Method to reduce depth delta between dense and wide features in dual damascene structures

1. A method of forming a device comprising:

providing a substrate prepared with a dielectric layer where interconnects are to be formed,

the dielectric layer comprising

trenches for lines and

vias for contacts,

the trenches being above the vias,

the dielectric layer having first and second regions,

wherein the first region comprises wide trenches and the second region comprises narrow trenches, and

wherein a depth delta exists between bottoms of the wide and narrow trenches;

forming a non-conformal layer on the substrate,

the non-conformal layer lining the wide and narrow trenches in the first and second regions;

etching the non-conformal layer in the wide and narrow trenches

to expose areas of the dielectric layer in the narrow trenches and

to remove the non-conformal layer from the bottom of the vias

while leaving an remaining amount of the non-conformal layer over the wide trenches; and

reducing the depth delta between the bottoms of the wide and narrow trenches in the first and second regions

by etching the remaining amount of the non-conformal layer and the dielectric layer,

the non-conformal layer having a lower etch rate than the dielectric layer, thereby allowing the narrow trenches to be etched further and faster than the wide trenches.

2. The method of claim 1 wherein a depth of the wide trenches in the first region is deeper than a depth of the narrow trenches in the second region.

3. The method of claim 2 wherein a percentage of the depth delta between the wide and narrow trenches is reduced by at least about 20-50%.

4. The method of claim 3 wherein forming the non-conformal layer comprises forming a non-conformal oxide layer.

5. The method of claim 1 wherein a percentage of the depth delta between the wide and narrow trenches is reduced by at least about 20-50%.

6. The method of claim 5 wherein forming the non-conformal layer comprises forming a non-conformal oxide layer.

7. The method of claim 1 wherein forming the non-conformal layer comprises forming a non-conformal oxide layer.

8. The method of claim 1

wherein removing the non-conformal layer exposes contact regions for communication with the interconnects to be formed within the vias.

9. The method of claim 8

wherein the contact regions for communication with the interconnects to be formed within the vias comprise lower interconnects.

10. The method of claim 1 wherein the non-conformal layer comprises silicon oxide or a low temperature oxide.

11. The method of claim 1 wherein thickness of the non-conformal layer in the first region is greater than in the second region.

12. A method of forming a device comprising:

providing a substrate prepared with a dielectric layer having first and second regions,

wherein the first region comprises wide dual damascene features and the second region comprises narrow dual damascene features,

the dual damascene features comprising trenches for lines and vias for contacts, the vias being below the trenches,

wherein a depth delta exists between bottoms of wide and narrow trenches;

forming a non-conformal layer on the substrate,

the non-conformal layer lining the wide and narrow dual damascene features in the first and second regions; and

etching the non-conformal layer in the wide and narrow trenches

to expose areas of the dielectric layer in the narrow trenches and

to remove the non-conformal layer from the bottom of the vias

while leaving a remaining amount of the non-conformal layer over the wide trenches; and

reducing the depth delta between the bottoms of the wide and narrow trenches in the first and second regions

by etching the remaining amount of the non-conformal layer and the dielectric layer,

the non-conformal layer having a lower etch rate than the dielectric layer, thereby allowing the narrow trenches to be etched further and faster than the wide trenches.

13. The method of claim 12 wherein a depth of the wide trenches in the first region is deeper than a depth of the narrow trenches in the second region.

14. The method of claim 13 wherein a percentage of the depth delta between the wide and narrow trenches is reduced by at least about 20-50%.

15. The method of claim 12 wherein forming the non-conformal layer comprises forming a non-conformal oxide layer.

16. The method of claim 15 wherein a percentage of the depth delta between the wide and narrow trenches is reduced by at least about 20-50%.

17. The method of claim 12 wherein the thickness of the non-conformal layer

in the narrow trench is about 40-60% less than the thickness in the wide trench.

18. The method of claim 17 wherein removing the non-conformal layer further comprises performing a cleaning process after performing the etch to remove the remaining non-conformal layer.