Through silicon via dies and packages
View Patent ↗A method for preparing a die for packaging is disclosed. A die having first and second major surfaces is provided. Vias and a mask layer are formed on the first major surface of the die. The mask includes mask openings that expose the vias. The mask openings are filled with a conductive material. The method includes reflowing to at least partially fill the vias and contact openings to form via contacts in the vias and surface contacts in the mask openings.
1. A method of packaging comprising:
providing n number of dies of a die stack, wherein a die of the die stack includes
first and second major surfaces,
a mask layer with a mask opening on the first major surface, and
a through via contact having a via portion which extends from the first to the second major surface and an upper portion disposed in the mask opening, wherein the through via contact is formed by reflowing a first conductive material disposed in the mask opening to cause it to flow into a via in communication with the mask opening to form the via portion of the through via contact while the upper portion partially fills the mask opening and contacts inner walls of the mask opening while leaving a space therein;
stacking the n number of dies to form the die stack, wherein a bottom die of the die stack is the first die and a top die of the die stack is the n th die, the n number of dies of the die stack are stacked such that the mask of a die below (i th −1 die) contacts the second surface of a die above (i th die), wherein the through via contact of the die above is aligned with the partially filled mask opening of the die below; and
reflowing the first conductive material of the through via contacts of the die stack, wherein the space of the partially filled mask opening of the i th −1 die is completely filled by the reflowed conductive material of the through via contact of the i th die to form connections between the dies of the die stack.
2. The method of claim 1 wherein the first conductive material comprises solder.
3. The method of claim 1 comprising filling the mask opening with the first conductive material, wherein filling the mask opening comprises printing with solder paste using a stencil.
4. The method of claim 3 comprises removing the stencil after filling the mask opening.
5. The method of claim 1 wherein the mask layer includes a die attach film for attaching another die on the first surface of the die.
6. The method of claim 1 wherein bottom of the through via contact is coplanar with the second major surface of the die.
7. The method of claim 1 wherein:
the through via contact is formed by forming a via having a blind via in the die; and
backgrinding the second major surface of the die to expose the bottom of the via contact such that the bottom of the through via contact is coplanar with the second major surface of the die.
8. The method of claim 7 wherein the via comprises tapered sidewalls.
9. The method of claim 1 wherein:
upper dies of the stack comprises second major surfaces with exposed bottom via contacts; and
a bottom die of the stack (n=1) comprises an ungrinded second major surface with an unexposed via contact.
10. The method of claim 9 comprises backgrinding the second surface of the bottom die (n=1) to expose bottom of the via contact.
11. The method of claim 1 wherein n comprises more than two dies.
12. A method of packaging comprising:
providing n number of dies, wherein a die of the n number of dies comprises
first and second major surfaces with a mask prepared on the first major surface with mask openings, and
through via contacts, wherein each of the through via contacts has a via portion which extends from the first to the second major surface and an upper portion disposed in the mask opening, wherein the through via contact is formed by reflowing a single conductive material disposed in the mask opening to cause it to flow into a via in communication with the mask opening to form the via portion of the through via contact while the upper portion partially fills the mask opening and contacts inner walls of the mask opening while leaving spaces therein;
stacking the n number of dies to form a die stack, wherein a bottom die of the die stack is the first die and a top die of the die stack is the n th die, the n number of dies of the die stack are stacked such that the mask of a die below (i th −1 die) contacts the second surface of a die above (i th die), wherein the through via contacts of the die above are aligned with the partially filled mask openings of the die below; and
reflowing the single conductive material of the through via contacts of the die stack, wherein the spaces of the partially filled mask openings of the i th −1 die is completely filled by the reflowed single conductive material of the through via contacts of the i th die to form electrical connections between the dies of the die stack.
13. The method of claim 12 wherein the mask includes a die attach film.
14. The method of claim 12 wherein the bottom die of the die stack (n=1) comprises an ungrinded second major surface with unexposed via contacts and further comprises backgrinding the second surface of the bottom die to expose bottoms of the via contacts after forming the die stack.
15. The method of claim 12 wherein the through via contacts comprise tapered sidewalls.