Selective cobalt deposition on copper surfaces

Abstract

Embodiments of the invention provide processes to selectively form a cobalt layer on a copper surface over exposed dielectric surfaces. In one embodiment, a method for capping a copper surface on a substrate is provided which includes positioning a substrate within a processing chamber, wherein the substrate contains a contaminated copper surface and a dielectric surface, exposing the contaminated copper surface to a reducing agent while forming a copper surface during a pre-treatment process, exposing the substrate to a cobalt precursor gas to selectively form a cobalt capping layer over the copper surface while leaving exposed the dielectric surface during a vapor deposition process, and depositing a dielectric barrier layer over the cobalt capping layer and the dielectric surface. In another embodiment, a deposition-treatment cycle includes performing the vapor deposition process and subsequently a post-treatment process, which deposition-treatment cycle may be repeated to form multiple cobalt capping layers.

1 . A method for capping a copper surface on a substrate, comprising:
 positioning a substrate within a processing chamber, wherein the substrate comprises a contaminated copper surface and a dielectric surface;   exposing the contaminated copper surface to a reducing agent while forming a metallic copper surface during a pre-treatment process;   exposing the substrate to a cobalt precursor gas to selectively form a cobalt capping layer over the metallic copper surface while leaving exposed the dielectric surface during a vapor deposition process; and   depositing a dielectric barrier layer over the cobalt capping layer and the dielectric surface.   
   
   
       2 . The method of  claim 1 , further comprising chemically reducing copper oxides on the contaminated copper surface to form the metallic copper surface during the pre-treatment process. 
   
   
       3 . The method of  claim 1 , wherein the contaminated copper surface is exposed to the reducing agent and a plasma is ignited during the pre-treatment process, the reducing agent comprises a reagent selected from the group consisting of nitrogen (N 2 ), ammonia (NH 3 ), hydrogen (H 2 ), ammonia/nitrogen mixture, and combinations thereof. 
   
   
       4 . The method of  claim 3 , wherein the contaminated copper surface is exposed to the plasma for a time period within a range from about 5 seconds to about 15 seconds. 
   
   
       5 . The method of  claim 1 , wherein the reducing agent comprises hydrogen gas, the pre-treatment process is a thermal process, and the substrate is heated to a temperature within a range from about 200° C. to about 400° C. during the thermal process. 
   
   
       6 . The method of  claim 1 , further comprising exposing the cobalt capping layer to a reagent and a plasma during a post-treatment process prior to depositing the dielectric barrier layer, the reagent is selected from the group consisting of nitrogen (N 2 ), ammonia (NH 3 ), hydrogen (H 2 ), ammonia/nitrogen mixture, and combinations thereof. 
   
   
       7 . The method of  claim 6 , wherein a deposition-treatment cycle comprises performing the vapor deposition process and subsequently the post-treatment process, and the deposition-treatment cycle is performed 2, 3, or more times to deposit multiple cobalt capping layers. 
   
   
       8 . The method of  claim 7 , wherein each of the cobalt capping layers is deposited to a thickness within a range from about 3 Å to about 5 Å during each of the deposition-treatment cycles. 
   
   
       9 . The method of  claim 1 , wherein the cobalt capping layer has a thickness within a range from about 4 Å to about 20 Å. 
   
   
       10 . The method of  claim 1 , wherein the cobalt capping layer has a thickness of less than about 10 Å. 
   
   
       11 . The method of  claim 10 , wherein the substrate is exposed to a deposition gas comprising the cobalt precursor gas and hydrogen gas during the vapor deposition process, the vapor deposition process is a thermal chemical vapor deposition process or an atomic layer deposition process. 
   
   
       12 . The method of  claim 1 , wherein the cobalt precursor gas comprises a cobalt precursor which has the general chemical formula (CO) x Co y L z , wherein:
 X is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12;   Y is 1, 2, 3, 4, or 5;   Z is 1, 2, 3, 4, 5, 6, 7, or 8; and   L is a ligand independently selected from the group consisting of cyclopentadienyl, alkylcyclopentadienyl, methylcyclopentadienyl, pentamethylcyclopentadienyl, pentadienyl, alkylpentadienyl, cyclobutadienyl, butadienyl, allyl, ethylene, propylene, alkenes, dialkenes, alkynes, nitrosyl, ammonia, derivatives thereof, and combinations thereof.   
   
   
       13 . The method of  claim 1 , wherein the cobalt precursor gas comprises a cobalt precursor selected from the group consisting of tricarbonyl allyl cobalt, cyclopentadienyl cobalt bis(carbonyl), methylcyclopentadienyl cobalt bis(carbonyl), ethylcyclopentadienyl cobalt bis(carbonyl), pentamethylcyclopentadienyl cobalt bis(carbonyl), dicobalt octa(carbonyl), nitrosyl cobalt tris(carbonyl), bis(cyclopentadienyl) cobalt, (cyclopentadienyl) cobalt (cyclohexadienyl), cyclopentadienyl cobalt (1,3-hexadienyl), (cyclobutadienyl) cobalt (cyclopentadienyl), bis(methylcyclopentadienyl) cobalt, (cyclopentadienyl) cobalt (5-methylcyclopentadienyl), bis(ethylene) cobalt (pentamethylcyclopentadienyl), derivatives thereof, complexes thereof, plasmas thereof, and combinations thereof. 
   
