Modified Probe

Probe (primary)

Response (secondary)

Probe: photo Response: photo
electron electron
ion ion
phonon phonon

XRF, TXRF, FTIR, Raman

e-BeamTechniques

Primary Electron Beam

Types of information provided by chemical analysis

Elemental Molecular

Surface ( <10 Å) Thin film (<100Å-1mm)

Bulk (>10mm)

(EDS)

X-ray Fluorescence

electron

Survey Spectrum of Particle

    • Near surface and bulk elemental information
      • Films > few hundred Å thick can be detected
      • Sampling depth to several microns can be achieved
      • Quantitative for some classes of samples
    • Particles and small area analysis
      • Used primarily on particles > few thousand Å
      • Parallel detection makes elemental imaging fast
      • Quick ‘first look’ technique for failure analysis

Excellent “first look” tool

Elemental Imaging

Image and EDS spectrum of 0.3 micron alumina particle on Si (3 keV beam)

Higher Beam Energy Samples Deeper

3 keV 10 keV

SEM of residue

Sub-Micron Resolution

Elemental images of Al inclusion in coating Overlay of C, O and Al (red) images

EDS

Quantitative Yes Destructive No
Detection Limits 0.1-1.0at% Lateral Resolution/ Probe Size 0.2-2µm
Chemical Bonding No Analytical Depth 0.5-3µm

Comment: Excellent “first look” tool

    • Strengths
      • Quick, ‘first look’ analysis
      • Versatile, inexpensive, and widely available
      • Quantitative for some samples (flat, polished, homogeneous)
    • Weaknesses
      • Semi-quantification for samples that are not flat, polished & homogeneous
      • Size restrictions on samples
      • Samples must be vacuum compatible
      • Analysis (and coating) may spoil subsequent surface analysis
      • Poor low Z sensitivity
      • Not very surface sensitive
      • No depth resolution

(AES)

X-ray Fluorescence

electron

Derivatized data is used for peak identification

    • Particles and small area analysis
    • Particles as small as 25 nm can be analyzed
    • Sub-monolayer analysis
    • Films too thin for EDS
    • Thin film elemental analysis
      • Where high depth resolution is needed
      • Sampling depth to several microns with sputtering
      • Quantitative (best with standards)

SEM

Auger Spectra

55555

l27o154.spe l27o155.spe l27o136.spe l27o122.spe l27o106.spe

x10x10x10x10x10

6

4.5

3.2

4.5

4

3

5.5

4

2.8

4

3.5

5

2.6

3.5

3.5

4.5

2.4

3

3

2.2

3

4

2.5

2

2.5

3.5

2.5

1.8

2

3

2

1.6

200 400 600 800 1000 1200 1400 1600 1800 2000 2200 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 200 400 600 800 1000 1200 1400 1600 1800 2000
Kinetic Energy (eV) Kinetic Energy (eV) Kinetic Energy (eV) Kinetic Energy (eV) Kinetic Energy (eV)
Elements
Mo, As C, As Si, O Al, O, F K, Na, O

2007 GaAs Mantech Workshop / Yumin Gao Copyright 2007, Evans Analytical Group LLC

200 600 1000 1400 1800

Kinetic Energy (eV)

Auger spectra show the defect is composed of regions high in Ti or Al, and that the whole Si wafer is covered with a thin

Ti film. Y. Uritsky, et al., J. Vac. Sci. Technol. A 15(3), 1319 (1997)

Secondary Electron Image Color Composite Auger Image

Red=Ti Green=Al Blue=Si

Auger maps for Ti, Al and Si show the defect consists of separate phases of Ti and Al.

Y. Uritsky, et al., J. Vac. Sci. Technol. A 15(3), 1319 (1997)

  • Ion milling (sputtering) is used to remove material only!
  • Auger analysis is performed on the surface at the bottom of the sputtered crater, and is independent of the sputtering process.

