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Scanning Electron Microscopy Very Important Characterization tool ! What is ? 카이스트 신소재 공학과 09학번 김홍경

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Scanning Electron Microscopy

Very Important Characterization tool !

What is ?

카이스트 신소재 공학과 09학번 김홍경

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Pop Quiz !

2. Sample Coating

Prevention of charge-up by sampling

Sputter coating with C, Cr, or Au-Pd

Carbon tape, carbon paint, In foil

3 . Contamination

Dark image (SE↓)

Resolution↓X-ray absorption

N2 Blowing

Vacuum status of the chamber

Hydrocarbon, pump, O-ring oil

1. Color

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Light Optical Microscope

Low Resolution ~0.2 um

4x -1000x

Small Depth of Field

Scanning Electron Microscope

High Resolution 1~10 nm

10x – 3000000x

Large Depth of Field

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Scanning Electron Microscopy

A scanning electron microscope (SEM) is a type of electron

microscope that produces images with a focused beam of

electrons.

The electrons interact with electrons in the sample

Incoming electrons

Secondary electrons(이차전자)

Backscattered

electrons

Auger electrons

X-rays

Cathodo-

luminescence (light)

Sample

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How an Electron Beam is Produced?

Electron Gun Properties

Source Brightness Stability(%) Size Energy spread Vacuum

W 3X105 ~1 50mm 3.0(eV) 10-5 Torr

LaB6 3x106 ~2 5mm 1.5 10-6

C-FEG 109 ~5 5nm 0.3 10-10

T-FEG 109 <1 20nm 0.7 10-9

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Main Informations

Topography The surface features of an object and its texture.

Morphology The shape and size of the particles making up the object

Composition The elements and compounds that the object is composed of and the

relative amounts of them

Topography How the grains are arranged in the object

BaTiO3

5mSE image

BSE image from flat surface of an Al (Z=13) and Cu (Z=29) alloy

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Important SEM Controls

1. Accelerating Voltage (kV)가속전압 ↑

High resolution

Unclear surface structure

More edge effect

More charge-up

More damage

2. Probe Current 접속렌즈세기 ↑

Condenser Lens (C1) current↑⇒ 𝑑𝑝 ↓, 𝑖𝑝 ↓

Smooth image

Deteriorated resolution

More damage

3. Aperture Size대물조리개크기↑

Controls𝛼,전자빔의수렴각조절Large current (BEI, X-ray analysis)

Low resolution

Smaller depth of field

4. Working Distance시편 z-축조절↑

Greater depth of field

Low resolution

Spot size ↓, Beam angle ↓ , Beam Current ↑⇒ Trade-off exists!

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Summary

2. Specimen-beam interaction

𝑉𝑖𝑛𝑡 : Interaction volume

𝑅𝐾−𝑂: e – Range

Signals : SE, BSE, X-ray

3. Signal detection &

Image formation

Detector system

Pixel vs. Magnification

Image contrast (topo, compo)

1. Electron beam parameters

𝛼𝑝 : Probe convergence angle

𝑖𝑝 : Probe current

𝑑𝑝 : Probe diameter

0. Sample preparation