Image sensors with stress adjusting layers

An image sensor, comprising:

• a substrate with a front side surface and a back side surface opposite to the front side surface;
• an anti-reflective coating (ARC) layer disposed on the back side surface of the substrate;
• a dielectric layer disposed on the ARC layer;
• a metal layer disposed on the dielectric layer;
• a stress adjusting layer disposed on the metal layer,
• wherein the stress adjusting layer comprises a silicon-rich oxide layer, and
• wherein a concentration profile of silicon in the stress adjusting layer and a concentration profile of oxygen atoms in the stress adjusting layer are non-overlapping and different from each other;
• and
• an oxide grid structure disposed on the stress adjusting layer.

A semiconductor structure, comprising:

• a metallization layer disposed on a front side surface of a substrate;
• a high-k dielectric layer disposed on a back side surface of the substrate;
• a stress adjusting layer disposed on the high-k dielectric layer, wherein the stress adjusting layer comprises a silicon-rich oxide layer with a silicon-to-oxygen concentration ratio profile having a decreasing slope from a bottom surface to a top surface of the stress adjusting layer;
• a pixel grid structure disposed on the stress adjusting layer;
• and
• a pad structure disposed on the metallization layer and in the substrate.