Toughness, adhesion and smooth metal lines of porous low K dielectric interconnect structures

Abstract

A structure useful for electrical interconnection comprises a substrate; a plurality of porous dielectric layers disposed on the substrate; an etch stop layer disposed between a first of the dielectric layers and a second of the dielectric layers; and at least one thin, tough, non-porous dielectric layer disposed between at least one of the porous dielectric layers and the etch stop layer. A method for forming the structure comprising forming a multilayer stack of porous dielectric layers on the substrate, the stack including the plurality of porous dielectric layers, and forming a plurality of patterned metal conductors within the multilayer stack. Curing of the multilayer dielectric stack may be in a single cure step in a furnace. The application and hot plate baking of the individual layers of the multi layer dielectric stack may be accomplished in a single spin-coat tool, without being removed, to fully cure the stack until all dielectric layers have been deposited.

What is claimed is: 
     
       1. A structure comprising:
 a substrate; 
 a plurality of porous dielectric layers disposed on said substrate; 
 an etch stop layer disposed between a first of said porous dielectric layers and a second of said porous dielectric layers; and 
 at least one thin, non-porous dielectric layer disposed between at least one of said porous dielectric layers and said etch stop layer, 
 wherein said thin, non-porous dielectric layer and said porous dielectric layers are associated with an identical reactive functionality. 
 
     
     
       2. The structure of  claim 1 , wherein a thin, non-porous dielectric layer is disposed between only one of said porous dielectric layers and said etch stop layer. 
     
     
       3. The structure of  claim 1 , wherein a thin, non-porous dielectric layer is disposed between each of two of said porous dielectric layers and said etch stop layer. 
     
     
       4. The structure of  claim 1 , wherein a thin, non-porous dielectric layer is disposed above one of said porous dielectric layers and below said etch stop layer. 
     
     
       5. The structure of  claim 1 , wherein a thin, non-porous dielectric layer is disposed below one of said porous dielectric layers and above said etch stop layer. 
     
     
       6. The structure of  claim 1 , wherein said thin, non-porous dielectric layer has a thickness of substantially 25 to 150 Angstroms. 
     
     
       7. The structure of  claim 1 , wherein said thin, non-porous dielectric layer has a composition with reactive functionalities identical to those of said porous dielectric layers. 
     
     
       8. The structure of  claim 1 , wherein said thin, non-porous dielectric layer has a composition which forms a covalent bond with the a composition of said porous dielectric layers. 
     
     
       9. The structure of  claim 1 , wherein said thin, non-porous dielectric layer is comprised of a material selected from low k dielectric materials that exhibit fracture toughness values greater than 0.30 MPa-m1/2 and will covalently bond to the porous dielectric layer. 
     
     
       10. The structure of  claim 1 , wherein at least one of said porous dielectric layers is comprised of a material selected from porous low k dielectric materials. 
     
     
       11. The structure of  claim 1 , wherein at least one of said porous dielectric layers has a thickness of substantially 600-5000 Angstroms. 
     
     
       12. The structure of  claim 1 , wherein said at least one of said porous dielectric layers has the a same chemical composition as another of said porous dielectric layers. 
     
     
       13. The structure of  claim 1 , wherein said at least one of said porous dielectric layers has substantially the same thickness as another of said porous dielectric layers. 
     
     
       14. The structure of  claim 1 , wherein said etch stop layer has a chemical composition comprising silicon, carbon, oxygen, and hydrogen. 
     
     
       15. The structure of  claim 1 , wherein said etch stop layer is selected from the a group consisting of organo silsesquioxanes, hydrido silsesquioxanes, hydrido-organo silsesquioxanes, and siloxanes, and other spin-on material with etch selectivity to the porous dielectric.    
     
     
       16. The structure of  claim 1 , wherein said etch stop layer has a thickness of substantially 200-600 Angstroms. 
     
     
       17. The structure of  claim 1 , further comprising a plurality of patterned metal conductors formed within a multilayer stack of porous dielectric layers on the substrate, said stack including said plurality of porous dielectric layers. 
     
     
       18. The structure of  claim 17 , wherein at least one of the patterned metal conductors is an electrical via. 
     
     
       19. The structure of claim  17  18, wherein at least one of the patterned metal conductors is a line connected to said via. 
     
