Discovery of

Sputtering

In 1852, William Robert

Grove, born in Wales in

1811, was studying the

electrical conductivity

of gases when he

noticed the deposition

of metallic particles on

a glass tube.

First Commercial SIMS

J.J. Thomson, born in England in

1856, observed at the Cavendish lab,

the emission of positive ions from a

metal surface induced by primary

ions bombardment.

First SIMS

Prototype

Richard Franz Karl

Herzog, born in Austria

in 1911, published an

article based on the

thesis of his student F.P.

Viebock at the University

of Vienna describing the

first SIMS prototype.

Discovery of Emission

of Secondary Ions

From the early 60’s, R.F.K. Herzog (center) had

moved to US and teamed up with Helmut Liebl

left), born in Germany in 1927. Together they

produced the IMS101 at GCA Corporation in

Massachusetts.

1910

1949

1967

1852

1968

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HOW DID WE GET HERE?

CUSTOMER SERVICE WORKFLOW

HOW DOES IT WORK?

Principles of Secondary Ion Mass Spectrometry (SIMS):

In parallel, in France, licensing

the work of Raimond Castaing,

born in Monaco in 1921, and

several of his students including

Georges Slodzian initially at the

University of Toulouse and then

Paris, Orsay, CAMECA released

its first SIMS equipment.

SMI300

Unlike neutral particles (atoms, molecules, or clusters), ions (charged particles) can be

spatially controlled to form a beam (called ion beam) with controlled kinetic energy, flux

density, and spot size.

When a solid sample is irradiated by an ion beam with keV energy, fragments of surface

material are ejected. Those fragments include: electrons, neutral atoms or clusters, ions or

charged clusters. Only 1 – 5% of the ejected particles are ions. SIMS analyzes the charged

particles (atomic or cluster ions) in the ejected materials.

There is a general correlation between the primary ion beam type and the ions ejected:

Positively charged primary ions will favor the production of negative ions and negatively

charged primary ions will favor the production of positive ions. In SIMS, these ions are then

accelerated, focused, and analyzed by a mass spectrometer.

A high energy ion beam is focused on to the target sample surface and ejects: neutral or

ionized particles and electrons. These ejected ions are called secondary ions and are

collected by ion lenses and filtered according to each particle’s mass to charge ratio (mass

analyzer), then projected to detectors such as electron multiplier, Faraday cup, or CCD.

Operation Modes:

There are two types of SIMS operation depending on the area of interest – Static SIMS and

Dynamic SIMS.

1. Static SIMS is highly surface sensitive technique for molecular characterization of surfaces.

Relatively low flux (< 1E12 atoms/cm2) ion beam may either defocus or raster scan across

the sample for analysis. To avoid artifacts, the analysis beam should be a different element

from those in the sample. Higher-level analysis can reveal significant groups of higher masses.

2. Dynamic SIMS is used to study thin films along a depth. It is usually equipped with

oxygen (O) and cesium (Cs) sputtering ion beams to enhance, respectively, positive and

negative secondary ion intensities. The ejected ionic species are continuously analyzed

while the surface is sputtered by the ion beams. The detection limit of SIMS is very low

(typically ppm or ppb level), that is why SIMS is often used to understand the in-depth

distribution of trace elements like dopants or contaminants in semiconductor applications.

Analyzer Types:

SIMS equipment is usually defined by its analyzer type – magnetic, quadrupole, and

time-of-flight (ToF) analyzers.

1. Magnetic sector SIMS uses a magnetic sector field to separate the secondary ions

by their mass-to-charge ratio. It is usually used in high speed dynamic mode for

selected species. Non selected elements are not analyzed since they do not reach

the detector.

2. Quadrupole mass analyzer separates the masses by resonant electric fields which

allow only the selected masses to pass through the quadrupole. Again, only the chosen

species will be measured.

3. Time-of-Flight (ToF) SIMS separates the ions in a field-free drift path according to their

velocity. Since all ions possess the same kinetic energy, the velocity and therefore

time-of-flight varies according to the mass of each ionic species. This measurement

is achieved by using pulsed ion beams. As it is the only analyzer type that can detect

all generated secondary ionic species simultaneously, ToF SIMS is used for applications

that require thorough analysis. It is the standard analyzer for static SIMS.

Strength and Limitations:

1. Strength:

a. Strong lateral and vertical sensitivity.

b. Very low detection limit which can go down to ppb level and allows the analysis of

isotopic ratios

c. In-situ analysis that eliminates the need for complex sample preparation

d. One of the few metrologies that can analyze hydrogen

2. Limitations: As SIMS only analyzes ion species from the ejected particles, which depends

on many parameters such as primary beam type, ionization probability of components,

and surface’s electronic states, the elemental ratio detected doesn’t reflect the actual

composition of the sample. Therefore, SIMS results can’t be quantitative and can only

be used for the relative comparison of samples within a batch or for the trace element

profile analysis.

SIMS is widely used in most of materials science and engineering including biotechnology areas.

1. Application areas:

a. Semiconductor: dopant species and profiles, diffusion profiles, and trace element analysis

b. Light Emitting Diode (LED): Compositional and structural analysis of p-n layer

stack, analysis of interface and polymer contaminant identification in packaging

c. Geoscience: Mainly to analyze trace elements and isotopes with high mass

resolution analyzer

d. Bioscience: Analysis of hydrogen (H) and physiologically important elements such as Na,

K, Mg, and Ca. Ion imaging of elements in areas as large as 250 micrometers in diameters

with a lateral resolution of 0.5 micrometers. Three-dimensional analysis of sequential layers.

Secondary Ion Mass Spectrometry

State-of-the-art equipment: Both magnetic sector and ToF-SIMS

Advanced analysis including organic molecule identification and 3D SIMS

Integrated reports with analysis of measured data

Seamlessly combined with other metrology such

as Auger/XPS, RBS, nano-FTIR, and others

Industry’s most affordable pricing

WHY CHOOSE OUTERMOST TECHNOLOGY FOR SIMS?

Figure 1. Ion beam and surface interaction (www.cameca.com/products/sims/technique)

Figure 2. Typical forward geometry SIMS/ion microprobe configuration (Cameca IM 6f) showing

CAMECA IMS 7f-Auto

APPLICATIONS

1. Negative primary beam source

2. Positive primary beam source

3. Electrostatic lens for primary beam

4. Sample stage and sputtering

5. Electrostatic sector

6. Magnetic sector

7. Collectors

8. Ion imaging detector

1 2

5 6

Figure 3. Various examples of data from SIMS technology:

a. Example of static SIMS showing some of components on sample surface

(http://publish.uwo.ca/~hnie/tof-sims.html)

b. Example of dynamic-SIMS analysis of GaAs/AlGaAs superlattice

(https://www.ulvac-phi.com/en/products/tof-sims/nanotof2/)

c. PC1 vs. PC2 scores plot generated using Principal Component Analysis (PCA)-Assisted ToF-SIMS,

which is based on static SIMS data. PCA assisted ToF-SIMS is used to identify large molecules.

(Analytical chemistry 2014, DOI: 10.1021/ac500059a)

d. Example of 3D ToF-SIMS bio-imaging – Rat kidney cells generated based on PCA assisted ToF-SIMS

(Biointerphases 10, 018902 (2015))

Example Data from Various Applications: