Method of forming stressed SOI layer
One or more embodiments of the invention concerns a method of forming a semiconductor layer having uniaxial stress including: forming, in a surface of a semiconductor structure having a stressed semiconductor layer and an insulator layer, at least two first trenches in a first direction delimiting a first dimension of at least one first transistor to be formed in the semiconductor structure; performing a first anneal to decrease the viscosity of the insulating layer; and forming, in the surface after the first anneal, at least two second trenches in a second direction delimiting a second dimension of the at least one transistor.
1. A method of forming a semiconductor layer, the method comprising:
forming, in a surface of a semiconductor structure having a stressed semiconductor layer and an insulator layer having a viscosity, at least two first trenches in a first direction delimiting a first dimension of at least one first transistor to be formed in said semiconductor structure;
decreasing the viscosity of said insulating layer by performing a first anneal step; and
forming, in said surface after said first anneal step, at least two second trenches in a second direction delimiting a second dimension of said at least one transistor.
2. The method of claim 1 , further comprising:
forming first isolation trenches by depositing an insulating material to at least partially fill said at least two second trenches, the insulating material having a viscosity; and
decreasing the viscosity of said insulating material by performing a second anneal step.
3. The method of claim 2 , wherein said first anneal step has at least one of a temperature and a duration that is greater than said second anneal step.
4. The method of claim 2 , wherein:
said first anneal step is performed at a temperature of between 1000° C. and 1150° C.; and
said second anneal step is performed at a temperature of between 900° C. and 1000° C.
5. The method of claim 2 , wherein:
said first anneal step is performed for a duration of between 30 and 90 minutes; and
said second anneal step is performed for a duration of between 15 and 30 minutes.
6. The method of claim 2 , wherein depositing said insulating material further comprises forming second isolation trenches by at least partially filling said at least two first trenches.
7. The method of claim 1 , further comprising, prior to said first anneal step, forming first isolation trenches by depositing an insulating material to at least partially fill said at least two first trenches.
8. The method of claim 1 , wherein:
each of said at least one first transistor is a p-channel MOS transistor, said stressed semiconductor layer has a compressive stress, and wherein said first dimension is the width of said at least one first transistor; or
each of said at least one first transistor is an n-channel MOS transistor, said stressed semiconductor layer has a tensile stress, and wherein said first dimension is the width of said at least one first transistor.
9. The method of claim 1 , further comprising:
prior to said first anneal step, forming, in the surface of said semiconductor structure, at least two third trenches in said second direction delimiting said second dimension of at least one second transistor to be formed in said semiconductor structure, wherein:
said at least one first transistor is a p-channel MOS transistor and said first dimension is the width of said at least one first transistor; and
said at least one second transistor is an n-channel MOS transistor and said second dimension is the width of said at least one second transistor.
10. The method of claim 1 , wherein said stressed semiconductor layer has a thickness of between 5 and 20 nm.
11. The method of claim 1 , wherein said first dimension of each of said at least one first transistor is between 50 and 100 nm.
12. The method of claim 1 , wherein said semiconductor structure is an SOI (semiconductor on insulator) structure.
13. The method of claim 1 , wherein said semiconductor layer comprises a plurality of semiconductor fins.
14. A method comprising:
in a surface of a semiconductor structure, forming a plurality of first trenches in a first direction delimiting a first dimension of one or more transistors to be formed in the semiconductor structure, the semiconductor structure including a stressed semiconductor layer and an insulator layer having a viscosity;
in an annealing step, decreasing the viscosity of the insulating layer; and
after the annealing step, forming, in the surface of the semiconductor substrate, a plurality of second trenches in a second direction delimiting a second dimension of the one or more transistors.
15. The method of claim 14 , further comprising depositing an insulating material in the plurality of second trenches.
16. The method of claim 14 , wherein the annealing step is a first annealing step, wherein the insulating material has a viscosity, the method further comprising further decreasing the viscosity of said insulating material in a second annealing process.
17. The method of claim 16 , wherein said first annealing step has at least one of a temperature and a duration that is greater than said second annealing step.
18. The method of claim 16 , wherein:
said first annealing step is performed at a temperature of between 1000° C. and 1150° C.; and
said second annealing step is performed at a temperature of between 900° C. and 1000° C.
19. The method of claim 16 , wherein:
said first annealing step is performed for a duration of between 30 and 90 minutes; and
said second annealing step is performed for a duration of between 15 and 30 minutes.
20. The method of claim 15 , further comprising forming the one or more transistors in the semiconductor structure.
21. A method comprising:
in a surface of a semiconductor structure, forming a plurality of first trenches in a first direction delimiting a first dimension of one or more transistors to be formed in the semiconductor structure, the semiconductor structure including a stressed semiconductor layer and an insulator layer having a viscosity;
in an annealing step, decreasing the viscosity of the insulating layer;
after the annealing step, forming, in the surface of the semiconductor substrate, a plurality of second trenches in a second direction delimiting a second dimension of the one or more transistors; and
forming the one or more transistors in the semiconductor structure.
22. The method of claim 21 , wherein each of the one or more transistors are delimited by two of the first trenches and two of the second trenches.
23. The method of claim 21 , further comprising depositing an insulating material in the plurality of second trenches.
24. The method of claim 1 , wherein the method forms a uniaxial stress in the semiconductor layer.
25. The method of claim 1 , wherein forming the uniaxial stress in the semiconductor layer comprises transforming a biaxial stress in the semiconductor layer into the uniaxial stress.