Image sensor and manufacturing method thereof

The invention discloses an image sensor and a manufacturing method thereof, and the method at least comprises the following steps: S1, providing a substrate which is provided with a plurality of photodiode regions and isolation regions; s2, ion implantation is carried out on the substrate, so that a first well region is formed in the photodiode region, and a second well region is formed in the isolation region; s3, sequentially forming a gate oxide layer and a polycrystalline silicon layer on the substrate; s4, performing low-temperature heat treatment on the substrate so as to reduce metal impurity ions in the photodiode region; the temperature range of the low temperature ranges from 400 DEG C to 700 DEG C, and the heat treatment time ranges from 1 h to 20 h. According to the manufacturing method, the problem of white pixels can be greatly improved without excessively adjusting the ion doping level of the photodiode region and sacrificing more full well capacity, the image quality is improved, and the perfo