Bonding scheme for semiconductor packaging

A method of forming a semiconductor package, the method comprising:

• forming a first integrated circuit over a first substrate;
• forming a patterned plating mask over the first integrated circuit, the patterned plating mask comprising openings;
• forming first connector structures, forming the first connector structures comprising:
• forming base layers in corresponding ones of the openings;
• forming intermediate layers over corresponding ones of the base layers, the intermediate layers comprising nickel;
• forming capping layers over corresponding ones of the intermediate layers, the capping layers being free of nickel;
• and
• forming first solder regions over corresponding ones of the capping layers, the first solder regions being free of nickel;
• removing the patterned plating mask;
• performing an etch process using an etchant selective to a material of the base layers and the capping layers;
• depositing a polymer material over and between the first connector structures;
• planarizing the polymer material to be level with upper surfaces of the first solder regions;
• and
• depositing a non-conductive film over the polymer material.

A semiconductor device comprising:

• a first interconnect structure over a first substrate;
• a first metal pillar over the first interconnect structure, the first metal pillar comprising:
• a first base layer over the first interconnect structure, the first base layer having a first lateral width;
• a first intermediate layer over the first base layer, the first intermediate layer having a second lateral width, the second lateral width being greater than the first lateral width;
• and
• a first capping layer over the first intermediate layer, the first capping layer having the first lateral width;
• a solder region over and around sidewalls of the first capping layer;
• a second metal pillar over the solder region, the second metal pillar comprising:
• a second capping layer, the solder region being around sidewalls of the second capping layer, the second capping layer having a third lateral width;
• a second intermediate layer over the second capping layer, the second intermediate layer having a fourth lateral width, the fourth lateral width being greater than the third lateral width;
• and
• a second base layer over the second intermediate layer, the second base layer having the third lateral width;
• and
• a second interconnect structure over the second metal pillar.