Package structure for heat dissipation

1. A method comprising:

attaching a first heat dissipation feature to a substrate over a device area of the substrate;

depositing a first fill material over the first heat dissipation feature, the first fill material laterally surrounding the first heat dissipation feature;

planarizing the first fill material to expose a top surface of the first heat dissipation feature;

bonding a second heat dissipation feature to the first heat dissipation feature;

depositing a second fill material over the second heat dissipation feature, the second fill material laterally surrounding the second heat dissipation feature; and

forming a first trench in the first fill material adjacent the first heat dissipation feature, wherein the first fill material remains on sidewalls of the first heat dissipation feature.

2. The method of claim 1 , further comprising:

depositing a thermal interface material in the first trench and over the first heat dissipation feature.

3. The method of claim 2 , further comprising:

attaching a third heat dissipation feature to the second heat dissipation feature, the thermal interface material interposed between the second heat dissipation feature and the third heat dissipation feature.

4. The method of claim 1 , wherein the first heat dissipation feature is a thermal metal block, and wherein the second heat dissipation feature is a thermal metal block.

5. The method of claim 1 , wherein the second heat dissipation feature is directly bonded to the first heat dissipation feature without a eutectic material there between.

6. The method of claim 1 , further comprising:

forming second trenches in an upper surface of the second heat dissipation feature; and

depositing a thermal interface material in the second trenches.

7. The method of claim 1 , further comprising:

forming first connectors on a side of the substrate opposite the first heat dissipation feature.

8. The method of claim 1 , further comprising:

attaching a first chip to the substrate adjacent the first heat dissipation feature;

depositing the first fill material over the first chip, the first fill material laterally surrounding the first chip, wherein planarizing the first fill material further exposes a back surface of the first chip and exposes a conductive feature at the back surface of the first chip;

bonding a front side of a second chip to the back surface of the first chip; and

depositing the second fill material over the second chip, the second fill material laterally surrounding the second chip, wherein the first trench is disposed between the first heat dissipation feature and the first chip.

9. A method comprising:

bonding a first die and a second die to a structure, the structure including a wafer;

depositing a first fill material between the first die and the second die;

thinning the first die and the second die to expose first conductive features at a top surface of the first die and second conductive features at a top surface of the second die;

bonding a third die to the top surface of the first die and a fourth die to the top surface of the second die, the bonding comprising:

aligning third conductive features of the third die to the first conductive features of the first die, and

forming a metal-to-metal bond directly between the first conductive features and the third conductive features, without a separate bonding material; and

depositing a second fill material between the third die and the fourth die.

10. The method of claim 9 , wherein the bonding further comprises:

fusing a dielectric material of the third die to a dielectric material of the first die.

11. The method of claim 9 , wherein the first conductive features include metal vias extending from a front side of the first die to a back side of the first die.

12. The method of claim 9 , wherein a first die stack includes the first die and the third die and a second die stack includes the second die and the fourth die, further comprising:

singulating the first die stack from the second die stack.

13. The method of claim 12 , wherein the first die stack further includes a singulated portion of the wafer, the singulated portion of the wafer including active devices disposed therein.

14. The method of claim 12 , wherein following singulating, the first die stack includes the first fill material on sidewalls of the first die and the second fill material on sidewalls of the third die.

15. The method of claim 12 , wherein the first die stack comprises a memory cube.

16. A method comprising:

attaching a first heat dissipation feature and a first die to a substrate;

depositing a first fill material between the first die and the first heat dissipation feature;

bonding a second heat dissipation feature to the first heat dissipation feature and a second die to the first die;

depositing a second fill material between the second die and the second heat dissipation feature;

forming a trench between the first heat dissipation feature and the first die, the trench extending through the second fill material and the first fill material; and

filling the trench with a thermal interface material.

17. The method of claim 16 , wherein the first heat dissipation feature has a first thickness, the second heat dissipation feature has a second thickness, and the first thickness is different than the second thickness, the second thickness corresponding to a thickness of the second die.

18. The method of claim 16 , wherein the first heat dissipation feature comprises a dummy chip with thermal vias disposed therein, the thermal vias extending from a first surface of the first heat dissipation feature to a second surface of the first heat dissipation feature, the thermal vias bonded to corresponding thermal vias of the second heat dissipation feature.

19. The method of claim 16 , further comprising:

etching grooves in the top surface of the second die; and

filling the grooves with the thermal interface material.

20. The method of claim 16 , further comprising:

dissipating heat from a logic area of the substrate through metal elements of the first heat dissipation feature, through metal elements of the second heat dissipation feature, and through a heat dissipation lid disposed over the second heat dissipation feature.