Laser Spike Annealing: A Novel Post-Porosity Treatment for Significant Toughening of Low-k Organosilicates

Laser thermal treatment of organosilicate coatings in a process characterized by extremely short dwell times and extremely high temperatures, generally referred to as laser spike anneal (LSA) appears to be a viable approach to post-porosity enhancement of mechanical properties. Exposure of organosilicates in both the dense and porous state to very high temperatures (500-1300 degC) for extremely short periods of time, ranging from 200 to 800 musecs, yielded increases in the modulus by a factor of 3-5times without adversely affecting the dielectric constant. Chemical analysis of the treated methyl silsesquioxane structure indicated significant changes in the chemical composition of the film as evidenced by the disappearance of the methyl infra-red absorption associated with methyl groups attached to silicon. However, this disappearance in the methyl absorption was not reflected by a concomitant decrease in the carbon content of the film as determined by Rutherford back scattering (RBS) measurements. RBS analysis yielded a chemical composition which could be represented empirically by Si
_x
O
_y
C
_m
H
_n
, the exact composition depending on the exact processing conditions