Chip protected against back-face attacks

A method for fabricating a semiconductor chip, the method comprising:

• forming a first plurality of conducting pads at a front face of a substrate;
• etching a rear face of the substrate to form a first plurality of openings under each of the first plurality of conducting pads, each of the first plurality of openings comprising walls and a bottom;
• depositing a layer of dielectric on the walls and the bottom of each of the first plurality of openings;
• and
• forming a first conductive region at the rear face in each of the first plurality of openings, the first conductive region being electrically connected to each of the first plurality of conducting pads.

A method of determining whether a hack attempt is made on an electronic chip that includes a first and second conducting pads at a front face that are capacitively coupled by a conducting strip at a rear face opposite the front face, the method comprising:

• measuring a capacitance between the first conducting pad and the second conducting pad;
• determining the existence of a hack attempt when the measured capacitance is higher than a threshold capacitance value;
• and
• determining the absence of a hack attempt when the measured capacitance is lower than the threshold capacitance value.