NanoSIMS 50

Secondary Ion Mass Spectrometer for trace element and isotope analysis

at sub-micron resolution

INTRODUCTION TO THE INSTRUMENTATION

NanoSIMS 50/ 50L

NanoSIMS 50

Key componentsKey components

Co-axial primary and secondary ion beams

Parallel detection of five (NS50) or seven (NS50L) ionic species

High transmission at High Mass Resolution

UHV technology, dry primary pump, turbomolecular pumps, ion pumps and titanium getter

Duoplasmatron source: O-

Wien mass filter for the duo

Magnetic sector mass analyzer

Multi-collection:5 EM plus 1-2 FC (NS50),

7 EM-FC (NS50L)Fixed

Large Detector(NS50 LD option)

Retractable Cesium source: Cs+

Ion pump + Ti sublimatorfor Analysis chamber

Ion pumpfor intermediatechamber

Optical microscope

NEG Normal Electron

flood Gun (option)

X-Y samplestage motors

NanoSIMS 50

Standard 2-inch load-lock with turbo pumping, heating lamp for sample degasing, mechanical transfer rod to the storage chamber.

8-position intermediate storage chamber with ion pumping, transfer rod to the analysis chamber.

Vacuum automation with independant processor

SampleSample introductionintroduction

Intermediate chamber

Intermediate/ AnalysisIsolation Valve

Transfer RodIntermediate/ Analysis

Transfer RodLoad-lock/ Intermediate

Load-lockHeating lamp, turbo-pump

Load-lock/ IntermediateIsolation Valve Selection of sample

holder on Carrousel (8 parking positions)

Vacuum controller

NanoSIMS 50

1) FUNDAMENTAL LIMITATION: SIMS sensitivity gets poorer as lateral resolution gets better (SIMS is destructive) There are typically 1.25M atoms in a volume of 50 x 50 nm x 10 nm. With an ionisation of 0.005 and a transmission of 1, one can detect around 6000 atomic ions, meaning a detection limit of roughly 0.1at. % level from a single pixel volume.For comparaison, using a CAMECA IMS instrument with larger beam current over a larger area(50 x 50 µm x 10 nm), one will sputter 1.25E12 atoms and be able to reach ppb level from the whole area. This illustrates the compromise between lateral resolution and sensitivity, exacerbated in a destructive technique (one can not only accumulate longer, as sample is sputtered away).

2) HIGH LATERAL RESOLUTION together with HIGH BEAM DENSITY:==> short working distance, normal incidence, high brightness ion sources

5) HIGH MASS RESOLUTION together with SMALL SPOT:==> MAGNETIC SECTOR (no TOF analyzer: small spot OR high mass resolution , no quadrupole analyzer: Low Mass Resolution)

4) HIGH TRANSMISSION MASS SPECTROMETER and PARALLEL DETECTION Small volumes available + perfect image or isotope registration ==> TOF or MAG. No quadrupole (low transmission and monocollection). High transmission together with high lateral resolution ==> Microprobe mode (ion microscopemode not usable for sub-micron resolution: low transmission)

3) HIGH IONIZATION YIELD OF SPUTTERED PARTICLES (small and limited volumes available, SIMS is destructive):The use of reactive primary ions (Oxygen and Cesium) is mandatory in order to enhance atomicsecondary ions, in dynamic SIMS mode (sputtering of at least a few nm for trace element analysis). Gallium gives 100-1000x less elemental signal in general.No LMIS Gold or Bismuth as used on TOF-SIMS: enhancing molecular ion yield for static SIMS mode is of no use for element or isotope analysis in dynamic SIMS.

Ultra fine feature Ultra fine feature SIMS analysis requirementsSIMS analysis requirements

6) REASONABLE ACQUISITION TIME:==> MAGNETIC SECTOR (no TOF: much too low duty cycle & data rate: 200-1000 longer acquisition time for same element or isotope signal)

NanoSIMS 50

Normal, co-axial primaries & secondaries

Parallel detectionof five ionic species(NS50) or seven (NS50L)

NanoSIMS 50 synopsisNanoSIMS 50 synopsis

Two reactive ion sources:O-, Cs+

NanoSIMS 50

Advantages of co-axial configuration :• Short working distance of the probe forming lens/ extraction

1) smaller spot size for a given beam current2) higher collection efficiency and dramatical reduction of the broadening of the secondary ion beam due to the initial angular and energy distribution.This will favour transmission of the analyzer at high mass resolution.

