Performance and spatial sensitivity variations of single photon avalanche diodes manufactured in an image sensor CMOS process

• In this letter we present the results from a series of single-photon avalanche diode (SPAD) structures implemented in a commercial 0.18 μm CMOS process intended for CMOS image sensors. Variations without effect on the performance and variations that produced non-functional devices are described. Devices based on the P+/NWELL and deep-NWELL/P-EPI SPADs junctions were found to work well in this process. When biased for 10% QE the best 10 μm diameter P+/NWELL SPADs exhibited a DCR of about 1 kHz, whereas the DCR of the deep-NWELL/P-EPI SPADs was only 10 Hz under the same conditions. We also show that the former type exhibited local sensitivity variations within the SPADs ranging from a factor 4 at low excess voltage to 1.2 at an excess voltage of about 0.5 V. No significant sensitivity variations were found for the deep- NWELL/P-EPI SPADs, but they were found to exhibit significant sensitivity outside the central junction, contributing from 8.3 % at low excess voltage to approximately 70% at high excess voltage

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TEKNIK OCH TEKNOLOGIER  -- Elektroteknik och elektronik -- Annan elektroteknik och elektronik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Electrical Engineering, Electronic Engineering, Information Engineering -- Other Electrical Engineering, Electronic Engineering, Information Engineering (hsv//eng)

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