Complementary Metal-Oxide-Semiconductor Transistor (CMOS) image sensor and production method thereof

Abstract

A Complementary Metal-Oxide-Semiconductor Transistor (CMOS) image sensor comprises a photodiode, a shifting transistor, a reset transistor, a first floating node and a second floating node which are arranged in a semiconductor substrate and an isolation structure used for device electric isolation. The photodiode is provided with at least two zones, namely a first zone and a second zone, having different indium doping concentrations, and the indium doping concentration of the first zone located at the far end of the shifting transistor is smaller than that of the second zone located at the near end of the shifting transistor. At least two-time ion injection at different angles is adopted, and an internal electric field E pointing from the second zone to the first zone is formed in the photodiode through the shielding effect of ion injection, so that photoelectron transmission speed is improved, the number of photoelectrons detained in the photodiode is reduced, photoelectron collection efficiency of the photodiode is improved, and image delay or information losing is reduced.

Description

technical field [0001] The invention relates to the technical field of semiconductors, in particular to a CMOS image sensor and a preparation method thereof. Background technique [0002] CMOS image sensor (CMOS Image Sensor, CIS) has obvious advantages over existing charge coupled device (Charge Coupled Device, CCD) by virtue of its manufacturing process and general integrated circuit standard process flow compatibility. CMOS image sensors do not have the inherent defects of large size, high power consumption, and poor compatibility in CCD technology. Instead, they can make full use of existing processes and equipment, and integrate with associated processing circuits, with a high degree of system integration. In addition, compared with CCDs, CMOS image sensors have the advantages of small size, low power consumption, high speed, and low cost, and have been widely used in photography and camera products. [0003] Traditional active pixels use photodiodes as image sensing d...

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Problems solved by technology

[0008] The present invention is aimed at the prior art, the dark current in the traditional 3T structure limits the detection limit and dynamic range of the image sensor; in the 4T structure, the electrons in the photodiode cannot be completely transferred to the floating node caused by the junction distribution problem in the pinning diode defects such as image delay to provide a CMOS image sensor

[0009] Another object of the present invention is to aim at the prior art, the dark current in the traditional 3T structure limits the detection limit and the dynamic range of the image sensor; Defects such as image delays transferred to floating nodes provide a fabrication method for CMOS image sensors

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