Patent ID: 11942505
Assignee: SHANGHAI IC R&D CENTER CO., LTD.
Field: Semiconductors (Electrical engineering)
Classification: CPC H | IPC H

Claim 7:
8. A preparation method for a pixel structure of a stacked image sensor, comprising:
providing a first silicon wafer, forming a first photodiode array on the front surface of the first silicon wafer, and forming a first isolation layer around and at the bottom of each the first photodiode in the first photodiode array, forming control transistors and a metal interconnect layer above the front surfaces of the first photodiode array and the control transistors;
providing a second silicon wafer, forming a second photodiode array on the front surface of the second silicon wafer, and forming a second isolation layer around and at the bottom of each the second photodiode in the second photodiode array;
flipping the first silicon wafer, and aligning the front surface of the first silicon wafer with a front surface of a third silicon wafer and then performing a bonding process;
thinning the back surface of the first silicon wafer until the first isolation layer at the bottom of the first photodiode is removed completely, so as to expose the bottom of the first photodiodes completely;
aligning the front surface of the second silicon wafer with the back surface of the first silicon wafer and then performing a bonding process;
thinning the back surface of the second silicon wafer until the second isolation layer at the bottom of the second photodiode is removed completely, so as to expose the bottom of the second photodiodes completely;
forming and filling TSVs in both the second silicon wafer and the first silicon wafer, connecting the lower ends of the TSVs with the control transistors on the first silicon wafer, and exposing the upper ends of the TSVs on the back surface of the second silicon wafer;
forming a PAD layer on the back surface of the second silicon wafer, connecting the PAD layer with the upper ends of the TSVs.