電子顯微鏡

電子光學理論的重大貢獻―

電子顯微鏡

張茂男

Mao-Nan Chang

ASSL, Department of Physics, National Chung Hsing University, Taichung, Taiwan

STEM EDS

EELS

穿透式電子顯微鏡 TEM (Transmission Electron

Microscope, TEM)

Digital image system

120kV TEM

JEM-1400

JEOL JEM-2010

200kV TEM

JEM-2100

200kV TEM

JEOL JEM-3000F

300kV TEM

JEM-1230 JEM-2100F JEM-3200FS JEM-ARM1300

10.90m

3.33m 2.53m

2.49m 1.7m

1.3 MV

JEM 2010 硬體結構

Intermediate lens

(Zoom, D/I mode) Projector lens

(Zoom)

Objective lens (Zoom, Focus) Field limiting aperture

Electron gun

Condenser lens

(Spot size: Cond 1,2,3) (Brightness: Cond 3) Sample holder

Condenser aperture

Objective aperture

Film

Viewing screen

Hardware for TEM

Acc Voltage: 100 KV~1.3 MV (200 KV is a general type) Gun Type: W, LaB ₆ , FEG (Field Emission Gun)

Pole piece type: UHR, AHR, HT

Attachment: EDS, EELS (GIF), STEM, TV, CCD, 3D Tomography, PC integration

Maintenance

TEM holder

for

various

purpose

左上面板

左下面板

右上面板

右下面板

TEM 的主要操作模式

1st condenser lens

2nd condenser lens Condenser aperture Condenser mini lens

Objective lens

Prefield Specimen Postfield

Information

Information from TEM

Lattice image

GaAs/AlAs CBED

Electron Diffraction EDS

EELS or GIF

光 圈 電子束

試 片

底 片

TEM

Image Diffraction pattern 電子

束

二次電 子檢測 器

試片

SEM

電子束

試片

環形 檢測器

STEM

Image Diffraction

穿透式電子顯微鏡

(Transmission Electron Microscope, TEM)

Incident Electron Beam

Specimen (thin foil)

Inelastically Scattered Electrons

EELS & Kikuchi Bands Elastically Scattered Electrons

Structural Information

Unscattered Electrons

Thickness Information

Electron/Specimen Interaction

試片製備 (I)

Epoxy

Epilayer 3 mm

3 mm

3 mm 3 mm

A B

Polytetrafluoroethylene Pressure

Heat

Epoxy

(-110) (110)

(001)

Conductive carbon paint

Glass

試片製備 (II)

Slot copper grid

Sample

Copper holder

Metal cap Sidewal

l Steel plate

Conductive carbon paint

試片製備 (III)

θ=15^o~12^o

Thin film area Ion gun

Liquid Nitrogen

θ=10^o~4^o

Thin film area Ion gun

PIPS Ion milling

or

(110)

Surfac e (001)

Substrate

Glass

試片製備 (IV)

Copper holder Metal cap

Steel plate

Conductive carbon paint

Glass

θ=15^o~12^o Thin film area

試片製備 (V)

At the exact position on the wafer, a small strip of platinum is placed as a protective cover. On one side of the strip a trench is milled out with an FIB. The same is done on the other side of the strip. Now the strip itself is first milled on both sides to make sure that it is thin enough to be transparent in the TEM. Then the sides connecting the strip to the wafer are cut through. Finally, the wafer is tilted so the ion beam coming from above can be used to cut through the final connection to the wafer at the bottom of the strip. When cut through the strip is loose and falls over in the hole.

The strip is then picked up with special tweezers and deposited on a TEM grid with carbon film.

Source: fei - Phillips

Focused Ion Beam (FIB)

Major Factors Affecting TEM Image Contrast

Thickness Atomic number Orientation

Scattering Scattering Diffraction

substrate amorphous

Electron beam Electron beam

入射電子偏折路徑圖

Bright Dark

k k

k k

k k

G d d k

G k

d d

i s

i

s     









































,

1 sin

2 1

sin 2

sin 1 2







 



Bragg condition ^{入射波 k i , 散射波 k s}



d

/2



k i 

k s

θ

k k

∆k

Miller Index

(hkl)

T D

Thin foil

Interaction of electrons and unit cells

  ^{  }   ^



r F e ikr r

k e i

i r f

e ikr

A _i ⁱ

2 2 2

0     



 

