good 4 problems, process dev, materials dev, r&d & qc x ...film thickness fractures haze...

Weaknesses / Limits: • Ultimate detection limit 100 ppm (time=5-10hr)

• Smallest analysis area: 30 (for <20 go to AES)

• Depth Profile to 5,000Å (4 elem) takes 2-4 hr

• Etch Depth based on etch rate of thermally grown SiO2

• Accuracy of Depth Profiled Thickness Estimates: 20%

• Chem. state accuracy depends on (NIST) ref. BEs.

• BE of conductors 0.5 eV, BE of insulators 1.0 eV

XPS good 4 Problems, Process Dev, Materials Dev, R&D & QC X-rays IN → Electrons Out (1-12 nm)

BASIC ANALYSIS PARAMETERS

Vacuum Level: 10-8 to 10-10 torr

Probe Size: 30-500 (0.03-0.5mm)

Sample Size: XY Max: 60 x 60mm

Z Max: 20mm

Detects: all elements, except H & He

Detect Limit: 0.1 to 0.5 atom% (B: 4%)

Depth Resoln: 1-12 nm (10-120Å)

Quant. Accur: 10% of atomic%

Energy Precision: 0.2 – 0.5eV

Probe Energy: 1486 eV (Al0 X-rays, 8.3Å)

Strengths / Advantages: • chemical states (Si vs SiO vs SiO2)

• good quant. ( 5%) on pure material

• analyze insulators easily

• define empirical formula

• no damage normally

Analysis times: survey 5-10 min,

high res: 5-10 min, depth profile: 2-4 hr

AR-XPS: 2-8 hr, map 2-4 hr

Insulator Analysis? Yes, easy

Materials: wafers, metal, glass, polymer, (no liquids)

Analysis Methods: survey, atom%, chem. state, depth profile,

non-destructive dependent profile (AR-XPS),

elem. mapping, line profile, air fracture

Position Alignment: uses 2 CCDs

Etch Depth Limit: typically 1 micron (10,000Å)

Etch Crater Size: typically 2 x 2 mm

Auto-rotation profiling: possible – improves interface resoln

Overnight analysis: possible

Ion Milling Particle: Argon ions (1-4 kV) causes some degradation

X-ray Damage? RARE - depends on material and dose

PROBLEMS / FEATURES

ANALYZED

Adhesion

Blistering

Bond failure

Bubbles

Contamination

Corrosion

Defects

Degradation

Delamination

Diffusion

Discoloration

Film thickness

Fractures

Haze

Leaching

Particles

Peeling

Poor solderability

Residues

Solder failure

Spots

Stains

Trace contamination

Wear marks

PARTS / MATERIALS

ANALYZED (UHV)

Adhesives

Alloys

Alloys

Ball grid arrays

BGA

Biomaterials

Bond pads

BPSG

Ceramics

Cloths

Coatings

Diamond-like carbon

DLC

Fibers

Glass

GMR structures

Hard disks

Hybrid circuits

Insulators

Lead frames

LEDs

Lo-K dielectrics

Magnetics

Metal hydride batteries

Minerals

Oils ok

Paints

Papers

Plasma treated surfaces

Plastics

Polymers

Powders

Read/write heads

Ribbons

Semiconductors

Silicon

Solder balls

Solder bumps

Solders

Sol-gels

Space materials

Thin films

Unknowns

Wires

MATERIAL PROCESSES /

TREATMENTS ANALYZED

Surface modification

Plasma treatments

Heat treatments

Anodization

Film thickness

Dopant profiles

Plating

Electroless plating

CVD coating

MBE coating

Magnetron sputtering

MATERIALS/PRODUCTS

ANALYZED

Porous Si

GaAs

InGaAs

GaN

GaP

SiON

SiOC

SICN

BloK

Blk Diam GeSi

ZrO2

HfO2

CuSe

NiSi

Etc. etc. etc.

