Etch damage and ESL free dual damascene metal interconnect

1. A semiconductor device comprising:

a semiconductor substrate;

a first dielectric layer arranged over the semiconductor substrate;

first and second metal vias disposed in the first dielectric layer, the first and second metal vias having nearest outer sidewalls that are spaced apart from one another by a first region of the first dielectric layer;

a second dielectric layer arranged over and abutting the first dielectric layer;

first and second metal lines disposed in the second dielectric layer and contacting the first and second metal vias, respectively, the first and second metal lines having nearest outer sidewalls that are spaced apart from one another by a second region of the second dielectric layer, wherein no other metal lines are disposed in the second dielectric layer between the first and second metal lines; and

first and second air gaps disposed in lower corner regions of the second dielectric layer, the first air gap being closer to the first metal line than the second metal line, and the second air gap closer to the second metal line than the first metal line.

2. A semiconductor device comprising:

a semiconductor substrate;

a first dielectric layer arranged over the semiconductor substrate;

first and second metal vias disposed in the first dielectric layer, the first and second metal vias having nearest outer sidewalls that are spaced apart from one another by a first region of the first dielectric layer;

a second dielectric layer arranged over and abutting the first dielectric layer;

first and second metal lines disposed in the second dielectric layer and contacting the first and second metal vias, respectively, the first and second metal lines having nearest outer sidewalls that are spaced apart from one another by a second region of the second dielectric layer;

first and second air gaps disposed in lower corner regions of the second dielectric layer, the first air gap being closer to the first metal line than the second metal line, and the second air gap closer to the second metal line than the first metal line;

wherein the first air gap has a lowermost extent and an uppermost extent, and the lowermost extent is spaced apart from a lowermost surface of the second dielectric layer by a first distance and the uppermost extent is spaced below an upper plane corresponding to an uppermost surface of the first metal line by a second distance, the second distance being greater than the first distance.

3. A semiconductor device comprising:

a semiconductor substrate;

a first dielectric layer arranged over the semiconductor substrate;

first and second metal vias disposed in the first dielectric layer, the first and second metal vias having nearest outer sidewalls that are spaced apart from one another by a first region of the first dielectric layer;

a second dielectric layer arranged over and abutting the first dielectric layer;

first and second metal lines disposed in the second dielectric layer and contacting the first and second metal vias, respectively, the first and second metal lines having nearest outer sidewalls that are spaced apart from one another by a second region of the second dielectric layer extending continuously in a lateral direction between the nearest outer sidewalls;

first and second air gaps disposed in lower corner regions of the second dielectric layer, the first air gap being closer to the first metal line than the second metal line, and the second air gap closer to the second metal line than the first metal line;

a first metal cap layer arranged in a lower portion of the first dielectric layer and contacting the first metal via; and

a second metal cap layer arranged in an upper portion of the second dielectric layer and contacting the first metal line, the second metal cap layer having a metal composition which differs from that of the first and second metal lines and which differs from that of the first metal cap layer.

4. The semiconductor device of claim 3 :

wherein the first metal via has outermost sidewalls spaced apart by a first distance;

wherein the first metal cap layer has outermost sidewalls spaced apart by a second distance greater than the first distance; and

wherein the second metal cap layer has outermost sidewalls spaced apart by a third distance, the third distance being greater than the first distance and greater than the second distance.

5. The semiconductor device of claim 1 , further comprising:

a first metal cap layer disposed in a lower portion of the first dielectric layer, the first metal cap layer having outermost sidewalls spaced apart by a first distance;

wherein the first metal via contacts an upper portion of the first metal cap layer, the first metal via having outermost sidewalls spaced apart by a second distance less than the first distance.

6. The semiconductor device of claim 5 , wherein the first metal line has outermost sidewalls spaced apart by a third distance, wherein the third distance is greater than the second distance and is greater than the first distance.

7. The semiconductor device of claim 5 , further comprising:

a second metal cap layer arranged in an upper portion of the second dielectric layer and contacting an upper surface of the first metal line.

8. The semiconductor device of claim 7 , wherein the second metal cap layer has an upper surface that is level or co-planar with an upper surface of the second dielectric layer.

9. The semiconductor device of claim 8 , wherein the second metal cap layer has a metal composition that differs from that of the first and second metal lines.

10. The semiconductor device of claim 8 , wherein a lower surface of the second metal cap layer is at a height corresponding to the second dielectric layer and an upper surface of the second metal cap layer is co-planar or level with an upper surface of the second dielectric layer.

11. The semiconductor device of claim 7 , wherein the first metal via and the first metal line are a continuous metal structure, wherein a lower portion of the continuous metal structure contacts an upper portion of the first metal cap layer and an upper portion of the continuous metal structure contacts a lower portion of the second metal cap layer.

12. The semiconductor device of claim 11 , further comprising:

a barrier layer lining sidewalls of the first and second metal lines and sidewalls of the first and second metal vias to separate the continuous metal structure from the first dielectric layer and from the second dielectric layer.

13. The semiconductor device of claim 1 , wherein the first dielectric layer has a porosity less than 20% and the second dielectric layer has a porosity greater than 20%.

14. The semiconductor device of claim 1 , wherein:

the first dielectric layer has an effective dielectric constant greater than 2.1 and less than 3.5; and

the second dielectric layer has an effective dielectric constant less than 2.1.

15. The semiconductor device of claim 5 , wherein the first metal cap layer is sandwiched between the first metal via and a conductive feature, the conductive feature in or over the semiconductor substrate but beneath the first metal cap layer.

16. The semiconductor device of claim 1 , wherein the first dielectric layer includes an organo-silicate glass.

17. The semiconductor device of claim 1 , wherein the first and second metal lines comprise copper.

18. The semiconductor device of claim 2 , wherein the first dielectric layer has a porosity less than 20% and the second dielectric layer has a porosity greater than 20%.

19. The semiconductor device of claim 2 , wherein:

the first dielectric layer has an effective dielectric constant greater than 2.1 and less than 3.5; and

the second dielectric layer has an effective dielectric constant less than 2.1.

20. The semiconductor device of claim 3 , wherein:

the first dielectric layer has an effective dielectric constant greater than 2.1 and less than 3.5; and

the second dielectric layer has an effective dielectric constant less than 2.1.