Multilayer dielectric structures with graded composition for nano-scale semiconductor devices

1. A method for fabricating a multilayer dielectric structure, comprising:

depositing a first SiCN (silicon carbon nitride) film;

performing a first in-situ plasma treatment process on the first SiCN film to convert the first SiCN film to a first SiCNO (silicon carbon nitride oxide) film having a first composition profile of C, N, and O atoms;

depositing a second SiCN film on the first SiCNO film; and

performing a second in-situ plasma treatment process on the second SiCN film to convert the second SiCN film to a second SiCNO film having a second composition profile of C, N, and O atoms;

wherein the first composition profile of C, N, and O atoms of the first SiCNO film differs from the second composition profile of C, N, and O atoms of the second SiCNO film; and

wherein at least one of the first in-situ plasma treatment process and the second in-situ plasm treatment process comprises both a plasma oxidation process and a plasma nitridation process;

wherein the first SiCNO film and the second SiCNO film form a multilayer dielectric structure comprising a graded composition profile of C, N, and O atoms.

2. The method of claim 1 , wherein an atomic percentage of O atoms in the first SiCNO film is in a range of about 0% to about 25%, and wherein an atomic percentage of O atoms in the second SiCNO film is in a range of about 5% to about 35%.

3. The method of claim 1 , wherein an atomic percentage of C atoms in the first SiCNO film is in a range of about 10% to about 40%, and wherein an atomic percentage of C atoms in the second SiCNO film is in a range of about 0% to about 30%.

4. The method of claim 1 , wherein an atomic percentage of N atoms in the first and second SiCNO films differs in a range of about 2% to about 20%.

5. The method of claim 1 , wherein the multilayer dielectric structure consists only of SiCNO films.

6. The method of claim 1 , further comprising forming at least one or more of a SiN film, a SiNO film, a SiCO film, a SiCN film, or a combination thereof, as part of the multilayer dielectric structure.

7. The method of claim 1 , wherein each dielectric film is formed to have a thickness in a range of about 1.0 nanometer to about 5 nanometers.

8. The method of claim 1 , wherein a total thickness of the multilayer dielectric structure is about 10 nanometers or less.

9. The method of claim 1 , comprising engineering the first and second composition profiles to fabricate a multilayer dielectric structure having an effective dielectric constant of about 5.5 or less.

10. The method of claim 1 , comprising engineering the first and second composition profiles to fabricate a multilayer dielectric structure having a target adhesion property.

11. The method of claim 1 , comprising engineering the first and second composition profiles to fabricate a multilayer dielectric structure having a target etch resistance property.

12. The method of claim 1 , comprising engineering the first and second composition profiles to fabricate a multilayer dielectric structure having a target diffusion barrier property.

13. The method of claim 1 , comprising fabricating the multilayer dielectric structure as a spacer formed on a sidewall of a gate structure of a transistor device.

14. The method of claim 1 , comprising fabricating the multilayer dielectric structure as a stress liner layer that is conformally formed over a transistor device to impart a tensile or compressive stress.

15. The method of claim 1 , comprising fabricating the multilayer dielectric structure as a conformal liner layer or a conformal barrier layer on a sidewall and bottom surface of an etched trench of a trench isolation structure.

16. The method of claim 1 , comprising fabricating the multilayer dielectric structure as a conformal liner layer or a conformal barrier layer of a through-silicon via (TSV) structure.

17. The method of claim 1 , wherein the first and second SiCNO films each have a thickness which is no more than about 2 nm.

18. A method for fabricating a multilayer dielectric structure, comprising:

depositing a first SiCN (silicon carbon nitride) film;

performing an in-situ plasma treatment process on the first SiCN film to convert the first SiCN film to a first SiCNO (silicon carbon nitride oxide) film having a first composition profile of C, N, and O atoms;

depositing a second SiCN film;

performing an in-situ plasma treatment process on the second SiCN film to convert the second SiCN film to a second SiCNO film having a second composition profile of C, N, and O atoms;

wherein the first and second composition profiles are different; and

engineering the first and second composition profiles to fabricate a multilayer dielectric structure having a target current leakage property.

19. A method for fabricating a multilayer dielectric structure, comprising:

depositing a first SiCN (silicon carbon nitride) film;

performing an in-situ plasma treatment process on the first SiCN film to convert the first SiCN film to a first SiCNO (silicon carbon nitride oxide) film having a first composition profile of C, N, and O atoms;

depositing a second SiCN film;

performing an in-situ plasma treatment process on the second SiCN film to convert the second SiCN film to a second SiCNO film having a second composition profile of C, N, and O atoms;

wherein the first and second composition profiles are different; and

engineering the first and second composition profiles to fabricate a multilayer dielectric structure having a target hydrophobic property.