Methods of Forming Through-Substrate Vias
A method of forming through-substrate vias includes separately electrodepositing copper and at least one element other than copper to fill remaining volume of through-substrate via openings formed within a substrate. The electrodeposited copper and the at least one other element are annealed to form an alloy of the copper and the at least one other element which is used in forming conductive through-substrate via structures that include the alloy.
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Embodiments disclosed herein pertain to methods of forming through-substrate vias.
BACKGROUNDA through-substrate via is a vertical electrical connection passing completely through a substrate comprising integrated circuitry. Through-substrate vias may be used to create 3D packages in 3D integrated circuits and are an improvement over other techniques such as package-on-package because the density of through-substrate vias may be substantially higher. Through-substrate vias provide interconnection of vertically aligned electronic devices through internal wiring that significantly reduces complexity and overall dimensions of a multi-chip electronic circuit.
Common through-substrate via processes include formation of through-substrate via openings through most, but not all, of the thickness of the substrate. A thin dielectric liner is then deposited to electrically insulate sidewalls of the through-substrate via openings. Adhesion and/or diffusion barrier material(s) may be deposited to line over the dielectric. The through-substrate via openings are then filled with conductive material. Substrate material is removed from the opposite side of the substrate from which the via openings were formed to expose the conductive material within the via openings.
One highly desirable conductive through-substrate via material is elemental copper that is deposited by electrodeposition. Copper may be formed by initially depositing a seed layer within the through-substrate via openings followed by electrodepositing elemental copper from an electroplating solution. An example copper electroplating solution includes copper sulfate as a source of copper ions, sulfuric acid for controlling conductivity, and copper chloride for nucleation of suppressor molecules.
Current through-substrate via structures composed of elemental copper-fill exhibit stress relaxation damage to the dielectric via liner after the liner and copper are exposed through the backside of the substrate. The copper-fill metal is under high stress while constrained within the substrate. However, when the copper and dielectric are exposed and project out of the backside of the substrate, the copper becomes unconstrained which results in stress relaxation and swelling of the copper structure to an equilibrium, lower stress state. As the copper expands, the dielectric via liner has a tendency to crack, which creates a path for copper migration to short to the substrate.
Embodiments of the invention encompass methods of forming through-substrate vias and include separately electrodepositing copper and at least one element other than copper to fill remaining volume of through-substrate via openings that are formed within a substrate. The electrodeposited copper and the at least one other element are annealed to form an alloy of the copper and the at least one other element which is used in forming conductive through-substrate via structures comprising the alloy. Initial example embodiments are described with reference to
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Through-substrate via openings 20 have been formed into substrate 12. In one embodiment, openings 20 extend partially through substrate 12 and are formed from first substrate side 16. Alternately, through-substrate via openings 20 may extend completely through substrate material 12 and/or may be formed from second substrate side 16. Regardless, through-substrate via openings 20 may be formed by chemical and/or physical means, with chemical etching, drilling, and laser ablation being a few examples. Substrate material 12 may comprise silicon. Through-substrate vias have also been referred to in the art as through silicon vias (TSVs). In this document, “through-substrate vias” encompass or are generic to through-silicon vias, and through-substrate vias include conductive vias extending through substrate material regardless of whether any of that material is silicon.
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In one embodiment, the annealing is conducted in an inert atmosphere. In one embodiment the annealing is conducted at a temperature of from about 150° C. to 450° C. for from about 0.5 hour to about 3 hours, although sufficient annealing may occur in much less time. Atmospheric, subatmospheric, or pressures higher than atmospheric may be used. The annealing may be a dedicated anneal for purposes of forming the alloy or may occur in conjunction with other thermal processing of the substrate.
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The copper may be electrodeposited first and the one other element or elements electrodeposited to fill the voids. Alternately, the one other element or elements may be electrodeposited first and the copper electrodeposited to fill the voids. In one embodiment and as shown, the outwardly opening voids and the filled voids may be centered radially within through-substrate via openings 20. In one embodiment, all conductive material within through-substrate via openings 20 consists essentially of alloy 30, but for any conductive copper diffusion barrier material (not shown) that might be present radially outward of said alloy, and independent of whether the filled voids are centered radially within the through-substrate via openings.
The first electrodeposited material 26 and the second electrodeposited material 28 may be of the same lateral thickness (not shown) or of different lateral thicknesses (as shown). If of different thicknesses, either may be thicker than the other. For example, the embodiments of
The separate electrodepositings may be of copper and only one other element or of copper and multiple elements other than copper. In one embodiment, the alloy consists essentially of copper and zinc, copper and tin, or copper and nickel.
