Abstract

While conventional silicon photonic (SiP) waveguides achieve high data rates with low loss, they can only be placed on top of the chip surfaces horizontally. In this article, we present a design approach for multimode chip-to-chip interconnects with similar low-loss and high-bandwidth density properties as SiP waveguides. The state-of-the-art fabrication of optical through silicon via (OTSV) requires conventional back end of line (BEOL) processing with an additional step: metal coating lowers the loss of air-filled TSVs. Alternatively, the TSV is converted into a polymer waveguide by filling of low-loss polymer (Ormocore) to achieve <0.1 dB optical power loss over 380 μm distance. A 3D multimode optical interconnect is measured at 40 Gbit/s with the bit error rate (BER) <10⁻¹² at 1550 nm wavelength. The proposed solution supplies a new path for 3D integration of optical waveguides capable of delivering high-speed data within 3D stacked chips.

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