Doping barrier layer to facilitate metal fill with large grain size
A method for forming a semiconductor structure includes providing a substrate with an opening in or on the substrate. The method further includes conformally forming a barrier layer in the opening and on the substrate and performing an implantation process to implant a dopant into the barrier layer. The method further includes conformally forming a capping layer on the barrier layer and performing an annealing process, such that the dopant diffuses into the grain boundary of the barrier layer. The method further includes removing the capping layer and filling the opening with a conductive material.
1 . A method of forming a semiconductor structure, comprising:
providing a substrate with an opening in or on the substrate;
conformally forming a barrier layer in the opening and on the substrate;
performing an implantation process to implant a dopant into the barrier layer;
conformally forming a capping layer on the barrier layer;
performing an annealing process, such that the dopant diffuses into a grain boundary of the barrier layer, wherein the capping layer is present during the annealing process;
entirely removing the capping layer; and
then filling the opening with a conductive material.
2 . The method as claimed in claim 1 , wherein after filling the opening with the conductive material, a portion of the dopant remains trapped in the grain boundary of the barrier layer.
3 . The method as claimed in claim 1 , wherein a dielectric layer is disposed on the substrate, and the opening is a contact opening disposed in the dielectric layer.
4 . The method as claimed in claim 1 , wherein the opening is a word line trench disposed in the substrate.
5 . The method as claimed in claim 1 , wherein the dopant is boron, and the conductive material is tungsten.
6 . The method as claimed in claim 1 , wherein filling the opening with the conductive material comprises:
forming a conductive material layer on the barrier layer; and
performing a planarization process to expose a top surface of the substrate.
7 . The method as claimed in claim 6 , wherein the conductive material layer is formed at a temperature that is greater than or equal to a temperature of the annealing process.
8 . The method as claimed in claim 7 , wherein the temperature of the annealing process is between 200° C. and 400° C.
9 . The method as claimed in claim 7 , wherein the conductive material layer is formed at the temperature of 300° C. to 400° C.
10 . The method as claimed in claim 1 , wherein an implantation energy of the implantation process is between 100 eV and 10 MeV, and an implantation dosage of the dopant in the implantation process is between E10 atoms/cm 2 and E18 atoms/cm 2 .
11 . The method as claimed in claim 1 , wherein while filling the opening with the conductive material, at least a portion of the dopant is diffused from the grain boundary of the barrier layer to a surface of the barrier layer in contact with the conductive material.
12 . A method of forming a semiconductor structure, comprising:
providing a substrate with an opening in or on the substrate;
conformally forming a barrier layer in the opening and on the substrate;
forming a capping layer on the barrier layer, wherein a thickness of the capping layer above a bottom surface of the opening is less than a thickness of the capping layer above a top surface of the substrate;
performing an implantation process to implant a dopant through the capping layer and into the barrier layer;
performing an annealing process, such that the dopant diffuses into a grain boundary of the barrier layer, wherein the capping layer is present during the annealing process;
entirely removing the capping layer; and
then filling the opening with a conductive material.
13 . The method as claimed in claim 12 , wherein the barrier layer comprises a first concentration of the dopant at the bottom surface of the opening, the barrier layer comprises a second concentration of the dopant at the top surface of the substrate, and the first concentration is greater than the second concentration.
14 . The method as claimed in claim 12 , wherein a formation rate of the conductive material at the bottom surface of the opening is greater than a formation rate of the conductive material at sidewalls of the opening.
15 . The method as claimed in claim 12 , wherein the dopant is boron, and the conductive material is tungsten.