US 12,295,177 B2
Method for preparing pixel cell of CMOS image sensor
Lu Wang, Shanghai (CN); and Cuiyu Mei, Shanghai (CN)
Assigned to Shanghai Huali Microelectronics Corporation, Shanghai (CN)
Filed by Shanghai Huali Microelectronics Corporation, Shanghai (CN)
Filed on Aug. 18, 2022, as Appl. No. 17/890,376.
Claims priority of application No. 202111050256.X (CN), filed on Sep. 8, 2021.
Prior Publication US 2023/0073606 A1, Mar. 9, 2023
Int. Cl. H10F 39/00 (2025.01); H04N 25/75 (2023.01); H04N 25/77 (2023.01)
CPC H10F 39/014 (2025.01) [H04N 25/75 (2023.01); H04N 25/77 (2023.01)] 7 Claims
OG exemplary drawing
 
1. A method for preparing a pixel cell of a CMOS image sensor, comprising the following steps:
step 1, defining an N-type ion implantation area of a photodiode on a P-type semiconductor substrate by means of photolithography and etching, and performing first photodiode N-type ion implantation;
step 2, performing a photoresist dry etching descum process to increase a size of a photoresist open area, so that the N-type ion implantation area is enlarged, and performing second photodiode N-type ion implantation, wherein a depth of the second photodiode N-type ion implantation is less than the depth of the first photodiode N-type ion implantation;
step 3, removing the photoresist, forming a gate polysilicon layer on the semiconductor substrate, and forming a polysilicon gate of each MOS transistor of a CMOS pixel readout circuit by means of photolithography and etching;
step 4, removing the photoresist, and performing first photodiode P-type ion implantation by using the polysilicon gate as a mask, wherein the depth of the first photodiode P-type ion implantation is less than the depth of the second photodiode N-type ion implantation; and
step 5, depositing a spacer oxide layer, and forming a spacer of the polysilicon gate of each MOS transistor of the CMOS pixel readout circuit by means of photolithography and etching.