Method of manufacturing an encapsulation device

A method for fabricating an encapsulation device for a micro-electromechanical system characterized in that the method includes the following steps:

• a) forming the micro-electromechanical system, a main portion forming a cavity and a cover;
• b) depositing, on the main portion and the cover respectively, a first and a second metallizations respectively including at least a first metal protected by a first anti-oxidation material, and at least a second metal protected by a second anti-oxidation material;
• c) depositing a layer of a material whose melting point is lower than 250° C. on solely one of the first and second metallizations;
• d) partially diffusing the material whose melting point is lower than 250° C. in solely one of the first and second anti-oxidation materials in order to entirely transform said one of the first and second anti-oxidation materials into an intermetallic compound formed of said one of the first and second anti-oxidation materials and of said material whose melting point is lower than 250° C. in order to protect one of the at least one first and at least one second metals, and to leave a non-diffused portion of the material whose melting point is lower than 250° C.;
• e) mounting the micro-electromechanical system in the cavity of the main portion;
• f) assembling the portion of the material whose melting point is lower than 250° C. which was not diffused in step d) against the other of the first and second metallizations;
• g) totally diffusing the portion of material whose melting point is lower than 250° C. which was not diffused in step d) in the other of the first and second metallizations in order to entirely transform the portion of material whose melting point is lower than 250° C. which was not diffused in step d) into a second intermetallic compound formed by the other of the first and second anti-oxidation materials, the material whose melting point is lower than 250° C. and the other of the at least one first and at least one second metals, so as to hermetically close the micro-electromechanical system inside the encapsulation device.