Methods for directly bonding together semiconductor structures, and bonded semiconductor structures formed using such methods
View Patent ↗Embodiments of the present invention include methods of directly bonding together semiconductor structures. In some embodiments, a cap layer may be provided at an interface between directly bonded metal features of the semiconductor structures. In some embodiments, impurities are provided within the directly bonded metal features of the semiconductor structures. Bonded semiconductor structures are formed using such methods.
1. A method of directly bonding a first semiconductor structure to a second semiconductor structure, comprising:
forming a cap layer comprising a metal and silicon at a surface of a first metal feature on the first semiconductor structure, a surface of the cap layer defining a first bonding surface of the first metal feature; and
directly bonding a second bonding surface of a second metal feature on the second semiconductor structure to the first bonding surface of the first metal feature on the first semiconductor structure.
2. The method of claim 1 , further comprising forming the first metal feature to comprise copper.
3. The method of claim 2 , wherein forming the cap layer comprising a metal and silicon comprises forming a copper compound comprising silicon at the surface of the first metal feature.
4. The method of claim 1 , wherein forming the cap layer comprising a metal and silicon comprises forming a metal silicide.
5. The method of claim 1 , wherein forming the cap layer comprising a metal and silicon comprises forming a cap layer comprising a metal and silicon and nitrogen.
6. The method of claim 1 , further comprising:
forming the first bonding surface to have a first size; and
forming the second bonding surface to have a second size different from the first size of the first bonding surface.
7. The method of claim 1 , further comprising:
forming the first bonding surface to have a first shape; and
forming the second bonding surface to have a second shape different from the first shape of the first bonding surface.
8. The method of claim 1 , wherein directly bonding the second bonding surface to the first bonding surface comprises an ultra-low temperature direct bonding process.
9. The method of claim 1 , wherein directly bonding the second bonding surface to the first bonding surface comprises a surface assisted bonding process.
10. The method of claim 1 , wherein directly bonding the second bonding surface to the first bonding surface comprises abutting the first bonding surface directly against the second bonding surface in an environment at a temperature less than about two hundred degrees Celsius (200° C.).
11. The method of claim 10 , further comprising applying pressure between the first bonding surface and the second bonding surface in the environment at a temperature less than about two hundred degrees Celsius (200° C.).
12. The method of claim 11 , wherein applying pressure between the first bonding surface and the second bonding surface in the environment at a temperature less than about two hundred degrees Celsius (200° C.) comprises applying pressure between the first bonding surface and the second bonding surface in an environment at a temperature less than about one hundred degrees Celsius (100° C.).
13. The method of claim 12 , wherein applying pressure between the first bonding surface and the second bonding surface in the environment at a temperature less than about one hundred degrees Celsius (100° C.) comprises applying pressure between the first bonding surface and the second bonding surface in an environment at about room temperature.
14. The method of claim 1 , further comprising doping the first metal feature on the first semiconductor structure with impurities prior to directly bonding the second bonding surface to the first bonding surface.
15. The method of claim 1 , further comprising forming a cap layer comprising a metal and silicon at a surface of the second metal feature on the second semiconductor structure prior to directly bonding the second bonding surface to the first bonding surface, a surface of the cap layer at the surface of the second metal feature defining the second bonding surface of the second metal feature.
16. A method of directly bonding a first semiconductor structure to a second semiconductor structure, comprising:
doping a first metal feature on the first semiconductor structure with impurities; and
directly bonding a second metal feature on the second semiconductor structure to the first metal feature on the first semiconductor structure.
17. The method of claim 16 , further comprising selecting the impurities to comprise at least one of aluminum, silver, and manganese.
18. The method of claim 16 , wherein doping the first metal feature comprises:
forming a metal seed layer including the impurities; and
forming the first metal feature over the metal seed layer and diffusing the impurities from the metal seed layer into the first metal feature.
19. The method of claim 16 , further comprising forming the first metal feature to comprise copper.
20. The method of claim 16 , further comprising:
forming the first bonding surface to have a first size; and
forming the second bonding surface to have a second size different from the first size of the first bonding surface.
21. The method of claim 16 , further comprising:
forming the first bonding surface to have a first shape; and
forming the second bonding surface to have a second shape different from the first shape of the first bonding surface.
22. The method of claim 16 , wherein directly bonding the second bonding surface to the first bonding surface comprises an ultra-low temperature direct bonding process.
23. The method of claim 16 , wherein directly bonding the second bonding surface to the first bonding surface comprises a surface assisted bonding process.
24. The method of claim 16 , wherein directly bonding the second bonding surface to the first bonding surface comprises abutting the first bonding surface directly against the second bonding surface in an environment at a temperature less than about two hundred degrees Celsius (200° C.).
25. The method of claim 24 , further comprising applying pressure between the first bonding surface and the second bonding surface in the environment at a temperature less than about two hundred degrees Celsius (200° C.).
