How Buried Channel CCDs Move Data Deep Inside Silicon Chips

A foundational 1974 invention that improved how computer chips store and move electrical charges by keeping them away from messy surface defects.

What it covers

This patent describes a way to move electrical charges through the middle of a semiconductor material rather than along its surface. By creating a 'buried channel'—a specific potential energy path deep inside the silicon—the device prevents charges from getting trapped by surface defects, which were a major problem in early chip designs. The device uses a series of electrode plates on the surface to pull these charges along this internal path, essentially acting like a bucket brigade for electrons. This allows for much faster and more reliable movement of data within the chip.

What it doesn't cover

• —Does not cover charge-coupled devices that store or transfer charge directly on the semiconductor surface.
• —Does not cover memory structures that rely on traditional floating-gate transistors for long-term storage.
• —Does not cover devices lacking the specific ohmic contact means required to bias the storage medium for internal depletion.

The clever bit

Instead of fighting surface defects, the inventors moved the 'highway' for electrons into the bulk of the material, using an electrical bias to create a potential energy 'valley' that keeps charges safely away from the surface.

Why it matters

This invention was critical for the evolution of digital imaging and high-speed signal processing. By solving the charge-trapping problem, it enabled the creation of high-quality Charge-Coupled Device (CCD) sensors, which became the standard for early digital cameras and video recorders. It essentially allowed engineers to build more reliable and sensitive silicon-based sensors.

Real-world examples

• 1.Digital camera image sensors
• 2.Early digital video camcorders
• 3.High-speed analog signal delay lines