Structure and method for 3D IC package

1. A method of forming a chip package comprising:

bonding a plurality of first dies on a carrier;

encapsulating in a first molding compound the first dies on the carrier;

coupling a plurality of second dies on the first dies using conductive elements;

adding an underfill between the second dies and the first dies, the underfill surrounding the conductive elements;

encapsulating in a second molding compound the second dies and the underfill; and

de-bonding the carrier after the encapsulating in the second molding compound, the de-bonding exposing a surface of the plurality of first dies.

2. The method of claim 1 , wherein the second dies are coupled to the first dies via the conductive elements without an interposer between the second dies and the first dies.

3. The method of claim 1 , wherein the conductive elements include solder balls or bumps.

4. The method of claim 1 further comprising:

forming a redistribution layer (RDL) on the exposed surface of the plurality of first dies; and

forming an interconnect structure that provides three-dimensional fan-out on the RDL.

5. The method of claim 1 , wherein the first dies are bonded on the carrier using an adhesive layer, and wherein de-bonding the carrier comprises removing the adhesive layer.

6. The method of claim 1 further comprising:

forming the first dies as repeated adjacent structures on a wafer;

separating the first dies; and

placing the first dies on the carrier with spacing between the first dies.

7. The method of claim 1 further comprising sawing the first dies encapsulated in the first molding compound with the underfill and the second dies encapsulated in the second molding compound to obtain a plurality of chip packages that have a three-dimensional fan-out structure.

8. A method of forming a chip package comprising:

adding first conductive elements on a first die;

adding second conductive elements on a second die larger than the first die;

placing the second die on the first die to couple the second conductive elements to the first conductive elements without an interposer; and

adding an underfill between the first die and the second die, wherein the underfill encapsulates the first conductive elements and the second conductive elements.

9. The method of claim 8 further comprising:

before placing the second die on the first die, bonding the first die on a carrier;

encapsulating the first die in a first molding compound on the carrier;

after placing the second die on the first die and adding the underfill between the first die and the second die, encapsulating the second die and the underfill in a second molding compound on the first molding compound; and

debonding the first die from the carrier.

10. The method of claim 8 , wherein the second conductive elements are coupled to the first conductive elements via bump of solder balls placed between the second conductive elements and the first conductive elements in the underfill.

11. A method of forming a chip package, the method comprising:

encapsulating a first die in a first molding compound;

coupling a second die on the first die via conductive elements disposed between the first die and the second die without an interposer between the first die and the second die;

encapsulating the conductive elements in an underfill between the first die and the second die; and

encapsulating, in a second molding compound, the second die and the underfill on the first die.

12. The method of claim 11 further comprising placing the second molding compound in contact with the first molding compound.

13. The method of claim 11 further comprising:

placing a redistribution layer (RDL) on one side of the first die opposite to the underfill; and

placing a plurality of connectors on one side of the RDL opposite to the first die, the connectors providing a three-dimensional fan-out structure.

14. The method of claim 13 further comprising:

coupling the first die to first conductive elements;

coupling the second die to second conductive elements; and

coupling, inside the underfill, the first conductive elements to the second conductive elements.

15. The method of claim 14 further comprising:

coupling the connectors through the RDL to a combination of through vias and pads in the first die; and

coupling the through vias and pads to the first conductive elements.

16. The method of claim 11 further comprising forming a plurality of layers of stacked chip logic in the first die and the second die.

17. A method of forming a chip package comprising, the method comprising:

encapsulating a first chip in a molding compound;

coupling, via conductive elements, a second chip to the first chip, wherein the second chip is larger than the first chip;

encapsulating the conductive elements in an underfill without an interposer between the first chip and the second chip; and

encapsulating the second chip and the underfill in a second molding compound in contact with the molding compound.

18. The method of claim 17 further comprising:

forming stacked chip logic layers in the first chip;

forming through vias and pads across the stacked chips logic layers;

coupling a semiconductor substrate to the first chip; and

coupling second through vias in the semiconductor substrate to the through vias and pads.

19. The method of claim 17 further comprising:

placing one or more chip logic layers in the second chip; and

coupling a semiconductor substrate to the one or more chip logic layers.

20. The method of claim 17 further comprising:

adding first conductive elements to the first chip;

adding second conductive elements to the second chip;

encapsulating the first conductive elements and the second conductive element in the underfill; and

couple the first conductive elements and the second conductive elements via joints.

21. The method of claim 17 further comprising:

coupling a redistribution layer (RDL) to the first chip;

positioning the first chip between the underfill and the RDL;

coupling, to the RDL, an interconnect structure comprising a plurality of connectors for three-dimensional fan-out; and

positioning the RDL between the first chip and the interconnect structure.

22. The method of claim 21 further comprising:

forming in the RDL a conductive layer and a polymer layer;

coupling the conductive layer to the first chip and the interconnect structure; and

coupling the polymer layer to the conductive layer and the interconnect structure.