26. A bonded semiconductor structure, comprising:
a first semiconductor structure comprising a first metal feature; and
a second semiconductor structure comprising a second metal feature, the second metal feature of the second semiconductor structure directly bonded to the first metal feature of the first semiconductor structure; and
impurities at a bonding interface between the first metal feature and the second metal feature.
27. The bonded semiconductor structure of claim 26 , wherein the impurities comprise at least one of aluminum, silver, and manganese.
28. The bonded semiconductor structure of claim 26 , wherein the impurities comprise at least one of silicon and nitrogen.
29. The bonded semiconductor structure of claim 26 , wherein the impurities comprise at least one of cobalt, tungsten, and phosphorous.
30. The bonded semiconductor structure of claim 26 , wherein at least one of the first metal feature and the second metal feature comprises copper.
31. The bonded semiconductor structure of claim 26 , wherein:
the first metal feature has a first cross-sectional area in a plane parallel to a bonded interface between the first metal feature and the second metal feature; and
the second metal feature has a second cross-sectional area in a plane parallel to the bonded interface between the first metal feature and the second metal feature, the second cross-sectional area differing from the first cross-sectional area.
32. The bonded semiconductor structure of claim 26 , wherein:
the first metal feature has a first cross-sectional shape in a plane parallel to a bonded interface between the first metal feature and the second metal feature; and
the second metal feature has a second cross-sectional shape in a plane parallel to the bonded interface between the first metal feature and the second metal feature, the second cross-sectional shape differing from the first cross-sectional shape.
33. A bonded semiconductor structure, comprising:
a first semiconductor structure comprising a first metal feature comprising a first major surface;
a second semiconductor structure comprising a second metal feature at least partially surrounded by a dielectric material, the second metal feature of the second semiconductor structure having a second major surface directly bonded to a portion of the first major surface of the first metal feature of the first semiconductor structure; and
a cap material disposed directly between a surface of the dielectric material and another portion of the first major surface of the first metal feature of the first semiconductor structure, the cap material not present at a bonded interface between the second major surface of the second metal feature and the portion of the first major surface of the first metal feature, and the cap material having a composition differing from a composition of the first metal feature.
34. The bonded semiconductor structure of claim 33 , wherein the cap material comprises a dielectric material.
35. The bonded semiconductor structure of claim 34 , wherein the cap material comprises at least one of CuSiN, SiC, and SiN.
36. The bonded semiconductor structure of claim 33 , wherein the cap material comprises a conductive material.
37. The bonded semiconductor structure of claim 36 , wherein the cap material comprises CoWP.
38. The bonded semiconductor structure of claim 33 , wherein at least one of the first metal feature and the second metal feature comprises copper.
39. The bonded semiconductor structure of claim 33 , wherein:
the first metal feature has a first cross-sectional area in a plane parallel to a bonded interface between the first metal feature and the second metal feature; and
the second metal feature has a second cross-sectional area in a plane parallel to the bonded interface between the first metal feature and the second metal feature, the second cross-sectional area differing from the first cross-sectional area.
40. The bonded semiconductor structure of claim 33 , wherein:
the first metal feature has a first cross-sectional shape in a plane parallel to a bonded interface between the first metal feature and the second metal feature; and
the second metal feature has a second cross-sectional shape in a plane parallel to the bonded interface between the first metal feature and the second metal feature, the second cross-sectional shape differing from the first cross-sectional shape.
41. A method of directly bonding a first semiconductor structure to a second semiconductor structure, comprising:
doping a first metal feature on the first semiconductor structure with impurities;
forming a metal cap layer at a surface of the first metal feature on the first semiconductor structure, a surface of the metal cap layer defining a first bonding surface of the first metal feature, the first metal feature configured to carry electrical current during use of the first semiconductor structure, the metal cap layer having a composition hindering electromigration of atoms of the first metal feature during use of the first semiconductor structure; and
directly bonding a second bonding surface of a second metal feature on the second semiconductor structure to the first bonding surface of the first metal feature on the first semiconductor structure.
42. A method of directly bonding a first semiconductor structure to a second semiconductor structure, comprising:
forming a metal cap layer at a surface of a first metal feature on the first semiconductor structure, a surface of the metal cap layer defining a first bonding surface of the first metal feature, the first metal feature configured to carry electrical current during use of the first semiconductor structure, the metal cap layer having a composition hindering electromigration of atoms of the first metal feature during use of the first semiconductor structure;
forming another metal cap layer at a surface of a second metal feature on the second semiconductor structure, a surface of the another metal cap layer at the surface of the second metal feature defining a second bonding surface of the second metal feature; and
directly bonding the second bonding surface of the second metal feature on the second semiconductor structure to the first bonding surface of the first metal feature on the first semiconductor structure.