handbook of carbon, graphite, diamond and fullerenes

5.3 DLC Coatings in Lithography
Diamond-Like Carbon 353
X-ray lithography is necessary to produce submicron patterns and
gratings for integrated circuits (ICs). A major problem of this new technology
is the development of a suitable mask. This has been solved, at least
partially, by using DLC films (a-C;H) which have performed better than any
other materials. These films form the bottom-layer etch mask below an
electron-beam resist in a bilayer system. DLC is readily etched with oxygen
reactive-ion etching and has a low-level etch rate with the dry etch used for
the Si or GaAs substrates. The high mechanical integrity of DLC permits
high-aspect ratios. With this technique, patterns as small as 40 nm have
been transferred to the substrate.^ 3 '! 27 !
5.4 Miscellaneous DLC Applications
DLC coatings are found in the following applications:
• Biomedical: Coatings for hip joints, heart valves and
other prostheses. DLC is biocompatible and blood
compatible. 1281
5.5 Summary
• Biochemical: Coating for tissue culture flasks,
microcarriers, cell culture containers, etc.
• Acoustical: DLC-coated tweeter diaphragm for dome
speaker.^ 29 '
DLC coatings are already in production in several areas (optical and
IR windows) and appear particularly well-suited for abrasion and wear
applications due to their high hardness and low coefficient of friction. They
have an extremely smooth surface and can be deposited with little restriction
of geometry and size (as opposed to CVD diamond). These are
important advantages and DLC coatings will compete actively with existing
hard coatings such as titanium carbide, titanium nitride, and other thin film
materials. The major drawback of DLC is it lack of high temperature
resistance which may preclude it from cutting- and grinding-tool applications,
and limitations in thickness to a few microns due to intrinsic stresses.