Thinned image sensor with trench-insulated contact terminals

A method of fabricating an image sensor with thinned silicon substrate, having fabrication steps carried out from the front face of a silicon substrate then the transfer of the front face onto a transfer substrate then the thinning of the silicon substrate to a thickness of a few micrometers, and finally fabrication steps carried out on the rear face of the thinned silicon substrate, wherein the fabrication steps are carried out from the rear face comprising the steps of:

• etching at least one localized contact opening through the thinned substrate, on a surface area reserved for the creation of an external connection terminal for the sensor, the opening locally exposing a first conductive layer formed during the fabrication steps carried out from the front face;
• depositing a second conductive layer on the rear face, in contact with the silicon in the opening, the second layer coming into contact with the first layer;
• etching the second layer to delimit a connection terminal;
• opening a peripheral trench through the entire thickness of the thinned silicon substrate to an insulating layer located under this substrate, this trench completely surrounding the connection terminal and the bottom of the trench being entirely formed by the insulating layer, so forming an island of thinned silicon covered by the connection terminal and insulated by the trench from the rest of the thinned silicon.