Patent ID: 11948965
Assignee: OMNIVISION TECHNOLOGIES, INC.
Field: Semiconductors (Electrical engineering)
Classification: CPC H | IPC H

Claim 19:
20. A method for fabricating a pixel cell, comprising:
simultaneously etching (i) a first region of a semiconductor substrate exposed by a small aperture of an apertured mask located on a surface of the semiconductor substrate to yield a shallow trench having a shallow bottom surface, and (ii) a second region of the semiconductor substrate exposed by a large aperture of the apertured mask to yield a deep trench having a deep bottom surface, in a direction parallel to the surface, a width of the large aperture in a first direction exceeding a width of the small aperture in the first direction;
the semiconductor substrate including a floating diffusion region and a photodiode region;
the shallow trench being located between the floating diffusion region and the photodiode region and extending into the semiconductor substrate from a front surface of the semiconductor substrate, a distance between the shallow bottom surface and the front surface defining a shallow depth of the shallow trench that exceeds a junction depth of the floating diffusion region relative to the front surface;
a deep trench located between the floating diffusion region and the photodiode region and extending into the semiconductor substrate from the front surface, a distance between the deep bottom surface and the front surface defining a deep depth, of the deep trench, that exceeds the shallow depth;
the distance defining the shallow depth being in a depth direction, the shallow trench and the deep trench being located between the floating diffusion region and the photodiode region in a first direction, the shallow trench being laterally displaced from the deep trench in a second direction that is perpendicular to the first direction, each of the first direction and the second direction being perpendicular to the depth direction.