Thermo K-Alpha
Mono XPS System
Vince Crist, PhD
Director of XPS Services
B. Vincent Crist, PhD, 35 yrs hands-on in XPS, 3 XPS spectra books by Wiley, SDP v7.0 software by XPS
International, 2 PDF spectra books on XPS, website author: www.xpsdata.com, main author of XPS page on
Wikipedia, member of ISO TC201 on XPS & AES, Google my name
Page 1
Thermo K-Alpha
Mono XPS System
Customer friendly by design
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Customer always Welcome On-Site to work with scientist collecting data
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While on-site our XPS experts offer suggestions on causes/app tables
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Our IP, XPS methods, XPS calculations are always open to customers
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Succinct interpretation of results (4-8 lines) – not verbose
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Peer reviewed by XPS expert
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PowerPoint – Landscape format used – XPS results are ready to present - easy
Page 2
Thermo K-Alpha
Mono XPS System
Essential information always included
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Chemical state spectra always peak-fitted with assignments
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Peak-fit BEs and FWHMs always printed on chemical state spectra
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Chemical state BE tables always provided as Excel tables
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Common and alternative chemical states always provided
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Overlays of survey and chemical state spectra always provided
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Survey spectra always expanded vertically (5-10X) in the 0-500 eV range – this
vertical expansion is essential to detect presence/absence of weak signals
Page 3
Thermo K-Alpha
Mono XPS System
Quality 1st
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Nanolab deliberately maximizes S/N, step-size, dwell time, energy window, pass
energy to maximize data quality to detect trace contaminants (eg 0.02 atom%)
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Nanolab appendix - XPS for beginners & application data tables
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Weight % table and thickness calculation of thin films (<80 ang)
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Chemical state spectra are displayed 4 spectra per page – easy to review
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All spectra available as ASCII text data-files (Origin, Excel, SDP…)
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Extensive table of ion etch rates for various common materials – no charge
Page 4
Thermo K-Alpha
Mono XPS System
#1 in XPS Hardware, XPS Software, XPS Reference Spectra
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XPS reference spectra from XPS spectra database of 40,000
monochromatic spectra, not BEs from NIST – free of charge
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SDP v4.6 software is free of charge so you can process spectra by yourself.
Normal cost of SDP v4.6 is: $785 per seat.
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Our XPS is latest generation with 60° deg collection lens (vs 30°),
using unique 128 channel detector (vs 16) from XPS leader
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128 channel SnapShot™ detector speeds work 3-4X faster than old 16 ch detectors
11.3 sec Snapshot™ spectrum of Ag 3d
32.3 sec scanned spectrum of Ag 3d
K-alpha XPS 128 ch
Quantum 2000 16 ch
Page 5
measured by
Nanolab Technologies
www.nanolab1.com
XPS Services
Director of XPS Services: Vince Crist, PhD
Tel #: 1-408-433-3320 xtn 136 or 116
E-mail: [email protected]
Samples Received at Nanolab: Feb xx, 2013
Data-Report E-mailed: Feb xx, 2013
Reviewed by J. Gold, Feb xx, 2013
Job#: ORD - xxx
Key Capabilities of K-Alpha:
Surface chemistry (<100 Å), >1MCPS, atom% accuracies ~±5%, elemental composition, high energy resolution chemical states, 128
channel SnapShot™ detector makes profiles and maps 4-5X faster than scanned mode, SnapShot™ parallel mode spectra , 2 methods to
control charging of insulators, beam sizes down to 30μ, angle-resolve XPS, AR-PROCESS™, rotated depth profiles, depth profiling using
500 V Ar+ for minimal degradation, line profiles, time studies, degradation studies, glove box, very gentle ion cleaning…
Thermo K-Alpha
Monochromatic XPS System
Thermo K-Alpha
Mono XPS System
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Purpose (Objective):
