Hailed as one of the most promising industrial-production candidates, silicon photonics has long been expected to bring breakthroughs in very high speed data communications, telecommunications and supercomputing.

In 2012, the European Commission launched a 15-member PLAT4M project to build a Si photonics supply chain in Europe. The goal was to advance existing silicon photonics research foundries and seamlessly transition to pilot line operation and industrial manufacturing of products based on silicon photonics.

The supply chain is based on three different but complementary technology platforms of Leti, STMicroelectronics and imec, according to Leti.

Leti's 8,500m2 cleanroom facility includes a 200mm pilot line that enables fabrication of passives, detectors, modulators and integrated lasers with a focus on high-bandwidth devices. The project team developed a new Si-photonic platform based on a 310nm silicon film on top of an 800nm buried oxide (BOX) on a high-resistivity silicon substrate. Since the targeted applications for the project were O-band transceivers and receivers, most of the developed devices are suitable for 1310nm operations.

20170721_EETA_PLAT4M_01 (cr) Figure 1: The CEA-LETI R&D facility in Grenoble, based on 200mm pilot line, on which passives, detectors, modulators and integrated lasers can be fabricated, with a focus on high bandwidth devices. (Source: PLAT4M)

CEA-LETI has developed 3 PDKs which are dedicated to Multi Project Wafers (MPW) runs on this silicon photonics technology which is now offered via the brokers CMP and Europractice. Moreover, III-V Lab has designed and co-fabricated a state-of-the-art integrated hybrid III-V/Si transmitter using a wafer bonding technique on this platform.

Meanwhile, STMicroelectronics—the first 300mm wafer silicon photonics device manufacturer—developed another silicon photonics technology during the PLAT4M project to generate and nurture further application specific industrial nodes.

The technology platform creates an advanced photonic nanoscale environment and combines state-of-the-art CMOS foundry tools with the flexibility necessary to support R&D efforts. Collaboration with research partners such as CEA LETI and University Paris Sud have been devoted to advanced studies in power consumption management, optical excess loss reduction and higher data-rate transmissions using complex modulation formats, signal multiplexing and higher Baud-rate devices.

ST has also evaluated notions of device and circuit footprints toward Large System Integration (LSI).

In the context of PLAT4M, the participants chose a 4×25G transceiver as a Wavelength Division Multiplexing (WDM) data communication demonstrator to validate both LETI and ST R&D platforms. The device functionalities were evaluated for compatibility with the 100GBase-LR4 standard, implying a signal transmission over 4 channels, spaced by 800GHz around 1310nm window, one fibre out and one fibre in.

In the course of the PLAT4M project, imec has consolidated and further developed its silicon photonics technology platform ISIPP25G using its 200mm pilot line facilities located in Leuven to support industrial prototyping for various applications and markets.

20170721_EETA_PLAT4M_02 (cr) Figure 2: The imec R&D facility in Leuven, based on 200mm pilot line, enabling passives, detectors and modulators, with additional process modules optimized for sensing. (Source: PLAT4M)

The imec platform component portfolio has been expanded to specific devices for sensing and high power free space applications. The technology also supports state-of-the-art modulation and detection at 50Gb/s and beyond with a variety of modulator options (GeSi EAM, Si MZM, Si MRM) now offered under its ISIPP50G technology along with both edge and surface fibre coupling technology and a library of O-Band and C-Band high quality passive components.

The technology is accessible through imec's PDK, which is supported by software tools from several vendors including project partner PhoeniX Software. In collaboration with Mentor, a Siemens business, imec has also explored LVS verifications to reduce design errors and performed litho-friendly design analysis to improve the patterning predictability.

Using the imec technology with new processing steps, TNO has demonstrated a multi-channel ring resonator based sensor system. Polytec demonstrated the operation of Multichannel Laser Doppler Vibrometer. THALES has demonstrated an integrated FMCW LiDAR system with eight switchable output channels, enabling to scanning directions as well as a coherent beam combiner with 16 beams with linear operation up to a maximum input power of 26dBm. The thermal phase-shifter elements achieved a power efficiency of 10mW for a -phase shift.

imec also demonstrated new advances in its technology such as a very low loss silicon waveguide technology (~0.6dB/cm for a 220nm x 450nm waveguide) applying leading edge CMOS patterning technology developed in its 300mm pilot line with immersion lithography. It has also demonstrated a further reduction of thermal phase-shifter elements down to 4mW for a π-phase shift.

Unified design environment

The PLAT4M project has led to a qualitative leap of the design flow for silicon photonics, allowing the photonics community to design more complex and more robust circuits. Mentor and PhoeniX Software have worked closely together on an integrated electronics/photonics co-design workflow.

The supply chain includes EDA solutions such as Mentor's Pyxis and Calibre, which were extended to "understand" photonics. Interfaces were developed between these tools and Photonic IC design solution OptoDesigner from PhoeniX Software to create integrated design flows using the best practices from both photonics and electronics design. In addition, process design kit elements were developed for Mentor's Calibre DRC, Calibre LVS and Pyxis tools, incorporating new components, added models and fabrication information.

Packaging played a key role in the development of the project demonstrators. The skills and processes developed by Aifotec and Tyndall, advanced the development of the Silicon Photonic packaging toolkit. This toolkit establishes standardised packaging processes for optical fibres, active devices, electronic components and thermo-mechanical systems to ensure that PICs can be more easily packaged in a timely and cost-effective way. A design rule document was made available through EuroPractice by Tyndall and also implemented into PDKs for OptoDesigner.

"The consortium developed advanced technologies and tools by building a coherent design flow, demonstrating manufacturability of elementary devices and process integration, and developing a packaging toolkit," said Jean-Marc Fedeli, coordinator of the PLAT4M project. "The high level of maturity of the technology offered by these platforms makes them readily accessible to a broad circle of users in a fabless model."