Auger electron depth profiling of the CrAl2O3 metallization system

Auger electron spectroscopy (AES) technique has been employed successfully to study the formation of the CrAl2O3 interfaces. The results indicated that the interfacial region formed by deposition of metal Cr on Al2O3 substrate consists of a mixture, which is a double oxide of Cr and Al or two separated oxides. The metallic Al produced by reduction of the Al3+ ions due to the interfacial reaction was also detected. We suggest that the interfacial reaction occurs mainly by the charge transfer from the 3d electrons of Cr atoms to O 2p orbitals, whether the Al2O3 substrate is sapphire or alumina. The annealing at higher temperature (∼ 973 K) is favourable to promote the reaction between the surface oxygen and the initial few atomic monolayers of the deposited chromium. The chromium oxide was detected by AES at the interface, it is consistent with the strong CrO bonding. The results also showed that the change of the relative Auger peak-to-peak height (APPH (%)) of the Cr LMM group peaks and the APPH ratio for O KLLCr LMM group can be used as an index to identify the oxidation states of chromium at the CrAl2O3 interface. In this paper, the differences in chemical reactivity between those two substrates: sapphire and alumina, are discussed in detail.