Impact of TSV Mechanical Stress on Silicon Waveguides Using Phase Shift Interferometry

To overcome the bandwidth and latency limitations of electrical links, the next breakthrough in high performance computing and data center performance will come through the use of silicon photonics technology thanks to Co-Packaged Optics (CPO) and Optical Network-on-Chip (ONoC) systems. These technologies involve the co-integration of integrated silicon photonic devices and Through Silicon Vias (TSV). This study investigates the mechanical stress induced by by$10 \mu \mathrm{m}$diameter and$100 \mu \mathrm{m}$deep copper filled TSVs on the waveguides of a Mach-Zehnder interferometer (MZI). Based on a dedicated analytical model, the optical phase shift measurement has been analyzed and an effective index variation of$0.9 \times 10^{-3}$was found. This stress measurement approach will be discussed with respect of its perspectives and limitations. This study can lead to improvements in the co-integration density of silicon photonic elements in 3D packaging architectures.