Single-photon avalanche diodes’ (SPADs) capabilities of detecting even a single photon with excellent timing resolution and compatibility with strong magnetic fields make them the most promising sensor for positron emission tomography imaging systems. With the advancements of silicon fabrication techniques, SPADs designed in standard planar complementary metal-oxide-semiconductor (CMOS) processes show competitive performance and a lower manufacturing cost. Additionally, CMOS SPADs have the potential for monolithic integration with other CMOS signal conditioning and processing circuits to achieve simple, low-cost, and high-performance imaging solutions. This work targets the design and optimization of SPAD sensors to improve their performance using low-cost standard CMOS technologies.
Firstly, a detailed review on the SPADs in recent literature is presented. Then, the random telegraph signal (RTS) noise is investigated based on n+/p-well SPADs fabricated in a standard 130 nm CMOS process. Through the measurements and analysis, the RTS noise of a SPAD is found to correlate with its dark count rate and afterpulsing. Next, we design n+/p-well SPADs with field poly gates to improve the noise performance. Furthermore, a SPAD pixel, consisting of a p+/n-well SPAD and a compact and high-speed active quench and reset circuit is designed and fabricated in a standard TSMC 65 nm CMOS process. The post-layout simulations show that this pixel achieves a short 0.1 ns quenching time and a 3.35 ns minimum dead time. The measurement results show that the SPAD pixel has a dark count rate of 21 kHz, a peak photon detection probability of 23.8% at a 420 nm wavelength and a timing jitter of 139 ps using a 405 nm pulsed laser when the excess voltage is set to 0.5 V. Due to the short quenching time, almost no afterpulsing is observed even at a low operating temperature of -35 °C. Finally, a new differential quench and reset (QR) circuit consisting of two QR circuits on both the cathode and anode to quench and reset the SPAD through both terminals is proposed to reduce the reset time, to increase the count rate, to reduce the afterpulsing and to reject the common-mode noise. / Thesis / Doctor of Philosophy (PhD) / Positron emission tomography (PET) imaging is a powerful tool for diagnosis and assessment of cancers and tumors in the clinical field. Due to their capabilities of detecting even a single photon, excellent timing resolution, and their compatibility with magnetic fields to build PET/MRI (magnetic resonance imaging) multimodal imaging systems; single-photon avalanche diodes (SPADs) become the most promising sensor technology for PET imaging applications. SPADs fabricated in standard complementary metal-oxide-semiconductor (CMOS) technologies allow for a lower manufacturing cost and present the potential to integrate with other CMOS circuits to form a complete imaging system. In this thesis, random telegraph signal noise in SPADs is investigated first. Then, the poly gate is used in the design of an n+/p-well SPAD to improve the noise performance. In addition, a compact and high-speed SPAD pixel is designed and fabricated using an advanced standard CMOS process. Thanks to the fast quench and reset circuit, the SPAD pixel achieves a very short quenching time and a high-count rate. Finally, a differential quench and reset (QR) circuit consisting of two QR circuits on both the cathode and anode to quench and reset the SPAD through both terminals is proposed and studied.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/26990 |
| Date | January 2021 |
| Creators | Jiang, Wei |
| Contributors | Deen, M. Jamal, Biomedical Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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