Interconnect structures and fabrication method thereof

1. A method for fabricating an interconnect structure, comprising:

forming a first conductive layer within a substrate and having a coplanar surface with the substrate;

forming a sacrificial layer on the substrate and the first conductive layer, the sacrificial layer being made of one of a photoresist, an organic bottom anti-reflective material, and an organic top anti-reflective material;

forming an opening in the sacrificial layer to expose a surface portion of the first conductive layer;

forming carbon nanotube bundles on the sacrificial layer and on the surface portion of the first conductive layer;

removing the sacrificial layer and the carbon nanotube bundles on the sacrificial layer simultaneously to leave the carbon nanotube bundle on the surface portion of the first conductive layer and to expose surface portions of the substrate; and

forming a first dielectric material layer covering to seal a top surface of the carbon nanotube bundle on the surface portion of the first conductive layer and on the exposed surface portions of the substrate to seal side surfaces of the carbon nanotube bundle in a space.

2. The method according to claim 1 , after forming the first dielectric material layer, further including:

performing a planarization process on the first dielectric material layer using the top surface of the carbon nanotube bundle as a stop layer to form a first dielectric layer with a top surface leveled with the top surface of the carbon nanotube bundle.

3. The method according to claim 2 , after performing the planarization process, further including:

forming a second dielectric layer on the top surface of the carbon nanotube bundle and a top surface of the first dielectric layer; and

forming a second conductive layer electrically contacting with the top surface of the carbon nanotube bundle in the second dielectric layer.

4. The method according to claim 1 , further including:

forming a catalyst layer on the sacrificial layer and on the surface portion of the first conductive layer exposed by the sacrificial layer, wherein:

the carbon nanotube bundles are formed from the catalyst layer;

the catalyst layer includes dispersed metal particles; and

the particles are made of Au, Ag, Cu, Fe, Co, or Ni.

5. The method according to claim 4 , wherein:

a diameter of the metal particles is smaller than approximately 10 nm; and

a distance between adjacent metal particles is in a range of approximately 1 nm˜5 nm.

6. The method according to claim 4 , wherein forming the catalyst layer further includes:

forming the metal particles by a laser ablation process;

dispersing the metal particles in a solution;

spin-coating the dispersed metal particles in the solution on the exposed surface portion of the first conductive layer at a bottom of the opening and a top surface of the sacrificial layer; and

performing a baking process to evaporate solvent in the solution spin-coated on the first conductive layer.

7. The method according to claim 6 , wherein:

a metal bulk or a metal film is used as a target of the laser ablation process;

a pulse laser is used to ablate the target to form the metal particles;

a power density of the pulse laser is in a range of approximately 3 J/cm 2 ˜10 J/cm 2 ; and

a frequency of the pulse laser is in a range of approximately 8 Hz˜12 Hz.

8. The method according to claim 6 , after forming the metal particles, further including:

screening the metal particles to obtain metal particles with a uniform size distribution; and

dispersing the metal particles with the uniform size distribution in the solution.

9. The method according to claim 1 , wherein:

the carbon nanotube bundles are formed by a plasma-enhanced chemical vapor deposition process.

10. The method according to claim 9 , wherein:

a reaction gas of the plasma-enhanced chemical vapor deposition process includes CH 4 , C 2 H 6 , C 2 H 4 , or C 2 H 2 ;

a carrier gas of the reaction gas is H 2 ;

a flow rate of the reaction gas is in a range of approximately 5 sccm˜100 sccm;

a flow rate of H 2 is in a range of approximately 50 sccm˜1000 sccm; and

a reaction temperature of the plasma-enhanced chemical vapor deposition process is in a range of approximately 400° C.˜1000° C.

11. The method according to claim 10 , wherein:

a diameter of an individual carbon nanotube of the carbon nanotube bundles is in a range of approximately 1 nm˜10 nm.

12. The method according to claim 1 , wherein forming the first dielectric layer further includes:

forming a first dielectric material layer covering a surface of the substrate and the carbon nanotube bundle formed within the opening; and

performing a chemical mechanical polishing process on the first dielectric material layer using the top surfaces of the carbon nanotubes of the carbon nanotube bundle as a stop layer.

13. The method according to claim 1 , after forming the opening, further including:

forming a diffusion barrier layer on the exposed surface portion of the first conductive layer at the bottom of the opening and the top surface of the sacrificial layer; and

forming an electrical contact layer on the diffusion barrier layer, wherein the carbon nanotube bundles are formed on the electrical contact layer.

14. The method according to claim 13 , wherein:

the diffusion barrier layer and the electrical contact layer are formed by a sputtering process.

15. The method according to claim 1 , before forming the second dielectric layer, further including:

forming a second barrier layer on the first dielectric layer and the top surfaces of the carbon nanotube bundles.

16. The method according to claim 1 , wherein:

the first dielectric layer is made of an ultra-low dielectric constant material.

17. The method according to claim 13 , wherein:

the diffusion barrier layer is a stacked structure made of Ta and TaN; and

the electrical contact layer is made of TiN.