COMMON ANALYSIS PARAMETERS

Strengths / Advantages: Limits:

Sample Size: < 60 x 60 x 20 mm X-ray Spot Size: min= 30µ (0.03 mm)

X-ray Spot Size: max= 500µ (0.50 mm)

30µ

(0.03 mm)

Thermo K-Alpha XPS instrument

(based on SSI S-Probe Technology)

500µ

(0.5 mm)

1 million cps

Ultra High

Vacuum

10-9 torr Sample Types: Solids or Heavy Oils

(no water or volatile liquids)

XPS

Empty box is the sample

being analyzed

AES EDS

ToF-SIMS FT-IR

0.1 - 0.5

Dep

th f

rom

To

p S

urf

ace

0.3 - 0.5 0.5 – 1.0

0.5 – 5.0

XPS DETECTION LIMIT

~1000 ppm = no dopants

Instrument

(measures)

Auger

(electrons)

EDS

(X-rays)

XPS

(electrons)

Depth (Z) 1-6 nm 400-1,000 nm 1-12 nm

Min Size (XY) 15 nm

max (100)

300 nm @ 3 kV 400 nm @ 5 kV

1,000 nm @ 10 kV

30,000 nm (30)

max 500

Chem States

Si (0) or Si (4+) Possible No EASY

Insulators OK, but hard May coat w Au/C EASY

Atom % +/- 30% +/- 30% +/- 10% © B. Vincent Crist, 2009

XPS

1-12 nm

3-30 layers

Empty box is the sample being analyzed

AES EDX ToF-SIMS

1-6 nm

3-30 layers 300-3,000 nm

1,000 – 6,000 layers

FT-IR

0.1-1 nm

1-3 layers 500–5,000 nm

1,500–10,000 layers

NOTE:

Depth is roughly drawn to scale

0.1 - 0.5

Dep

th f

rom

To

p S

urf

ace L

ayer

0.1 - 0.3

XPS Auger EDX FTIR XRF ToF-SIMS

Analysis Area Range 20-1000 μ 0.02-100 μ 1-3 μ 10-500 μ 100-2000 μ 100-500 μ

Depth of Information Range 10-120 Å 10-60 Å 0.1-3

μ 0.5-5 μ 2-3 μ 5-10 Å

Identify Unknown Chemistry

Adhesion Failure

Surface Contamination

Bonding Problem

Soldering Problem

Haze or Discoloration

Residues

Chemical Surface Modification

Metallization Failure

Corrosion or Rusting

Biotech and Biomaterials

Organic Polymers

Fiber Analysis

Thin Film Analysis

QC/QA Routines

Rough Guide for Selecting Tool to Use for Type of Problem

XPS vs AES, EDX, XRF, FTIR, ToF-SIMS, Ellipsometry

COMMON SOURCES of SURFACE CONTAMINATION

Silicone products: the world’s most common contaminant

Material production & handling: S, Cl, C, O, Na, Ca, K, N & F

Cleaning baths, gears, rollers & lubricants: heavy carbon-based oils, long chain organic acids/salts

Plastic gloves: Si, Ca, Na, Mg, S, Cl, R4NX, SO4, CO3…

Clean room materials: HCl, HF, H2SO4, HNO3 & NH4Cl fumes, clean room gloves, plastic gloves

Forbidden clean room materials: cosmetic powders, hair treatments, residual cigarette smoke,

HV sputter chamber shields: Fe, Cr, W, Ta, Cu, O ...

Antistatic or anti-caking additives: Sn, Ca, O, SO4, CO3

Adhesives: silicone products, cyano (CN) groups, epoxies (C,O, trace N)

Elastomers: organic esters (COOR), acetates (CH3COOR), glycols (C-OH), silicones

Mold release agents & slip agents: silicone oil, oleic acid, heavy hydrocarbons

Soaps: long chain fatty acids, esters, aromatics, Ca, Na, O

Water Stains: Ca, C, O, Na, Fe, SO4, 0

2

4

6

8

0 2 4 6 8Ellipsometry Measurements (nm)

PA

RX

PS

Mea

sure

men

ts (n

m)

Ellipsometry included

Carbon layer in thickness

AR-XPS on Theta-300 versus Ellipsometry – Excellent Correlation

XP

S T

hic

kn

ess

Measu

rem

en

ts

COMMON CONTAMINANTS

0.3 – 2.0

0.5 – 5.0

Thickness Measurements

Optical Based versus Electron Based

© B. Vincent Crist, 2009

0 200 400 600 800 1000

Binding Energy (eV)

