product review
Secondary Ion Mass Spectrometry From the geological past to the biological future. Judith Handley
“I
f it ain’t broke, don’t fix it” seems a fit description of secondary ion mass spectrometry (SIMS). This technique had been tweaked and modified enough between its inception in the 1950s and the previous Analytical Chemistry review in 1996 (683 A–687 A) that there is little that is new. Greg Gillen of the National Institute of Standards and Technology says that the instruments have reached a “fairly sophisticated” level. SIMS instruments are highly sensitive and capable of analyzing practically any ionizable element from both inorganic and organic samples, down to low parts-per-billion levels. The technique is used primarily in the semiconductor industry, although Peter Todd of Oak Ridge National Laboratory is among those who believe SIMS will become increasingly important for biological applications by providing information about trace elements, isotopes, and molecular composition. The main functions of SIMS are depth profiling and imaging. Gillen characterizes depth profiling as SIMS’s “bread and butter.” This application typically uses dynamic-mode SIMS—a process that mixes up the sample “like a blender.” On the other hand, imaging, which requires mapping the distribution of an element or molecule on a surface, uses the “gentler” static mode. “Static SIMS imaging is most often used for molecules because they’re more susceptible to degradation,” notes Gillen. This product review recapitulates some
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product review
Table 1. Representative SIMS instruments. Product
LTFSIM S-100
SIM S4500,SIM S4600
SHRIM P II
SHRIM P RG
Com pany
Atom Sciences 114 Ridgeway Center Oak Ridge, TN 37830 865-483-1113
Atomika Instruments Bruckmannring 40 D-85764 Oberschleissheim Munich, Germany 49 89 315891-0
Australian Scientific Instruments 111-113 Gladstone St. Fyshwick, Canberra ACT 2609, Australia 612 6280 7570
Australian Scientific Instruments 111-113 Gladstone St. Fyshwick, Canberra ACT 2609, Australia 612 6280 7570
URL
www.atom-sci.com
www.atomika.com
www.anutech.com.au/asi/
www.anutech.com.au/asi/
Approxim ate price (USD)
400,000–500,000
1,000,000
1,800,000
2,100,000
Applications
Static SIMS, surface imaging, depth profiling
Dynamic SIMS/depth profiling of Static analysis for isotope geoimplants, analysis of layer systems chemistry, geochronology, trace elements, depth profiling, raster ion imaging
Static analysis for isotope geochemistry, geochronology, trace elements, depth profiling, raster ion imaging
Prim ary ion source
Dual filament electron impact, 5-keV Ar+ source
O, Cs, Ga
Duoplasmatron
Duoplasmatron
Vacuum cham ber features
500 l/s turbomolecular pump (TMP) on main chamber, sample loadlock with four-compartment transfer area pumped by 60 l/s TMP
For conventional samples up to 4 in. (SIMS4500), for wafers up to 300 mm (SIMS4600), ultrahigh vacuum down to the low 10–1 torr range, electron gun
Four-sample vacuum lock, two-sample analysis chamber, x-y-z sample positioning, cryo pump for hydride reduction
Four-sample vacuum lock, two-sample analysis chamber, x-y-z sample positioning, cryo pump for hydride reduction
Quadrupole
Forward geometry, double focusing, magnetic sector
Reverse geometry, double focusing, magnetic sector
M ass analyzer TOF, reflectron available
M ass range
1–5000 u (higher masses with optional high-voltage detector)
1–250 u (350 u and higher as an option)
1–350 u
1–350 u
M ass resolving pow er
m /⌬m >800 at 41 and >2200 at 430
1/800
~13,000, abundance sensitivity ~2 ⫻ 10–8 at 1 mass unit for uranium oxide
~50,000, abundance sensitivity 1 nm/decade, Cs and O beam energy down to 150 eV for ultrashallow layers, free selection of primary ion beam angle (vertical to glancing), queued mode for 7 d/24 h with one operator
Optimized for trace isotope analysis, high sensitivity at high mass resolution, Köhler focusing for uniform primary beam density, relatively simple ion optics and operation
of the SIMS operating principles presented in the previous review and pools the thoughts of SIMS experts about what may lie ahead. Representative SIMS systems and additional components are summarized in Tables 1 and 2, respectively. Readers are encouraged to contact
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ETP active film electron multiplier, ETP active film electron multiplier, Keithley 6430 electrometer Keithley 6430 electrometer
manufacturers for more comprehensive information.
The works The basic principle of SIMS is that when a primary ion beam strikes a surface, it transfers energy to particles within the
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Labview custom software on PC, high-speed fiber-optic communications
Optimized for very high resolution trace isotope analysis, high sensitivity at very high mass resolution, Köhler focusing for uniform primary beam density, dynamic mass-dependent refocusing
sample and causes “sputtering”—the ejection of positive, negative, and neutral secondary ions. The particles ejected from the sample in the secondary beam may be positive, negative, or neutral. An electric field directs secondary ions to a magnetic-sector, quadrupole, or time-
product review
Table 1. Representative SIMS instruments (continued). Product
IM S 3f–6f,NanoSIM S 50
SIM S W orkstation
TOF-SIM S IV Series
TOF-SIM S 300
Com pany
Cameca Instruments 103 Boulevard Saint-Denis BP 6 92403 Courbevoie Cedex France 203-459-0623 (U.S.)