Diffraction amplitude: A ₀  繞射振幅 Structure factor: F(θ)

  ^    ^{     }  ⁿ   ^  ^{ } 

i

lr kq

hp e i

f i n

i

r k e i

f i

F   ²  ⁱ  ²  ^{i i i}

F(θ)=0 無繞射點

F(θ)≠0 有繞射點

單就繞射理論而言

Selection Rule

結構因素導致繞射點不存在於繞射圖形上

 

  k R

當 但繞射電子束強度為零

Case 1: Simple Cubic Crystal (SCC)

One atom per unit cell, atom coordinate [000]

f

F 

 (  )

  ^  ¹   ^  ^{ } 

1

1 e 2 i hp ¹ kq ¹ lr ¹ f

F   

p1 = q1 = r1 = 0

Case 2: Body-centered Cubic Crystal (BCC)

 

0 2

) (

0 )

( ) ] 1 (

[



























 



f F

even l

k h if

F odd

l k h if

l k h e i

f F





 

2 ] 1 2 1 2 [ 1 [000], coordinate

atom cell,

unit per

atoms

Two

Case 3: Face-centered Cubic Crystal (FCC)

 

0 )

( F odd

1 even 2

or even

1 odd 2

l , k , h if

0 f

4 )

( F odd

or even all

l , k , h if

] e

e e

1 [ f

F ^{i ( h k ) i ( h l ) i ( k l )}



























 ^{        }

2 ] 1 2 0 1 [ 2 ], 0 1 2 [ 1 ], 2 0 1 2 [ 1 [000], coordinate

atom cell,

unit per

atoms

Four

Case 4: Diamond Cubic Crystal (DCC)

 

 

0 )

( F others

0 )

( F ...

3 , 2 , 1 , 0 n

, n 4 l

k h

and even

all l

, k , h if

0 )

( F odd

all l

, k , h if

] e

1 [ F

] e

e e

1 ][

e 1

[ f F

2

) l k h ( i

) l k ( i )

l h ( i )

k h ( 2 i

) l k h ( i

FCC









































































 







other each

to 4 ] 1 4 1 4 [ 1 shift with

structures FCC

two to

similar base

Atomic

cell unit

per atoms

Eight

How about GaAs?

Si

Ga _FCC + As _FCC Same as FCC

Case 5: Hexagonal Close-packed Crystal (HCP)

 

 

 

  ^{2 0}

2 0 ...

3 , 2 , 1 , 0 ,

3 2

2 ) 1 3

( 2 cos 2

4 2 2

] 2 ) 1 3

( 2 2 1

[















 



 

 











 

F others

F odd

is l and n

n k

h if

k f h

F

k i h

e f

F

2 ] 1 3 2 3 [ 1 [000], coordinate

atom cell,

unit per

atoms

Two

r L





k i _  k s

 1



G

r d L

d r L

k G L

r _{  }  _{ } 





繞射圖形大小

λ: 電子波長，L(Camera length): 試片與底片之距離，R: 繞射向 量，d: 晶面間距，r: 繞射點到中央穿透點之距離

T D

Electron Beam Diffraction of Thin Films

繞 射 點 分 析

(uvw)面的法向量 倒晶格面上之向量

Selection Rule + Zone Law

0 lw

kv hu

] C l B

k A

h [ ) c w b

v a

u

(         

[hkl]

[uvw] // e-beam

Reciprocal lattice point

000 [h’k’l’]

screen

0 G

T

1

G : vector lattice

Reciprocal

T : vector on

translati Crystal

hkl uvw









































































































b C a

C c

B a

B c

A b

A

c C b

B a

A

C l B k A h

c w b

v a u

整數

 (h k l)面

2 2

2 2 / 1

2 2 2

2 2

2

1 1

l k

h

a c

l b

k a

G h d

h kl

h kl   

 

 



  



 _ For SCC

a=b=c

Review

Poly-structure

繞射環

r = λL/d

Selection rule

d _hkl

r _hkl

Diffraction ring

r ₂

r ₃

r ₁

繞射環分析(SCC, BCC, FCC and DCC)

       

       

       

4 : 11 :

8 :

3 :

: :

. 4

11 :

8 :

2 : 3 :

: :

. 3

8 :

6 :

2 : 2 :

: :

. 2

2 : 3 :

2 :

1 :

: :

