Development of a Charge-Multiplication CMOS Image Sensor Based on Capacitive Trench for Low-Light-Level Imaging

Area of Science:

• Semiconductor device physics
• Solid-state electronics
• Photonics and imaging technology

Background:

• Electron multiplication charge-coupled devices (EMCCDs) are crucial for low-light imaging.
• Capacitive deep trench isolation (CDTI) offers improved charge transfer efficiency and low dark current in CMOS devices.
• Adapting CDTI registers for electron multiplication presents unique challenges.

Purpose of the Study:

• To develop and evaluate a novel EMCCD using CDTI technology.
• To investigate the performance limitations of CDTI registers in electron multiplication mode.
• To propose and validate a design modification to enhance EMCCD functionality.

Main Methods:

• Implementation of a CDTI transfer register within a CMOS technology framework.
• Adaptation of the timing diagram for electron multiplication operation.
• Technology computer-aided design (TCAD) simulations in 2D and 3D for design validation.

Main Results:

• The CDTI transfer register demonstrated excellent charge transfer inefficiency (<10-4) and low dark current (0.11 nA/cm2).
• Electron multiplication mode revealed an unexpected increase in dark current.
• A modified design with an added electrode on top of the register successfully addressed the limitations.

Conclusions:

• The proposed design modification enables electron multiplication functionality while preserving the high transfer performance of the CDTI register.
• TCAD simulations indicate a highly promising structure for future EMCCD development.
• This advancement paves the way for more efficient and reliable low-light imaging sensors.