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Deposition Systems: Meeting the Demands

Photonics Spectra
Jan 2002
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.

Technology impacts

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.

Monitoring, automation

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 and optoelectronics.

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