Modeling, design, and demonstration of 2.5D glass interposers for 16-channel 28 Gbps signaling applications

This paper describes the modeling, design, and demonstration of high-speed differential transmission lines on a 130μm thin glass interposer with two re-distribution layers (RDL), line lengths of 1-50mm, and turn radii of 0.15-8mm for 16-channel signal transmission at 28 Gbps per channel. Next generation photonic systems such as 400 Gigabit Ethernet (400 GbE) require low power and low loss channels between photodetectors and trans-impedance amplifiers (TIA) or between laser arrays and driver ICs. Glass, with low dielectric constant and loss tangent, has higher electrical performance and channel power efficiency compared to silicon interposers. Furthermore, low surface roughness and high-dimensional stability of glass enable finer lithographic dimensions and higher interconnection density during large panel processing compared to organic interposers. Interconnection of optical and electrical ICs on 2.5D glass interposers provides the best combination of electrical and optical signal performance. For 400 GbE modules, a 16-channel bus at 28 Gbps per channel is required for communication to the backplane. Electrical modeling and simulation was performed to arrive at an appropriate design for the 16×28 Gbps I/O interface on a two-metal layer glass interposer. An ultra-thin 130μm glass interposer was fabricated using low-cost, double-side panel processing providing for a lower cost, higher performance solution compared to silicon interposers.