• Minimization of shadowing effects for non flat surfaces; hole or trench bottom analysiscapability• Obtention of deep craters of small size• Reduction of the beam and raster distorsion

Constraints due to co-axial configuration :• Primary and secondary ions must be of opposite polarity and equal energy (Cs+/ negative ions, O-/ positive ions). This excludes MCs+ technique and the use of O2+ ions for electropositive elements.• Oxygen flooding can not be used

Conventional and coConventional and co--axial probe axial probe forming systemsforming systems

SampleSample

Secondary beam

Extractionoptics

Probeformingoptics

Primary beam

ConventionalSIMS

Primary beamSecondary beam

Deflectionplates

Extractionand probe

formingoptics

Co-axialNanoSIMS

Any design of a SIMS instrument must accommodate two conflicting needs: the objective lens of the primary ion column must be as close as possible to the sample in order to optimize its optical properties, leading to smalland intense ion beam.On the other hand, secondary ions are emitted in a half-space, with a large energy spectrum (~ 0-200eV). In order to collect as a large fraction of these ions as possible, the extraction optics should also be placed as close as possible to the sample. As the extraction and objective optics have their own physical size, a compromizemust be found leading to large sample/optics distances. The NanoSIMS design has escaped from this dilemnaby switching to a totally new co-linear optics capable of simultaneously focusing the primary ions with highquality, and collecting most of the secondary ions.

NanoSIMS 50

LateralLateral resolutionresolution withwith cesiumcesium

The use of cesium primary ions is mandatory in SIMS for the analysis of electro-negative elements (H, C, O, N, F, Cl, P , Ge, Se, As, Br, Te, I, Au…). It enhances the ionization yield (= sensitivity) by several orders of magnitude compared to non-reactive primary species (Ar, Ga, Au, Bi…).

The NanoSIMS is equipped with the patented CAMECA Microbeam cesium ion source, guaranteeing the highest brightness available among commercial cesium ion sources. The source brightness (in mA/sr/cm2) measures the ion current available within a given solid angle from a given source area. It is an invariant in optics: a perfect (= withoutoptical aberration) primary ion column could at maximum re-obtain this brightness in the final spot size. The high brightness of the ion source, the short final objective working distance, its reduced aberration coefficients, and the normal incidence guarantee the best performance available from a SIMS microprobe for electronegative secondary ion microanalysis.

Beam spot size (= lateral resolution) is determined by extracting the 16%-84% intensity line-scan from a SIMS image of a TiCN sample giving sharp grain boundaries without artifact. Condition: 16 keV Cs+, negative secondaries.

Conservative spot size specification (16-84%) for Cs+ : 50nm/0.3pA, 100nm/2pA.

12C212C14N

300nm 300nm

Field: 4 X 4 µm, 512X512 pixels, Acq time: 30min.

12C212C14N

200nm 200nm

Field: 2.5 X 2.5 µm, 256X256 pixels, Acq time: 22min.

Measured lateralresolution: 25nm

Sample by courtesy of LAM, Luxemburg

NanoSIMS 50

The NanoSIMS is equipped with the high brightness CAMECA duoplasmatron ion source. Although it can generate positive ions (02

+), it is mainly used in the NanoSIMS to generate 0- ions. Due to the opposite polarity scheme, one can benefit from the strong ionization enhancement of electropositive elements with oxygen implantation. Additionally, the use of primary negative ions offers the well-known advantage of much lower sample charging problems compared with positive primary ions (the sample always tends to charge positively due to the secondary electron emission).

The beam spot size is determined by extracting the 16%-84% intensity line-scan from a 27Al+ SIMS image recorded here on a sample containing Al grains.

Conservative spot size specification (16-84%) in O- :200nm/0.3pA, 400nm/2pA.

