Photoelectric diode structure and method for making the same

Abstract

The invention provides a method of preparing photoelectricity diode, the method includes providing a basis, and adulteration area is at the basis, besides, dielectric layer, the first polysilicon layer are formed on the basis. And an opening is formed to expose part of surface of adulteration area, then, the second polysilicon layer are formed above the first polysilicon layer and in the opening. And, the second polysilicon layer is patterned to form lead wire, the first polysilicon layer is patterned to form gate electrode, at last the source electrode and drain electrode are formed.

Description

technical field [0001] The invention relates to a photodiode structure and a manufacturing method thereof, in particular to a photodiode applied to an active pixel sensor and a manufacturing method thereof. Background technique [0002] An active pixel sensor (active pixel sensor, APS) is a common solid-state image sensing element. Since the active pixel sensor includes complementary metal oxide semiconductor elements, it is also called a CMOS image sensor, which is manufactured using a traditional semiconductor process, and has the advantages of low manufacturing cost and small element size, making the CMOS image sensor existing. The trend of gradually replacing the charge-coupled device (CCD). In addition, CMOS image sensors also have the advantages of high quantum efficiency and low noise (read-out noise), so they have been widely used in electronic products such as personal computer cameras (PC cameras) and digital cameras (digital cameras). [0003] A general active p...

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Problems solved by technology

[0005] However, the lattice structure of the surface of the photo-sensing region 108 of the photodiode 100 in the prior art is easily damaged by high-dose N dopant implantation.

Furthermore, in the process of making subsequent contact plugs (contact plugs), the etching process for making buried contacts (buried contacts, BCs) is likely to damage the surface of the doped region 120, and when the titanium (Ti) in the contact plugs Compounds such as titanium silicide (TiSi) will be produced after metal components and silicon in the substrate interact

All of the above situations will generate a large amount of leakage current, which will increase the noise and reduce the photosensitive effect of the photodiode.

[0006] Furthermore, because the PN junction depth of the light sensing region 108 of the photodiode 100 in the prior art is relatively deep, when the photodiode 100 is irradiated by short-wavelength light (for example: blue light), it will be affected by the short-wavelength light The penetration depth of the chip is relatively shallow, which in turn makes the photocurrent induced by the PN junction of the photodiode 100 to short-wavelength light relatively small, thus causing the photodiode 100 to have poor photosensitivity to short-wavelength light.

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