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Sample Names/Descriptions
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Survey and chemical state spectra
Interpretation of Spectra, Profiles - Observations, Notes and Suggestions:
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Names: LiCoMnNiO powder – as recd
XPS Analyses Requested:
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Measure atom% values for each element and collect chemical state spectra
Atom% and Weight % values are provided (page 3). Due to the weakness of the Li signal and its’ overlap with Mn 3p we
can not generate a valid atom%. Advanced work is needed try to generate a useful value for Li atom%.
A series of reference spectra from Mn, Co and Ni oxide compounds are provided in the appendix.
This powder is heavily contaminated with carbonates, probably starting material.
Minor contaminants include: Na, Cl, Cd and S.
Mn is best assigned to a MnO2 chemical state.
Co is best assigned to a Co-X chemical state. The Co 2p3 shape does not match that of CoO or Co(OH2) or Co2O3.
Ni is best assigned to Ni(OH)2 chemical state. The Ni 2p3 shape does not match that of NiO.
Li can only be assigned as Li+, which can be LiOH or Li2CO3.
Please call or e-mail us for any questions regarding the data and the report. We welcome on-site visits to work with us while
collecting your data-report or to discuss future or current analysis needs.
Analysis Conditions:
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Standard X-ray beam size is our 400 x 600 μ spot. The smallest spot size available is 30 μ.
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Samples were not exposed to X-rays until measurement was started to minimize the chance of degradation
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Charge compensation, if used, was a combined beam of low voltage Ar+ and e◦
X-rays are monochromatic Al Kα 1486 eV (8.3383 Å). The X-ray angle of incidence is 30º
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Electron take-off-angle is 90º that gives a depth of information, depending on material, between 60 and 120 Å
Other Details:
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An Appendix lists practical information about XPS limits, contamination, sources of contamination and more.
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Chemical state assignments are based on the 40,000 monochromatic XPS spectra stored in the SpecMaster Database of Monochromatic XPS Spectra
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Free of charge, Nanolab will provide you will a copy of a spectral data processing software called SDP v4.3 for a period of 6 months when you submit a request for SDP by e-mail.
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Overlaid spectra, if requested, are found just after the surface composition tables.
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Detection limits for XPS range from 0.1 to 0.2 atom% (i.e. 1000-2000 ppm) for most elements.
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Because XPS measurements are normally done once, the statistical confidence level is modest, roughly 75%.
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Your data and report will be retained for at least one year.
Page 7
Thermo K-Alpha
Mono XPS System
Atom% and Weight %s
Uncertainty in Atom % value in the surface composition table, shown above, depends on intensity of signal: strong signals are +/- 10% of the value shown, weak
signals are +/- 30% of the value shown. The actual depth of information depends on atomic number (Z) and electron Take-Off-Angle (TOA) . The standard
electron TOA on the K-Alpha XPS is a 90 deg angle which gives a depth of information ranging from 60-120 Angstroms, which depends on elements in the material.
The limit for detection for most elements is roughly parts per thousand (ppth). The standard detection limits range from: 0.1-1.0 atom % for nearly all elements.
XPS does not easily measure ppm level. XPS is often done only once, so statistical accuracy is limited.. Samples are rarely, but sometimes damaged by X-rays
during analysis (eg PVC, nitro-cellulose). Samples can lose gases and liquids in UHV. XPS detects all elements, except H or He. Please read the appendix for
additional information on XPS, contamination, energy resolution settings, data quality, calibration, and reference energies.
Page 8
Thermo K-Alpha
Mono XPS System
Page 9
Thermo K-Alpha
Mono XPS System
Sample Name
LiCoMnNiO powder as recd.txt
Lithium
Carbon
Oxygen
Manganese
Cobalt
Nickel
Li 1s