O1s

C1s

Si2

p

Hf4

f A

l2p

Hf3

d

Hf3

p3

Si2

s

OKLL

Routine XPS Analysis: Examples of Survey Scan (wide scan) (usual BE range 0-1,100 eV)

measures All Elements (except H and He) with Excellent Atom % Quantification

175180185190

Binding Energy (eV)

Zr3d

System Name: XI ASCIIPass Energy: 150.00 eVShift (Bias): 0.0 (3.0) eVThursday 6/2/1988

NATIVE SILICON OXIDE / SILICON WAFER (90DEG TOA)

(as receiv ed,no etching, no cleaning)Counts

Binding Energy, (eV)02004006008001000

0

10000

20000

30000

40000

50000

60000

70000

80000

90000

100000 Peak ID Atomic % BE (eV)F 1s 0.3% 687.19O 1s 29.2% 533.72Sn 3d 0.1% 487.78N 1s 1.4% 402.74C 1s 24.1% 285.43Si 2p 44.9% 99.71

O K

LL

-1

F 1

s O l

oss

O 1

s

Sn

3d

N 1

s

C 1

s

Si

sat.

Si

sat.

Si

sat.

Si

2s

Si

sat.

Si

sat.

Si

2p

C 2

sO

2p

Aluminum foil sample

was touched by soft

plastic latex glove. High

resol’n scan confirmed

Silicone. Silicon found

Typical Time Required: 1-10 minutes

Typical Detection limits: 0.1-0.5 atom%

Typical Analysis Condition: As Received

Atomic% comes from top 60Å (6 nm).

Atomic% Accuracy: 10% of value

Atomic% Precision: 5% of value

Standard Depth of Info: 60Å (6 nm)

Minimum Depth (AR-XPS): 10Å (1 nm)

Maximum Depth (AR-XPS): 120Å (12 nm)

Largest Analysis Area (no raster): 500

Smallest Analysis Area: ~20

Widest Sample: 60 mm Tallest : 20 mm

Material Types: wafer, semiconductor, glass, plastic, metal, alloy, ceramic, heavy oil (no liquids)

Material Problems: invisible contamination, spots, defects, residues, smears, etc.

Light Ion Etch: Removes 10-100Å of surface to learn if oxide layer (or contam.) is unusual.

Very short light ion etch (1-5 sec) at 1 kV is used to remove carbon left behind by SEM work.

Longer ion etching causes some degradation of the chemical states and atom % ratios.

For XPS analyses deeper than 100Å, must change to Depth Profile mode or expose bulk.

Extended Analysis Time and # of Scans improves

Detection Limits by decreasing S/N. 50 scans takes

1 hour and increases S/N by 300% (3X).

Silicon wafer that was stored

in anti-static bag. Mylar (PET) film that was

freshly scraped in air to

remove contamination.

O 1s C 1s

O Auger C Auger

O 1s

Signal Overlaps: Rare, but easily corrected for: e.g. Al-Cu, Ru-C, Sb-O, Mo-S, Ga-S

Hf3

p1

F1

s

O lo

ss

C lo

ss

O 2s

HfO2 film on Si


Naturally Formed Native Oxide found on Any

New or Old Aluminum Metal Surface

Despite 50Å Thickness of Al2O3 . This sample

behaved CONDUCTIVELY – NO CHARGE-UP

Al 0 metal

BE= 73.0 eV

Hydrocarbon

(C-H, C-C, C=C)

Routine XPS Analysis: Examples of High Energy Resolution Scan (usually 20 eV wide)

measures Chemical States (species) for most Elements. Differences in BE (chemical shifts) are due to

different levels of electron polarization between two bonded atoms. (Caused by differences in electronegativities.)




Organic acid

organic ester

(O=C-OH)

Al2O3 overlayer

BE= 75.0 eV

Al (2p) signal

C (1s) signal

Sub-oxide

Alcohol/Ether

(C-OH, C-O-C)


Very short light ion etch (1-5 sec) at 1 kV is used to remove carbon left behind by SEM work.













