Global exposure pixel unit, capacitor structure and preparation method

Abstract

The invention provides a global exposure pixel unit, a capacitor structure and a preparation method. Through forming a first capacitor structure, a second capacitor structure and a third capacitor structure at a longitudinal direction, and connecting the three capacitor structures together in a parallel connection manner, on the basis of not increasing the area of the capacitor structure of the global exposure pixel unit, the storage capacitance value of the capacitor structure is increased, and the readout noise is reduced; and meanwhile, the area of a photodiode photosensitive area of the whole global exposure pixel unit is not affected, and the performance of a device is improved.

Description

technical field [0001] The invention relates to the field of semiconductor technology, in particular to a global exposure pixel unit, a capacitor structure and a preparation method thereof. Background technique [0002] An image sensor refers to a device that converts optical signals into electrical signals. Generally, large-scale commercial image sensor chips include 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, biotechnology and medical fields. . [0004] The pixel unit of the CMOS image sen...

AI Technical Summary

Problems solved by technology

The capacitance value depends on the area of ​​the overlapping area between the polycrystalline upper plate and the N-well lower plate. Therefore, to increase the capacitance value, it is necessary to increase the area of ​​the capacitor on the silicon substrate. Due to the MOS capacitance and the photosensitive The photodiode is located in the silicon substrate. If the area of ​​the storage capacitor is increased, the photosensitive area of ​​the photodiode needs to be reduced, which will reduce the sensitivity of the pixel unit. Therefore, in order to ensure the photosensitive area of ​​the photodiode area in the pixel unit, the area of ​​the storage capacitor is limited.

Images