Hiden Analytical 75 Hancock Rd., Ste. H Peterborough, NH 03458 888-964-4336
ION-TOF GmbH Mendelstrasse 11 D-48149 Muenster Germany 49 251 980 1636
ION-TOF GmbH Mendelstrasse 11 D-48149 Muenster Germany 49 251 980 1636
URL
www.cameca.fr
www.hidenanalytical.com
www.ion-tof.com
www.ion-tof.com
Approxim ate price (USD)
Not available
From 300,000
850,000 (depending on configuration)
1,100,000 (depending on configuration)
Applications
Static and dynamic SIMS, depth profiling and imaging
Static and dynamic SIMS, Both static and dynamic SIMS, static and dynamic secondary ion depth profiling, 3-D analysis, ion neutral MS (SNMS) mapping
Both static and dynamic SIMS, depth profiling, 3-D analysis, ion mapping
Prim ary ion source
Oxygen, cesium, duoplasmatron
Choice of metal ion, inert gas ion, or fast atom bombardment guns
Field emission source (Ga, In), electron impact source (O2, Ar, Xe, SF6), thermal ionization source (Cs)
Field emission source (Ga, In, Au), electron impact source (O2, Ar, Xe, SF6), thermal ionization source (Cs)
Vacuum cham ber features
Titanium sublimation with ion or TMP
14-Port domed ultrahigh vacuum analysis chamber with sample manipulators, load-lock transfer mechanism and large viewport
Oil and cooling water-free pumping system, horizontal and groundpotential sample stage configuration, sample size up to 200 mm, five-axis manipulator (x, y, z rotation, tilt)
Oil and cooling water-free pumping system, horizontal and groundpotential sample stage configuration, sample size up to 300 mm, five-axis manipulator (x, y, z rotation, tilt), laser interferometer
Triple quadrupole SIMS and SNMS combined
Reflectron-type, full mass resolution and full transmission simultaneously
Reflectron-type, full mass resolution and full transmission simultaneously
300 u, 500 u, 1000 u
1 to >10,000 u
1 to >10,000 u
Better than 1 amu over entire mass range
>14,000
>14,000
M ass analyzer TOF and magnetic sector
M ass range
1–25,000 u
M ass resolving pow er Detector(s)
Hardw are/ softw are
Options
Special features
Electron multiplier
Seven-decade positive- and nega- Secondary electron detector and tive-ion counting secondary ion detectors: microchannel plate/scintillator/photomultiplier tube type Windows-based 32-bit software platform with integral raster con- PC under Windows 2000; data retrol and SIMS imaging capabilities duction software for imaging, profiling, and 3-D analysis; high mass resolution spectra library Choice of primary guns, residual gas analyzers, and bolt-on Temperature-controlled heating components and cooling in load-lock and analysis chamber (–130 °C, +600 °C), customized sample preparation chambers on-line, vacuum connection to other techniques Positive- or negative-ion analysis, Low footprint workbench, analysis low-energy acceleration-deceler- chamber designed in two sections Parallel mass detection, modular ation system for duoplasmatron includes split flange to enable fu- design open to retrofits, patented avoids space-charge effects, ture upgrades and easier chamber burst mode, sample viewing by post-acceleration system encleaning two cameras, raw data stored hances multiplier performance, for retrospective analysis, flexieucentric rotating stage for IMSble for customized configuration 3f–6f improves depth resolution and sample handling (five-axis manipulation)
Secondary electron detector and secondary ion detector are both microchannel plate/scintillator/ photomultiplier tube type PC under Windows 2000; data reduction software for imaging, profiling, and 3-D analysis; high mass resolution spectra library Temperature-controlled heating and cooling in load-lock and analysis chamber (–130 °C, +600 °C), customized sample preparation chambers on-line, vacuum connection to other techniques Parallel mass detection, modular design open to retrofits, patented burst mode, sample viewing by two cameras, raw data stored for retrospective analysis, flexible for customized configuration and sample handling (five-axis manipulation)
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product review
Table 1. Representative SIMS instruments (continued). Product
M C 300 Chem icalM icroscope
ADEPT-1010
TRIFT-III
Com pany
Ionwerks 2472 Bolsover, Ste. 255 Houston, TX 77005 713-522-9880
Millbrook Instruments, Ltd. Blackburn Technology Centre Challenge Way, Blackburn, BB1 5QB, U.K. 44 1254 699606
Physical Electronics, Inc. 6509 Flying Cloud Dr. Eden Prairie, MN 55344 952-828-6100
Physical Electronics, Inc. 6509 Flying Cloud Dr. Eden Prairie, MN 55344 952-828-6100
URL
www.ionwerks.com
www.millbrook-instruments.com
www.phi.com
www.phi.com
Approxim ate price (USD)
350,000
100,000–200,000
Applications
Combined TOF SIMS, direct recoil Static, dynamic, and imaging ion scattering, and MS of recoiled SIMS for research and QC ions applications
Prim ary ion source
15-keV Pulsed alkali ions
6-keV Ga+
O2, Cs, and Ga liquid metal ion gun Ga liquid metal ion gun, Cs and O2 dual source column, Ar gas option gun
Vacuum cham ber features
Attaches to standard analytical chambers, but more commonly used in thin-film growth chambers for surface analysis during processing at pressures up to 50 mtorr
Single standard mains, electrical socket required for operation, base pressure