. 1

3 1 1 2 2 0

2 0 0 1 1 1

2 2 0 2 1 1

2 0 0 1 1 0

2 0 0 1 1 1

1 1 0 1 0 0









r r

r r

DCC

r r

r r

FCC

r r

r r

BCC

r r

r r

SCC rd=λL

l L k

h

r a  



 ^{2 2}

2

0

a ₀

晶 格

常 數

Diffraction

b

c

Poly crystal

Single crystal

Double Diffraction

於繞射圖中出現Selection Rule之forbidden spots Unit Cell中只含一個原子者不會發生，含兩個或兩個

以上原子者可能由雙重繞射產生額外的繞射點

源自電子的多次散射，第一次產生的繞射電子束強

如DCC在[011]方向的(200)點與[112]方向的(222)點

[220] [311]

g

1

g

2

31]

1 [ g

g

₂



₁



0 )

( ...

3 , 2 , 1 , 0 ,

4 ,

,

0 )

( ,

,

























F n

n l

k h

and even

all l

k h

F odd

all l

k

h

Amorphous materials

Diffused ring pattern

The wave vector of the primary electron beam is rather large compared to typical reciprocal lattice vectors; any small part of the Ewald sphere is almost a straight line or plane in 3-D, respectively.

 For a thin foil the points in reciprocal space become elongated perpendicular to the foil; the flat Ewald sphere the can cut through many reciprocal lattice points - many reflexes are excited!

 In very thin specimens where inelastic scattering is negligible, the diffraction pattern then consists of many reflexes with intensities that decrease as the excitation error increases. It is nearly impossible to establish precise diffraction conditions; e.g. a two- beam case with a defined excitation error.

Fortunately, with a bit of inelastic scattering, electrons that are first scattered inelastically and then elastically , form a system of lines, so-called Kikuchi lines, which give a precise picture of the diffraction conditions.

 In next page, there are some diffraction patterns; on the left from "thick" specimens with Kikuchi lines, on the right from "thin" cases with the same orientation and without visible Kikuchi lines.

 So, simply move to thick part of your specimen, where with some practice and the

help of a "Kikuchi Map", it is easy to tilt the specimen to any desired orientation with high

precision, and then go back to a thin part.

Kikuchi map Diffraction map

Thick specimen Thin specimen

bright

Kikuchi lines

dark

(hkl)

C’

B’

C B

A

θ θ

Kikuchi lines are formed in diffraction patterns by diffusely scattered electrons, e.g., as a result of thermal atom vibrations. The main features of their geometry can be deduced from a simple elastic mechanism proposed in 1928 by Seishi Kikuchi

^[1]

, although the dynamical theory of diffuse inelastic scattering is needed to understand them quantitatively

^[2]

.

1. S. Kikuchi (1928). "Diffraction of Cathode Rays by Mica". Japanese Journal of Physics 5: 83–96.

2. P. Hirsch, A. Howie, R. Nicholson, D. W. Pashley and M. J. Whelan (1965/1977). Electron microscopy of thin crystals. Butterworths/Krieger, London/Malabar FL. ISBN 0-88275-376-2.

Kikuchi lines pair up to form bands in electron diffraction from single crystal specimens, there to serve as "roads in orientation-space" for microscopists not sure what they are looking at. In transmission electron microscopes, they are easily seen in diffraction from regions of the specimen thick enough for multiple scattering

^[1]

. Unlike diffraction spots, which blink on and off as one tilts the crystal, Kikuchi bands mark orientation space with well-defined intersections (called zones or poles) as well as paths connecting one intersection to the next.

Experimental and theoretical maps of Kikuchi band geometry, as well as their direct-space analogs

e.g. bend contours, electron channeling patterns, and fringe visibility maps are increasingly useful

tools in electron microscopy of crystalline and nanocrystalline materials

^[2]

. Because each Kikuchi

line is associated with Bragg diffraction from one side of a single set of lattice planes, these lines

can be labeled with the same Miller or reciprocal-lattice indices that are used to identify individual

diffraction spots. Kikuchi band intersections, or zones, on the other hand are indexed with direct-

lattice indices, i.e., indices which represent integer multiples of the lattice basis vectors a, b and c.

The relationship of various poles and the corresponding

diffraction patterns for an

FCC structure.

From one Kikuchi pattern we can extend the lines

to create a second pattern. For example, knowing

the [001] pattern we can construct the [101] pattern

since a pair of lines is common to both. So we draw

the 020 and 020 lines from the [001] pole 45 ^o to

the [101] pole.

