PSD type transmission gate image sensor capable of reducing feed-forward effect and manufacturing method thereof

Abstract

The invention relates to an analog integrated circuit design, and aims to realize large full well and low electric leakage and improve the signal-to-noise ratio and the dynamic range of an image. Therefore, according to the technical scheme adopted by the invention, a PSD type transmission gate image sensor for reducing the feedforward effect comprises a photosensitive region PD, a transmission gate TG for controlling charge transfer from the PD to a storage node FD and a reset tube RST; when light irradiates a semiconductor, a part of light is absorbed by the semiconductor, when the absorbed energy is higher than the width of a silicon forbidden band, and an electron hole pair is generated; under the action of a built-in electric field, photo-induced electrons are collected by a depletion region in the PD; during reading, the TG is turned on, the TG under-gate channel is in a conducting state, photo-generated charges in the PD are transferred into the storage node FD, heavily-doped P-type doping is carried out on the transmission gate TG, low channel closing potential is obtained, and the barrier height of the PD and the channel is increased. The method is mainly applied to the design and manufacturing occasion of the CMOS image sensor.

Description

technical field [0001] The invention relates to the field of analog integrated circuit design, in particular to the field of image sensor pixel circuit design. Background technique [0002] With the rapid development of CMOS image sensors, their applications cover camera, industry, medicine, military and other fields, and people pay more and more attention to the performance of CMOS image sensors. Among them, Signal-to-Noise Ratio (SNR) and Dynamic Range (Dynamic Range, DR) are important parameters to evaluate the imaging performance of the sensor. The signal-to-noise ratio is the ratio of signal to noise, and the maximum signal-to-noise ratio is determined by the full well and the noise. Increasing the full well can improve the signal-to-noise ratio. The dynamic range is the ratio of the maximum signal to the minimum signal detected in the same frame. For a linear sensor, the maximum signal corresponds to the full well capacity of the pixel, while the minimum signal corres...

AI Technical Summary

Problems solved by technology

The working temperature and integration time can be adjusted according to the requirements of the index. Therefore, the current research focus is mainly to adjust the barrier height of the photodiode and the transmission gate by changing the potential distribution under the transmission gate and the gate. The existing methods to reduce the feedforward effect The method is to adjust the potential distribution by applying negative pressure on the transfer gate (Transfer gate, TG) or changing the doping of the channel under the TG gate. Adding negative pressure can directly pull down the potential under the gate, thereby increasing the PD and TG gate channel. The barrier height of the channel can effectively suppress the feedforward effect, but it also increases the power consumption of the chip, and adjusting the doping under the TG gate increases the complexity of the process

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