Method of forming an infrared filter associated with an image sensor

A method of simultaneously forming an infrared bandpass filter on a filter side and interconnection levels on an interconnect side of an image sensor, comprising the steps of:

• a) forming a first layer of a dielectric material having a refraction index smaller than 2.5 at the maximum transmission wavelength of the filter on a semiconductor substrate;
• b) depositing an etch stop layer;
• c) depositing at least one silicon layer having a first thickness;
• d) removing, on the interconnect side, said at least one silicon layer;
• e) depositing a second layer of the dielectric material having a second thickness greater than the first thickness;
• f) forming in the second layer metal tracks and interconnection vias, on the interconnect side;
• g) planarizing the surface to a level corresponding to the level of the surface of the second layer, where the second layer does not cover said at least one silicon layer;
• and
• h) repeating steps b) to g) at least once, the values of the first and second thicknesses being selected from one repetition to another, according to calculations implying a simulation step and/or according to the desired electric performances.