Widest Sample: 60mm Tallest : 20 mm

Counts

Binding Energy, eV290 288 286 284 282 280 2780

200

400

600

800

1000

1200

1400

1600

1800

2000 A

B

C

D

0

500

1000

1500

2000

270 280 290

Binding Energy (eV)

C (1s) signal

C (1s) signal

Before 5 sec Ion

Etch at 1keV

After 5 sec Ion

Etch at 1 keV

INSULATING FILM CHARGE-UP Mylar (PET) bulk exposed by cutting sample in

half. Because of charge-up, the Charge Control Gun

(electrons at 4 eV) had to be used. As a result all

peaks shifted to lower BE values. All signals will shift

by the same amount. Low energy electrons (<20 eV)

do not cause any damage for most materials.

Hydrocarbon Peak

(C-H, C-C, C=C)

BE = 285.0 eV

(after Charge

correction)

Ether Type Peak

(C-O-C)

BE = 286.3 eV

Ester Type Peak

(O=C-OR)

BE = 288.6 eV

ION-BEAM INDUCED DAMAGE Mylar (PET) was immediately degraded

by only 5 sec of argon ion etching at 1 keV.

Mylar lost oxygen and carbon as CO and CO2.

Various metal oxides are also damaged

by ion beam etching, but some, such as Al2O3

are not degraded. All organics are readily

degraded and form a “graphite” type of

material.

Elem Elec Neg Elem Elec Neg Elem Elec Neg

H 2.20 C 2.55 P 2.19

Si 1.90 Ga 1.81 Hf 1.30

O 3.44 As 2.18 N 3.04

F 3.98 Al 1.61 Cu 1.90

SEM Induced Contamination of Analysis Area

SEM contaminates the surface of the analysis

area used by XPS. It is better to do XPS first,

then SEM afterwards. If SEM is done, then a light

ion etch (1-10 sec) may remove most of the

Carbon that builds up from the SEM work.

LIGHT (5s) ION

ETCH effect on

PET (Mylar)


Routine XPS Analysis: MORE Examples of High Energy Resolution Scan

measures Chemical States (species) for most Elements. Differences in BE (chemical shifts) are due to

different levels of electron polarization between two bonded atoms. (Caused by differences in electronegativities.)





Very short light ion etch (1-5 sec) at 1 kV is used to remove excessive surface carbon.













Widest Sample: 60mm Tallest : 20 mm

520525530535540

Binding Energy (eV)

95 98 101 104 107

Binding Energy (eV)

1 nm SiO2

1 nm SiO2 HfO2 (MOCVD)

1 nm SiO2 HfO2 (ALD)

O (1s) Signal

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

3000

3200

390 394 398 402 406 410

Cou

nts

/ s

Binding Energy (eV)

System Name: XI ASCIIPass Energy: 25.00 eVCharge Bias: 0.0 (3.0) eVThursday 6/2/1988

Sample Description: NATIVE SILICON OXIDE / SILICON WAFER (90 DEG TOA)(as receiv ed,no etching, no cleaning)

Counts

Binding Energy, (eV)106.5 105 103.5 102 100.5 99 97.5

200

600

1000

1400

1800

2200

2600

3000

3400

3800

4200

A

B

C

DE

F

Peak Label/ID BE (eV) FWHM (eV) Height Gauss % Asymmetry % Norm. Area Rel. Area %A 99.65 0.44 3300.9 80.0% 0.0% 106.208 46.8%B 100.22 0.51 1708.05 100.0% 0.0% 58.5183 25.8%C 100.46 0.64 214.258 100.0% 0.0% 9.1276 4.0%D 101.00 0.80 114.801 100.0% 0.0% 6.11009 2.7%E 102.77 1.14 117.025 100.0% 0.0% 8.86176 3.9%F 103.76 1.34 426.464 100.0% 0.0% 38.0014 16.8%

Peak-Fit Baseline: 106.33 to 97.63 eVReduced Chi-Square: 1.73807

1 nm SiO2 1 nm SiO2 HfO2 (MOCVD)

1 nm SiO2 HfO2 (ALD)

Si (2p3)

Si (2p1)

Si metal

Si2O

Si (1+)

Si (2+) Si (3+)

Si (4+)