Field: 10 µm x 10 µm, 16-84% spot size: 340 nm, O-: 2pA

Field: 7.5 µm x 7.5 µm, 16-84% spot size: 170 nm, O-: 0.3pADistance (microns)

Inte

nsity

(A.U

)

100%

O-: 0.3pA,16-84% < 170 nm

0.0 2.01.0

84%

16%

Distance (microns)0.0 2.01.0

Inte

nsity

(A.U

)

100%

O-: 2pA,16-84% < 340 nm

84%

16%

0%

O2- current specs typically four time lower than O-.

27Al+

27Al+

LateralLateral resolutionresolution withwith oxygenoxygen

NanoSIMS 50

0

10

20

30

40

50

60

70

80

90

100

2000 3000 4000 5000 6000 7000 8000 9000 10000

mass resolving power

rela

tive

tran

smis

sion

Optimized for lateral resolution and sensitivity, the NanoSIMS is a pure ion Microprobe (scanned focused ion beam) and has no ion microscope mode (transport of a stigmatic, magnified mass filtered ion image) as on the CAMECA IMS analyzers.

One of the characteristics of the NanoSIMS is to work in high mass resolution: by design, there is no low mass resolution mode on the NanoSIMS, even when removing all apertures.

In addition, the analyzer transmission is maintained very high (see plot above), even when increasing the Mass Resolution. This is the result of:

- a very high, normal extraction field allowing a very early secondary ion focusing,- a limited field of view together with a dynamic emittance matching,- a careful transport and rectangular shaping of the secondary beam resulting in

the use of small slit compared to the magnet size, reducing aberrations, - the correction of the second order mass spectrometer optical aberrations.

Mass Revolving Power

Rel

ativ

e Tr

ansm

issi

on

Analyzer Transmission Analyzer Transmission versus Mass Resolutionversus Mass Resolution

MRP T (%)3500 1005910 686120 656770 567120 517390 457885 39.99470 299615 24.5

Without any slit, mass resolution is 3500 and

transmission is taken as 100%. Other transmissions

are referred to this one.

Mass resolution is taken as M/dM = R/4 * L10-90, where R is trajectory radius and L10-90 is line width corresponding to 80 % of intensity

NanoSIMS 50

NanoSIMS 50 NanoSIMS 50 main optionsmain options

NEG. Normal incidence Electron flood Gun for the analysis of strong electrical insulators in Cs+ withnegative secondary ions, when gold coating method is not sufficient, at high beam current. SED. Secondary Electron Detector. Works in negative secondary polarity with cesium. Can give nicely contrasted topographical images for illustration and sample visualization.Full-MDA. Motor Driven Apertures. Automation of diaphragms, apertures and hexapole for an easier operation, a better reproducibility and a higher throughput.Z-motor. Automation of the sample stage Z-axis. Allows to re-adjust the sample Z position for highest precision isotopic measurements in geochemistry, in unattended chain acquisition mode. Geo-Faraday. Low-noise FC electrometer for geological applications in single FC-EMs mode. Dual-Faraday. Special trolleys #1 & #2 derived from NS50L design, equipped with both E.M. and F.C., allowing FC-EMs as well as FC-FC-EMs acquisition modes. LD. Large Detector. Equipped with continuously adjustable exit slit and electrostatic sector.

Note: all options are field-retrofittable

NanoSIMS 50

7 masses in parallel (ex: all O and Si isotopes in parallel, or 50-52-53-54Cr + 51V +48Ti + 55Mn)

Up to 58Fe in multicollection and single mass separation (Ti, Cr, Mn, Fe isotopes accessible)

Multiple Faraday Cup option.

NS50

M max/M min

= 13.2

NS50LM/58

Mmax/Mmin = 21

NanoSIMS 50NanoSIMS 50LL

The Multicollection analyzer of the NanoSIMS 50 can measure five masses with two key characteristics:

2) Due to the finite width of the detectors and theirangle relative to the focal plane, the minimum Mass Interval between two adjacent detectors is M/30.Ex: 27, 28, 29, 30amu can be analyzed simultaneously but 57, 58, 59, 60amu require two acquisitions: 57 & 59 then 58 & 60.