Electron Beam Electron Beam Ion Beam Electron Beam

Ion Beam

Analysis Area

Analysis Area

0 min 10 min 20 min

Decorative Coating

0 250 500 750 1000 1250 1500 1750
Depth (nm)
2007 GaAs Mantech Workshop / Yumin Gao Copyright 2007, Evans Analytical Group LLC 29

Good Bond Pad Bad Bond Pad Normal wire bond strength Poor wire bond strength

100

100 90

90Al -metallic

0

0 1 2 3 4 5 6 7 8 910

Atomic Concentration (%)

80 70 60 50 40 30 20 10

Atomic Concentration (%)

0

80

70

60

50

40

30

20

10

Sputter Time (min) Sputter Time (min)

Al oxide ~4 nm thick Al oxide ~160 nm thick

AES

Quantitative Yes Destructive No
Detection Limits 0.1-1.0at% Lateral Resolution/ Probe Size 0.01-2µm
Chemical Bonding Some Analytical Depth 10-60Å

    • Strengths
      • Surface sensitive
      • Good depth resolution
      • Often the only choice for small area analysis
    • Weaknesses
      • Best quantification requires standards
      • Relatively low sensitivity (0.1 at%)
      • No or little chemical information
      • Insulators are difficult

(XPS/ESCA)

e-

  • Measure kinetic energy (KE) of photoelectrons ejected from sample
  • Calculate photoelectron binding energy (BE) in electronvolts, eV

BE = hn – KE – f + d

hn = excitation x-ray energy (fixed energy) f = electron spectrometer work function d = net surface charge

gSurvey spectrum: identifies elements at surface

g High resolution spectrum: identifies chemical state from peak position and peak shape

Poly(ethylene terephthalate)

1000 400600800 Binding Energy (eV) 200 0 300 285290295 Binding Energy (eV) 280
XPS survey spectra provide quantitative elemental information High resolution XPS spectra provide quantitative chemical state information

Silicides

Silicon

Carbides

Nitrides

Silicones

Silicates

Silica

Measurement of oxide chemistry as a function of processing -thickness -Ga°, GaN, Ga2O3, As°, As2O3, As2O5, etc -Ga-rich vs As-rich vs. stoichiometric -impurities (fluorides, chlorides from etch)

Issues related to metallization -interface chemistry -metals oxidation -interdiffusion

Cleaning residues -quantitative organic and inorganic contamination with sub-monolayer sensitivity

Oxidation of GaAs under different conditions

Sample 1

Ga3d 5 Ga3d 5

Sample 2

25 x103 x103 25

20 20

15 15

10

10

5

5

Oxidation of GaAs under different conditions

As-5

Intensity

30

25

20

15

10

5

As3d 4

Sample 1

x 103

Species % As GaAs 76 As2O3 13 As2O5 11

5654 5250 48 46 44 42 40 38 Binding Energy (eV)

As3d 4

Sample 2

x 103 16

14

12

10

8

6

4 5654 5250 484644 4240 38 Binding Energy (eV)

520 x102

20

18

490

480

470 16

14

12

450

440

10

430

43

2007 GaAs Mantech Workshop / Yumin Gao Copyright 2007, Evans Analytical Group LLC

  • Objective: Determine the thickness of thin SiO2 layers on Si.
  • Using intensities of film and substrate peaks along with parameters derived from standard samples, film thicknesses determined with sub-Angstrom precision.

    • Destructive (Organic information typically lost)
      • Energetic ion beam sputtering
      • Sputter rates 10 to 500 Å/min
    • Non-destructive
      • Angle resolved analysis
      • Sampling depths 10 to 100 Å
      • May also employ different x-ray sources

Architectural Glass Coating

0 50 100 150 200 250

Sputter Depth (nm)

e:

e:

  • Sample is tilted with respect to x-ray source and analyzer
  • Angle determines sampling depth (d)

Analyzer Analyzer

d = Sampling Depth = ~3lsinq d2 < d1 even though l is constant

o

q = 10

High Sensitivity Mode

Greater sampling depth

More surface

sensitive

Binding Energy (eV)

