Method of forming metal contact pads and terminals on semiconductor chips

A method of forming metal contact terminals (35) of a determined size on a structure (23) of the type having an insulating substrate (17) with a metal land (18) formed thereon and a passivating layer (19) provided with a contact opening exposing a part of said metal land, said method characterized by the steps of:

• a) depositing a metal layer (28) onto the structure through a metal mask (27) having holes greater than said determined size whereby an intermediate metal contact pad (33') is formed in said contact opening and at the close vicinity thereof;
• b) applying a photoresist layer (31) onto the structure and, patterning said photoresist layer to leave a pattern (31) of said determined size aligned and above said intermediate contact pad (33') and leaving exposed a part of said intermediate contact pad in excess of said determined size;
• (c) delineating the intermediate metal contact pad (33'), said pattern (31) providing an in-situ mask, and removing the excess part to provide a final metal contact pad (33) of said determined size;
• d) removing the remaining photoresist pattern (31);
• e) aligning the structure with a metal mask having a hole centered with said final metal contact pad (33);
• f) depositing a lead-tin solder layer (34') over the metal mask forming a solder bump (34') on each said final metal contact pad and,
• g) reflowing each said solder bump to form a solder ball (34), whereby the metal contact terminals are formed (35) at each final metal contact pad.