Definition: BSPDN

(BackSide Power Delivery Network) The latest method of building the layers on a chip to accommodate ever-increasing AI applications. Instead of both power and signal at the top, which has been the approach for decades, only the signal lines remain at the top while the power lines are placed at the bottom.

As transistors get smaller and more are packed per square millimeter, power and signal on the same plane causes interference and connection bottlenecks. By separating them, each wiring section is better optimized for its purpose. The power reaches the signal layer by tunneling vias (see below). In 2021, Intel announced its BSPDN approach (see Intel 18A), and TSMC and Samsung followed in 2024.

Flip the Wafer and Make It Thinner
BSPDN is a radical change in chip manufacturing adding new steps and weeks to completion. After the transistors and signal lines have been built, the wafer is actually flipped over and made thinner. The vias and power lines are then added. See chip and chip manufacturing.

Better Resource Organization

Separating power and signal allows for better organization of both. Higher frequencies are obtained, and power leakage is reduced. TSVs (through-silicon vias), which connect the power and signal lines, are considerably narrower than traditional tunnels (see via).