C 1s
O 1s
Mn 2p3
Co 2p3
Ni 2p3
Mn-O2
Co-X
Ni(OH)2 Shake-up
Co(OH)2
780.49
854.9
856.16
100.0% 65.3%
34.7%
Common
Li+
C-C,C-H C-OC,C-OR C=O C-O3 mtl O-metal O-H mtl CO3 mtl ads H2O
Alternative
Li2CO3
Binding Energy (eV) 54.62 285.32
286.73
288.6 290.73 529.75 531.64 532.62 533.78
Relative %
100.0% 56.4%
11.8%
7.4% 24.4%
53.6% 24.9%
15.9%
5.6%
642.4
100.0%
High energy resolution spectra are peak-fitted to resolve the presence or absence of chemical states of many elements. Peak-fitting depends on the FWHM of the
chemical states so FWHM are important to the peak-fitting process. Nanolab uses pass energy and step size settings that allows us to maximize the detection of
multiple species within a peak-fit envelop. The conditions that Nanolab uses produces FWHM that range from 1.0 to 1.5 eV. When a FWHM is >1.8 eV, we
normally add another peak. Uncertainty in the Binding Energy (BE) values listed in the chemical states table, shown above, is roughly +/-0.1 to +/-0.3 eV. Peaks
(signals) that have obvious peak maxima are slightly more accurate. Raw peak-fit BE values are rounded from 2 decimal places (e.g. 0.xx) down to 1 decimal
place. Chemical state assignments are often due to the presence of 1-3 different chemical states / chemical species that have the same or very nearly the same BE.
The chemical state assignments shown at the top of each column are based on BEs listed in various sources of BE, including the XPS SpecMaster Pro Database
System. The BE difference between chemical states for an element depends on the degree of electron polarization between the atoms that affect the element of
interest. As a result, chemical shifts that are relative to the elemental form can be as small as 0.1 eV to as much as 5.0 eV.
Page 10
Thermo K-Alpha
Mono XPS System
When to use XPS ?
We have a problem feature, bigger than 50 μ across, and the chemistry is unknown = use Survey Spectra
The chemistry of the top 5-10 nm (50-100 Å) is contaminated - has the wrong chemistry = use Survey Spectra
The thicknesses and chemistry of a multi-layered film (0-1 μ) needs to be analyzed = use Depth Profiling
The chemistry at the top surface seems to be segregated or diffused due to heat processing = use Line Profiling
The XY distribution of elements in the top 10 nm seems to be wrong = use XY Mapping
We need to measure a chemical state profile of a very thin oxide with no Ar+ damage = Angle Resolved XPS
Thickness of chemicals in the top layer is unknown, and needs to be measured = use Chemical State Spectra
We changed our process chemistry and need to check chemistry of the top 10 nm = use Chemical State Spectra
A competitor has a new product that we want to analyze = use Survey Spectra Mode Depth Profiling
New Capability
300 mm XPS
Page 11
Thermo K-Alpha
Mono XPS System
Thermo K-Alpha
Mono XPS System
Exposed vs NON-exposed
C
O
F
O
F
Si Si
Ar
Page 13
Thermo K-Alpha
Mono XPS System
C 1s
O 1s
F 1s
Si
Si 2p
2p
xxx
Page
14
Thermo K-Alpha
Mono XPS System
Survey and Chemical State Spectra – Examples
Page 15
Thermo K-Alpha
Mono XPS System
LiCoMnNiO powder – As Received
Survey
+
+
Page 16
Thermo K-Alpha
Mono XPS System
LiCoMnNiO pwder – As Received
+
+
*The expanded view of the survey spectra is provided to more clearly reveal the presence or absence of weak signals in the 0500 eV or the 500-1100 eV range where many contaminants, if present, will appear as very weak signals.
Page
17
Thermo K-Alpha
Mono XPS System
LiCoMnNiO powder – As Received
+
+
*The expanded view of the survey spectra is provided to more clearly reveal the presence or absence of weak signals in the 0500 eV or the 500-1100 eV range where many contaminants, if present, will appear as very weak signals.
Page
18
Thermo K-Alpha
Mono XPS System
C 1s
O 1s
Ni 2p3
Co 2p3
Analyzed for:
Page
19
Thermo K-Alpha
Mono XPS System
This assignment as Li 1s is quite
uncertain. Mn 3p loss overlaps Li 1s.
Mn 2p3
( Li 1s ) ?
O Auger
Valence Band
Analyzed for:
Page
20
Thermo K-Alpha
Mono XPS System
Thermo K-Alpha
Mono XPS System
Etch Crater Size:
X-ray Beam Size:
Etch rate for SiO2:
Argon beam voltage:
Angle of incidence:
4x2 mm
0.4 mm
0.7 A/sec
0.5 kV
30 deg
S2 - Control
Si
O
Si
Page 22
Thermo K-Alpha
Mono XPS System
Etch Crater Size:
X-ray Beam Size:
Etch rate for SiO2:
Argon beam voltage:
Angle of incidence:
4x2 mm
0.4 mm
0.7 A/sec
0.5 kV
30 deg
S2 - Control
O
O
N
Page 23
Thermo K-Alpha
Mono XPS System
Etch Crater Size:
X-ray Beam Size:
Etch rate for SiO2:
Argon beam voltage:
Angle of incidence:
4x2 mm
0.4 mm
0.7 A/sec
0.5 kV
30 deg
S2 - Control
Page 24
Thermo K-Alpha
Mono XPS System
Etch Crater Size:
X-ray Beam Size:
