Deposition Systems: Meeting the Demands
Vacuum deposition equipment must produce coatings with greater precision and uniformity.
Dr. Des Gibson
The key to growing
the market for vacuum deposition equipment is in meeting the demands that drive
it: higher throughput, enhanced automation and more precise control of layer thickness.
The focus of these demands includes dense wavelength
division multiplexers (DWDMs), phase-corrective coatings and gain-flattening filters.
Filter manufacturers want deposition equipment that can control layer thickness
to less than ±0.01 percent and that can coat wafers with diameters greater
than 6 in. — even up to 12 in. — with uniformity of less than ±0.02
to 0.1 percent. Reduced optical insertion loss and process times, which now vary
from 10 to 50 hours, also are being sought.
High-performance antireflection coatings
(>40 dB) with <0.1 percent thickness control are needed for the end facets
of laser diode bars and lithium niobate integrated optic devices, as well as flip
tooling for coating both ends of a device without breaking its vacuum.
Low-batch-size/fast-cycle-time coaters have had
an impact on technology developments. They provide automated operation for integrated
loading and handling systems, which are well-suited to deposition onto small-scale,
high-added-value components such as laser diode facets, fiber pigtails, gain-flattening
filters, launch lenses and DWDMs, and erbium-doped fiber amplifiers.
Another development that offers the
potential to increase deposition system throughput is dynamic masking of the coating
area to enhance thickness uniformity. Many companies also are developing high-deposition-rate
sputtering methods that benefit from the inherent rate stability. And real-time
control of the spatial distribution of the evaporation plume and increased use of
barrel sputter coater configurations offer a significantly larger usable area than
standard calotte tooling does.
The use of plasma/ion-assisted deposition
for “cold” processes is increasing in optical coating equipment, particularly
plasma-based sources, which provide wider and more uniform coverage than the ion
type. Reduced cycle times (thanks to the elimination of heat-up/cool-down time),
optically “shift-free” spectral performance and close-to-bulk optical
properties are all drivers for use of assist technology.
The use of plasma/ion-assisted deposition for “cold” processes is an increasing
trend in optical coating equipment.
Satis produces a high-output plasma
source with a throw distance >1 mA/cm2 at 500 mm that can achieve a reproducible
density of commonly used film-oxide materials such as titania, silica, tantala and
alumina at high deposition rates over extended areas (see figure). These sources
have been successfully used in box coaters as large as 1.5 m. Besides using assist
technology with new systems, retrofitting such plasma sources to existing deposition
systems is gaining in popularity.
Optical coating designs have become increasingly
complex because of the demands of new photonic products and applications. This trend
has led to the need for direct monitoring of the actual parts to achieve high precision.
Automation has also become a key requirement, not only to reduce operating costs,
but also for integrated loading, load-locks and handling systems that address enhanced
cleanliness issues within cleanroom environments.
In addition, the deposition systems
market is growing, with turnkey precision coating equipment providing full process
capability to companies that have minimal internal coating expertise. This trend
is motivated by the need to manufacture photonic devices within a cleanroom environment
and with integrated coating capability for logistics and device yield.
And, finally, volume optical coating
work has been moving into low-cost manufacturing environments in the Far East, particularly
in China, Vietnam and Thailand. This is affecting the deposition systems market,
with a number of coating machine suppliers emerging in that part of the world.
Meet the author
Des Gibson is sales and marketing director of
photonic products for Satis Vacuum Industries Vertriebs AG in Baar/Zug, Switzerland.
He has 20 years of industrial experience in deposition systems, optical coatings
MORE FROM PHOTONICS MEDIA