Kikuchi lines in a convergent beam diffraction pattern of single crystal silicon taken with a 300 keV electron beam tilted 7.9 degrees away from the [100] zone along the (004) Kikuchi band.

The camera length of this image, taken with a Philips EM430ST

microscope and recorded on Kodak electron image film, was

Map of Kikuchi line pairs for 300 keV electrons in hexagonal sapphire (Al ₂ O ₃ ),

Kikuchi map

centered on [0001]

 

 

^

10 2 1

 

 

^

0 1 10











  10 1

0

 

 

^

100 1

 

 

^

0 1 1

 2

 



^

20 1 1

晶面間距愈大者，其菊池線愈窄

GaN [0001]之繞射圖顯示ion milling參數設定對表 面狀態的影響

 

 

^ 1 1 10

 

 

^ 0 1 10



⁰⁰⁰²





0001



GaN 之繞射圖，繞射點強度變化顯 示雙重繞射之現象

 

  1 2

^

10

TEM 的成像條件

成像條件 明視野像

（Bright Field, BF）

暗視野像

（Dark Field, DF）

適用狀況

雙電子束繞射 Two beam diffraction

condition

BF 一般影像觀察

雙電子束繞射 Two beam diffraction

condition

DF 析出物、缺陷、差

排

微弱電子束繞射 Weak beam diffraction

condition

BF 氣泡、孔洞

微弱電子束繞射 Weak beam diffraction

condition

DF 差排（較佳解析度）

多重電子束繞射 Multi- beam diffraction condition

晶格影像觀察

TEM diffraction contrast

Two-beam conditions

T D

θ θ 2θ

Incident beam

000 +g(hkl) strong -g(hkl)

weak

T D

Sample

2θ

Sample

2θ

Incident beam

θ θ 2θ

3θ

2θ

000 +g(hkl) weak

+2g(hkl) weak

+3g(hkl) strong

T D

θ θ

-g(hkl) 000 strong

D T

The screen is normal to the incident e-beam.

Central dark field

Data from Dr. 鮑忠興

(000) (hkl) 得 (hkl)

A close-up of the area inside the objective lens. The tip of the specimen holder is placed in the middle of the gap in the magnetic circuit (the dark gray areas at top and bottom). The objective aperture stops the scattered electrons. The beam (green) passes through one of the four aperture holes present. The objective aperture sits at the same height in the microscope as the diffraction pattern. The beam we selected for the bright-field image was the central (transmitted) beam of the diffraction pattern.

Selecting other diffracted beam produces the

Bright-field image of particles in Al-Cu alloy.

Only the particles running northeast-southwest are truly parallel to the viewing direction. All others are slightly tilted.

Dark-field image of the same area. In this image the dark-field conditions were selected to show the particles seen on their side.

Another dark-field image, this time showing the conspicuous, close to vertical particles.

Bright-field (BF) and Dark-field (DF) Images

BF與DF影像

BF

Cu

Si

TaN

50 nm

DF

TaN

Doping Effect on As Precipitation

A sandwiched n-p2-n-p3-n multi-layer annealed at (a) 600 and (b) 800 ^oC

 The distribution of As precipitates in Fig. (a) is opposite to that in Fig. (b).



p  2  10 ¹⁷ cm ^{ 3} , p  2  10 ¹⁶ cm ^{ 3}

n

n

n p

2

p

3

(a) (b)

InGaAs Q. dots on GaAs

平面影像顯示差排缺陷之表面端點呈現 六角形之輪廓

image field

bright 10

2

1  

  ^

Al

₂

O

₃

基板與GaN緩衝層之界面

P–type GaN

image field

bright

 

  ^

13

2

1

Dislocation Effect on As Precipitation

An annealed LT-GaAs with higher than usual density of dislocation

 Considerably larger As precipitates are found attached to dislocations than those distributed in the bulk region.

 Vacancy clusters as large as the attached precipitates have been identified with TEM.

 The dislocation serves as a vacancy source for As precipitation.

晶體中含空洞相當於一個完整的晶體變薄

t1

t2

t3

(A) Intensity contours from a

simulated image of a particle

like that shown schematically

in B. Notice the line of no

contrast which corresponds to

the plane that is not distorted

by the strain field of the

particle. (c) Experimental

image of coherent particles in

Cu-Co showing strain

contrast.