Etch rate for SiO2:
Argon beam voltage:
Angle of incidence:
4x2 mm
0.4 mm
0.7 A/sec
0.5 kV
30 deg
S2 - Control
Consistent with a trace concentration
of nitrogen as nitride, in the poly Si.
Page 25
Thermo K-Alpha
Mono XPS System
Thermo K-Alpha
Mono XPS System
Optical vs XPS of Al2O3 only
Optical Image
Al2O3 XPS Image
Page 27
Thermo K-Alpha
Mono XPS System
C, O, Si and Re maps
Page 28
Thermo K-Alpha
Mono XPS System
XPS Reference Spectra
from XPS SpecMaster Database
Page 29
Thermo K-Alpha
Mono XPS System
Reference Spectra
Page 30
Thermo K-Alpha
Mono XPS System
Reference Spectra
Page 31
Thermo K-Alpha
Mono XPS System
Reference Spectra
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Thermo K-Alpha
Mono XPS System
Reference Spectra
Page 33
Thermo K-Alpha
Mono XPS System
Reference Spectra
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Thermo K-Alpha
Mono XPS System
Reference Spectra
Page 35
Thermo K-Alpha
Mono XPS System
Thermo K-Alpha
Mono XPS System
Constants, Variables and Limits
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Depth of information varies from 10 to 120 Å
Depth of information depends on Electron Take-Off-Angle (TOA) and the inelastic mean free path (IMFP) of electrons which
varies with the element analyzed
XPS Limit for Detection is usually: parts per thousand (ppth) (XPS does not easily measure ppm level)
Lowest Detected Concentration: 0.1-1.0 atom % for nearly all elements
Ultimate Level of Detection Limit: Requires extremely long analysis (10 hr) to detect 100 ppm
Detection of Li, Be, and B require longer analysis times because they give weak signals
Uncertainty in Atom % value depends on intensity of signal: Strong signals are ~ +/- 10%, weak signals are +/- 30%
XPS measurements are usually done only once, so statistical accuracy of any value is limited.
XPS identifies chemical states, not molecular structure (chemical states are similar to oxidation states, but are not)
XPS directly measures differences in electron density between adjacent atoms (electron polarization)
Samples are rarely, but sometimes degraded by X-rays during analysis (eg PVC, nitro-cellulose)
Samples can lose gases (O2, N2, CO, CO2) and liquids (water, elastomers, solvents) after entering UHV
XPS can be used to analyze heavy oils or solution residues smeared onto aluminum foil or other smooth surfaces
XPS uses monochromatic Aluminum X-rays with 1.486 keV energy (8.3383 Å)
Charge compensation is achieved by using low voltage electrons (0.1-5.0eV) and low voltage Ar ions
Vertical (depth) resolution varies from 1-2 nm
XPS detects all elements, except H or He
Pag
e 37
Thermo K-Alpha
Mono XPS System
Pag
e 38
Thermo K-Alpha
Mono XPS System
Design and Capabilities of K-Alpha
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This XPS instrument is a ThermoScientific system manufactured in 2009 by Thermo Fisher Scientific
The smallest beam size on the K-Alpha is 30 micron in diameter.
The largest beam size on the K-Alpha is 400 x 600 microns for general work.
The standard electron Take-Off-Angle (TOA) on the K-Alpha XPS is a 90 deg angle that gives information from 60-120 Å
depending on material
Max sample size: 50 x 40 x 15 mm (wdt)
The electron collection angle is: 60º
The electron detector has 128 channels which can be scanned or measured in parallel to produce SnapShot spectra
The X-ray angle of incidence on the standard sample mount is: 30º
The tilt stage can be rotated from -90 to +90 deg.
The azimuthal rotation stage produces depth profiles with improved interface resolution especially for crystalline materials
The K-Alpha XPS uses monochromatic Aluminum X-rays with 1.486 keV energy (8.3383 Å)
Charge compensation uses low voltage electrons (0.1 to 5.0 eV) and low voltage Ar ions
With ion beam etching, a depth profile down to 5,000 Å is common with or without rotation
Vertical (depth) resolution varies from 1-2 nm
When the analysis area is smaller than 50 microns, we recommend using a FE-Auger that has a hemispherical energy
analyzer and an electron retardation lens which allow us to measure chemical states and to obtain reliable atom%s
The ultimate vacuum, produced by using turbo-molecular and a titanium sublimation pumps, is 5x10(-10) torr
The usual working pressure is roughly 5x10(-8) torr
The argon ion gun on the K-Alpha is programmed to give argon ions with voltages between 3000 and 200 volts
Pag
e 39
Thermo K-Alpha
Mono XPS System
Instrument Calibration
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The reference BEs used to calibrate the BE scale are Cu 2p3 at 932.67 eV and Au 4f7 at 83.98 eV. Checking reference
