Method for eutectic sealing of two substrates

A method for eutectic sealing of two substrates, the method comprising:

• a) providing a first substrate having a first face covered by a first bead made of a first material, and optionally by one or more microelectronic devices the first material comprising a first element;
• b) providing a second substrate having a first face covered by a second bead made of a second material, and optionally by one or more microelectronic devices, the second material comprising a second element, capable of forming a eutectic alloy with the first element;
• c) placing the first bead and the second bead in contact;
• and
• carrying out a heat treatment to form a eutectic phase alloying the first element of the first bead and the second element of the second bead, whereby a sealing bead comprising the eutectic alloy is formed and the first substrate is sealed to the second substrate, the formation of the eutectic phase being accompanied by the formation of run-outs of eutectic alloy,
• wherein at least one of the first substrate and the second substrate is covered locally by a wettability layer, the contact angle of a drop of eutectic alloy on the wettability layer being smaller by at least 20°, on the one hand, than the contact angle of eutectic alloy on the first face of the first substrate and, on the other hand, than the contact angle of eutectic alloy on the first face of the second substrate, whereby during step c), the run-outs of eutectic alloy form on the wettability layer.