Surface area and Schottky barrier height engineering for contact trench epitaxy
Forming a contact is disclosed. A trench through an interlayer dielectric layer is opened down to a substrate. The interlayer dielectric layer is formed on the substrate such that the substrate is the bottom surface of the trench. A cleaning process of the trench is performed. The bottom surface of the trench is recessed. A trench contact epitaxial layer is formed in the trench. An oxide layer is formed on top of the trench contact epitaxial layer in the trench. A metal oxide layer is formed on top of the oxide layer in the trench. A metal contact is formed on top of the metal oxide layer, where the oxide layer and the metal oxide layer together form a dipole layer.
1. A method of forming a contact, the method comprising:
opening a trench through an interlayer dielectric layer down to a substrate, wherein the interlayer dielectric layer is formed on the substrate such that the substrate is a bottom surface of the trench;
performing a cleaning process of the trench;
recessing the bottom surface of the trench in the substrate, the recessing forms angled planes at a bottom of the trench such that a center of the recessed angled planes of the trench is a lowest part of the trench compared to both sides of the recessed angled planes of the trench;
forming a trench contact epitaxial layer in the trench in the substrate, such that the trench contact epitaxial layer is formed to extend from within the substrate and protrude above an uppermost surface of the substrate, the trench contact epitaxial layer being in direct contact with the bottom surface of the trench, wherein an angled portion of the trench contact epitaxial layer protrudes in an opposite direction to the center of the recessed angled planes of the trench, the angled portion being substantially above the center of the recessed angled planes;
forming an oxide layer on top of the trench contact epitaxial layer in the trench;
forming a metal oxide layer on top of the oxide layer in the trench; and
forming a metal contact on top of the metal oxide layer, wherein the oxide layer and the metal oxide layer together form a dipole layer.
2. The method of claim 1 , wherein the cleaning process of the trench includes baking in hydrogen gas.
3. The method of claim 2 , wherein the cleaning process of the trench further includes in-situ plasma cleaning of the trench.
4. The method of claim 3 , wherein the in-situ plasma cleaning is with a compound of hydrogen and nitrogen, a compound of nitrogen and fluorine, or both the compound of hydrogen and nitrogen and the compound of nitrogen and fluorine.
5. The method of claim 1 , wherein recessing the bottom surface of the trench includes anisotropic etching of the bottom surface of the trench along planes, the planes being at angles defined by a bottom surface plane of the trench.
6. The method of claim 1 , wherein the dipole layer is configured to reduce contact resistance between the trench contact epitaxial layer and the metal contact as compared to having no dipole layer present.
7. The method of claim 1 , wherein the trench contact epitaxial layer includes facets.
8. The method of claim 1 , wherein the substrate is a fin of a transistor.
9. The method of claim 1 , wherein the trench contact epitaxial layer is formed over a source or a drain.
10. The method claim 1 , wherein the trench contact epitaxial layer is doped with p-type dopants or n-type dopants.
11. The method of claim 1 , wherein the metal oxide layer includes material for a p-type transistor or an n-type transistor.
12. The method of claim 1 , wherein the metal oxide layer includes lanthanum and oxygen for an n-type transistor.
13. The method of claim 1 , wherein the metal oxide layer includes aluminum and oxygen for a p-type transistor.
14. The method of claim 1 , wherein the recessed angled planes are not formed in the interlayer dielectric layer but are formed below the interlayer dielectric layer in the substrate.
15. The method of claim 1 , wherein the dipole layer comprises a shape of the angled portion of the trench contact epitaxial layer.
16. The method of claim 1 , wherein the angled portion forms a peak of the trench contact epitaxial layer above the center of the recessed angled planes.
17. A method of forming a contact, the method comprising:
performing a cleaning process of a trench formed in a substrate;
recessing a bottom surface of the trench in the substrate, the recessing etches a groove with angled surfaces such that a center of the recessed angled planes of the trench is a lowest part of the trench compared to both sides of the recessed angled planes of the trench;
forming a trench contact epitaxial layer in the trench in the substrate, such that the trench contact epitaxial layer is formed to extend from within the substrate and protrude above an uppermost surface of the substrate, the trench contact epitaxial layer being in direct contact with the bottom surface of the trench, wherein an angled portion of the trench contact epitaxial layer protrudes in an opposite direction to the center of the recessed angled planes of the trench, the angled portion being substantially above the center of the recessed angled planes;
forming a dipole layer on top of the trench contact epitaxial layer, the dipole layer comprising an oxide layer and a metal oxide layer; and
forming a metal contact on top of the dipole layer.
18. The method of claim 17 , wherein the oxide layer is formed on top of the trench contact epitaxial layer in the trench and the metal oxide layer is formed on top of the oxide layer in the trench.
19. The method of claim 17 , wherein the cleaning process of the trench includes baking in hydrogen gas and in-situ plasma cleaning of the trench.
20. The method of claim 19 , wherein the in-situ plasma cleaning is with a compound of hydrogen and nitrogen, a compound of nitrogen and fluorine, or both the compound of hydrogen and nitrogen and the compound of nitrogen and fluorine.