SiO2

Si2O3 SiO

Si (2p) Signal

Si metal

Si metal

SiO2

Si (2p) Signal

O in SiO2

O in

HfO2

Si (2p) Signal O (1s)

Signal N (1s) Signal

N in

Si3N4

N in

SixNyOz

Si Oxynitride

film

Si Oxynitride

film

Native Oxide of

Si


Routine XPS Analysis: Examples of Ion-Etched Depth Profiles (usually 4-5 elements, 5kÅ depth limit)

are used to measure the Atom % amount of each element as a function of depth. The etch rate of SiO2 is

used to calibrate the etch depth of all materials. Therefore all thickness values have an uncertainty of at least

10%. Argon ions at 1kV are normally used for the etching.

X-ray

Beam

Ar(+)

Ion

Beam Electron

Collection

Lens

Ion-Etched Depth Profile Plot

Level #

Montage Plot from

Survey Scan based Ion-Etched Depth Profile

Montage Plot from one Element – Ta Oxide on Ta Metal

Bulk

Surface

Montage Plots from

element data are very

useful to understand

changes in Chemical

States as a Function of

Depth for any element.

Montage plot for Pure Silver Al2O3

Al0

Al0

Al2O3

Al0

Al0

Ta0

Ta2O5

Ta2O5 Ta

O

C

Original Surface – Not Etched

Al2O3

Al0

Ion-Etch Depth Profiling


Binding Energy, eV

862 856 850

Binding Energy, eV 720 714 708

Fe 0

Cr (2p3/2) Cr 0 Cr2O3

Bulk

Surface

Fe (2p3/2)

Fe2O3

Bulk

Surface

0

20

40

60

80

100

0 1 2 3

Depth (nm)

Ato

mic

Con

cent

ratio

n (%

)

Si n+

Hf 4+

Si 0

O

0

20

40

60

80

100

0 2 4 6 8 10

Depth (nm)

Ato

mic

Con

cent

ratio

n (%

)

Sin+

Hf0

Si0

O

Hf4+

Ion Etched “Destructive” Depth Profile

500 eV Ar+ with Azimuthal Rotation

Angle Resolved “NON-Destructive” Depth

Profile (AR-XPS) is Limited to Top 8 nm

Routine XPS Analysis: Chemical State Ion-Etched Depth Profiles Chemical State depth profiling is possible, but often suffers from degradation of chemical states or preferential

sputtering loss of one element.

Ni (2p3/2) Ni 0

Bulk

Surface

O (1s)

Surface

Bulk

Binding Energy, eV 538 530 522

587 581 575

Surface

AR-XPS

Depth

Profile

Ion Etched

Depth

Profile

Alternative Depth Profiling Method – AR-XPS – Top 80Å Only

Depth profiling is normally done by using Argon ions because

film thickness used to be more than 100Å thick. Today, many

layers are thinner than 50Å thick so we now need to use a

different capability of XPS. This other capability is the variation

of signal intensity as a function of electron take-off angle which is

a totally non-destructive technique called AR-XPS.

The limitation of this AR-XPS technique is that it can only

collect data from the very top 80Å of the surface.

The advantage of this technique is that we retain all of the

chemical state information which is lost if we use argon ions to

ion etch the top 80Å.

These two Depth Profile plots show the radical difference in

information obtained by these two methods.

Alternative Depth Profiling Method – Chemical States

Depth profiling is normally done by measuring only the total

amount of each element as a function of depth. This method is

done using many techniques such as AES, SIMS, RBS etc.

XPS, which can readily reveals differences in chemical state,

sometimes retains some or all of the chemical state information

as a function of depth. The ability to see these states depends

on the chemical stability of the various chemical states as they

are being ion etched with Argon ions having 1-2kV of energy.

This set of Montage Plots from an ion-etched depth profile

done on Electrochemically Polished Stainless Steel Tubing

allows us to know how deep the Chromium Oxide layer extends

and how deep the pure Nickel layer is buried. A list of some of

the chemicals that survive ion etching is shown below.

Oxides that are Stable to or Reduced by Ar Ions

Montage Plots from a Ion-Etched Depth Profile of Electrochemically Polished Stainless Steel Tubing


good 4 problems, process dev, materials dev, r&d & qc x ...film thickness fractures haze...

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