Sg. Lee et al., Stress behavior of high density plasma chemical vapor deposition oxide deposited on a metal-patterned wafer, JPN J A P 1, 37(12B), 1998, pp. 6965-6969
A high density plasma chemical vapor deposition (HDPCVD) oxide was used as
an inter metal dielectric (IMD) due to its good gap-fill properties for com
pensating the tensile stress of Al metal layers. When the HDPCVD oxide was
deposited on a metal patterned wafer, however, the oxide showed tensile str
ess. In order to understand the mechanism of the characteristic stress beha
vior of the HDPCVD oxide on a metal patterned wafer, the change in magnitud
e of the wafer bow was measured as a function of oxide thickness, and was m
odeled quantitatively using the density of metal patterns and the stress ch
ange of the metal film. In the model, the oxide deposited between metal lin
es was assumed to have tensile stress due to the relatively high shrinkage
of the neighboring metal pattern. When the deposited HDPCVD oxide thickness
was thinner than that of the metal film, only the stress of the lower part
s of the metal film, which was connected to the oxide, could affect the cha
nge of the wafer bow value. When the deposited oxide thickness was greater
than that of the metal film, the stress of the oxide above the metal film w
as assumed to be compressive. Using the above assumptions and a simple math
ematical model, the change in magnitude of the wafer bow was calculated and
compared with experimental results. The calculated data were in good agree
ment with the experimental values.