Devices employing thermal and mechanical enhanced layers and methods of forming same

1. A method comprising:

attaching a dummy wafer to a carrier;

attaching a first first-level device die and a second first-level device die to the dummy wafer through a first adhesive film and a second adhesive film, respectively, wherein the first adhesive film and the second adhesive film are in physical contact with the dummy wafer;

encapsulating the first first-level device die and the second first-level device die in a first encapsulating material; and

forming redistribution lines over and electrically coupling to the first first-level device die and the second first-level device die.

2. The method of claim 1 , wherein the first encapsulating material is in physical contact with the dummy wafer, and wherein an entirety of the dummy wafer is formed of a homogeneous material.

3. The method of claim 1 further comprising:

after the dummy wafer is attached to the carrier and before the first first-level device die is attached, thinning the dummy wafer.

4. The method of claim 1 further comprising, before the forming the redistribution lines:

growing a through-via directly from a metal pad in the first first-level device die;

attaching a second-level device die comprising a first portion overlapping the first first-level device die and a second portion overlapping the second first-level device die; and

encapsulating the through-via and the second-level device die in a second encapsulating material.

5. The method of claim 4 , wherein the encapsulating the first first-level device die and the second first-level device die and the encapsulating the through-via and the second-level device die are performed in separate encapsulation processes.

6. The method of claim 1 , wherein the dummy wafer comprises a dummy silicon wafer.

7. The method of claim 1 , wherein the dummy wafer comprises a metal wafer.

8. The method of claim 1 , wherein the dummy wafer, the first first-level device die, the second first-level device die, and the first encapsulating material form parts of a composite wafer, and the method further comprises detaching the composite wafer from the carrier.

9. A method comprising:

attaching a dummy wafer over a carrier, wherein the dummy wafer is free from integrated circuit devices;

attaching a first-level device die to the dummy wafer;

stacking a second-level device die over the first-level device die;

forming redistribution lines over and electrically coupling to the first-level device die and the second-level device die; and

detaching the dummy wafer from the carrier to form a reconstructed wafer, wherein the reconstructed wafer comprises the dummy wafer, the first-level device die, the second-level device die, and the redistribution lines.

10. The method of claim 9 , wherein the attaching the dummy wafer comprises attaching a first homogeneous material over the carrier.

11. The method of claim 10 , wherein the carrier is further formed of a second homogeneous material.

12. The method of claim 10 further comprising encapsulating the first-level device die in an encapsulant, wherein the encapsulant is in direct contact with the dummy wafer.

13. The method of claim 10 further comprising performing a die-saw process on the reconstructed wafer, with the dummy wafer being sawed apart, wherein the first-level device die, the second-level device die and a dummy die in the dummy wafer forming a package.

14. The method of claim 10 , wherein both of the dummy wafer and the carrier are free from integrated circuits and conductive lines therein.

15. The method of claim 10 , wherein the dummy wafer comprises a silicon wafer free from passive devices therein, and free from active devices therein, and wherein the carrier comprises a glass carrier.

16. A method comprising:

thinning a dummy wafer;

after the dummy wafer is thinned, attaching a first-level device die to the dummy wafer that has been thinned, with a die-attach film being between, and in contact with, the dummy wafer and the first-level device die;

encapsulating the first-level device die in a first encapsulating material, wherein the first encapsulating material contacts silicon or a metal in the dummy wafer;

stacking a second-level device die over the first-level device die;

encapsulating the second-level device die in a second encapsulating material;

forming redistribution lines over and electrically coupling to the first-level device die and the second-level device die; and

sawing through the dummy wafer, the first encapsulating material, and the second encapsulating material.

17. The method of claim 16 further comprising:

attaching the dummy wafer to a carrier through an adhesive film, wherein the thinning the dummy wafer is performed when the dummy wafer is on the carrier.

18. The method of claim 17 further comprising:

after the redistribution lines are formed, detaching the dummy wafer from the carrier, with the dummy wafer remaining to be attached with the first-level device die after the dummy wafer is detached from the carrier.

19. The method of claim 16 , wherein the attaching the first-level device die to the dummy wafer comprises attaching the first-level device die to a blank metal plate, a blank semiconductor plate, or a blank dielectric plate.

20. The method of claim 16 , wherein an entirety of the dummy wafer is formed of a homogeneous material.