     
       20. The structure of  claim 17 , wherein the first porous dielectric layer has a metal via formed therein. 
     
     
       21. The structure of  claim 17 , wherein the second porous dielectric layer has a metal line formed therein. 
     
     
       22. A method for forming an electrical interconnect structure on a substrate, the structure having a plurality of porous dielectric layers disposed on said substrate and an etch stop layer between a first of said dielectric layers and a second of said dielectric layers comprising:
 forming at least one thin, non-porous dielectric layer between at least one of said porous dielectric layers and said etch stop layer, 
 wherein said thin, non-porous dielectric layer and said at least one of said porous dielectric layers are formed such that each is associated with an identical reactive functionality. 
 
     
     
       23. The method of  claim 22 , wherein a thin, non-porous dielectric layer is formed between only one of said porous dielectric layers and said etch stop layer. 
     
     
       24. The method of  claim 22 , wherein a thin, non-porous dielectric layer is formed between each of two of said porous dielectric layers and said etch stop layer. 
     
     
       25. The method of  claim 22 , wherein a thin, non-porous dielectric layer is formed above one of said porous dielectric layers and below said etch stop layer. 
     
     
       26. The method of claim  23  22, wherein a thin, non-porous dielectric layer is formed below one of said porous dielectric layers and above said etch stop layer. 
     
     
       27. The method of  claim 22 , wherein said thin, non-porous dielectric layer is formed to a thickness of substantially 25 to 150 Angstroms. 
     
     
       28. The method structure of  claim 22 , wherein said thin, non-porous dielectric layer is formed to have a composition with reactive functionalities identical to those of said porous dielectric layers. 
     
     
       29. The method of  claim 22 , wherein said thin, non-porous dielectric layer is formed to have a composition which forms a covalent bond with the a composition of said porous dielectric layers. 
     
     
       30. The method of  claim 22 , wherein said thin, non-porous dielectric layer is comprised of a material selected from low k dielectric materials that exhibit fracture toughness values greater than 0.3 MPa-m 1/2  and covalently bond to the porous dielectric layer. 
     
     
       31. The structure method of  claim 22 , wherein at least one of said porous dielectric layers is comprised of a material selected from porous low k dielectric materials. 
     
     
       32. The method of  claim 22 , wherein at least one of said porous dielectric layers is formed to have a thickness of substantially 600-5000 Angstroms. 
     
     
       33. The method of  claim 22 , wherein said at least one of said porous dielectric layers is formed with the a same chemical composition as another of said porous dielectric layers. 
     
     
       34. The method of  claim 22 , wherein said at least one of said porous dielectric layers is formed to be of have a substantially the same thickness as another of said porous dielectric layers. 
     
     
       35. The method of  claim 22 , wherein said etch stop layer is selected from the a group consisting of organo silsesquioxanes, hydride silsesquioxanes, hydrido-organo silsesquioxanes, and siloxanes, and other spin-on material with etch selectivity to the porous dielectric. 
     
     
       36. The method of  claim 22 , wherein said etch stop layer has a chemical composition comprising silicon, oxygen, carbon, and hydrogen. 
     
     
       37. The method of  claim 22 , wherein said etch stop layer is formed to have a thickness of substantially 200-600 Angstroms. 
     
     
       38. The method of  claim 22 , further comprising forming a multilayer stack of porous dielectric layers on the substrate, said stack including said plurality of porous dielectric layers, and forming a plurality of patterned metal conductors within said multilayer stack. 
     
     
       39. The method of  claim 38 , wherein at least one of the patterned metal conductors is formed as an electrical via. 
     
     
       40. The method of claim  38  39, wherein at least one of the patterned metal conductors is a line connected to said via. 
     
     
       41. The method of  claim 38 , wherein the first porous dielectric layer has a metal via formed therein. 
     
     
       42. The method of  claim 38 , wherein the second porous dielectric layer has a metal line formed therein. 
     
     
       43. The method of  claim 38 , wherein said multilayer dielectric stack is applied to said substrate by spin coating. 
     
     
       44. The method of  claim 38 , further comprising baking each layer of said multilayer dielectric stack. 
     
     
       45. The method of  claim 44 , wherein said baking is accomplished on a hot plate. 
     
     
       46. The method of  claim 38 , further comprising curing said multilayer dielectric stack in a single cure step. 
     
     
       47. The method of claim  38  46, wherein said curing of the multilayer stack is a furnace curing process that is carried out at a temperature from about 300° C. to about 450° C. for a time period of from about 15 minutes to about 3 hours. 
     
