How to Use Air-Gaps to Insulate High-Voltage Semiconductor Chips

A design for semiconductor chips that uses empty air-filled trenches to provide better electrical insulation for high-voltage transistors without needing complex filling materials.

What it covers

This patent describes a way to isolate high-voltage transistors on a chip by surrounding them with a trench containing an air-gap. Instead of filling the entire trench with a solid insulating material, which can be difficult and expensive to do perfectly, the process uses an insulating film to cover the device and the trench in a way that leaves an empty space inside. This air-gap acts as a highly effective electrical barrier. The design ensures that the side of the trench at the bottom of the air-gap touches the semiconductor substrate directly, creating a robust isolation structure that prevents electrical leakage between components.

What it doesn't cover

• —Does not cover semiconductor devices that use solid dielectric materials to completely fill the isolation trenches.
• —Does not cover designs where the air-gap does not extend through the specific semiconductor layers defined in the manufacturing process.
• —Does not cover transistors that are not surrounded by a trench in a plan view.

The clever bit

The innovation lies in using the deposition process of the insulating film to intentionally create an air-gap that is trapped within the trench, turning a potential manufacturing defect into a functional, high-performance insulation feature.

Why it matters

In power electronics, managing high voltages on a tiny chip is a major challenge. If transistors are not properly isolated, they can interfere with each other or break down. This patent offers a simpler, more cost-effective way to achieve high-voltage isolation by leveraging the natural insulating properties of air, which helps manufacturers produce more reliable power-management chips for automotive and industrial applications.

Real-world examples

• 1.Power management integrated circuits (PMICs)
• 2.High-voltage lateral MOS transistors in automotive control units