energies is a simple process because the sample stage inside the analysis chamber holds pure samples of Copper (Cu),
Gold (Au) and Silver (Ag).
X-ray beam size and alignment with the desired analysis area is checked by using the ZnS phosphor that is permanently
resident on the sample stage inside the analysis chamber.
Charge referencing of insulators, if needed, is done by setting the hydrocarbon C 1s peak max to 285.0 eV.
The instrument transmission function, which affects atom% quantification results, is verified by generating atom% values
from the four major peaks (Cu 2p1, Cu 2p3, Cu 3s and Cu 3p) of freshly ion etched Copper (Cu)
Data Quality and Reliability
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The step size for survey spectra is set to either 1.1 or 1.3 eV per channel. This step size allows us to maximize the data
quality (S/N) of survey spectra since they are used to detect the expected strong signals as well as the very weak signals
that are contaminants. Survey spectra range from -10 to 1,100 eV. Few signals appear above 1100 eV. When key
signals above 1,100 eV are needed, the range is expanded to 1,400 eV. Spectra run with smaller step sizes and larger
ranges make it difficult to detect weak signals and are a waste of time.
The BEs produced from survey spectra are accurate to roughly +/- 1 eV and are not normally useful for chemical state
identification. It is possible to identify a few chemical states by looking at peak BEs in a survey spectrum.
For most chemical state spectra, it would be sufficient to use a Pass Energy of 90 eV which gives a Ag 3d5 FWHM = 1.1
eV because the natural FWHM of most chemical compounds when analyzed under practical conditions, are larger than 1.2
eV. Even so, we prefer to use a pass energy = 50 eV, which produces a Ag 3d5 FWHM = 0.8 eV. This level of energy
resolution is more than sufficient to resolve chemical states of all chemical compounds.
The step size for chemical state spectra is 0.1 eV per step (channel). Because peak-fitting extrapolates the data points,
the relative error in the peak maxima BEs is <0.1 eV.
We deliberately designed our survey spectra to detect those weak XPS signals that might be contaminants.
In the appendix, there are charts that show the Signal/Noise (S/N) ratios as a function of the number of scans. To help
customers to identify their desired level of S/N we normally collect data based on square numbers (e.g. 22, 32, 42, 52…).
Pag
e 40
Thermo K-Alpha
Mono XPS System
Survey Spectra (aka wide scan spectra)
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Survey spectra are collected by using a pass energy = 200 eV. The maximum pass energy is 500 eV.
The usual X-ray beam size is 400 um x 600 um.
The step size for survey spectra is set to either 1.1 or 1.3 eV per channel.
The electron take-off-angle for a non-tilted sample is 90 deg.
Signal is collected until the signal to noise ratio gives a 0.05 atom% detection limit for most elements
Chemical State Spectra (aka high resolution spectra)
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The step size is 0.1 eV per step (channel).
Spectra windows are normally 20 eV wide.
The pass energy is normally set to 50 eV which produces a Ag 3d5 FWHM = 0.8 eV.
The smallest pass energy on the K-Alpha is 5 eV which produces a Ag 3d5 FWHM <0.47 eV.
Depth Profiles
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The argon ion etch crater is roughly 4 mm x 2 mm for all depth profiles.
The etch rate of thermally grown SiO2 is used as a rough measure of etch depth.
Ar ion etching is normally done at 1 kV, which gives an etch rate between 1.2 and 1.4 Ang/sec for SiO2. If a 3 kV etch rate
is used, then the etch rate is between 2.6 and 2.8 Ang/sec.
Depth profiles are collected by using the parallel SnapShot mode at a pass energy of 150 eV which produces a 20 eV
window.
The normal angle of incidence of Ar+ is 30 deg
The normal X-ray beam size is 400 um x 600 um
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Sample Preparation & Carbon Removal by Very Light Ion Etch
•
Wafers that are larger than the sample stage are held by a pair of wafer tweezers, turned upside down, scribed on the
back at the edge with a diamond or carbide tip and then cleaved by using a standard wafer cleaving tool
Samples that are larger than the sample mount are carefully cut or broken to a suitable size.
Clean room twill cloth is placed under any sample while cleaving it or cutting it
The adventitious carbon on any as-received surface of any sample can be selectively removed by exposing it to a 0.5 or
