIRConfocalXRFEllipsometry

Audience Poll

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N8 NEOS AFM Fitted with Senterra Raman

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N8 TITANOS

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N8 TITANOS

Sn02contact mode

ZnOintermittent contact mode

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NANOS – The Simple Add-On for Optical Microscopy

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NANOS

We have created a easy to use, customizable high resolution metrology solution that couples research quality microscopy with state of the art scanning probe technology. Whether you need a basic research system or a 300 millimeter highly automated system, Bruker has a AFM that will meet your needs.

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Bruker Nano Instruments

NANOS N8 NEOS

N8 ARGOS

N8 RADOS

N8 TITANOS

upgrade AFM √

routine lab instrument

√ √

routine lab instrument, automated

localized objects, defect inspection

√ √ √ √

sample sizes up to 50 mm

√ √ √ √

sample sizes up to 100 mm

√ (√) √

sample sizes up to 150 mm

(√) (√) √

sample sizes up to 300 mm

application in liquids

√ √ √

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Bruker Nano Instruments

NANOS N8 NEOS

N8 ARGOS

N8 RADOS

N8 TITANOS

req. resolution ~ 1 nm

√ √ √ √ √

req. resolution ~ 0.1 nm

√ √ √ √

req. resolution > 0.05 nm

√ √ √

quasi atomic resolution

semiconductor industry

√ √

Industry, R&D, QA √ √

basic research √ √

automated systems

√ √

teaching instrument

√ √

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