Indium oxide diffusion barriers for Al/Si metallizations

Abstract

Indium oxide (In2O3) films were prepared by reactive rf sputtering of an In target in O2/Ar plasma. We have investigated the application of these films as diffusion barriers in 〈Si〉/In 2O3/Al and 〈Si〉/TiSi2.3/In 2O3/Al metallizations. Scanning transmission electron microscopy together with energy dispersive analysis of x ray of cross-sectional Si/In2O3/Al specimens, and electrical measurements on shallow n+-p junction diodes were used to evaluate the diffusion barrier capability of In2O3 films. We find that 100-nm-thick In2O3 layers prevent the intermixing between Al and Si in 〈Si〉/In2O3/Al contacts up to 650°C for 30 min, which makes this material one of the best thin-film diffusion barriers on record between Al and Si. (The Si-Al eutectic temperature is 577°C, Al melts at 660°C.) When a contacting layer of titanium silicide is incorporated to form a 〈Si〉/TiSi2.3/In 2O3/Al metallization structure, the thermal stability of the contact drops to 600°C for 30 min heat treatment.