1.0 kV Ar+ ion beam for 3-5 seconds. This method removes roughly 80-90% of the adventitious carbon and does not
harm the surface.
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General
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We deliberately designed our survey spectra to detect those weak XPS signals that might be contaminants.
In this appendix, there are charts that show the Signal/Noise (S/N) ratios as a function of the number of scans. To help
customers to identify their desired level of S/N we normally collect data based on square numbers (e.g. 22, 32, 42, 52…).
Pag
e 41
Thermo K-Alpha
Mono XPS System
Survey Spectra
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Relative sensitivity factors (RSFs), which are used to generate atom%s, are based on Scofield’s theoretically calculated
photo-ionization cross-sections by using a self-consistent central field potential model
The instrument transmission function (TF) aka instrument response function (IRF) uses an exponent of 1.0 for pass energies
ranging from 10 to 200 eV.
Chemical State Spectra
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Charge referencing is done by setting the hydrocarbon C 1s peak max to 285.0 eV. Please note that charge referencing of
native oxide materials is not used (or recommended) as native oxides are thin enough to allow electrons to tunnel through
the grain boundaries and effect charge compensation of thin insulating overlayers.
The BEs produced from survey spectra are accurate to roughly +/- 1 eV and are not normally useful for chemical state
identification.
Chemical State Assignments
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Chemical state assignments are made by referring to one or more references that include the:
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SpecMaster XPS Database of 40,000 Monochromatic XPS Spectra (XPS International LLC)
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Handbook of Monochromatic XPS Spectra – The Elements and Native Oxides (Wiley & Sons)
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Handbook of Monochromatic XPS Spectra - Semiconductors (Wiley & Sons)
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Handbook of Monochromatic XPS Spectra - Polymers and Polymers Damaged by X-rays (Wiley & Sons)
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Handbook of X-ray Photoelectron Spectroscopy – 2nd edition (PHI)
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Internal reference spectra collected from various pure chemicals
Reference BE data in NIST database are useful as a rough guide for BEs, but can have errors >0.4 eV for conductors and
>1.0 eV for insulators. This problem is due to the way the XPS machines were operated at universities over many years
time, and due to the various reference BEs recommended by the XPS instrument makers. We recommend caution when
using this database. For critical work, we recommend buying or making your own reference material and then analyzing
them.
Pag
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Thermo K-Alpha
Mono XPS System
Using K-Alpha XPS System
Absolute Etch Rates
NANOLAB Technologies
K-Alpha XPS Tool
Thickness of
Film Profiled
Material
Profiled
620ang
425ang
1000ang
poly-Si
SiO2
SiOC
Argon Ion
Etch Rate
Etch Rate
Etch Rate
Tilt Angle
Ang/sec
Ang/sec
Ang/sec
Voltage
3000 V
2.64
2.90
35 deg
2000 V
2.15
2.20
1.75
35 deg
1000 V
1.47
1.60
1.20
35 deg
500 V
0.66
0.82
35 deg
200 V
0.20
0.33
35 deg
Argon Gas Pressure: 3e-7 torr, Etch Crater Size: 4x2 mm
Thickness of
Film Profiled
Material
Profiled
500ang
500ang
2000ang
1,300ang
1000ang
600ang
500ang
1000ang
SiCN
Si1N1
Al
AlN
Al2O3
Au
BN
Cu
Etch Rate
Etch Rate
Etch Rate
Etch Rate
Etch Rate
Etch Rate
Etch Rate
Etch Rate
Ang/sec
Ang/sec
Ang/sec
Ang/sec
Ang/sec
Ang/sec
Ang/sec
Ang/sec
3.00
2.63
3.00
2.50
1.67
2.38
1.86
1.36
0.72
0.90
12.00
6.74
4.44
1.56
1.33
0.45
1.61
1.23
0.82
0.42
0.16
2.78
2.22
1.38
1000ang
1000ang
100ang
800ang
1050ang
1000ang
180ang
600ang
550ang
25ang
Ta2O5
Cr
GaN
TiN
TiO2
TaN
WN
WO3
W
HfO2
Etch Rate
Ang/sec
Etch Rate
Ang/sec
Etch Rate
Ang/sec
Etch Rate
Ang/sec
Etch Rate
Ang/sec
Etch Rate
Ang/sec
Etch Rate
Ang/sec
1.25
1.00
0.61
1.65
1.35
0.77
1.32
1.01
0.70
0.30
0.92
0.64
0.38
0.13
1.47
1.05
0.47
0.28
Argon Ion
Etch Rate
Etch Rate
Etch Rate
Tilt Angle
Ang/sec
Ang/sec
Ang/sec
Voltage
3000 V
2.10
1.30
35 deg
2000 V
1.00
35 deg
1000 V
1.14
0.71
1.65
35 deg
500 V
0.55
0.30
35 deg
200 V
0.22
0.17
35 deg
Argon Gas Pressure: 3e-7 torr, Etch Crater Size: 4x2 mm
© B. Vincent
Crist, 2011
Thermo K-Alpha
Mono XPS System
Page 44
Thermo K-Alpha
Mono XPS System
Common Surface Contaminants