M/30

8mm

1) Mass Dispersion (Mmax/Mmin in a parallel acquisition)= 13.2 (or 14.4 with LD option).

For ex, one can follow 12C on trolley #1 and get mass 12 x 13 = 156amu on the fixed detector #5 at large radius.

The NanoSIMS 50L receives a larger Multicollection analyzer improving several specifications:- with the introduction of exit cylindrical sectors, the Mass Separation between adjacent detectors is M/58.- the magnet size is enlarged in order to reach a Mass Dispersion Mmax/Mmin = 21.- seven masses can be measured in parallel (five on the NS50)- each trolley can be equipped with E.M. and FC (switch at atmospheric pressure, multicollection opened).

Side view of four trolleys of the NS50L multicollection

NanoSIMS 50

Standard NS50

NanoSIMS NanoSIMS 50/50/5050LL

The NanoSIMS 50L mainly differs from the NS50 by its larger multicollection and associated larger turbo-pump. Some other, minor differences: the Z-motor, optional on the NS50, is standard in the NS50L, and the LD large detector option of the NS50 is not available on the NS50L. The general size of the instrument is not changed dramatically as can be seen from photos below:

NS50L

NS50L

NanoSIMS 50

EMFC

Automated D0 primary diaphragm

Entrance & Aperture Slits

New options: FullNew options: Full--MDA (NS50/50L)MDA (NS50/50L)and Multiand Multi--Faraday (NS50L)Faraday (NS50L)

1) Full-MDA: the NanoSIMS 50 and 50L can both be equipped or retrofitted with the automation of D0 and D1 diaphragms, entrance, aperture and energy slits, hexapole centering, and individual trolley exit slit exchange. The benefits are an easier operation (important specially for multi-user operation), a better reproducibility for high precision isotopic ratios and a higher throughput (ex: pre-sputter at high current followed by analysis at high resolution in a chain analysis).

2) Multi-Faraday: the new trolleys of the NanoSIMS 50L can be equipped simultaneously with E.M and F.C. The standard Multi-Faraday option includes 7 E.Ms and 3 FCs. More trolleys can be equipped with FC and associatedpre-amp, on request, up to a maximum of 7 EMs and 7FCs. The EM/FC selection is done multicollection opened atatmospheric pressure by mechanically sliding the detector behind the exit slit.

D1 co-axial lensdiaphragm

Automated exit slit exchange

Synoptic of NS50L Multi-Faraday option

NS50L detector trolley showing scanning plates, exit slit mechanism, cylindricalsector and detectors (EM and FC)

Energy Slit

Z-axis of the samplestage

Thermostated low-noise Multiple FCpreamplifier chamber allowing

intercalibration of the FC signals.

NanoSIMS 50

The standard NanoSIMS holder is 50mm in diameter. The front plate can be customized depending on the user needs. Sample thickness can be up to 9mm. The sample surface must be flat. The Z movement of the sample stage can be used to keep sample/extraction distance at 400µm +/- 50µm. Due to the small sample-lens distance, the sample must not degas too much in order to avoid risks of arcing. Typical working condition is in the E-9/ E-10 torr range. We thus recommend to minimize, if any, the embedding material volume. Gold coating of the sample is generally used in order to reduce sample charging problems.

Below is a schematic of a NanoSIMS sample holder with 10mm holes (different hole sizes are available), with parts giving an idea of some possible mountings. For an easier viewing, the schematics are not at scale.

NanoSIMS sNanoSIMS sample mountingample mounting 1/21/2

Gold film

Metallic cylinder.Material: ARCAP AP4

Part #: 45620693

Ø10mm+0, -0.1

4mm

Intermediate ring.Material: ARCAP AP4

Ø10mm+0, -0.1

variable

Thin plate with holes.Four holes of diam. 3mm.

Material: Z2-CN18-10, Part #: 45620694

Ø10mm+0, -0.10.1mm

Thin flat sample glued or fixed with non-degasing(< 1E-9 Torr) conductive double-side sticky tape

Thicker flat sample glued or fixed with non-degasing(< 1E-9 Torr) conductive, double-side sticky tape

Small particles pressed into a gold foil

Small sample(s) analyzed through the holes of the thin top « grid » or « plate »

Embedding in high vacuum resin or metal in metallic cylinder, then polished (or not if it is flat) and gold coated if needed.

