Hiden Analytical
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Instruments for exact science
HIDEN SIMS
Hiden Analytical
www.HidenAnalytical.com
Instruments for exact science
Hiden SIMS
Secondary Ion Mass Spectrometry
• Analysis Technique
• Instrumentation
•SIMS Workstation
•Bolt on components
•Applications
• Summary
Hiden Analytical
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Instruments for exact science
Sputter Erosion of the Specimen
Sputtered Neutrals
-ve Molecules
+ve Ions
- +ve Molecules
-Ve Ions
COLLISION CASCADE
ALTERED LAYER
Electrons
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Sputter Erosion of the Specimen
Static SIMS
•Very low ion dose (~1E12 ions cm-2) gives surface specific measurement.
• Ideal for investigation of contamination, oxidation and monolayer coatings.
Dynamic SIMS
• Higher ion dose erodes surface exposing deeper material.
• Monitoring mass resolved ion signals results in depth profile.
• Ideal for investigation of impurities (dopants) and layer structures.
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Sputter Erosion of the Specimen
Scanning the beam across the sample
• Flat bottom crater for depth profiling
• Imaging
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SIMS Depth Profiling - Gating
For high dynamic range analysis measured signal must come only from
the centre of the crater.
Hiden spectrometer interface unit and MASsoft electronically gates signal
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Anatomy of a Depth Profile
Pre-equilibrium region
before bombardment
chemistry stabilises
Usually a log scale
due to the very high
dynamic range of
SIMS
Signal monitored
as a function of
time
Matrix signal provides a
reference for quantification
and helps confirm validity
of data
Dip in matrix combined with
rise in impurity indicates
impurity is not dilute
Sharp decay shows good
depth resolution / flat crater /
adequate gating
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Primary ion beams
The probability of ion emission is affected greatly by the sample
chemistry.
As the ion beam species becomes incorporated into the specimen
it can be used to modify the surface chemistry and enhance
probability of ionised emission.
• Oxygen enhances ionisation of electropositive elements
• many metals and semiconductor matrix species
• Caesium enhances ionisation of electronegative elements
• halogens, many contamination species, some metals
• Caesium can also be used to collect secondary cluster
ions (MCs+) of most species (M) at lower sensitivity.
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Sensitivity
SIMS is the most sensitive generally available surface analysis
technique.
• in static SIMS <<1% monolayer concentrations are detected
• in dynamic SIMS detection limit can be ppb.
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The SIMS Workstation comprises
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MAXIM SIMS/SNMS analyser
IG20 gas ion gun and controller
IG5C Cs ion gun and controller
Charge compensation electron gun
Viewing camera and lighting
UHV multiport chamber
Fast entry loadlock and transfer mechanism
PC control software
Compact bench housing pumping
Provision for expansion
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Hiden SIMS Products – Ion Guns
IG20 Gas Ion Gun
•1-5 keV, 1µA, 100µm (50µm
imaging)
•Reliable, long life, electron
impact ion source
•Integral bend to remove neutral
particles
•May be used with reactive and
inert gases (e.g. H, He, O, N, Ar,
Xe, air)
•Differential pumping to preserve
chamber UHV
•Bakeable to 250C
•Mounts on CF35
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Hiden SIMS Products – Ion Guns
IG5C Caesium Ion Gun
•1-5 keV, 100nA, 80µm (20µm
imaging)
•Miniature low power Cs Ion source
(~8W), long life, easy replacement.
•Air stable
•Double bend to remove neutral
particles
•Differential pumping to preserve
chamber UHV
•Bakeable to 250C
•Mounts on CF35
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Hiden SIMS Products – Ion Guns
Ion Gun Control
PC controlled
Settings can be saved and recalled
Automatic ion source warm up /
cool down
EHT ramp rate control
Gun diagnostics
Connect via TCP/IP, USB or serial
Upgradeable software and firmware
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Hiden MAXIM
Very high sensitivity
Off axis geometry
Integrated high efficiency
SNMS ioniser
< 100V extraction potential
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SNMS (sputtered neutral Mass Spectrometry)
– Post Ionisation
• Electron impact cell ionises the sputtered neutral material
• Secondary ions deflected from analyser
• Separating the sputter and ionisation events removes
most of the matrix effect associated with SIMS
• Easily quantifies large changes in matrix material
• Detection limit typically <0.1 atomic%
• Excellent for alloy multilayers
• No requirement for matrix matched reference materials
• Neutral species are unaffected by surface charging
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Hiden MAXIM
For SNMS operation an
electron impact cell is used at
the very front of the probe.
This maximises the solid angle
for the emitted neutrals that
can be collected – improving
sensitivity.
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Sample Viewing
•Important to be able to accurately target sample
areas and navigate around the specimen.
•Normal incidence USB colour camera and LED
white light source.
•Save images to other applications and
documents.
