Effect of the Ti/TiN bilayer barrier and its surface treatment on the reliability of a Ti/TiN/AlSiCu/TiN contact metallization

Abstract

The use of an AlSiCu/TiN bilayer for the metallization of 1.0-m-diam and 1.4-m-deep straight wall contacts to 0.2-m-deep n ϩ and p ϩ diffusions, results in a n ϩ /p Ϫ and a p ϩ /nϪ junction leakage lower than 10 pA even after nine heat treatments ͑60 min each͒ at 450°C. However, there is a very important degradation of the contact chain resistance statistics at small contact size. On the other hand, the use of a Ti/TiN bilayer barrier under the AlSiCu/TiN interconnect maintains a n ϩ /p Ϫ and a p ϩ /n Ϫ junction leakage lower than 20 pA and prevents the degradation of the contact chain resistance statistics after the nine heat treatments. It is finally demonstrated that a vent in nitrogen followed by a momentary air exposure of the Ti/TiN bilayer barrier results in larger contact resistance than a vent in nitrogen followed by a one hour long air exposure of the Ti/TiN bilayer barrier before the deposition of the AlSiCu/TiN interconnect.