Planar-view image of

InAs Q. Dots

A. Translational moiré fringes; B. rotational moiré fringes;

C. mixed moiré fringes

HRTEM image shows a precipitate (β-FeSi2) at the Si/SiO2 interface in Si wafer with 1×10 ¹⁴ Fe/cm ² and oxidized at

J. Appl. Phys. 83, 580 (1998)

The LTG GaAs/Al0.3GaAs MQW structure annealed at 800

^o

C for 30 seconds

Arsenic precipitates are present in GaAs region.

Bond Strength Effect on

As Precipitation

High-resolution image of silicon displaying dumbbells (pairs of silicon atom columns). The distance between the atom columns in a dumbbell is 0.14 nm. The real structure is drawn in color.

This would be a good view for high- resolution imaging. In practice, we would not see columns in the TEM image because the first atom blocks the view of the atoms behind it.

In this orientation there is no hope of seeing anything in high resolution.

High Resolution TEM (HRTEM)

TEM影像

50 nm

Poly-Si SiO2

Si

BF HR TEM

Poly-Si

SiO2

1nm

Amorphous silicon

(100) Si substrate

Poly-Si

Thermal Oxide

IC connectors in (five) stages. Pillars made of tungsten (hollow, dark) are connected by pieces of Al (lighter).

Thin layers of TiN prevent the tungsten

Al

Si Ti TiN

20 nm

Si Al

Ti

HRTEM

TEM analyses : Al/TiN/Ti/Si after annealing

Si Al

TiN/Ti

Si Al-Ti Spiking

450

^o

C Improve

Al

TiN

SAD之影像

BF

CL=40cm

Scanning transmission electron image

(STEM)

Bright field mode Dark field mode

Scintillator electron detector Aperture

Incident electrons

Thin sectioned specimen

Transmitted

electrons

STEM analyses : Al/Ti/Si after annealing for 1 hour.

Al

Si TiN/Ti

barrier layer

Si Al

TiN/Ti barrier

layer

Bright Field Image Dark Field Image

20 nm

20 nm

5. 00 µm

Original image FFT

Inverse FFT

1D Noise reduction

顯微分析技術配件

名稱 主要用途

EELS（電子能量損 失圖譜）

對10 nm 微區內成分變化分 析

EDS 元素成分分析

特性X-ray

O N M L K

e ^-

Emission of characteristic x-ray lines induced by x-ray irradiation or

E-beam

(1)

(2) Cu Fe

Al

Cu

Cu Cu Al

Energy dispersive x-ray spectra of Al- 2.0 at. % Fe alloy film after annealing at 300 ^o C for 1 h: (1) dark region and (2)

Energy Dispersive Spectroscopy (EDS)

Electron noise

Background

Peaks

Typical EDS spectrum

Liquid Nitrogen Tank

Profile of EDS detector

Electron Trap Window

Detector FET

Grid

Window

Ｓi (Li) detector

Expectation:

a large intrinsic region to improve the efficiency

In fact:

owing to the imperfection of material(electron hole) , Li doping is necessary

Li-drifted Si (intrinsic layer)

300~900 V

n-type Si p-type Si

Window

Au film

FET +

-

Liquid N ₂

Cryostat (77 ⁰ K)

EDS in TEM

• Higher Beam energy

• Smaller probe size

• Thinner specimen

(Absorption and Florescence effect can be ignored)

EDS with spatial

resolution

EDS mapping

STEM

Ti Al

STEM-BF STEM-DF STEM-AADF

Al-map. Ti-map. W-map.

JEM-2100

EDS mapping

Si-K STEM

N-K O-K

RGB

Si Al

TiN/Ti

Si Ti TiN

Al

EDS analyses : Al/TiN/Ti/Si after annealing

Oxford X-Max Large Active Area SDDs

大尺寸矽飄移EDS偵測器

Small Size

科儀新知179

32卷3期 (12月)

穿透式電子顯微鏡 - 電子能損儀 (TEM-EELS)

Schematic diagram of TEM-EELS

Y. Mitsui et al., IEDM'98

X Y Z

游離電子

w 真空能階

費米能階

能損電子

Chemical shift of core-loss edge energy in EELS spectra of some Si compounds.

N-K

Ti-L Si-L _2,3

EELS analyses : Al/TiN/Ti/Si after annealing

Si

Si Ti

TiN Al

Si Ti TiN

Al

Ti N