A pixel unit structure and manufacturing method with increased floating drain capacitance

Abstract

The invention discloses a pixel unit structure for increasing suspended drain capacitance. The pixel unit structure comprises a photodiode, a transmission tube and a reset tube arranged on a substrate, wherein additional gates are arranged above the drain beyond a control gate of the transmission tube and / or above the drain beyond a control gate of the reset tube; the boundary of the additional gates extends to the space above shallow-trench isolation beyond the drain; the additional gates are isolated from the drain by virtue of a thin gate oxide layer so as to form additional gate and activeregion overlap capacitance, so that the capacitance of the suspended drain can be increased under the condition that the capacity area of the suspended drain is not increased, that is, the area of the photodiode is not decreased. The invention further discloses a manufacturing method of the pixel unit structure for increasing the suspended drain capacitance.

Description

technical field [0001] The invention relates to the field of image sensors, and more specifically, to a pixel unit structure and a manufacturing method capable of increasing floating drain capacitance. Background technique [0002] Generally, an image sensor refers to a device that converts an optical signal into an electrical signal. According to different manufacturing processes and working principles, image sensors can be further divided into charge-coupled device (CCD) and complementary metal-oxide semiconductor (CMOS) image sensor chips. [0003] Compared with traditional CCD sensors, CMOS image sensors have the characteristics of low power consumption, low cost and compatibility with CMOS technology, so they are more and more widely used. CMOS image sensors are now not only used in consumer electronics, such as miniature digital cameras (DSC), mobile phone cameras, video cameras and digital single-lens reflex (DSLR), but also in automotive electronics, monitoring, bio...

AI Technical Summary

Problems solved by technology

However, increasing the area will inevitably lead to a decrease in the photosensitive area of ​​the pixel unit, thereby affecting the sensitivity of the pixel unit.

At the same time, because in order to obtain a higher output voltage, the pixel unit usually uses a thick gate oxide of the IO tube, so the thickness of the gate oxide under the transfer tube is also difficult to change

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