Deep isolation trench structure and deep trench capacitor on a semiconductor-on-insulator substrate
Two trenches having different widths are formed in a semiconductor-on-insulator (SOI) substrate. An oxygen-impermeable layer and a fill material layer are formed in the trenches. The fill material layer and the oxygen-impermeable layer are removed from within a first trench. A thermal oxidation is performed to convert semiconductor materials underneath sidewalls of the first trench into an upper thermal oxide portion and a lower thermal oxide portion, while the remaining oxygen-impermeable layer on sidewalls of a second trench prevents oxidation of the semiconductor materials. After formation of a node dielectric on sidewalls of the second trench, a conductive material is deposited to fill the trenches, thereby forming a conductive trench fill portion and an inner electrode, respectively. The upper and lower thermal oxide portions function as components of dielectric material portions that electrically isolate two device regions.
1. A method of forming a semiconductor structure comprising:
forming a first trench and a second trench in a semiconductor-on-insulator (SOI) substrate including a stack, from bottom to top of, at least one semiconductor layer, a buried insulator layer, and a top semiconductor layer;
providing a contiguous oxygen-impermeable layer on sidewalls of said first trench and second trench in said SOI substrate;
depositing a fill material layer on said contiguous oxygen-impermeable layer, wherein a cavity is present within said first trench after said depositing said fill material layer in said first trench, and wherein after said depositing said fill material layer said second trench is completely filled with said fill material layer and said contiguous oxygen-impermeable layer;
isotropically etching said fill material layer, wherein said fill material layer is completely removed within said first trench, and a remaining portion of said fill material layer is present within said second trench;
removing said oxygen-impermeable layer from said sidewalls of said first trench, but not said second trench;
oxidizing semiconductor materials on said sidewalls of said first trench, while said oxygen-impermeable layer covers said sidewalls of said second trench; and
depositing a conductive material in said first trench and said second trench.
2. The method of claim 1 , wherein a semiconductor material of said at least one semiconductor layer around said first trench is oxidized to form a bottom semiconductor oxide portion, and a semiconductor material of said top semiconductor layer around said first trench is oxidized to form a top semiconductor oxide portion.
3. The method of claim 1 , wherein a first conductive material portion comprising said conductive material is formed in said first trench, and a second conductive material portion comprising said conductive material is formed in said second trench.
4. The method of claim 3 , wherein a node dielectric is formed in said second trench, and wherein said second conductive material portion, said node dielectric, and a portion of said at least one semiconductor layer collectively constitute a trench capacitor.
5. The method of claim 4 , further comprising removing a portion of said oxygen-impermeable layer from above a top surface of said second conductive material portion within said second trench, wherein a remaining portion of said oxygen-impermeable layer provides said node dielectric.
6. The method of claim 1 , wherein a top surface of said remaining portion of said fill material layer is located above a level of a topmost surface of said buried insulator layer.
7. The method of claim 2 , further comprising:
removing said oxygen-impermeable layer from said second trench; and
depositing a contiguous node dielectric layer on sidewalls of said bottom semiconductor oxide portion and on said sidewalls of said second trench, wherein a portion of said contiguous node dielectric layer provides a node dielectric.
8. The method of claim 2 , further comprising depositing a contiguous node dielectric layer on sidewalls of said bottom semiconductor oxide portion and on said sidewalls of said second trench.
9. The method of claim 8 , wherein a stack of a portion of said oxygen-impermeable layer and a portion of said contiguous node dielectric layer provides a node dielectric.
10. The method of claim 3 , further comprising forming a first shallow trench isolation structure within said first trench and above said first conductive material portion.
11. The method of claim 10 , wherein a lower portion of said first shallow trench isolation structure is formed below a horizontal plane including a top surface of said buried insulator layer.