Jc. Chiou et al., DIELECTRIC DEGRADATION OF CU SIO2/SI STRUCTURE DURING THERMAL ANNEALING/, Journal of the Electrochemical Society, 143(3), 1996, pp. 990-994
The impact of Cu on the dielectric SiO2 layer was studied using a Cu/S
iO2/Si metal oxide semiconductor capacitor and rapid thermal annealing
(RTA) treatment. With the RTA treatment, no chemical reaction was obs
erved up to 900 degrees C; however, dielectric degradation occurred fo
llowing RTA at 300 degrees C for 60 s and became worse with the increa
se of annealing temperature. The interface-trap density at the SiO2/Si
interface also increased from 5 x 10(10) to 5 x 10(13) eV(-1) cm(-2)
after 800 degrees C RTA treatment. The RTA anneal introduced a large n
umber of positive Cu ions into the dielectric SiO2 layer. Under bias-t
emperature stress, Cu ions drift quickly in the SiO2 layer and may dri
ft across the SiO2/Si interface and enter the Si substrate. With the u
se of 1200 Angstrom thick TiN and TiW barrier layers, respectively, th
e dielectric strength of the Cu/(barrier)/SiO2/Si structures was able
to remain stable up to 500 and 600 degrees C.