Technical Data Table

XPS

Quantitative Yes Destructive No
Detection Limits 0.050.5at% Lateral Resolution/ Probe Size 10µm
Chemical Bonding Yes Analytical Depth 1-10nm

Comments: Provides bonding information for organic and inorganic species

(Dynamic and Static SIMS)

Sample atoms

SIMS Technique Schema

IMAGE

SIMS Instrument Type

Magnetic sector Quadrupole Time of Flight

M+DM M ion pulse

M-DM

t-Dt ~ M-DM r = k/B(m/q)1/2 t ~ M t+Dt~ M+DM

m/q ~ B m/q ~V(f) m/q ~ t

primary ion ion: elemental information ion: molecular information

Ss = A

Dynamic SIMS

>1E12 ions/cm2 Elemental Depth profile Magnetic & Quad

Ion damage section, s Desorption area, D

Bombarded surface, A

Ss << A

Static SIMS

Primary ion dose <1E12 ions/cm2 Information Chemical Analysis Only surface Instrument TOF

(TOF-SIMS)

Typical Data

2000 0

20 40 60 80 100 120 140 160 180 200 m/z

50 100 150 200 250 300

Quantitative Limited Destructive No
Detection Limits 107-1011 at/cm2 Lateral Resolution/ Probe Size 0.2µm
Chemical Bonding Yes Analytical Depth 1-5 monolayers

Comments: Can identify specific organic compounds

(Depth profiling-SIMS)

• Material removal • Ultra surface analysis
• Elemental analysis • Elemental or molecular analysis
• Profiling • Analysis complete before significant
fraction of molecules destroyed

Mass Manufacturers Strengths Weaknesses Separation

Magnetic Cameca High transmission(~40%) Slow peak switching (magnet sector hysteresis effect.

High mass resolution (M/DM ~10,000)

Quadrupole PHI, Low primary beam energy Low mass resolution mass filter Atomika/Cameca (down to 100 eV) (M/DM ~200)

0 2 4 6 810

Depth (micron)

10 1

1018 0.1

Concentration (atoms/cm)

0.01

10-3 10-4

1013

10-6

DEPTH (nm)

Ga,In CONCENTRATION (group III atom fraction)

MT

MT

1019

107

101

1015

100

Depth (Å)

106 105 104

1018

O & Si Concentration (atoms/cc)

Al & In Intensity (a.u.)

1017 103 102 1016

Optimal analysis by O2+SIMS (positive ions detected)

Typical Detection Limits in InP, GaAs, GaN

For electropositive elements For electronegative elements

Element M+ (O2 +) M(Cs+)
Li 3E13 1E16
Be 3E14 1E20
B 1E15 3E15
Na 3E14 2E17
Mg 1E14 1E20
Al 2E15 1E17
K 2E14 2E18
Ca 3E14 1E20
Ti 2E14 1E18
V 1E14 1E17
Cr 1E15 2E17
Mn 3E14 1E18
Fe 1E15 3E17
Ni 1E16 5E17
Cu 3E16 1E16
Zn 1E16 1E20
Sr 5E15 1E20
Y 1E17 1E20
Zr 1E15 4E17
Nb 1E16 1E18
Mo 1E16 1E18
Cd 5E16 1E21
In 3E15 3E17
Element M(Cs+) M+ (O2 +)
H 2E17 2E18
C 1E16 2E18
N 5E15 (NGa-) 5E18
O 1E16 1E20
F 2E14 5E16
P 2E15 1E16
Si 2E15 1E16
S 1E15 1E19
Cl 3E15 2E17
Ge 5E15 2E16
Se 5E14 2E17
Br 5E13 1E17
Te 1E15 2E17
Ag 2E16 2E16
Au 1E15 1E17

1E+05

1E+04

1E+03

1E+02

1E+01

1E+00

0.2 0.4 0.6 0.8 1

0 50 100 150

CYCLES

DEPTH (microns)

Knowledge on the matrix effect

Precision: reproducibility between run

10% routinely by an experienced analyst or following a good protocol
2% can be achieved using the HPIC protocol

Simulations from TRIM (Transport of Ions in Matter)

D th Resolution

CONCENTRATION (atoms/cc)

1E+23 2 keV As Implant

Improved depth resolution is

1E+22

seen as impact energy is

1E+21 decreased.

