(45d) Topographically Selective Deposition of Dielectrics Using Ion Implantation

High
quality thin films are important for diffusion barriers, adhesive buffer
layers, etch stops and sacrificial layers in integrated circuits, MEMS and
NEMS. Achieving maximum performance requires great precision in the fabrication
technique. Advancements in technology and miniaturization of these devices
require uniform, conformal coatings of complex, high aspect ratio features
(steps, trenches, grooves and pores) on the nanoscale. Today’s device
fabrication is based on ‘top-down’ processes with multiple photolithography and
etch steps which serve as the main bottleneck for device downscaling.
Area-selective atomic layer deposition (AS-ALD) which combines surface
modification and ALD in a ‘bottom-up’ approach to nanopatterning provides a
promising alternative.

Previous
studies have found that selectivity in AS-ALD relies on a change in hydrophobicity
whereby more hydrophobic surfaces were found to cause an extended nucleation
delay. Most reports on AS-ALD typically exploit this property, using tightly
packed self-assembled monolayers (SAMs), which increase hydrophobicity, to
modify the substrate surface. There are several challenges associated with the
use of SAMs including degradation under ALD conditions, lengthy deposition
times, and a limited number of suitable chemistries. To overcome these
challenges, there is a need for new methods of surface modification to make
AS-ALD a more viable technique.

In
this presentation, a novel approach in AS-ALD will be described, whereby the
substrate surface (Si) is modified through fluorocarbon implantation. It has been
shown that through this process, a thin (~1.5 nm) fluorocarbon layer forms on
the Si surface, making it hydrophobic (WCA ~104°). In a previous study by this
group, this method was found to be successful in blocking Pt ALD up to 500
cycles. In this work, the implanted substrate’s ability to block ALD of
dielectrics (Al₂O₃, ZnO, HfO₂) is evaluated. Substrates
with two and three dimensional features are also investigated. Nucleation on
the implanted substrate (or regions) is investigated and compared to a non-implanted
reference surface. Several techniques including, atomic force microscopy,
scanning and transmission electron microscopy, X-ray photoelectron spectroscopy
and Auger electron spectroscopy are used for analyses and characterization. The
results show that there is reduced oxide growth on the more hydrophobic, implanted
substrate.  The potential and limitations
of the ion implantation approach to AS-ALD will be discussed.