APPLICATION OF SAMPLE ROTATION TO SECONDARY ION MASS-SPECTROMETRY DEPTH PROFILING OF ALUMINUM METALLIZATION

Aluminum films sputter-deposited on silicon have been analyzed using secondary ion mass spectrometry with sample rotation during O2+ ion bombardment. Sample rotation prevented bombardment-induced topography formation and associated loss of depth resolution. Analysis of silicon and boron ion implants into aluminum showed that, compared with the unrotated sample results, rotation did not significantly affect the implant shape, but dramatically improved the characterization of the interface at the bottom of the aluminum layer. For the analysis conditions used, silicon sputtered at approximately twice the rate for aluminum. Sample rotation allowed the correct sputtering rate to be applied to the layer and substrate and thereby provide an accurate depth scale that was not possible for the poorly defined interface without rotation. Aluminum films deposited on silicon at ambient temperature were shown to have an absence of silicon near the aluminum/silicon interface, whereas deposition at 300-degrees-C results in a silicon gradient as the interface is approached. Boron was detected below the 1 part-per-million atomic level using sample rotation, and boron at the aluminum/silicon interface was clearly defined.