Method of fabricating ultra-deep vias and three-dimensional integrated circuits using ultra-deep vias
View Patent ↗A method of forming a high aspect ratio via opening through multiple dielectric layers, a high aspect ratio electrically conductive via, methods of forming three-dimension integrated circuits, and three-dimensional integrated circuits. The methods include forming a stack of at least four dielectric layers and etching the first and third dielectric layers with processes selective to the second and fourth dielectric layers, etching the second and third dielectric layers with processes selective to the first and second dielectric layers. Advantageously the process used to etch the third dielectric layer is not substantially selective to the first dielectric layer.
1. A method, comprising:
(a) forming an etch stop layer on a top surface of a substrate;
(b) forming a first dielectric layer on a top surface of said etch stop layer;
(c) forming a profile modulation layer on a top surface of said first dielectric layer;
(d) forming a second dielectric layer on a top surface of said profile modulation layer;
(e) forming a photo-imaging layer on a top surface of said second dielectric layer;
(f) forming an opening in said photo-imaging layer, a region of said top surface of said second dielectric layer exposed in a bottom of said opening;
after (a) through (f), (g) performing a first reactive ion etching of said second dielectric layer using a first etch chemistry selective to said profile modulation layer to form an opening through said second dielectric layer;
after (g), (h) performing a second reactive ion etching of said profile modulation layer using a second etch chemistry selective to said first and second dielectric layers to extend said opening through said profile modulation layer;
after (h), (i) performing a third reactive ion etching of said first dielectric layer using a third etch chemistry selective to said profile modulation layer and selective to said etch stop layer to extend said opening through said first dielectric layer;
after (i), (j) performing a fourth reactive ion etching of said etch stop layer using a fourth etch chemistry selective to said first and second dielectric layers to extend said opening through said etch stop layer; and
after (j), (k) removing said photo-imaging layer, after said removing said photo-imaging layer, said opening extending from said top surface of said second dielectric layer, through said second dielectric layer, through said profile modulation layer, through said first dielectric layer and through said etch stop layer to said top surface of said substrate.
2. The method of claim 1 , wherein said third etch chemistry is not selective to said second dielectric layer.
3. The method of claim 1 , wherein said first and third etch chemistries are a same chemistry.
4. The method of claim 1 , wherein said second and fourth etch chemistries are a same chemistry.
5. The method of claim 1 , wherein removing said photo-imaging layer is performed between reactive ion etching said first dielectric layer and reactive ion etching said etch stop layer.
6. The method of claim 1 , wherein said first dielectric layer and second dielectric layer comprise silicon oxide and said profile modulation layer and said etch stop layer comprise silicon nitride.
7. The method of claim 1 , wherein:
a first width of said opening measured in first direction parallel to said top surface of said second dielectric layer at said top surface of said second dielectric layer is greater than a second width of said opening measured in said first direction at said top surface of said profile modulation layer and greater than a third width of said opening measured in said first direction at said top surface of said substrate, said second width greater than or equal to said third width; and
wherein a ratio of a depth of said opening measured in a second direction perpendicular to said first direction from said top surface of said second dielectric layer to said top surface of said substrate to said first width is equal to or greater than five.
8. The method of claim 1 , further including:
after said removing said photo-imaging layer, filling said opening with said electrical conductor.
9. The method of claim 8 , wherein said filling said opening with an electrical conductor comprises:
depositing a tantalum nitride layer over sidewalls and a bottom of said opening;
depositing a tantalum layer on said tantalum nitride layer;
depositing a seed copper layer on said tantalum layer;
electroplating an electroplated copper layer on said seed copper layer, said electroplated copper layer completely filling remaining spaces in said opening; and
performing a chemical-mechanical-polish to remove said tantalum nitride layer, said tantalum layer, said seed copper layer and said electroplated copper layer from over said top surface of said second dielectric layer.
10. The method of claim 1 , wherein said photo-imaging layer includes a photoresist layer over an antireflective coating on said top surface of said first dielectric layer and forming said opening in said photo-imaging layer comprises exposing said photoresist layer to actinic radiation through a patterned photomask, developing said exposed photoresist layer and performing a fifth reactive ion etching of said antireflective coating using with fifth etch chemistry where said anti-reflective coating is not protected by said photoresist layer.
11. The method of claim 10 , wherein said fifth etch chemistry is selective to said photoresist layer and said first dielectric layer and wherein said fifth, second and fourth etch chemistries are a same chemistry.
12. The method of claim 8 , wherein said photo-imaging layer is removed using an oxygen plasma.
13. The method of claim 9 , further including performing a DC sputter clean before depositing said tantalum nitride layer.
14. The method of claim 1 , wherein said first dielectric layer consists of a stack of a third dielectric layer on a fourth dielectric layer on a fifth dielectric layer, said third dielectric layer on said etch stop layer, said profile modulation layer on said fifth dielectric layer.
15. The method of claim 14 , wherein said third and fourth dielectric layers are low temperature oxide (LTO) and said fifth dielectric layer is high density plasma (HDP) oxide.
16. The method of claim 1 , wherein said opening extending said opening extending from said top surface of said second dielectric layer, through said second dielectric layer, through said profile modulation layer, through said first dielectric layer and through said etch stop layer to said top surface of said substrate is wider at a top surface of said second dielectric layer than at said profile modulation layer and has a about a same width from said profile modulation layer to said substrate.