Pixel structure of stacked image sensor and preparation method thereof

Abstract

The present invention discloses a pixel structure of a stacked image sensor and a preparation method thereof, by bonding processes to stack a first silicon wafer to a third silicon wafer up and down; wherein, a first photodiode array is set on the first silicon wafer located in middle, and a second photodiode array is provided on the second silicon wafer located above, and the surface of each the second photodiode in the second photodiode array is aligned and bonded correspondingly with the surface of each the first photodiode in the first photodiode array, so as to form a chip of the pixel structure of the stacked image sensor with a very deep junction depth, which is particularly suitable for near-infrared sensitization, and can effectively improve quantum efficiency in near-infrared wave bands; and by adopting a backlight technology, incident lights irradiating to photodiodes are not affected by the metal interconnect layers, both of sensitive and fill factor are high, especially for small-size pixels, which has very good photosensitive performance, so as to balance the near-infrared quantum efficiency and the small pixel size.