The effect of an oxygen plasma exposure on the reliability of a Ti/TiN contact metallization

This article demonstrates that the exposure of a TiN barrier to an ex situ oxygen plasma results in a more stable TiN/AlSiCu interface up to temperatures of 600 °C as shown by the time-of-flight elastic recoil detection measurements. A quaternary phase diagram of the Al–Ti–O–N system was calculated in the range of temperatures between 450 and 550 °C and suggests that the stabilization of the TiN/AlSiCu interface is possible since oxidized TiN reacts with Al to form AlN, TiAl3 and Al2O3 at the interface. A Ti/TiN/(oxygen plasma exposure)/AlSiCu/TiN contact metallization in 1.2-μm-diam and 1.4-μm-deep straight wall contacts to 0.2-μm-deep N+ and P+ diffusions, to gate polysilicon as well as to capacitor polysilicon shows stable electrical results even after a [(450 °C, 60 min)+(500 °C, 60 min)+(550 °C, 60 min)] combined thermal stress.