Liner-free through-silicon-vias formed by selective metal deposition
Structures for a through-silicon via and methods of forming a structure for a through-silicon via. The structure includes a substrate having a trench and surfaces that border the trench. The structure further includes a through-silicon via having a layer inside the trench. The layer is in direct contact with the surfaces of the substrate.
1. A structure comprising:
a substrate including a trench and a plurality of surfaces that border the trench; and
a through-silicon via including a layer inside the trench, the layer in direct contact with the plurality of surfaces of the substrate, the layer including a first portion adjoining the plurality of surfaces and a second portion that is positioned inside the first portion, the first portion of the layer having a first average grain size, and the second portion of the layer having a second average grain size that differs from the first average grain size.
2. The structure of claim 1 wherein the second average grain size is greater than the first average grain size.
3. The structure of claim 1 wherein the layer comprises a metal.
4. The structure of claim 1 wherein the layer comprises tungsten.
5. The structure of claim 1 wherein the layer exclusively contains tungsten.
6. The structure of claim 1 wherein the through-silicon via is free of a liner between the layer and the plurality of surfaces of the substrate.
7. The structure of claim 6 wherein the layer comprises tungsten.
8. The structure of claim 6 wherein the layer exclusively contains tungsten.
9. The structure of claim 1 wherein the through-silicon via is a single piece of continuous tungsten.
10. The structure of claim 1 wherein the through-silicon via exclusively includes the layer.
11. The structure of claim 1 wherein the trench includes a sidewall and a bottom, and the plurality of surfaces of the substrate are coextensive with the sidewall and the bottom of the trench.
12. The structure of claim 11 wherein the substrate is a bulk semiconductor substrate comprising single-crystal silicon.
13. The structure of claim 1 wherein the layer is surrounded by the plurality of surfaces of the substrate.
14. The structure of claim 1 wherein the through-silicon via is unitary.
15. The structure of claim 1 wherein the substrate comprises silicon, the layer comprises tungsten, and the plurality of surfaces define respective interfaces between the silicon of the substrate and the tungsten of the layer.
16. A method of forming a through-silicon via, the method comprising:
forming a trench in a substrate, wherein the substrate includes a plurality of surfaces that border the trench; and
forming a layer inside the trench to define the through-silicon via, wherein the layer directly contacts the plurality of surfaces of the substrate,
wherein the layer includes a first portion adjoining the plurality of surfaces, a second portion that is positioned inside the first portion, the first portion of the layer has a first average grain size, and the second portion of the layer has a second average grain size that is differs from the first average grain size.
17. The method of claim 16 wherein the layer comprises tungsten formed by a selective deposition process using tungsten hexafluoride and hydrogen as reactant gases.
18. The method of claim 16 wherein the layer comprises tungsten formed by a substantially selective deposition process using tungsten hexafluoride and hydrogen as reactant gases.
19. The method of claim 16 wherein the layer comprises tungsten that is formed by a deposition process using tungsten hexafluoride and hydrogen as reactant gases, and forming the layer inside the trench to define the through-silicon via comprises:
depositing an outer portion of the layer with a silicon reduction reaction; and
depositing an inner portion of the layer with a hydrogen reduction reaction.
20. The method of claim 16 wherein the second average grain size is greater than the first average grain size.