ANALYSIS PHOTONIC INTEGRATED CIRCUITS
Bare photonic die characterisation setup
Manufacturing challenges On the fabrication side, there is still a perceived lack of information about updated and solid foundry capabilities, schedules and pricings. A lot of effort could still be made on process design kit (PDK) adoption and optimisation for generic fabrication processes, including reliable building block performances and tolerances. Moreover, delays are common and manufacturing guarantees are still low on multi-project wafer runs and, while photonic
foundries are improving here by providing fabrication reports and better tracking, this is still not widespread.
Packaging challenges
Packaging has always been acknowledged to be one of the main roadblocks to photonic integration within ICs and, unfortunately, this is still the case. The cost still needs to be brought down, both at the prototyping stage and when moving into production. Significant efforts are being made in this area, and characterisation packages, or demo boards, have appeared in recent years, where customers can at least validate proof-of-concept PICs and showcase early prototypes. Further work on package standards and design templates that adapt to them is necessary but, from a customer perspective, the most important information still lacking is clearer descriptions of capabilities, packaging options, and tolerances.
Photonic integrated circuit in InP technology @electrooptics |
www.electrooptics.com
Test challenges One of the most underestimated challenges is testing, either bare dies, wafers or packaged devices. At a production level, this would be the equivalent of the quality control stage, but most of the time, photonic integration projects require early functional testing, like bare die characterisation of building blocks and circuits,
complex optical and electrical measurements, and statistical sampling over many dies or wafer points. Hence, a higher degree of automation is still desirable to lower the testing cost and time, especially since the investment required at this stage is quite high on measurement equipment and instrumentation. Outsourcing the testing can prove very valuable to speed up the process and avoid heavy initial investments. Moreover, things like environmental qualification or certification for several industries (including telecom, space, and military) can represent significant challenges for some customers, as these are not as advanced as in electronic integration. Overall, the current challenges when trying to do business with photonic integration are the same as in any industry: cost escalation, production transfer, performance guarantees, and lead times. But once all these challenges are identified, and proper support is found to overcome them, any company can develop and produce disruptive PICs that can break into many markets and open new ones. l
VLC Photonics provides various solutions for integrated optics: consultancy and engineering studies, in-house optical chip design, characterisation and test, and complete prototyping through external manufacturing and packaging/assembly partners. The company, as a pure-play fabless design house, assists companies and researchers in their photonic integration projects, and collaborates with a wide network of foundries in all main material platforms.
www.vlcphotonics.com
OCTOBER 2016 l ELECTRO OPTICS 15
VLC Photonics
VLC Photonics
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