Etching Burried Oxide at the Bottom of High Aspect Ratio Structures

Plasma based dry etching is a key
process widely used in micro-fabrication today. In
this article, we look at the challenges involved in the
anisotropic etching of buried SiO2 layers at the
bottom of high aspect ratio structures on SOI wafers.
We present our etch results that show the
limitations of using a process with radio frequency
(RF) substrate bias. This is followed by results
obtained with a newly developed dielectric etch
process based on a pulsed low frequency (LF) bias
which makes it possible to etch through even relatively
thick buried oxide layers. Finally we present
an application in which this newly developed process
was used.