Formation of buried color filters in a back side illuminated image sensor with an ONO-like structure

A method of fabricating a semiconductor image sensor device, comprising:

• providing a substrate that includes a pixel region, a periphery region, and a bonding pad region, wherein the pixel region contains a plurality of light-sensing pixels, the substrate having a first side and a second side opposite the first side;
• bonding the first side of the substrate to a carrier substrate;
• thinning the substrate from the second side after the bonding;
• forming a plurality of light-reflective structures over the second side of the substrate after the thinning, wherein the light-reflective structures partially define a plurality of openings that are each aligned with a respective one of the pixels;
• coating a first layer on each of the light-reflective structures;
• coating a second layer on the first layer, wherein the second layer and the first layer have different material compositions;
• filling the openings with a third layer, wherein the third layer and the second layer have different material compositions;
• removing portions of the substrate in the bonding pad region;
• thereafter forming a bonding pad in the bonding pad region;
• hereafter etching the third layer, wherein the second layer serves as a first etching-stop layer during the etching of the third layer;
• and
• thereafter etching the second layer, wherein the first layer serves as a second etching-stop layer during the etching of the second layer.

A method of fabricating a semiconductor image sensor device, comprising:

• bonding a first side of a device substrate to a carrier substrate, the device substrate including a pixel region and a bonding pad region, wherein the pixel region contains a plurality of light-sensing elements;
• thinning, after the bonding, the device substrate from a second side opposite the first side;
• forming a plurality of light-reflective components over the second side of the device substrate after the thinning, wherein the light-reflective components help define a plurality of trenches that are each vertically aligned with a respective one of the light-sensing elements;
• coating a first layer on each of the light-reflective components, the first layer containing a first type dielectric material;
• coating a second layer on the first layer, the second layer containing a second type dielectric material;
• filling the trenches with a third layer, the third layer containing the first type dielectric material;
• etching the third layer, wherein the second layer serves as a first etching-stop layer during the etching of the third layer;
• thereafter etching the second layer using a dry etching process, wherein the first layer serves as a second etching-stop layer during the etching of the second layer, and wherein a plurality of spacers are formed on sidewalls of the light-reflective components by portions of the second layer that remain after the etching of the second layer;
• and
• forming, after the etching of the second layer, a plurality of color filters in the plurality of trenches, respectively.