Imaging systems with backside illuminated near infrared imaging pixels

摘要

An imaging system may include an image sensor having backside illuminated near infrared image sensor pixels. Each pixel may be formed in a graded epitaxial substrate layer such as a graded n-type epitaxial layer. Each pixel may be separated from an adjacent pixel by an isolation trench formed in the graded epitaxial layer. The isolation trench may be a continuous isolation trench or may be formed from a combined front side isolation trench and backside isolation trench that are separated by a wall structure. A buried front side reflector may be provided that reflects light such as infrared light that has passed through a pixel back into the pixel, thereby effectively doubling the silicon absorption depth of the pixels.

主权项

1. An image sensor, comprising:
a graded n-type epitaxial substrate layer; a plurality of photodiodes formed in the graded n-type epitaxial substrate layer; a plurality of isolation trenches in the graded n-type epitaxial substrate layer that separate adjacent photodiodes; a reflective layer; and a dielectric stack on the reflective layer, wherein the reflective layer is interposed between the plurality of photodiodes and the dielectric stack.