Package-on-package structure and method of forming same

A device comprising:

• a top package mounted on a bottom package, wherein the bottom package comprises:
• a plurality of interconnection components;
• a plurality of first bumps formed on a first side of the bottom package;
• and
• a plurality of metal bumps formed on a second side of the bottom package, wherein the metal bump is of a width D1 and a height H1, and wherein D1 is greater than H1;
• a semiconductor die is bonded on the second side of the bottom package, wherein:
• the semiconductor die is electrically coupled to the first bumps through the interconnection components;
• and
• the semiconductor die is located between the top package and the bottom package, wherein a surface of a redistribution layer of the semiconductor die is in direct contact with a surface of a via of the interconnect components;
• and
• an underfill layer formed between the top package and the bottom package, wherein a top surface of the underfill layer is level with top surfaces of the metal bumps and a bottom surface of the underfill layer is level with bottom surfaces of the metal bumps.

A method comprising:

• attaching a plurality of metal bumps on a carrier through an adhesive layer;
• attaching a semiconductor die on the carrier through the adhesive layer;
• forming a molding compound layer over the carrier, wherein the semiconductor die and the metal bumps are embedded in the molding compound layer;
• grinding the molding compound layer until a top surface of the semiconductor die is exposed;
• forming a bottom package comprising a plurality of interconnect structures over the molding compound layer;
• attaching the bottom package on a tape frame;
• grinding the adhesive layer until the semiconductor die is exposed;
• and
• mounting a top package on the bottom package, wherein the semiconductor die is located between the top package and the bottom package.