Benchmarking the Thermal Impact of 2.5-D/3-D Copackaged Optics on Si Photonic Devices

Abstract

The ever-increasing demand for data and internet usage has put a strain on data center infrastructure. Optical I/O (OIO) promises to meet these demands, but this requires dense (2.5-D or 3-D) electronic-photonic integration and advanced packaging schemes. In this article, a thermal modeling study is presented for two advanced copackaged optics (CPOs) scenarios. First, a 2.5-D OIO case is considered (OIO2.5D), and second, a 3-D OIO case is considered (OIO3D). Computational fluid dynamics (CFD) simulations are carried out to accurately determine the cooling performance of Si μ channels that act as a liquid-cooled cold plate. A convective heat transfer coefficient (HTC) of 7⋅104 W/m 2⋅ K is extracted and used as a boundary condition for the thermal simulations. With this heat sink performance, the thermal wall of the system is investigated, and it is found to be very sensitive to the XPU power map: 823 W (CPU) and 1146 W (GPU). The thermal impact of this high-power XPU on the photonic layer is then benchmarked for both OIO2.5D/OIO3D. Thermal finite element simulations reveal strong thermal crosstalk from XPU to photonics: ΔTOIO2.5D=10 K and ΔTOIO3D=60 K, as well as strong thermal gradients ∇TOIO2.5D=0.9 K/mm and 0.03 K/ms, ∇TOIO3D=12 K/mm and 1.78 K/ms. These crosstalk and thermal gradient results are of high importance in photonic and electronic circuit design, as they determine the requirements for the thermal tuning of the ring-based photonic devices.