Optical filter for a multispectral sensor and method for manufacturing such a filter

A multispectral image sensor, comprising:

• a semiconductor substrate;
• an image sensor comprising a plurality of pixels formed inside and on top of the semiconductor substrate;
• and
• an optical filter that includes:
• at least one resonant cavity having a transparent region having a first refraction index and laterally delimited by a reflective peripheral vertical wall;
• and
• at least one resonant element formed in the transparent region.

A method, comprising:

• forming an optical filter in front of an image sensor that includes a plurality of pixels, the method comprising the following successive steps:
• a) forming, in a transparent layer, at least one resonant element for each pixel;
• and
• b) dividing the transparent layer into a plurality of transparent regions each comprising at least one of the resonant elements;
• and
• c) covering the sides of each transparent region with a reflective peripheral vertical wall,
• wherein the transparent region and the reflective peripheral wall form, for each pixel, a resonant cavity.

A device, comprising:

• a substrate;
• a plurality of pixels in the substrate;
• an optical filter on the plurality of pixels, the optical filter including:
• a first resonant element;
• a first transparent layer on the first resonant element;
• a first reflective wall that is transverse to a surface of the substrate;
• a second reflective wall that is transverse to the surface of the substrate, the first resonant element being between the first and second reflective walls.