An air bridge is a small, elevated conductor that is suspended above the surface of the die. These bridges are typically used to connect different parts of the integrated circuit (IC). Their purpose is to cross over other circuit elements without making contact with the surface, thereby avoiding electrical shorts and minimizing any interference with underlying components.
Purpose
Air bridges are primarily used to route electrical signals across different areas of the IC where conventional planar connections would introduce unwanted interference, increased parasitic, or shorts. By raising the bridge above the surface and placing air between the surface and the bridge, the signal pathway is effectively isolated from the underlying components of the die, preserving signal integrity.
What is it made of?
Air bridges are usually composed of metallic conductors fabricated using materials such as aluminum (Al) or gold (Au). They are supported by pillar-like structures at the endpoints.
What are they mainly used in?
Air bridges are mostly used in RF and microwave circuits, where avoiding or reducing parasitic capacitance and inductance is critical for maintaining high signal fidelity. They are also used in analog and high-speed digital circuits to optimize efficiency by mitigating signal degradation.
How are they fabricated?
The fabrication of air bridges involves a multi-step photolithography process. The first step is creating the pillar structures on the wafer. Then, the metallic conductor is deposited, and a sacrificial layer used during the process is removed to create the suspended bridge.
Lean about how Die Sorting or Die Bonding is done for devices with Air Bridges. Click Here
