Methods and structures for back end of line integration
Embodiments of the present invention provide a semiconductor structure for BEOL (back end of line) integration. A directed self assembly (DSA) material is deposited and annealed to form two distinct phase regions. One of the phase regions is selectively removed, and the remaining phase region serves as a mask for forming cavities in an underlying layer of metal and/or dielectric. The process is then repeated to form complex structures with patterns of metal separated by dielectric regions.
1. A method of forming a semiconductor structure, comprising:
depositing a first dielectric layer on a semiconductor substrate;
depositing a first layer of direct self-assembly (DSA) material on the first dielectric layer;
performing a phase separation of the first layer of DSA material into a first phase region and a second phase region;
selectively etching one phase region of the first phase region and second phase region of the first layer of DSA material;
forming cavities in the first dielectric layer;
depositing a metal fill layer in the cavities of the first dielectric layer;
depositing a second layer of DSA material over the metal fill layer;
performing a phase separation of the second layer of DSA material into a first phase region and a second phase region;
selectively etching one phase region of the first phase region and second phase region of the second layer of DSA material;
forming cavities in the metal fill layer; and
depositing a second dielectric layer over the metal fill layer and in the metal layer cavities.
2. The method of claim 1 , wherein depositing a first layer of DSA material comprises depositing PS-b-PMMA block copolymer.
3. The method of claim 2 , wherein performing a phase separation of the first layer of DSA material into a first phase region and a second phase region comprises performing an anneal at a process temperature ranging from about 200 degrees Celsius to about 350 degrees Celsius.
4. The method of claim 2 , further comprising recessing the first layer of DSA material using an ashing process.
5. The method of claim 4 , wherein the ashing process includes a plasma selected from the group consisting of O2 plasma, CO2 plasma, and N2/H2 plasma.
6. The method of claim 2 , further comprising depositing a barrier layer over the first metal layer after performing an etch to remove a portion of the first metal layer.
7. The method of claim 6 , wherein depositing a barrier layer comprises depositing tantalum nitride.