The etch depth during trench over via etch of a dual damascene structure
in a dielectric film stack is controlled to be the same over the dense
area and the open area of a substrate and solve micro-loading problems.
The trench etch process is adapted to include a forward micro-loading
etching process and a reverse micro-loading etching process using two
etch chemistries together with the inclusion of a dopant material layer
or an organic fill material layer during the deposition of the dielectric
film stack. In one embodiment, etching of trenches over vias is switched
from forward micro-loading to reverse micro-loading once etching of the
dielectric film stack is reached at a predetermined location of a dopant
material layer. In another embodiment, etching of an organic trench
filling material layer is performed in a reverse micro-loading process
followed by etching the dielectric film stack in a forward micro-loading
process.