Bulk semiconductor fins with self-aligned shallow trench isolation structures
View Patent ↗A silicon-carbon alloy layer and a silicon-germanium alloy layer are sequentially formed on a silicon-containing substrate with epitaxial alignment. Trenches are formed in the silicon-germanium alloy layer by an anisotropic etch employing a patterned hard mask layer as an etch mask and the silicon-carbon alloy layer as an etch stop layer. Fin-containing semiconductor material portions are formed on a bottom surface and sidewalls of each trench with epitaxial alignment with the silicon-germanium alloy layer and the silicon-carbon alloy layer. The hard mask layer and the silicon-germanium alloy layer are removed, and an oxygen-impermeable spacer is formed on sidewalls of each fin-containing semiconductor material portion. Physically exposed semiconductor portions are converted into semiconductor oxide portions, and the oxygen-impermeable spacers are removed. The remaining portions of the fin-containing semiconductor portions include semiconductor fins, which can be employed to form semiconductor devices.
1. A semiconductor structure comprising:
a silicon-carbon alloy layer located on a semiconductor substrate;
a silicon-containing semiconductor fin located on said silicon-carbon alloy layer, wherein said silicon-containing semiconductor fin and said silicon-carbon alloy layer are single crystalline and in epitaxial alignment with each other, and wherein a lower portion of said silicon-containing semiconductor fin has a variable width that decreases with a vertical distance from a horizontal plane including an interface between said silicon-carbon alloy layer and said silicon-containing semiconductor fin, and an upper portion of said silicon-containing semiconductor fin has a uniform width that is equal to a minimum width of said lower portion of said silicon-containing semiconductor fin; and
a shallow trench isolation structure contacting said silicon-containing semiconductor fin and said silicon-carbon alloy layer and including an oxide of a silicon-containing semiconductor material in an upper portion thereof.
2. The semiconductor structure of claim 1 , wherein said shallow trench isolation structure includes a portion in which an atomic concentration of silicon decreases with a vertical distance from a horizontal plane including a topmost surface of said shallow trench isolation structure toward said semiconductor substrate.
3. The semiconductor structure of claim 2 , wherein said shallow trench isolation structure includes another portion in which an atomic concentration of carbon decreases with a vertical distance from a horizontal plane including an interface between said silicon-containing semiconductor fin and said silicon-carbon alloy layer away from said semiconductor substrate.
4. The semiconductor structure of claim 1 , wherein said shallow trench isolation structure further comprises an alloy of at least silicon and carbon in a lower portion thereof.
5. The semiconductor structure of claim 2 , wherein said lower portion of said shallow trench isolation structure comprises an oxide of an alloy of silicon and carbon.
6. The semiconductor structure of claim 1 , further comprising another shallow trench isolation structure in contact with said silicon-carbon alloy layer and comprising an oxide of an alloy of silicon and carbon in an upper portion thereof.
7. The semiconductor structure of claim 6 , wherein a lower portion of said another shallow trench isolation structure extends into an upper portion of said semiconductor substrate.
8. The semiconductor structure of claim 7 , wherein an atomic concentration of carbon decreases with a vertical distance from a horizontal plane including an interface between said silicon-containing semiconductor fin and said silicon-carbon alloy layer toward said semiconductor substrate within said lower portion of said another shallow trench isolation structure.
9. The semiconductor structure of claim 6 , wherein said another shallow trench isolation structure is substantially free of germanium.
10. The semiconductor structure of claim 1 , further comprising a fin cap dielectric portion comprising an oxide of a semiconductor material in said silicon-containing semiconductor fin and laterally protruding outward from vertical planes including sidewalls of said silicon-containing semiconductor fin.
11. The semiconductor structure of claim 1 , wherein a first sidewall of said silicon-containing semiconductor fin is substantially vertical between an interface between said silicon-carbon alloy layer and said silicon-containing semiconductor fin and a top surface of said silicon-containing semiconductor fin, and a second sidewall of said silicon-containing semiconductor fin includes a substantially vertical upper portion and a convex surface that contacts said interface at a non-orthogonal angle.
12. A semiconductor structure comprising:
a silicon-carbon alloy layer located on a semiconductor substrate;
a silicon-containing semiconductor fin located on said silicon-carbon alloy layer, wherein said silicon-containing semiconductor fin and said silicon-carbon alloy layer are single crystalline and in epitaxial alignment with each other, and wherein a first sidewall of said silicon-containing semiconductor fin is substantially vertical between an interface between said silicon-carbon alloy layer and said silicon-containing semiconductor fin and a top surface of said silicon-containing semiconductor fin, and a second sidewall of said silicon-containing semiconductor fin includes a substantially vertical upper portion and a convex surface that contacts said interface at a non-orthogonal angle; and
a shallow trench isolation structure contacting said silicon-containing semiconductor fin and said silicon-carbon alloy layer and including an oxide of a silicon-containing semiconductor material in an upper portion thereof.
13. The semiconductor structure of claim 12 , wherein said shallow trench isolation structure includes a portion in which an atomic concentration of silicon decreases with a vertical distance from a horizontal plane including a topmost surface of said shallow trench isolation structure toward said semiconductor substrate.
14. The semiconductor structure of claim 13 , wherein said shallow trench isolation structure includes another portion in which an atomic concentration of carbon decreases with a vertical distance from a horizontal plane including an interface between said silicon-containing semiconductor fin and said silicon-carbon alloy layer away from said semiconductor substrate.
15. The semiconductor structure of claim 12 , further comprising another shallow trench isolation structure in contact with said silicon-carbon alloy layer and comprising an oxide of an alloy of silicon and carbon in an upper portion thereof.
16. The semiconductor structure of claim 15 , wherein a lower portion of said another shallow trench isolation structure extends into an upper portion of said semiconductor substrate.
17. The semiconductor structure of claim 12 , further comprising a fin cap dielectric portion comprising an oxide of a semiconductor material in said silicon-containing semiconductor fin and laterally protruding outward from vertical planes including sidewalls of said silicon-containing semiconductor fin.
18. The semiconductor structure of claim 12 , wherein a lower portion of said silicon-containing semiconductor fin has a variable width that decreases with a vertical distance from a horizontal plane including an interface between said silicon-carbon alloy layer and said silicon-containing semiconductor fin, and an upper portion of said silicon-containing semiconductor fin has a uniform width that is equal to a minimum width of said lower portion of said silicon-containing semiconductor fin.