Back end of line metallization structures
Back end of line (BEOL) metallization structures and methods according to aspects of the invention generally include forming an interconnect structure including a recessed via structure in an interlayer dielectric. The recessed via structure is lined with a liner layer and filled with a first metal such as copper, tungsten, aluminum, alloys thereof or mixtures thereof. The recessed portion is filled with a second metal such as tantalum, titanium, tungsten, cobalt, ruthenium, iridium, platinum, nitrides thereof, or mixtures thereof, which in combination with the liner layer provides effective barrier properties for the bulk first metal.
1. A back end of line (BEOL) metallization fabrication method comprising:
forming a second interconnect structure including a via structure by depositing a second interlayer dielectric onto a planar top surface of a first interconnect structure;
patterning the second interlayer dielectric to form a via opening and expose a surface of the first interconnect structure;
conformally depositing a liner layer onto the second interlayer dielectric;
depositing a first metal layer onto the liner layer so as to fill the via opening, the first metal layer comprising copper, tungsten, aluminum, alloys thereof, or mixtures thereof;
removing an overburden of the first metal layer from the liner layer on the second interlayer dielectric by a first planarizing process;
continuing the first planarizing process to form a recess in the via opening without removing the liner layer;
depositing a second metal layer different from the first metal layer so as to fill the recess with the second metal layer to form the via structure and provide an overburden of the second metal layer on the second interlayer dielectric, wherein the second metal comprises tantalum, titanium, tungsten, cobalt, ruthenium, iridium, rhodium, nitrides thereof, alloys thereof, or mixtures thereof;
depositing a third metal layer onto the second metal layer;
patterning the second and third metal layers to form a column of the second and third metal layers overlying the via structure of the second interconnect structure; and
depositing a third interlayer dielectric onto the second interconnect structure to form a third interconnect structure on the second interconnect structure, wherein the second metal in the column defines a bottom electrode.
2. The BEOL metallization method of claim 1 , wherein the second metal fills the recess in the via structure of the second interconnect structure.
3. The BEOL metallization method of claim 1 , wherein depositing the third metal layer onto the second metal layer further comprises alternatingly depositing insulating layers, wherein patterning the second and third metal layers to form the column defines a memory stack.
4. The BEOL metallization method of claim 1 , wherein depositing the third metal layer onto the second metal layer further comprises alternatingly depositing metal magnetic layers and insulating layers, wherein patterning the second and third metal layers to form the column defines an MRAM device.
5. The BEOL metallization method of claim 1 , wherein depositing the first metal layer comprises an electroplating process.
6. The BEOL metallization method of claim 1 , wherein subsequent to depositing the second metal layer and prior to depositing the third metal layer the method further comprises planarizing the substrate to remove the overburden of the second metal and the exposed liner layer.
7. The BEOL metallization method of claim 1 , wherein patterned third metal layer comprises copper, tungsten, aluminum, or alloys.
8. The BEOL metallization method of claim 1 , wherein the patterned third metal layer defines an interconnect line.
9. The BEOL metallization method of claim 1 , wherein subsequent to depositing the interlayer dielectric onto the second interconnect structure further comprising planarizing such that an uppermost surface of the interlayer dielectric is coplanar to the uppermost surface of the third metal layer.