Paper AS-TuA1
XPS, TEM, and SIMS Analysis of FIB Bombarded Surfaces Over the Range 500 eV to 30 keV

Tuesday, October 16, 2007, 1:40 pm, Room 610

Focused Ion Beam (FIB) instruments are known for the ability to provide material removal with a lateral resolution less than 10nm using a Ga+ beam. FIB capabilities continue to improve with low energy performance that allows routine use of glancing angle 2kV Ga+ beams for final polishing of TEM specimens. The lower energy reduces the penetration of gallium into the material under study and minimizes sample damage.¹ It is now routinely possible to reduce the energy of the Ga+ beam to 500eV. Previous work has shown that low energy Ga+ impinging at normal incidence results in Ga deposition.² There is also TEM evidence indicating that the use of Ga+ for glancing incidence polishing at energies below 2 keV does not further reduce surface damage in Si, but rather creates a Ga rich region since the sputter yield at these energies drops to a value less than 1.³ An FIB was used to sputter craters into (100) Si using normal incidence Ga energies from 500eV to 30keV. XPS and SIMS analyses were performed on these craters to determine the Ga surface concentrations and depth distributions at these energies. From 30keV down to 2keV, a decreasing Ga penetration was noted. For the SIMS analyses below 2keV, a surface effect was observed in the SIMS depth profiles which may be the result of an enhancement of silicon secondary ion yield. It my be that glancing incidence polishing at Ga+ energies below 2keV will not result in additional reduction of surface damage. However, the low energy FIB capabilities can provide a means for site specific deposition of Ga when the low energy Ga impinges at normal incidence.

¹L. Giannuzzi, R. Geurts, J, Ringnalda, Microscopy and Microanalysis Proceedings 11 (Suppl 2) 2005, p.828
²D.H. Narum and R.F.W. Pease, J. Vac. Sci. Technol. B6(6) (1988) p. 2115
³L. A. Giannuzzi, B. Van Leer, J. Ringnalda, Microscopy and Microanalysis Proceedings (2007).