Methods for forming via openings by using a lamellar triblock copolymer, a polymer nanocomposite, and a mixed epitaxy approach are disclosed. An example method includes forming a guiding pattern (e.g., a topographical guiding pattern, chemical guiding pattern, or mixed guiding pattern) on a surface of a layer of an IC device, forming lamellar structures based on the guiding pattern by using the lamellar triblock copolymer or forming cylindrical structures based on the guiding pattern by using the polymer nanocomposite, and forming via openings by removing a lamella from each of at least some of the lamellar structures or removing a nanoparticle from each of at least some of the cylindrical structures.