     
       48. The method of  claim 47 , wherein said curing step crosslinks the films and burns out sacrifical porogen from the porous dielectric layers. 
     
     
       49. The method of  claim 22 , further comprising applying a miltilayer dielectric stack to said substrate and baking said multilayer dielectric stack, said applying and baking being accomplished in a single spin-coat tool. 
     
     
       50. The method of  claim 22 , further comprising adding additional dielectric layers, and forming dual damascene conductors in said additional layers. 
     
     
       51. The method of  claim 22 , wherein said substrate is a dielectric, a metal region, an adhesion promoter, a semiconductor wafer or any combination thereof. 
     
     
       52. The structure according to claim 1, wherein said thin, non-porous dielectric layer has more than one reactive functionality identical to, respectively, more than one reactive functionality in said porous dielectric layers. 
     
     
       53. The structure according to claim 1, wherein said thin, non-porous dielectric layer has two reactive functionalities that are respectively identical to two reactive functionalities in said porous dielectric layers. 
     
     
       54. The structure according to claim 1, wherein said thin, non-porous dielectric layer has two distinct reactive functionalities that are respectively identical to two distinct reactive functionalities in said porous dielectric layers. 
     
     
       55. The structure according to claim 8, wherein said composition of said thin non-porous dielectric layer and said composition of said porous dielectric layers forms a covalent bond network. 
     
     
       56. The structure according to claim 1, wherein said thin, non-porous dielectric layer has a composition which forms a covalent bond network with a composition of said at least one porous dielectric layer. 
     
     
       57. The structure according to claim 56, wherein said thin, non-porous dielectric layer and said composition of said porous dielectric layers are such that said formed covalent bond network increases adhesion between said thin, non-porous dielectric layer and said at least one porous dielectric layer. 
     
     
       58. The method according to claim 22, wherein both said thin, non-porous dielectric layer and at least one of said porous dielectric layers are formed such that each comprises more than one reactive functionality that are identical to each other. 
     
     
       59. The method according to claim 22, wherein both said thin, non-porous dielectric layer and at least one of said porous dielectric layers are formed such that each comprises two reactive functionalities that are identical to each other respectively. 
     
     
       60. The method according to claim 22, wherein both said thin, non-porous dielectric layer and at least one of said porous dielectric layers are formed such that each comprises two distinct reactive functionalities that are identical to each other respectively. 
     
     
       61. The method according to claim 22, wherein said thin, non-porous dielectric layer has a composition which forms a covalent bond network with a composition of said porous dielectric layers. 
     
     
       62. The method according to claim 22, further comprising: increasing adhesion between said thin, non-porous dielectric layer and a composition of at least one of said porous dielectric layers by forming a covalent bond network between said thin, non-porous dielectric layer and said at least one porous dielectric layer. 
     
     
       63. The structure according to claim 1, wherein during the formation of the structure there was at least one reactive functionality in a composition of said thin, non-porous dielectric layer that is identical to that in said porous dielectric layers. 
     
     
       64. The method according to claim 22 further comprising:
 selecting materials for said thin, non-porous dielectric layer and said porous dielectric layers such that reactive functionalities between said thin, non-porous dielectric layer and said porous dielectric layers react to covalently bond said thin, non-porous dielectric layer and said porous dielectric layers, forming a covalent bond network there-between, and wherein at least one reactive functionality of said thin, non-porous dielectric layer and at least one reactive functionality of said porous dielectric layers is identical.   
     
     
       65. A structure comprising:
 a substrate;   a plurality of porous dielectric layers disposed on said substrate;   an etch stop layer disposed between a first of said porous dielectric layers and a second of said porous dielectric layers; and   at least one thin, non-porous dielectric layer disposed between at least one of said porous dielectric layers and said etch stop layer,   wherein said thin, non-porous dielectric layer has a composition which forms a covalent bond with a composition of said porous dielectric layers.