The 6 keV profile shape is

1E+20

entirely a product of ion

1E+19

beam mixing.

1E+18

The 1 keV profile shows dramatically improved depth

1E+17

resolution that reveals much

1E+16

of the true profile shape.

0 100 200 300 400 500 DEPTH (Angstroms)

MT

MT

1019 107

Si

Si

106

Al 1018 OSi O Al

105

O

104

1017

O & Si Concentration (atoms/cc)

Al & In Intensity (a.u.)

103 102 1016

101

1015

100

Depth (Å)

MT

MT

1019

1017

103

106

105

1018

O Concentration (atoms/cc)

104

Al & In Intensity (a.u.)

102

1016

101

1015

100

Depth (Å)

MT

MT

1019

1018

Si Concentration (atoms/cc)

1017

1016

1015

Depth (Å)

‹��Ga2O3 fi‹GaAs

23

10

1

As,H CONCENTRATION (atoms/cc)

22 10

21 10

O INTENSITY (arbitrary units)

0.1

0.01

20

-3

10

10

19

-4

10

10

DEPTH (nm)

Powerful analysis tool

Depth profiling dopants and impurities in III-V heterostructures
Surface, layer, substrate and interface
Stoichiometry in some cases

1E20

107

106

C, O, Si Concentration (atoms/cm3)

Al Secondary Ion Counts (cts/sec)

1E19

1E18

1E17

105 104 103

102

1E16

101

1E15

100

Depth (Angstroms)

InGaAs/AlGaAs/GaAs HBT SPC

Ga,In CONCENTRATION (group III atom fraction)

O, C, Si, H, Te, Se, S, Br CONCENTRATION (atoms/cc)

1020

10 1

1019

1018

0.1

1017

0.01

1016 10-3 10-4

1015 1014 10-5

1013

10-6

20

100 200 300 400 500 DEPTH (nm)

21

10

In CONCENTRATION (Group III atom fraction)

1

C, Si, Te CONCENTRATION (atoms/cc)

20

10

0.1

19

10

0.01

-3

18

10

10

17

-4

10

10

16

-5

10

10

15

-6

10

10

14

-7

10

10

DEPTH (µm)

GroupIIIAtomFraction

3– 5%Precisionover3yearspan
0.70
0.60
Al = 0.611 s= ± 3.6% emitterAl1
bufferAl2
0.50 In
0.40 In = 0.455 s= ± 3.1%
0.30
Al = 0.320 s= ± 2.6%
0.20
Apr-02 Oct-05
Date

4.E+19

Concentration(atoms/cm³)

3.E+19

2.E+19

1.E+19

2.E+17

Carbondoping =4.09E+19 s= – 4.5%

GaAsBase C ContactSi2 sub-collSi5

Sidoping = 5.43E+18 s= – 3.7%

Sidoping = 4.02E+18 s= – 3.8%

Apr-02 Oct-05 Date

2007GaAs Mantech Workshop/YuminGao Copyright 2007,EvansAnalyticalGroupLLC

Zn Diffusion in Good vs. Bad Photodiodes

20

DEPTH (µm)

1

1020

500 100 150 200 250 300 350
DEPTH (nm)
2007 GaAs Mantech Workshop / Yumin Gao Copyright 2007, Evans Analytical Group LLC 93

Al,In CONCENTRATION (atom fraction)

Si CONCENTRATION (atoms/cc)

1019

0.1

1018

0.01

1017

10-3

1016

10-4

4000 6000 8000

Depth (Angstroms)

1.0x1014
8.0x1013
6.0x1013
4.0x1013
2.0x1013
0 0.0 2007 GaAs Mantech Workshop / Yumin Gao 20 40 60 80 Position on wafer (mm) Copyright 2007, Evans Analytical Group LLC 100 95

1E+21

1E+20

ION INTENS ITY (a.u .)

