Annealing RIE Damage on Titanium Silicide Surface
Original Publication Date: 1989-Dec-01
Included in the Prior Art Database: 2005-Jan-29
During the opening of contact hole windows in a phosphor silicate glass layer by RIE (reactive ion etching), the chemical composition of the titanium silicide deposited on the surface changes. This change is due to the fact that after the etching of the phosphor silicate glass layer, the titanium silicide surface is exposed to CHF3 etch gas in the overetch phase. In this phase, the titanium silicide is differently affected, depending upon the dopant used (boron or phosphor). During the subsequent heat treatment in the ammonia oven (nitridation), titanium oxide is formed instead of the desired titanium nitride. This oxidation of the titanium silicide surface leads to high contact resistances and yield losses. Under the microscope, the change of the titanium silicide caused by the CHF3 etch gas is invisible.