Composition analysis of the insulating barrier in magnetic tunnel junctions by grazing angle of incidence RBS

Spin dependent tunnel junctions (Si/Al2O3/Ta/CoFe/AlNx/CoFe/Ta) were studied with grazing angle of incidence Rutherford backscattering spectrometry experiments using a 1.6 MeV He+ beam. While the sensitivity to light elements is too small to detect the N directly, the thickness and composition of the AlNx insulating barrier can be obtained by carefully simulating the signal of the Al and of two CoFe layers, which can be separated. From the observed Al signal the corresponding energy loss can be calculated, and the extra energy loss required to obtain the observed CoFe layer separation is assigned to the N. Eventual oxidation in the AlNx layer during film deposition can be further identified and quantified by analysing a similar tunnel junction, but deposited on a DLC substrate. A depth resolution of 25 Å at the CoFe layers ensures a highly precise measurement of this complex magnetic system.