Automated measurement flow for PDK development in a 300 mm silicon photonics foundry

As silicon photonics-based circuit designs transition from lab to fab, an end-to-end automated measurement flow is required to address a unique combination of high flexibility in test conditions and high volume. This paper describes such a flow for process design kit (PDK) development in the state-of-the-art 300 mm CMOS-compatible silicon photonics foundry at the Albany NanoTech Complex in Albany, NY. Presenting details of this measurement flow will offer considerable cost and time savings to new users in this area. The measurement flow begins at the layout stage, where users can instantiate various combinations of pre-characterized padsets that contain DC/RF pads and optical couplers, which are compatible with the automated electro-optic setup used for measurements. These padsets are offered via two options: (1) a script-based layout builder tool or (2) a parametric cell in a “Measurement Design Kit” offering in a design automation platform, which is an analog to a PDK. Special marker layers are added to the padsets, whose coordinates are extracted after the layout is complete. The coordinates are then passed to fiber positioners on the semi-automated prober while performing measurements. Electro-optic measurements are performed across the wafer using vertical coupling, which is well-suited for large-scale measurements. The wafer is placed on a 300 mm prober with automated fiber positioners that can optimize optical coupling across six degrees of freedom. The electro-optic measurement setup is based on the Keysight Photonic Application Suite. It includes a tunable laser, polarization synthesizer, and multi-channel detectors that measure transmission in both TE and TM polarizations. A lowloss optical switch matrix is programmed to switch connections between lasers and detectors to 16 grating couplers in the padset. The entire measurement setup, including the prober and instruments, is driven using the Python-based SweepMe! automation framework, which is modular and allows for the easy creation of test plans.