Regardless of whether the separate electrodepositings are of copper and only one other element, the total number of electrodepositings may be two or more than two. The above
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In one embodiment, only one other element than copper is used, and in one embodiment, the alloy consists essentially of copper and such other element.
Each of the above embodiments are but examples of methods of forming through-substrate vias. Such methods encompass separately electrodepositing copper and at least one element other than copper to fill remaining volume of through-substrate via openings that have been formed within a substrate. The electrodeposited copper and the at least one other element are annealed to form an alloy of the copper and the at least one element which ultimately forms conductive through-substrate via structures which comprise the alloy. Two or more electrodepositings may be conducted wherein a first of the separate electrodepositings is of copper or where the first of the separate electrodepositings is of an element other than copper. Regardless, embodiments of the invention also encompass the last of the separate electrodepositings being of copper, or the last of the separate electrodepositings being of an element other than copper.
CONCLUSIONIn some embodiments, methods of forming through-substrate vias comprise separately electrodepositing copper and at least one element other than copper to fill remaining volume of through-substrate via openings formed within a substrate. The electrodeposited copper and the at least one other element are annealed to form an alloy of the copper and the at least one other element, and which is used in forming conductive through-substrate via structures comprising the alloy.
In some embodiments, methods of forming through-substrate vias comprise forming through-substrate via openings partially through a substrate from a first side of the substrate. Sidewalls of the through-substrate via openings are lined with dielectric. Conductive seed material is lined laterally over the dielectric within the through-substrate via openings. Copper and at least one element other than copper are separately electrodeposited to fill remaining volume of the through-substrate via openings. The electrodeposited copper and the at least one other element are annealed to form an alloy of the copper and the at least one other element. After the annealing, substrate material is removed from a second side of the substrate opposite the first side to expose and project conductive through-substrate via structures comprising the alloy from the second side of the substrate.
In some embodiments, methods of forming through-substrate vias comprise electrodepositing one of copper or one element other than copper to form a metal lining within respective through-substrate via openings formed within a substrate. The metal lining forms an outwardly open void within the respective through-substrate via openings. The other of the copper or one element is electrodeposited to fill the voids. The electrodeposited copper and one element are annealed to form an alloy of the copper and one element, and which is used in forming conductive through-substrate via structures comprising the alloy.
In some embodiments, methods of forming through-substrate vias comprise electrodepositing one of copper or an element other than copper to form a first metal lining within respective through-substrate via openings formed within a substrate. The first metal lining is formed laterally inward of and directly against a conductive seed material formed over sidewalls of the respective through-substrate via openings. The first metal lining forms an outwardly open first void within the respective through-substrate via openings. The other of the copper or other element is electrodeposited to form a second metal lining within the respective through-substrate via openings. The second metal lining is formed laterally inward of and directly against the first metal lining. The second metal lining forms an outwardly open second void within the respective through-substrate via openings. The second voids are filled with electrodeposited metal. The substrate is annealed to form an alloy containing at least copper and the other element, and which is used in forming conductive through-substrate via structures comprising the alloy.
In compliance with the statute, the subject matter disclosed herein has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the claims are not limited to the specific features shown and described, since the means herein disclosed comprise example embodiments. The claims are thus to be afforded full scope as literally worded, and to be appropriately interpreted in accordance with the doctrine of equivalents.
Claims
1. A method of forming through-substrate vias, comprising:
- separately electrodepositing copper and at least one element other than copper to fill remaining volume of through-substrate via openings formed within a substrate; and
- annealing the electrodeposited copper and the at least one other element to form an alloy of the copper and the at least one other element, and forming conductive through-substrate via structures comprising the alloy.
2. The method of claim 1 wherein the electrodepositings are of copper and only one other element.
3. The method of claim 2 wherein the alloy consists essentially of either copper and zinc or copper and tin.
4. The method of claim 3 wherein the alloy consists essentially of copper and zinc, with the zinc being at from about 0.5% to 25% by weight in the alloy.
5. The method of claim 2 comprising a total of two electrodepostings.
6. The method of claim 2 comprising a total of more than two electrodepostings.
7. The method of claim 6 comprising a total of more than three electrodepostings.
8. The method of claim 7 comprising alternating every copper electrodepositing with electrodepositing of the other element.
9. The method of claim 1 wherein the electrodepositings are of copper and multiple elements other than copper.
10. The method of claim 9 comprising a total of three electrodepositings.
11. The method of claim 9 comprising a total of more than three electrodepositings.
12. The method of claim 1 comprising conducting the annealing in an inert atmosphere.
13. The method of claim 1 comprising conducting the annealing at from about 150° C. to 450° C. for from about 0.5 hour to about 3 hours.
