Semiconductor structure having copper pillar within solder bump and manufacturing method thereof

A method of manufacturing a semiconductor structure, comprising:

• providing a first substrate having a first pad disposed thereon and a passivation at least partially surrounding the first pad;
• forming a patterned mask over the passivation;
• forming a first bump portion over the passivation and the first pad and surrounded by the patterned mask;
• forming a first layer of an interfacial layer over the first bump portion and surrounded by the patterned mask;
• forming a conductive pillar on the first layer of the interfacial layer;
• forming a second layer of the interfacial layer on the first layer and covering the conductive pillar;
• forming a second bump portion over the second layer of the interfacial layer and surrounded by the patterned mask;
• and
• removing the patterned mask.