•Flexible positioning to allow optimum illumination
of samples (such as specula reflection for
observing craters on polished surfaces).
Craters visible on silicon wafer during
analysis using specula illumination
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Sample Charging
The surface of samples, principally insulators, charges during
bombardment. This is primarily due to secondary electrons
leaving the surface.
To overcome this problem an electron gun is used to balance
the lost electrons and maintain sample neutrality.
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Applications
•Static SIMS
•Contamination analysis
•Dynamic SIMS
•Depth profiling semiconductors and layer structures
•Imaging
•Semiconductors
•Industrial components
•SNMS
•Hard disc head
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SIMS Imaging
• SIMS signal from raster scanned ion beam is monitored
and presented as an image
• Chemical map shows distribution of species on the
surface
• Can be used to find areas for subsequent depth profile
or spectrum analysis
• Ideal for investigating transfer contamination, surface
diffusion and cross sections
• Can be used with bevelled samples for rapid
assessment of depth profile
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SIMS
SIMS - IMAGING
•Semiconductor bond pads must have a clean surface for
successful wirebonding (ultrasonic welding).
•SIMS imaging (27Al) reveals surface of some pads (circled)
obscured by contaminant.
•Real-time images can be used navigate to problem area for static
SIMS analysis – identified fluorocarbon from etching process.
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SNMS Depth Profiling
Integrated electron impact ionizer
100
Ni
Separation of sputtering from
ionization minimises matrix effects.
Does not require matrix matched
reference materials.
Depth profile shows a
NiCr/Cu/NiFe layer structure
primary ions 5 keV Ar from IG20
ion gun
Fe
Cu
Concentration / atomic %
Easily quantified composition to 100%
Cr
10
1
0.1
0
100
200
Depth / nm
300
400
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SNMS Depth Profile of Hard Disk Platter
Polymer / lubricant
N head S
Magnetic data layer
Nonmagnetic layer
Magnetic base
‘Contact’ layer
Substrate
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Hard disk Platter comprises magnetic and non-magnetic metal
layers on aluminium substrate.
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Polymer / lubricant
Magnetic data layer
Nonmagnetic layer
Magnetic base
‘Contact’ layer
SNMS Depth Profile of Hard Disk Platter
Substrate
100
Cr
Ni
concentration / atom %
Co
Al
10
C
1
0.1
0
1
2
3
4
5
depth / µm
6
7
8
9
10
N head S
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Polymer / lubricant
Magnetic data layer
Nonmagnetic layer
Magnetic base
‘Contact’ layer
Substrate
Near Surface Detail of Hard Disk Platter
concentration / atom%
100
Cr
90
Ni
80
Co
Al
70
C
60
50
40
30
20
10
0
0
20
40
60
80
100
120
depth / nm
140
160
180
200
N head
S
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Case Study – Contamination on Diesel Injector
After a period of intense engine running, a hard, stain like,
deposit was observed on a fuel injector component.
EDX (energy dispersive X-ray) analysis in the SEM was
inconclusive as the thin nature of the deposit meant that
most of the excited volume was in the underlying metal.
300µm
1cm
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Case Study – Contamination on Diesel Injector
The flexible sample handling of the SIMS Workstation
permitted mounting of the component, without further
preparation. Important because cutting or grinding of the
hardened steel would have exposed the component to
heat and contamination.
Image from instrument camera
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Case Study – Contamination on Diesel Injector
56Fe
SIMS images of the defective region. The right hand
image shows detail in the position of the arrow, where
something is blocking the iron signal from the steel.
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Case Study – Contamination on Diesel Injector
A localised mass spectrum from the steel shows typical constituents,
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Fe at 54-58, with the major isotope at 56
Cr at 50-54 with the major isotope at 52
and Na (23) and K(39 and 41) being contaminants to which SIMS is
extremely sensitive.
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Case Study – Contamination on Diesel Injector
The localised mass spectrum from the defect is dominated by Ca.
The defect is Ca based and it is suggested that this is due to a bio-diesel
catalytic production step. This known possible fuel contaminant is limited
by EU regulations to 5mg/kg (summed with the Mg content).
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Summary
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SIMS is the most sensitive surface analysis technique with ppb
detection limits in many cases. It detects across the entire
periodic table and provides isotopic information unavailable with
chemical, electrical or optical (incl. X-ray) techniques.
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Analysis of the uppermost monolayer (static SIMS)
Analysis of near surface and layers structure by depth profiling
Depth profiles may be quantified with high accuracy and
sensitivity.
Spatial distribution can be observed directly by imaging.
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Conclusion
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Bolt-on Hiden SIMS products provide a cost effective means of
adding high performance SIMS to existing instrumentation.
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The Hiden SIMS Workstation is a high flexibility SIMS/SNMS
tool designed specifically for ease of operation and low cost of
ownership.