TSV semiconductor device including two-dimensional shift
A semiconductor device is disclosed including semiconductor dies stacked with an offset in two orthogonal directions. TSVs may then be formed connecting corresponding die bond pads on respective dies in the stack. By offsetting the dies in two orthogonal directions, the overall stepped offset, and consequently the size of the unused keep-out area of the stack, is reduced.
1. A semiconductor device, comprising:
a plurality of semiconductor dies stacked on top of each other along a reference axis;
a plurality of die bond pads on each semiconductor die of the plurality of semiconductor dies, wherein corresponding die bond pads of a first group of the semiconductor dies are offset with respect to each other along a first axis, and corresponding die bond pads of a second group of the plurality of semiconductor dies are offset with respect to each other along a second axis that is non-parallel to the first axis, the first and second axes being perpendicular to the reference axis; and
a plurality of through silicon vias (TSVs) electrically coupling corresponding die bond pads in the different levels of the stacked plurality of semiconductor dies, a through silicon via of the TSVs extending through each of the semiconductor dies in the plurality of semiconductor dies.
2. The semiconductor device of claim 1 , wherein the first and second axes are orthogonal to each other.
3. The semiconductor device of claim 1 , wherein a shift pattern of the offset along the first and second axes is selected such that the die bond pad of each semiconductor die is exposed by a single vertical hole through the stack used to form a through silicon via.
4. The semiconductor device of claim 3 , wherein the vertical hole is formed with two-dimensional stepped sidewalls extending along the first axis and the second axis.
5. The semiconductor device of claim 3 , wherein the plurality of through silicon vias have a larger cross-sectional area at a top of the stacked semiconductor dies than at a semiconductor die distal from the top of the stacked semiconductor dies.
6. The semiconductor device of claim 1 , wherein the plurality of stacked dies comprise between five and nine dies, three sets of dies being offset along the first axis with respect to each other, and each die in the three sets being offset along the second axis with respect to each other, where the sequence stops if the number of dies is less than nine.
7. The semiconductor device of claim 1 , wherein the plurality of stacked dies comprise between ten and sixteen dies, four sets of dies being offset along the first axis with respect to each other, and each die in the four sets being offset along the second axis with respect to each other, where the sequence stops if the number of dies is less than sixteen.
8. The semiconductor device of claim 1 , further comprising adhesive film layers for affixing the plurality of stacked semiconductor dies to each other.
9. The semiconductor device of claim 8 , where the plurality of through silicon vias are formed through the adhesive film layers.
10. A semiconductor device, comprising:
a stack of semiconductor dies stacked on each other along a reference axis, each semiconductor die of the stack of semiconductor dies including a plurality of die bond pads distributed across surfaces of the semiconductor dies in the stack;
a plurality of through silicon vias for electrically interconnecting corresponding die bond pads on different levels of the stack;
wherein a single group of corresponding die bond pads of the plurality of die bond pads in the levels of the stack comprises a first group of die bond pads that are offset with respect to each other along a first axis, and a second group of die bond pads that are offset with respect to each other along a second axis that is non-parallel to the first axis, the first and second axes being perpendicular to the reference axis.
11. The semiconductor device of claim 10 , wherein the plurality of die bond pads are in different positions from each other on respective dies in the stack, and plurality of dies are aligned with each other.
12. The semiconductor device of claim 10 , wherein a shift pattern of the offset along the first and second axes is selected such that a die bond pad of each semiconductor die is exposed by a single vertical hole through the stack used to form a through silicon via.
13. The semiconductor device of claim 12 , wherein the vertical hole is formed with two-dimensional stepped sidewalls extending along the first axis and the second axis.
14. The semiconductor device of claim 12 , wherein the plurality of through silicon vias have a larger cross-sectional area at a top of the stacked semiconductor dies than at a semiconductor die distal from the top of the stacked semiconductor dies.
15. A method of fabrication a semiconductor device, comprising:
(a) defining a plurality of semiconductor dies in each of a plurality of semiconductor wafers, each semiconductor die of the plurality of semiconductor dies comprising a plurality of die bond pads;
(b) stacking the semiconductor wafers such that a group of corresponding die bond pads through the respective layers of semiconductor wafers are offset from each other in first and second non-parallel directions;
(c) forming though silicon vias through the stacked semiconductor wafers, one silicon via electrically connecting the group of corresponding die bond pads; and
(d) dicing the semiconductor device from the stacked wafers.
16. The method of claim 15 , wherein said step (d) of dicing the semiconductor device is performed during said step (c) of forming the through silicon vias.
17. The method of claim 15 , further comprising the step of mounting the plurality of wafers on a carrier.
18. The method of claim 15 , wherein the step of forming the through silicon vias comprises the step of performing a directional etching that creates a single vertical hole through the stack of wafers that exposes surfaces of the corresponding bond pads.
19. The method of claim 18 , further comprising the step of metal deposition in the vertical hole that creates electrical connection to all the exposed surfaces of the corresponding bond pads.
20. The method of claim 18 , wherein said step (d) of dicing the semiconductor device is performed in the same step as the directional etching that creates the single vertical hole.
21. The method of claim 15 , wherein said step (b) of stacking the semiconductor wafers such that a group of corresponding die bond pads are offset from each other comprises the step of stacking the wafers with offsets in the first and second non-parallel directions.
22. A semiconductor device, comprising:
a stack of semiconductor dies stacked on each other along a reference axis, each semiconductor die of the stack of semiconductor dies including a plurality of die bond pads distributed across surfaces of the semiconductor dies in the stack;
via means for electrically interconnecting corresponding die bond pads on different levels of the stack; and
means for offsetting a first group of die bond pads of corresponding die bond pads in the levels of the stack from each other along a first axis, and means for offsetting a second group of die bond pads of corresponding die bond pads in the levels of the stack from each other along a second axis, the first and second axes being perpendicular to the reference axis.