CMOS single-photon avalanche diode specific to long-wave-band weak light

Abstract

The invention provides a CMOS single-photon avalanche diode specific to long-wave-band weak light. According to the specific structure, a deep N well is manufactured on a P type substrate; next, a P type heavily doped region is manufactured in the deep N well; a PN junction is formed by a P+ layer and the deep N well to be used as an avalanche multiplication region; the P+ region is surrounded bya lightly doped P well to be used as a protection ring; and after incident light comes to a device, the deep N well region in a medium electric field strength is absorbed, and the generated photon-generated carriers move towards an avalanche multiplication region of a strong electric field region. Electron holes generated by light of relatively long waveband are formed in a relatively deep position of the device, so that the light signals can be detected effectively by the deep N well; by taking the deep N well / P substrate as a shielding diode, diffusion of the substrate photon-generated carriers to the PN junction can be prevented, thereby reducing influence of diffusion of substrate slow photon-generated carriers to the response speed of a photoelectric detector; and the absorption efficiency of the device in a long waveband can be improved.

Description

technical field [0001] The invention belongs to the technical field of photoelectric detection and relates to the structure of photoelectric devices, in particular to the design of a CMOS SPAD photoelectric device with high detection efficiency for long-wave weak light. Background technique [0002] Long-wavelength light can reduce cell damage and penetrate deeper into tissues. Therefore, research on improving the sensitivity of detectors in the infrared and near-infrared bands is of great significance in improving the quality of bioluminescent lifetime imaging and optical tomography. [0003] Avalanche photodiode (Avalanche Photodiode, APD) is a solid-state photoconductive device with a p-n junction operating under reverse bias. The principle of avalanche multiplication is: the incident light is absorbed in the depletion region of the reverse-biased p-n junction, and converted into electron-hole pairs. These primary electron-hole pairs drift under the action of a strong ele...

AI Technical Summary

Problems solved by technology

Although the STI guard ring has a relatively high fill factor, due to the direct contact between the active region of the APD and the STI, free carriers enter the sensitive region of the detector, resulting in a large noise in the dark count rate, which seriously restricts the detection of weak light by the detector. field development

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