Secondary Ion Mass Spectrometry

Secondary ion mass spectrometry (SIMS) is an important surface science technique that provides very high sensitivity for the detection of trace elements in solid samples, while also providing good spatial detail. The physical process involved in SIMS is similar to that of other surface analyzer techniques: the sample’s surface is probed with a highly collimated beam of particles or light, and detectors measure the response of the sample. In the case of SIMS, the probing beam is made of ions generated by an ion gun. Commonly, gallium ions are the particular species used in the gun. When the sample is bombarded by these ions, atoms in the sample are ionized and liberated from the surface. These secondary ions are then introduced into a mass spectrometer where the atomic composition of the sample can be measured.

There is typically a tradeoff between sensitivity and spatial resolution. Very roughly, SIMS provides spatial resolution of 1–100 microns, with the ability to detect atomic species down to part per trillion levels. As the ion gun scans across the surface, the instrument develops an image of the surface, with compositional information at every point. Most SIMS instruments use quadrupole mass analyzers, but there is also a market for time-of-flight instruments (TOF-SIMS).

SIMS instruments can be operated in two analysis modes, static and dynamic. In static SIMS, only the uppermost surface layers are examined. In dynamic SIMS (D-SIMS), an ion gun is used to sputter atoms off the sample, so that deeper layers of the sample can be analyzed. Thus, D-SIMS provides depth profiling information that can be of critical importance for laboratories studying thin films, semiconductor substrates and other advanced materials.

The leader in the SIMS market is Cameca, which was acquired by the Carlyle Group in April 2005 (see IBO 6/30/05). Later that year, Cameca also acquired the SIMS assets of Atomika from FEI (see IBO 7/15/05), which had acquired the company in 2002. Cameca’s largest competitor in the SIMS market is Ulvac-Phi, a company that resulted from the reorganization of what had previously been a joint venture of Physical Electronics and the Japanese company Ulvac. The SIMS business is now part of Ulvac-Phi, which has been wholly owned by Ulvac since 2003 (see IBO 4/30/03).

After Cameca and Ulvac-Phi, ION-TOF is the largest SIMS vendor. As its name suggests, ION-TOF manufactures TOF-SIMS instrumentation. ION-TOF released an automated SIMS system, the 300 R, in 2006, and the company reports that 2006 was its most successful year. Another automated system, the MiniSIMS HDA from Millbrook Scientific, was first shipped in November 2006. Other SIMS vendors include Hiden Analytical, Shimadzu and Varian. In total, the 2006 market for SIMS was approximately $60 million.

SIMS at a Glance:

Leading Suppliers

• Cameca

• Ulvac-PHI


Largest Markets

• Semiconductors

• Metals

• Academia

Instrument Cost

• $200,000–$2 Million

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