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Carbon & oxygen are normal contaminants on all materials (comes from air, contact w containers etc)
◦
Carbon mainly present as hydrocarbon with 2-3 C-O moieties (eg organic alcohol, ketone, ester or acid)
◦
Carbon is very loosely attached & easily etched off (3-5 sec argon ion etch at 2-3 keV)
◦
Carbon is between 5 to 50 angstrom thick (see above)
◦
Oxygen present mainly as oxide or hydroxide (water is also common for metal oxides)
◦
S, Cl, Na, Ca, and Si are also very common contaminants (eg Ag often has S and Cl)
◦
Silicon is often present as oil, lubricant, plasticizer, etc. (causes many problems for many industries)
◦
Gloves easily contaminate surfaces with silicone and others (especially soft latex gloves)
Material Type
◦
◦
◦
◦
◦
Typical Amount of Carbon Contamination
Metals
Ceramics
Semiconductors & glasses
Polymers
Gold (special case)
40-60 atom %
30-50 atom %
20-40 atom %
5-10 atom %
60-80 atom %
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
Page 45
Thermo K-Alpha
Mono XPS System
Aluminum Foil (Kitchen)
As Received
Control sample of
aluminum foil as
received
Aluminum Foil (Kitchen)
After Glove Touch
Control sample of
aluminum foil touched
by latex glove
Contamination Caused by Gloves
Un-gloved hands will contaminate products with various organic oils, NaCl, water and other
chemicals which a worker has unknowingly touched. To avoid such contamination, the worker
usually wears plastic, nylon or clean room gloves. We have tested for contamination from gloves
by wearing them and touching kitchen aluminum foil.
Al
C
O
Si
N
Na
Cl
S
Ca
F
Zn
Clean Al foil
29
29
41
---
---
---
---
---
---
---
---
Clean Al foil
30
21
48
---
---
---
---
Fingerprint / Al
6.6
76
16
0.6
0.6
---
---
0.3
0.7
0.1
---
---
0.6
---
---
---
---
---
---
0.3
---
#1 plastic/nylon
23
33
40
3.8
---
---
#2 off-white latex
22
40
34
2.1
---
0.4
#3 yellow latex
2.2
50
23
24.0
---
---
0.3
---
---
---
---
#4 pink PE
20
53
26
---
0.6
---
---
---
---
---
---
#5 pink latex
19
42
33
5.8
---
0.3
---
---
---
---
---
#6 yellow latex
23
42
33
---
0.6
0.5
---
1.1
---
---
---
#7 opaque vinyl
27
41
32
---
---
0.5
---
---
0.1
---
---
#8 clean rm nylon
29
22
47
1.4
0.1
0.3
---
---
---
---
---
#9 blk conductive
14
53
32
0.9
0.3
---
---
---
---
---
---
#10 white latex
7.4
54
26
10.0
---
0.2
0.8
1.1
---
---
#11 yellow latex 2
21
36
39
2.9
0.4
---
---
---
0.1
---
0.3
#12 clear PE
17
53
29
1
0.2
---
---
---
---
---
#13 white PE
27
25
47
0.4
0.5
---
0.1
---
---
---
---
Page 46
Thermo K-Alpha
Mono XPS System
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).
Page 47
Thermo K-Alpha
Mono XPS System
Overlay of Ag 3d5 Signal (normalized) for
Pass Energies 10-160 eV
Performance from Dirty Silver (Ag) Surface
Pass Energy
FWHM
Relative
of Ag 3d5
Count Rate
160
1.6
1000X
140
1.5
900X
120
1.3
800X
100
1.2
650X
90
1.1
560X
80
1.0
500X
70
1.0
400X
60
0.9
320X
50
0.8
250X
40
0.7
170X
30
0.7
100X
20
0.6
52X
10
0.6
20X
Page 48
Thermo K-Alpha
Mono XPS System
Page 49
Thermo K-Alpha
Mono XPS System
Page 50
Thermo K-Alpha
Mono XPS System
Energy Difference = 1.0 eV between peak maxima (i.e. a chemical shift of 1.0 eV)
Energy Difference = 1.0 eV between peak maxima (i.e. a chemical shift of 1.0 eV)
Counts of shifted spectra decreased by 2X
Page 51
Thermo K-Alpha
Mono XPS System
Energy Difference = 1.0 eV between peak maxima (i.e. a chemical shift of 1.0 eV)
Counts of shifted spectra decreased by 3X
Energy Difference = 1.0 eV between peak maxima (i.e. a chemical shift of 1.0 eV)
Counts of shifted spectra decreased by 4X
Page 52
Thermo Scientific
Thermo
Theta K-Alpha
300 mm
Mono
XPS
System
XPS
System
Thermo-Scientific Theta 300 mm XPS System
Thickness &
Chemistry Ratios of
•
•
•
•
•
•
•
•
TiN layer
SiOx layer
HfOx layer
AlOx layer
LaOx layer
SiO(N) layer
Surface Boron
Surface Arsenic
Page 53
Thermo K-Alpha
Mono XPS System
Page 54
Thermo K-Alpha
Mono XPS System

Landscape format – easier to review, easy to see weak peaks

Nanolab deliberately maximizes S/N to detect trace contaminants

PowerPoint used – ready to present to groups


Succinct interpretation of results (3-5 lines) – not verbose –
Survey spectra always expanded vertically in the 0-500 eV range –
essential to detect presence/absence of trace signals

Optical photos - beam size and analysis location

Chemical state spectra are displayed 4 per page

Spectra as JPG images

If only survey spectra we describe probable chemical states

Peer reviewed by XPS expert

All spectra available as ASCII text data-files

Appendix has in-depth info on instrument & XPS for beginners

Table of ion etch rates for various common materials – no charge

Atom% table w BEs always printed on survey spectra

Thickness of thin films (<80 ang) available at no charge.

Weight % composition table when requested


Chemical state spectra always peak-fitted w assignments
Reference spectra from XPS spectra database of 40,000
monochromatic spectra, not BEs from NIST – no charge

Peakfit BEs and FWHMs always printed on chem. state spectra


Chemical state BE tables always provided as live Excel tables
Appendix explains basic physics of XPS, common surface
contaminants, a glove contamination study,


Common and alternative chemical states always provided
SDP v4.6 is free of charge so you can process spectra by yourself.
Normal cost of SDP v4.6 is: $785 per seat.

Overlays of survey and chemical state spectra always provided
•
B. Vincent Crist, PhD, 35 yrs hands-on in XPS (before EAG opened), 3 XPS spectra books by Wiley, SDP
v7.0 software by XPS International, 2 PDF spectra books on XPS, website author: www.xpsdata.com,
main author of XPS page on Wikipedia, member of ISO TC201 on XPS & AES, Google my name
Page 55