Secondary Ion Mass Spectrometry (SIMS)

Used for detection and quantification of trace level impurities and dopants in semiconductors, metals and insulating materials with high sensitivity and excellent depth resolution.  It is a powerful surface analytical technique which can detect, identify and quantify dopants and impurity elements in thin films and bulk materials with high sensitivity (ppm to ppb for almost all elements) and excellent depth resolution (<50 Å). A beam of primary ions with energies ranging from 1 to 10 keV is used to sputter or erode the sample surface. An oxygen primary ion beam is used for detection of electropositive elements (e.g., B, Na, K, Ca, transition metals). Alternatively, a cesium primary ion beam is used for detection of electronegative elements (e.g., H, C, N, O, Si, P, Cl, As). Positive or negative secondary ions formed during the sputtering process are extracted from the sample and analyzed by a quadrupole mass spectrometer. An additional liquid gallium primary ion beam may also be used to provide high lateral resolution (0.1 µm). An electron gun with a W-filament is used for imaging and charge compensation. Continuous sputtering of the sample surface allows monitoring elements of interest as a function of depth (Dynamic SIMS). Quantification of the trace elements is done through the use of standards, which include ion-implanted reference materials or samples of known bulk doping density.

MICROFABRITECH provides SIMS analysis using a Perkin-Elmer/Physical Electronics model 6600 Quadrupole based Dynamic SIMS system. The system offers High sensitivity, excellent depth resolution, and analysis of both bulk and thin film insulators without coating.

Some Applications

• Surface contamination analysis
• Ion implant distributions
• Contamination associated with ion implantation
• Dopant diffusion of ultra-shallow implants in Si
• Dopant diffusion in Si (B, As, P), GaAs (Si, Zn, C), etc
• Dopants, impurities and matrix elements in thin films (e.g., Al, Ti, TiN, TiSi2) and III-V semiconductor thin films
• Multiple quantum wells

Advantages

• Identification of all elements (H to U)
• Isotopic information
• High sensitivity (ppm to ppb for almost all elements)
• Excellent detection limits: (1014-1017/cm3 for Quadrupoles)
• Good depth resolution (<50 Å)
• Spatial resolution: 30 µm (depth profiling), 0.1 µm (Liquid Ga source)
• Quantitative with standards

Sample Requirements

• Vacuum compatible (»ð10-8 Torr)
• Semiconductors, conductors, and insulators without sample coating
• [0.5-5] cm in diameter
• Optimum thickness: <1 cm

For more information, contact Dr. Maggie Puga-Lambers: (352) 392-7973

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