14. The method of claim 1 wherein the alloy is homogenous.
15. The method of claim 1 wherein all conductive material within the through-substrate via openings consists essentially of the alloy, but for any conductive copper diffusion barrier material that might be present radially outward of said alloy.
16. The method of claim 15 wherein the alloy is homogenous.
17. A method of forming through-substrate vias, comprising:
- forming through-substrate via openings partially through a substrate from a first side of the substrate;
- lining sidewalls of the through-substrate via openings with dielectric;
- lining conductive seed material laterally over the dielectric within the through-substrate via openings;
- separately electrodepositing copper and at least one element other than copper to fill remaining volume of the through-substrate via openings;
- annealing the electrodeposited copper and the at least one other element to form an alloy of the copper and the at least one other element; and
- after the annealing, removing substrate material from a second side of the substrate opposite the first side to expose and project conductive through-substrate via structures comprising the alloy from the second side of the substrate.
18. The method of claim 17 wherein the seed material comprises copper.
19. The method of claim 17 comprising lining diffusion barrier material over the dielectric within the through-substrate via openings before providing the conductive seed material within the through-substrate via openings.
20. The method of claim 17 wherein the first of the separate electrodepositings is of copper.
21. The method of claim 17 wherein the first of the separate electrodepositings is of an element other than copper.
22. The method of claim 17 wherein the last of the separate electrodepositings is of copper.
23. The method of claim 17 wherein the last of the separate electrodepositings is of an element other than copper.
24. The method of claim 17 wherein the at least one other element comprises at least one of tin or zinc.
25. A method of forming through-substrate vias, comprising:
- electrodepositing one of copper or one element other than copper to form a metal lining within respective through-substrate via openings formed within a substrate, the metal lining forming an outwardly open void within the respective through-substrate via openings;
- electrodepositing the other of the copper or one element to fill the voids; and
- annealing the electrodeposited copper and one element to form an alloy of the copper and one element, and forming conductive through-substrate via structures comprising the alloy.
26. The method of claim 25 wherein copper is electrodeposited first and the one element is electrodeposited to fill the voids.
27. The method of claim 25 wherein the one element is electrodeposited first and copper is electrodeposited to fill the voids.
28. The method of claim 25 wherein the outwardly open voids and the filled voids are centered radially within the through-substrate via openings.
29. The method of claim 25 comprising electrodepositing the copper to be laterally thicker than the electrodeposited one element.
30. A method of forming through-substrate vias, comprising:
- electrodepositing one of copper or an element other than copper to form a first metal lining within respective through-substrate via openings formed within a substrate, the first metal lining being formed laterally inward of and directly against a conductive seed material formed over sidewalls of the respective through-substrate via openings, the first metal lining forming an outwardly open first void within the respective through-substrate via openings;
- electrodepositing the other of the copper or other element to form a second metal lining within the respective through-substrate via openings, the second metal lining being formed laterally inward of and directly against the first metal lining, the second metal lining forming an outwardly open second void within the respective through-substrate via openings;
- filling the second voids with electrodeposited metal; and
- annealing the substrate to form an alloy containing at least copper and the other element, and forming conductive through-substrate via structures comprising the alloy.
31. The method of claim 30 wherein the alloy consists essentially of copper and said other element.
32. The method of claim 30 wherein filling the second voids comprises:
- electrodepositing the one of the copper or other element to form a third metal lining within the respective through-substrate via openings, the third metal lining being formed laterally inward of and directly against the second metal lining, the third metal lining forming an outwardly open third void within the respective through-substrate via openings; and
- filling the third voids with electrodeposited metal.
33. The method of claim 32 wherein the alloy consists essentially of copper and said other element.
34. The method of claim 32 wherein filling the third voids comprises:
- electrodepositing the other of the copper or other element to form a fourth metal lining within the respective through-substrate via openings, the fourth metal lining being formed laterally inward of and directly against the third metal lining, the fourth metal lining forming an outwardly open fourth void within the respective through-substrate via openings; and
- filling the fourth voids with electrodeposited metal.
35. The method of claim 34 wherein the alloy consists essentially of copper and said other element.
Type: Application
Filed: Sep 28, 2011
Publication Date: Mar 28, 2013
Applicant: MICRON TECHNOLOGY, INC. (Boise, ID)
Inventor: Luke G. England (Boise, ID)
Application Number: 13/247,769
International Classification: C25D 5/02 (20060101);