Ex: Korapox 439 epoxy (www.koemmerling-chemie.de), Varian Torr Seal Low Vapor Pressure Resin (www.varianinc.com).

Also used: Wood metal (In-Bi alloy melting at 78°C)

Amagnetic Spring

samepotential

Coaxial optics showing the short working distance

Metalcylinder

Sampleholder

EOW

EOP

EOS

0.3mm

Part of the sample holder.Material: ARCAP AP4

Ø9mm

0.1mm

Ø10.4mm+0, -0.05

Attention! If rectangular sample, check its diagonal to be less than 10.4mm !

Embedding ring.Material: ARCAP AP4, Part #: 45620692

Ø9mm

Ø10mm+0, -0.1

4mm

Attention! If rectangular sample to be embedded, check its diagonal to be less than 9mm !

PARTS SOME SAMPLE MOUNTINGS

NanoSIMS 50

It is possible to simultaneously load two shuttles on the NanoSIMS sample stage : two 1-inch sample holders, or one 1-inch and one 2-inch sample holder. Note that the second 1-inch sample holder can be brought in SIMS position but not in the optical microscope position. It is generally used to store standard samples.

The NanoSIMS is delivered with eight shuttles and nine sample holders: two “standard”, five “biology” and two “geology”. The respective numbers can be modified on request at the time of order.

25mm/ 1-inch diameter«Standard» sample holder

with four 10mm holes.Ref #: 45620641

50mm/ 2-inch diameter« Geology » sample holderwith one 1-inch , two half-inch and two 10mm holes.

Ref #: 45620643

50mm/ 2-inch diameter«Biology» sample holderwith eight 10mm holes.

Ref #: 45620642

ShuttleRef # : 45621551

Reverse view of the « Biology» sample holder, unscrewed from its shuttle. One can see the springs pushing the sample cylinders in their hole against their lips.

Ex. of wrong mounting ! Must beremounted with front reference.

4-hole thin plateRef #: 45620694

10mm metallic cylinderRef #: 45620693

10mm diam. embedding ringRef #: 45620692

Embedded sample

Embedded sample

Biological thin cross-section deposited on 7.3x7.3mm silicon square (diagonal=10.3mm).

Sample under 4-hole thin plate

Finger contacting the front electrode of the objective lens.

Thin samples (ex: biological sections) must be deposited on the POLISHEDside of the metallic cylinder !

NanoSIMS sNanoSIMS sample mountingample mounting 2/22/2

NanoSIMS 50

CORPORATE HEADQUARTERS

CAMECA 29 Quai des Grésillons92230 Gennevilliers - FranceTel.: +33 1 43 34 62 00Fax: +33 1 43 34 63 50Web-site: www.cameca.com

MAIN INTERNATIONAL OFFICESCAMECA Germany Bruckmannring 40, D-85764

Oberschleissheim - GermanyTel: +49 89 315 891-0, Fax: +49 89 315 59 21

CAMECA Instruments, Inc. 204 Spring Hill RoadTrumbull, CT 06611-1356 - U.S.A.Tel.: +1 203 459-0623Fax: +1 203 261-5506

CAMECA Instruments Japan K.K. 7F, Sumitomo Ikebukuro Ekimae Bldg.Higashi-Ikebukuro 1-10-1Toshima-ku, Tokyo 170-0013 - JapanTel.: + 81 35 396 0991Fax: + 81 35 396 0980

CAMECA Korea C°., Ltd. 4F, 1045-7 Youngtong-dongYoungtong-Ku, Suwon-city443-813 Kyunggi-Do - KoreaTel.: + 82 31 202 6344Fax: + 82 31 202 6347

CAMECA Taiwan Corp. Ltd. A2, 10F-6, No. 120, Sec. 2, GongDaoWu Rd.30056 Hsin Chu, Taiwan (R.O.C)Tel: + 886 3 5750099Fax: + 886 3 5750799

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