Backside redistribution layer (RDL) structure

1. A package on package (PoP) device comprising:

a first die at least laterally encapsulated in a molding compound, the first die having an active surface and a backside surface, the active surface being opposite the backside surface, the molding compound having a first surface and a second surface, the second surface being opposite the first surface, the active surface of the first die being substantially level with the second surface of the molding compound;

a metal via extending through the molding compound from the first surface to the second surface of the molding compound;

a passivation layer disposed over the first surface of the molding compound and the backside surface of the first die, the passivation layer including a passivation layer recess vertically aligned with the metal via;

a redistribution layer bond pad capping the metal via, a portion of the redistribution layer bond pad within the passivation layer recess projecting above the first surface of the molding compound; and

a solder joint contacting a top surface and sidewalls of the redistribution layer bond pad, the solder joint being within the passivation layer recess.

2. The PoP device of claim 1 , wherein a second portion of the redistribution layer bond pad is embedded in the molding compound.

3. The PoP device of claim 1 , wherein a redistribution layer bond pad diameter is greater than a metal via diameter.

4. The PoP device of claim 1 , wherein a portion of the passivation layer is disposed beneath the redistribution layer bond pad.

5. The PoP device of claim 1 , further comprising a buffer layer disposed over the passivation layer, the buffer layer including a buffer layer recess vertically aligned with the passivation layer recess and the metal via.

6. The PoP device of claim 1 , wherein sidewalls of the portion of the redistribution layer bond pad projecting above the first surface of the molding compound are spaced apart from sidewalls of the passivation layer recess.

7. The PoP device of claim 1 , wherein a diameter of the top surface of the redistribution layer bond pad is less than or equal to a diameter of a sidewall base of the redistribution layer bond pad.

8. The PoP device of claim 1 , wherein a profile angle of the redistribution layer bond pad defined by a sidewall and a bottommost surface of the redistribution layer bond pad is between about forty degrees and about ninety degrees.

9. The PoP device of claim 1 , wherein a height of the redistribution layer bond pad disposed above the molding compound is greater than or equal to a height of the passivation layer.

10. The PoP device of claim 1 , wherein a diameter d1 of the top surface of the redistribution layer bond pad satisfies the formula: d1=d2−2[h1(tan θ)], where d2 is a diameter of a sidewall base of the redistribution layer bond pad, h1 is a height of the passivation layer, and θ is a profile angle of the redistribution layer bond pad defined by a sidewall and a bottommost surface of the redistribution layer bond pad.

11. The PoP device of claim 1 , wherein a diameter of the redistribution layer bond pad is greater than or equal to a diameter of a sidewall base of the redistribution layer bond pad.

12. The PoP device of claim 1 , wherein a diameter of the metal via is less than or equal to a diameter of a sidewall base of the redistribution layer bond pad.

13. The PoP device of claim 1 , further comprising:

a die attach film interposed between the backside surface of the first die and the passivation layer, the molding compound at least laterally encapsulating the die attach film; and

a redistribution layer embedded in the die attach film.

14. The PoP device of claim 1 , wherein a first plane intersects the projecting portion of the redistribution layer bond pad and the passivation layer, the first plane being parallel to the backside surface of the first die.

15. A package on package (PoP) device comprising:

a first package comprising:

a molding compound having a first die and a metal via embedded therein, the molding compound having a first side and a second side, the second side being opposite the first side, the metal via extending from the first side to the second side of the molding compound;

a passivation layer adjoining a first side of the molding compound, the passivation layer being spaced apart from the first die, the passivation layer including a passivation layer recess vertically aligned with the metal via;

a first redistribution layer bond pad capping the metal via, the first redistribution layer bond pad having a first portion projecting from the first side of the molding compound into the passivation layer recess; and

a second redistribution layer adjoining the second side of the molding compound, the second redistribution layer being electrically coupled to the first die and the metal via;

a second package comprising a second die; and

a first set of solder joints coupling the first package to the second package, at least one of the first set of solder joints contacting a top surface and sidewalls of the first redistribution layer bond pad, the at least one of the first set of solder joints contacting sidewalls of the passivation layer within the passivation layer recess.

16. The PoP device of claim 15 , wherein the first portion of the first redistribution layer bond pad within the passivation layer recess includes sidewalls, the sidewalls tapering from bottom to top.

17. The PoP device of claim 15 , wherein a diameter of the first redistribution layer bond pad is greater than a diameter of the metal via.

18. A package on package (PoP) device comprising:

a die having an active surface and a backside surface, the active surface being opposite the backside surface;

a molding compound extending along sidewalls of the die, the molding compound having a first surface and a second surface, the second surface being opposite the first surface, the first surface of the molding compound and the backside surface of the die facing in a same direction;

a metal via embedded in the molding compound adjacent the die, a first portion of the metal via extending from the first surface of the molding compound to the second surface of the molding compound;

a passivation layer over the molding compound and the die, the first surface of the molding compound and the backside surface of the die facing the passivation layer, a second portion of the metal via extending above the first surface of the molding compound and into the passivation layer, a width of the second portion of the metal via decreasing as the second portion of the metal via extends into the passivation layer;

a redistribution layer bond pad extending along a top surface and a sidewall of the second portion of the metal via; and

a solder joint contacting a top surface and sidewalls of the redistribution layer bond pad, the solder joint extending through the passivation layer.

19. The PoP device of claim 18 , wherein a topmost surface of the redistribution layer bond pad is level with a topmost surface of the passivation layer.

20. The PoP device of claim 18 , wherein at least portion of the redistribution layer bond pad is embedded in the molding compound.