Pseudo-electroless, followed by electroless, metallization of nickel on metallic wires, as for semiconductor chip-to-chip interconnections

摘要

A nickel plug (31) filling an aperture in an insulating layer (30), such as polyimide, separating two metallization levels of copper wires (28, 25 and 38, 35) is formed by an electroless process in a plating bath (solution) containing ions of hypophosphite and of nickel. In preparation for this electroless process, the copper wires (28, 25) are first plated with a nickel layer (29) by a pseudo-electroless process--that is, a process in which the copper wires (28, 25) are located in contact with an underlying extended chromium layer (14) that is placed in electrical contact (including intimate physical contact) with an auxiliary metallic layer (41) that contains nickel, while both the copper wires (28, 25), the chromium layer (14), and at least a portion of the external metallic layer (41) are immersed in a plating solution likewise containing ions of hypophosphite and of nickel.