Design and Characterization of Backside Termination Structures for Thick Fully-Depleted MAPS

Area of Science:

• Semiconductor Devices
• Radiation Imaging Technology
• CMOS Sensor Development

Background:

• Hybrid detectors are common for radiation imaging.
• Fully Depleted Monolithic Active Pixel Sensors (FD-MAPS) offer an alternative.
• Previous work demonstrated FD-MAPS feasibility using adapted 110 nm CMOS technology.

Purpose of the Study:

• To present the design of backside diodes for FD-MAPS.
• To characterize test devices and understand limitations.
• To improve FD-MAPS performance through optimized backside processing.

Main Methods:

• Fabrication of FD-MAPS using 110 nm CMOS with high-resistivity substrates and backside post-processing.
• Integration of p/n junction diodes on the detector backside.
• Electrical characterization of test diodes with varying guard ring configurations.

Main Results:

• Termination structures with guard rings effectively increased breakdown voltage.
• Breakdown voltage exceeding 400 V was achieved with 30 guard rings (6 μm pitch).
• Demonstrated feasibility of full depletion for substrates ≥ 300 μm thick.
• Good agreement between measured pixel characteristics and 3D TCAD simulations.

Conclusions:

• Backside processing with guard rings is effective for FD-MAPS.
• The developed FD-MAPS technology supports high-resistivity substrates for advanced radiation imaging.
• TCAD simulations accurately predict device behavior, aiding future design.