Alignment mark design for packages

1. A package comprising:

a molding material;

a device die disposed in the molding material and comprising a metal pillar at a surface of the device die;

a first through-via disposed in the molding material and adjacent to the device die;

a second though-via penetrating through the molding material and adjacent to the first through-via, wherein the second through-via is an alignment mark, and is electrically floating;

a first redistribution line on a first side of the molding material;

a second redistribution line on a second side of the molding material, with the second side being opposite to the first side, wherein the first redistribution line is electrically coupled to the second redistribution line through the first through-via; and

a metal feature on the second side of, and outside of, the molding material, with the second through-via contacting the metal feature, wherein the second through-via and the metal feature in combination are fully enclosed in dielectric materials.

2. The package of claim 1 further comprising a first dielectric layer on the first side of the molding material, wherein the first dielectric layer is in physical contact with both a surface of the metal pillar and an entirety of a first end of the alignment mark.

3. The package of claim 2 further comprising a second dielectric layer on the second side of the molding material, wherein the second dielectric layer is in physical contact with a portion of a second end of the second through-via.

4. The package of claim 1 further comprising a die-attach film have edges co-terminus with edges of the device die, wherein the molding material is in contact with edges of the die-attach film.

5. The package of claim 1 , wherein an end of the alignment mark is substantially leveled with a surface of the metal pillar.

6. The package of claim 1 further comprising a plurality of through-vias comprising the first through-via, wherein the plurality of through-vias is arranged to form a rectangular region, and wherein the second through-via is outside of the rectangular region, and is between the rectangular region and a corner of the package.

7. A package comprising:

a device die;

an encapsulating material molding the device die therein;

a through-via penetrating through the encapsulating material;

an alignment mark penetrating through the encapsulating material;

a first dielectric layer underlying and in contact with the encapsulating material, wherein a bottom surface of the alignment mark is in contact with the first dielectric layer;

a second dielectric layer overlying and in contact with the encapsulating material, wherein a top surface of the alignment mark is in contact with the second dielectric layer;

a redistribution line in the first dielectric layer, wherein the redistribution line is electrically coupled to the through-via; and

a conductive feature connected to the alignment mark to form at least a part of a continuous conductive region, wherein the conductive feature is in the second dielectric layer, and wherein the continuous conductive region is fully enclosed by dielectric materials, with all surfaces of the continuous conductive region being in contact with dielectric materials.

8. The package of claim 7 , wherein the alignment mark is electrically floating.

9. The package of claim 7 , wherein the alignment mark is fully enclosed by dielectric materials, with all of surfaces of the alignment mark being in contact with the dielectric materials.

10. The package of claim 7 further comprising a dielectric layer, wherein both a surface of the alignment mark and a surface of the encapsulating material are in contact with the dielectric layer.

11. The package of claim 10 , wherein an entirety of a surface of the alignment mark is in contact with the dielectric layer.

12. The package of claim 7 comprising a plurality of through-vias, with the through-via being comprised in the plurality of through-vias, wherein each of the plurality of through-vias interconnects conductive features on opposite sides of the encapsulating material, and wherein the plurality of through-vias defines a rectangular design area, with the device die in the rectangular design area, and the alignment mark is outside of the rectangular design area.

13. A package comprising:

a device die comprising a metal pillar at a surface of the device die;

a plurality of through-vias surrounding the device die;

an alignment mark, wherein the alignment mark is electrically floating, and the alignment mark comprises a first surface and a second surface opposite to each other, and the first surface of the alignment mark is substantially coplanar with a surface of the metal pillar;

an encapsulating material molding the device die, the alignment mark, and the plurality of through-vias therein;

a first plurality of redistribution lines on a first side of the encapsulating material, wherein the second surface of the alignment mark is in contact with one of the first plurality of redistribution lines, and the alignment mark and the one of the first redistribution lines in combination are electrically floating; and

a second plurality of redistribution lines on a second side of the encapsulating material, with the second side being opposite to the first side, wherein the first plurality of redistribution lines is electrically coupled to the second plurality of redistribution lines through the plurality of through-vias.

14. The package of claim 13 , wherein the first surface of the alignment mark is coplanar with first surfaces of the plurality of through-vias, and the second surface of the alignment mark is coplanar with second surfaces of the plurality of through-vias.

15. The package of claim 13 further comprising a first dielectric layer on the first side of the encapsulating material, wherein an entirety of the first surface of the alignment mark is in contact with the first dielectric layer.

16. The package of claim 15 further comprising a second dielectric layer on the second side of the encapsulating material, wherein an entirety of the second surface of the alignment mark is in contact with the second dielectric layer.

17. The package of claim 13 , wherein the alignment mark is closest to a corner of the package than all through-vias in the package.

18. The package of claim 13 , wherein the alignment mark and the one of the first redistribution lines are parts of a continuous conductive region, and all surfaces of the continuous conductive region are in contact with dielectric materials.

19. The package of claim 7 , wherein the through-via and the alignment mark are formed of a same conductive material.

20. The package of claim 13 , wherein the plurality of through-vias and the alignment mark are formed of a same conductive material.