Design and Characterization of a Burst Mode 20 Mfps Low Noise CMOS Image Sensor

Area of Science:

• Solid-state physics
• Electrical engineering
• Materials science

Background:

• CMOS image sensors (CIS) are crucial for digital imaging applications.
• Existing CIS technologies face limitations in speed, noise, and conversion gain.
• Need for advanced CIS architectures to meet growing demands for high-performance imaging.

Purpose of the Study:

• To develop a novel ultra-high speed, high conversion-gain, low noise CIS.
• To implement charge-sweep transfer gates in a standard 180 nm CIS process.
• To optimize photodiode geometry and gate structure for enhanced performance.

Main Methods:

• Utilized charge-sweep transfer gates for rapid charge transfer (<10 ns).
• Optimized photodiode geometry to improve light sensitivity and reduce noise.
• Reduced floating diffusion capacitance through advanced gate structure design.
• Implemented in a standard 180 nm CIS process without modifications.

Main Results:

• Achieved ultra-high speed with charge transfer time below 10 ns.
• Demonstrated a high conversion gain of 183 µV/e-.
• Attained the lowest reported noise level of 5.1 e- rms.
• Successfully designed, taped-out, and characterized a proof-of-concept CIS.

Conclusions:

• The novel CIS architecture with charge-sweep transfer gates offers significant performance improvements.
• Optimized photodiode geometry and gate structure are key to achieving low noise and high conversion gain.
• This technology advances the capabilities of CMOS image sensors for demanding applications.