Using electrical resistance asymmetries to infer the geometric shapes of foundry patterned nanophotonic structures.

While silicon photonics has leveraged the nanofabrication tools and techniques from the microelectronics industry, it has also inherited the metrological methods from the same. Photonics fabrication is inherently different from microelectronics in its intrinsic sensitivity to 3D shape and geometry, especially in a high-index contrast platform like silicon-on-insulator. In this work, we show that electrical resistance measurements can in principle be used to infer the geometry of such nanophotonic structures and reconstruct the micro-loading curves of foundry etch processes. We implement our ideas to infer 3D geometries from a standard silicon photonics foundry and discuss some of the potential sources of error that need to be calibrated out. By using electrical measurements, pre-designed structures can be rapidly tested at wafer-scale, without the added complexity of optical alignment and spectral measurement and analysis, providing both a route towards predictive optical device performance and a means to control the geometry variation.