Introduction
In digital circuits, insulating dielectrics
separate the conducting parts (wire
interconnects and transistors) from one
another. As components have scaled
and transistors have gotten closer
and closer together, the insulating
dielectrics have thinned to the point
where charge build up and crosstalk
adversely affect the performance of
the device. It is this reduction in scale
which drives the need for insulating
materials with lower dielectric constant.
A ‘low-k’ material is one with a small
value for dielectric constant relative
to silicon dioxide (SiO2)—a former
dielectric of choice. The dielectric
constant of SiO2 is 3.9. This number
is the ratio of the permittivity of SiO2
divided by permittivity of vacuum,
SiO2/0,where 0 = 8.854x10-6pFμm.
There are many materials with lower
dielectric constants, but few of them
can be suitably integrated into a
semiconductor manufacturing
process [1].