Interconnection structure with insulation comprising cavities

Method for fabricating a damascene type structure of interconnections on a semiconductor device (10, 20, 30), with the structure of interconnections including at least a first level of conductors covered by a second level of conductors meant to ensure electric links with the first level conductors, with the structure of interconnections including an electric insulation associating the low permittivity material and the air or vacuum gaps, characterised by the fact that it includes the following steps:

• formation of the first level of conductors (13, 23, 33) in a first electric insulating layer and of the second level of conductors (12, 22, 32) in a second electric insulating layer (15, 35), with the conductors in the first level being arranged with a pre-determined spacing in order to allow, in a later step, the formation of air or vacuum gaps between the conductors in the first level,
• elimination of the second electric insulating layer (15, 35),
• elimination, at least partial, of the first electric insulating layer (12, 22, 32) in order to eliminate at least some parts of the first layer corresponding to the air or vacuum gaps to be formed,
• deposit, over the structure thus obtained, of a material with low permittivity (17, 27, 37), with this deposit not filling the space between the conductors in the first level whose spacing has been planned to allow the formation of air or vacuum gaps (18, 28, 38).