laser manufacturing technology
rhombus4
cleaning, ensure that yield is maintained even for the most
complex processes.
An advantage of such an approach is that no compromise
need be built in to the actual design – the best
semiconductor structure can still be independently used
for a waveguide, laser active region and modulator. We
believe this compares very favourably with the alternatives,
which use processes such as QWI (Quantum Well
Intermixing) or vertically coupled waveguide structures to
achieve multi-element functionality. The ‘etch and
regrowth’ methodology gives virtually complete flexibility in
design, as well as allowing smooth introduction of
improved processes.
Large compound semiconductor fab. costs are typically
several million dollars per quarter, so it is useful to ask at
what level the fab becomes ‘profitable’ to the company. A
reasonable ‘rule of thumb’ might be when the fab
supports revenue of five to ten times the overhead cost,
but as the level of functionality at the chip level is
enhanced, the effective ‘value’ of the chip within the (Above)
product significantly increases. Integrated
Tunable Laser
For the latest generations of components, such as tunable Mach Zehnder
transmitters , the costs are already favourable, and set to modulator chip
become increasingly so. We are now getting to the point for Tunable XFP
where the incremental cost of the chip fabrication is module testing
becoming dominated by materials and direct labour rather (Left) On-wafer
than overhead. test map of
tuneable lasers
There are perceived advantages to outsourcing in some
areas, such as process flexibility, as foundries must
support different processes and materials for a wide
range of customers. Initial entry costs are low, and capital
requirements for the user are minimal. Many of the
problems – such as design and IP protection can be
managed, provided appropriate controls and procedures
are put in place.
the materials and applications: the Zurich facility is used
The outsource model requires more emphasis on design for the fabrication of high power pump and industrial
IP, whereas insourcing enables more leverage from lasers as well as VCSELs based on GaAs; the Caswell
process IP and knowledge. For low volume and start ups, facility focuses mainly on InP based devices as well as
outsourcing is attractive; the barriers come in scaling this providing additional capacity for industrial lasers. Base
to global volume requirements the industry demands. material growth is by MBE exclusively for pump lasers
(Zurich) and by MOCVD (InP and GaAs) at Caswell.
Oclaro fabs....
Oclaro owns a number of fabrication sites, including The other Oclaro fabrication facilities are somewhat
facilities for Lithium Niobate, Thin Film filters, Liquid smaller scale, more specialist and largely independent of
Crystal (as part of the recent Xtellus WSS acquisition) the two major fabs, except in aspects of management and
and two major compound semiconductor fabs, at Zurich, best practice sharing. The availability of both InP based
Switzerland, and Caswell in the UK. and Lithium Niobate (LN) modulator technologies within
Oclaro is advantageous and cost effective, with the LN
The two compound semiconductor facilities differentiate in devices appealing as a ‘component’ play wheras InP is
January/February 2010 www.compoundsemiconductor.net 35
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