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

2. Pop Quiz !
1. Color
3 . Contamination
Dark image (SE ↓)
Resolution↓
X-ray absorption
2. Sample Coating
Prevention of charge-up by sampling
Sputter coating with C, Cr, or Au-Pd
N2 Blowing
Carbon tape, carbon paint, In foil
Vacuum status of the chamber
Hydrocarbon, pump, O-ring oil

3. 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

4. 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
Auger electrons
Secondary electrons
(이차전자)
Backscattered
electrons
Cathodoluminescence (light)
X-rays
Sample

5. How an Electron Beam is Produced?
Electron Gun Properties
Source
W
LaB6
C-FEG
T-FEG
Brightness
3X105
3x106
109
109
Stability(%)
~1
~2
~5
<1
Size
50mm
5mm
5nm
20nm
Energy spread
3.0(eV)
1.5
0.3
0.7
Vacuum
10-5 Torr
10-6
10-10
10-9

6. Main Informations
BaTiO3
5m
SE image
BSE image from flat surface of an Al
(Z=13) and Cu (Z=29) alloy
 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

7. Important SEM Controls
1. Accelerating Voltage (kV) 가속전압 ↑
High resolution
Unclear surface structure
More edge effect
More charge-up
More damage
2. Probe Current 접속렌즈 세기 ↑
Condenser Lens (C1) current ↑⇒ 𝑑 𝑝 ↓, 𝑖 𝑝 ↓
Smooth image
Deteriorated resolution
More damage
3. Aperture Size 대물 조리개 크기↑
Controls 𝛼, 전자빔의 수렴각 조절
Large current (BEI, X-ray analysis)
Low resolution
Smaller depth of field
4. Working Distance 시편 z-축 조절↑
Greater depth of field
Low resolution
Spot size ↓, Beam angle ↓ , Beam Current ↑
⇒ Trade-off exists!

8. Summary
1. Electron beam parameters
𝛼 𝑝 : Probe convergence angle
𝑖 𝑝 : Probe current
𝑑 𝑝 : Probe diameter
3. Signal detection &
Image formation
Detector system
Pixel vs. Magnification
Image contrast (topo, compo)
2. Specimen-beam interaction
𝑉𝑖𝑛𝑡 : Interaction volume
𝑅 𝐾−𝑂 : e – Range
Signals : SE, BSE, X-ray
0. Sample preparation