A vertical grid cmos image sensor and its manufacturing method

Abstract

The invention provides a vertical grid CMOS image sensor and a manufacturing method thereof, a transfer tube located on the epitaxial layer, a side of the transfer tube, and a photodiode in the epitaxial layer; the vertical grid of the transfer tube extends into the epitaxial layer and extends to the photodiode The depth where it is located; the reset transistor located on the epitaxial layer and on the other side of the transfer transistor; the epitaxial layers on both sides of the gate of the reset transistor are respectively provided with N+ regions; one of the N+ regions adjacent to the transfer transistor forms a floating diffusion point; The area of ​​the vertical gate of the transfer tube close to the photodiode is convex, and the area close to the floating diffusion point is concave. The invention forms a convex surface that is easy to collect near the photodiode area, and a concave surface that is easy to form an electron aggregation effect near the floating diffusion point, and can collect electrons in the largest area, and transfer them concentratedly when moving to the floating diffusion point, reducing losses. Thereby realizing the overall improvement of electrons from the multifaceted nature of transfer to the aggregation of collection.

Description

technical field [0001] The invention relates to the field of semiconductor manufacturing, in particular to a vertical gate CMOS image sensor and a manufacturing method. Background technique [0002] CMOS image sensors have developed rapidly in the past ten years, and are now widely used in mobile phones, computers, digital cameras and other fields. In order to meet market demand and integrate more pixel units per unit area, the pixel size of CMOS image sensors has been gradually reduced from 5.6mm to 1.0mm. However, the reduction of the pixel size cannot simply be equivalent to the reduction of the size of the photodiode (Photodiode) in all directions, which is due to the limitation of the effective full well capacity (FWC) of the photodiode. If the size is too small to store enough electrons, the image quality will be severely degraded. [0003] The basic structure of a traditional 4T CMOS image sensor is as follows: figure 1 As shown, there are photodiode (PD), transfer...

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Problems solved by technology

[0004] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a vertical gate CMOS image sensor and its manufacturing method, which is used to solve the problem that the vertical gate uses a planar sidewall structure in the prior art. After receiving electrons, The potential of the entire plane is uniform, and the potential at the same height becomes a separate area after transfer, which cannot realize the problem of effective transfer of electrons

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