The present invention relates to a method for providing a dielectric film
having a low dielectric constant that is particularly useful as an
intermetal dielectric layer. The method of the present invention deposits
a porous oxide gap fill layer from a process gas of ozone and TEOS. The
gap fill layer is deposited over a surface sensitive lining layer (as
opposed to a non-surface sensitive layer as is commonly done in the
industry) using deposition conditions that maximize the amount of carbon
that is incorporated into the gap fill layer and result in a porous
silicon oxide film. A typical SACVD ozone/TEOS gap fill layer has a carbon
content of about 2-3 atomic percent (at. %). An SACVD ozone/TEOS gap fill
layer deposited according to the present, however, has a carbon content of
at least 5 at. % and preferably has a carbon content of between about 7-8
at. %. Incorporating such a high carbon content into the porous SACVD gap
fill layer helps stabilize the layer so it is not susceptible to moisture
absorbtion and outgassing problems as is a lower carbon content porous
SACVD ozone/TEOS film. In one embodiment, the method of the present
invention increases the carbon content of the SACVD ozone/TEOS layer by
depositing the layer at a temperature of less than 400.degree. C. and
deposits a porous film over the surface sensitive layer by using a
relatively high ozone to TEOS ratio. Silicon oxide films deposited
according to the present invention have a dielectric constant of 3.2 and
below and exhibit good film stability. Such films are particularly useful
in sub-0.2 micron IMD applications.