1E+19

O Al

1E+18

Sn In

1E+17

1E+16

1E+15

1E+21

1E+20

1E+19

Al

1E+18

In

1E+17

1E+16

IN TE N S ITY (a.u .)

1E+15

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

DEPTH (microns)

300 x 300 micron chip

Before After

SIMS crater

Ball bond

1E+21

1E+07

1E+20 1E+06

1E+19 1E+05

1E+18

1E+04

1E+17

1E+03

1E+16

1E+02

1E+15

1E+01

1E+14

1E+00 0 500 1000 1500 2000 2500 3000 3500 4000 Depth (nm)

1E+21

1E+21

CONCENTRATION (atoms/cc)

1E+20 1E+20

Secondary Ion Intensity (a.u.)

1E+19

1E+19

Mg Si Al->

Ga-> In->

1E+18

1E+18

1E+17

1E+17

1E+16

1E+16

1E+15

1E+15

Difference in the film thickness* within analytical area 30 mm

1mm, 0.6Å/1mm

0.5mm 0.2Å/mm

200mm 0.125Å/mm

*The film thickness from center to edge

1E+20

1E+04

1E+19

Counts Per Second

CONCENTRATION (atoms/cc)

1E+03

1E+21

1E+20

1E+19

Counts Per Second

1E+18

1E+04

1E+17 1E+02

CONCENTRATION (atoms/cc)

1E+03

1E+18

1E+17

1E+16

1E+02

1E+01

1E+16

1E+15

1E+01

1E+15

1E+14

1E+00

1E+14

1E+00

103

1E+21

1E+21

1E+20

1E+20

CONCENTRATION (atoms/cc)

Secondary Ion Intensity (a.u.)

C O

Si Ga->

1E+19

1E+19

1E+18

1E+18

1E+17

1E+17

1E+16

1E+16

1E+15

1E+15

Pinholes: dislocations

1 23

Concentration

1

Dynamic SIMS

Quantitative Yes Destructive Yes
Detection Limits 1012-1016at/cc Lateral Resolution/ or Probe Size 10µm
Chemical Bonding No Depth Resolution 1-20nm

Comments: Detects all elements/isotopes, depth profiling

technique, excellent detection limits

    • Strengths
      • Excellent detection sensitivity for dopants, impurities and known contaminants
      • Depth profiles of layered structures
      • Can detect all elements and isotopes, including H
      • Stoichiometry in some applications
    • Weaknesses
      • Destructive
        • Element specific (poor survey technique)
        • Difficult to find unknown contaminants
      • No chemical information
      • Limited surface information

Substrate

Surface cleanness: metals: SEM-EDS, FE-AES, XPS, TOF-SIMS (trace) organic: m-FTIR, XPS, TOF-SIMS (trace)
Stains and discoloration: SEM-EDS (first look); XPS; TOF-SIMS;
Particles: <10 mm: SEM-EDS, FE-AES, TOF-SIMS, Raman >10 mm: above, as well as m-FTIR, m-XPS
Surface oxide: XPS
Bulk Impurities: SIMS, GDMS

Epitaxy and Implantation

Compound composition : AES; SIMS; RBS; LEXES
n and p Doping Control: SIMS;
Impurities such as H, C and O metals: SIMS
Thickness: SEM; TEM (QWs); SIMS
Stains and discoloration: SEM-EDS (first look); XPS; TOF-SIMS;
Particles: <10 mm: SEM-EDS, FE-AES, TOF-SIMS, Raman >10 mm: above, as well as m-FTIR, m-XPS

Metallization; Etching and Passivation

Metal diffusion: AES; SIMS; RBS;XPS
Impurities such as C, O and metal (Cu for example): SIMS
Interface studies: AES; SIMS; RBS;XPS
Residues: SEM-EDS (first look); XPS; TOF-SIMS;
Particles: <10 mm: SEM-EDS, FE-AES, TOF-SIMS, Raman >10 mm: above, as well as m-FTIR, m-XPS