   
       14 . The method of  claim 13 , wherein the cobalt precursor comprises cyclopentadienyl cobalt bis(carbonyl). 
   
   
       15 . A method for capping a copper surface on a substrate, comprising:
 positioning a substrate within a processing chamber, wherein the substrate comprises a copper oxide surface and a dielectric surface;   exposing the copper oxide surface to an ammonia plasma or a hydrogen plasma while forming a metallic copper surface during a pre-treatment process;   exposing the substrate to a cobalt precursor gas to selectively form a cobalt capping layer over the metallic copper surface while leaving exposed the dielectric surface during a vapor deposition process;   exposing the cobalt capping layer to a plasma during a post-treatment process; and   depositing a dielectric barrier layer over the cobalt capping layer and the dielectric surface.   
   
   
       16 . The method of  claim 15 , wherein a deposition-treatment cycle comprises performing the vapor deposition process and subsequently the post-treatment process, and the deposition-treatment cycle is performed 2, 3, or more times to deposit multiple cobalt capping layers. 
   
   
       17 . The method of  claim 16 , wherein each of the cobalt capping layers is deposited to a thickness within a range from about 3 Å to about 5 Å during each of the deposition-treatment cycles. 
   
   
       18 . The method of  claim 15 , wherein the copper oxide surface is exposed to the ammonia plasma or the hydrogen plasma for a time period within a range from about 5 seconds to about 15 seconds during a pre-treatment process. 
   
   
       19 . The method of  claim 15 , wherein a reagent and the plasma are exposed to the cobalt capping layer during the post-treatment process, and the reagent is selected from the group consisting of nitrogen (N 2 ), ammonia (NH 3 ), hydrogen (H 2 ), ammonia/nitrogen mixture, and combinations thereof. 
   
   
       20 . A method for capping a copper surface on a substrate, comprising:
 positioning a substrate within a processing chamber, wherein the substrate comprises a copper oxide surface and a dielectric surface;   exposing the copper oxide surface to an ammonia plasma or a hydrogen plasma while forming a metallic copper surface during a pre-treatment process;   exposing the substrate to a cobalt precursor gas and hydrogen gas to selectively form a cobalt capping layer over the metallic copper surface while leaving exposed the dielectric surface during a vapor deposition process; and   exposing the cobalt capping layer to a plasma and a reagent selected from the group consisting of nitrogen (N 2 ), ammonia (NH 3 ), hydrogen (H 2 ), ammonia/nitrogen mixture, and combinations thereof during a post-treatment process.   
   
   
       21 . The method of  claim 20 , wherein a deposition-treatment cycle comprises performing the vapor deposition process and subsequently the post-treatment process, and the deposition-treatment cycle is performed 2, 3, or more times to deposit multiple cobalt capping layers. 
   
   
       22 . The method of  claim 21 , wherein each of the cobalt capping layers is deposited to a thickness within a range from about 3 Å to about 5 Å during each of the deposition-treatment cycles. 
   
   
       23 . The method of  claim 20 , further comprising depositing a dielectric barrier layer over the cobalt capping layer and the dielectric surface. 
   
   
       24 . A method for capping a copper surface on a substrate, comprising:
 positioning a substrate within a processing chamber, wherein the substrate comprises a contaminated copper surface and a dielectric surface;   exposing the contaminated copper surface to a reducing agent while forming a metallic copper surface during a pre-treatment process;   depositing a cobalt capping material over the metallic copper surface while leaving exposed the dielectric surface during a deposition-treatment cycle, comprising:
 exposing the substrate to a cobalt precursor gas to selectively form a first cobalt layer over the metallic copper surface while leaving exposed the dielectric surface during a vapor deposition process; 
 exposing the first cobalt layer to a plasma comprising nitrogen, ammonia, an ammonia/nitrogen mixture, or hydrogen during a treatment process; 
 exposing the substrate to the cobalt precursor gas to selectively form a second cobalt layer over the first cobalt layer while leaving exposed the dielectric surface during the vapor deposition process; 
 exposing the second cobalt layer to the plasma during the treatment process; and 
   depositing a dielectric barrier layer over the cobalt capping material and the dielectric surface.   
   
   
       25 . The method of  claim 24 , further comprising:
 exposing the substrate to the cobalt precursor gas to selectively form a third cobalt layer over the second cobalt layer while leaving exposed the dielectric surface during the vapor deposition process; and   exposing the third cobalt layer to the plasma during the treatment process.