Block copolymers for
As the dimensions of integrated circuit elements continue to shrink and new device architectures are developed, there is a vast need for new technology to demonstrate reliable nanoscale doping with well defined and uniformly doped ultrashallow junctions. A monolayer doping (MLD) approach based on the self-limiting hydrosilylation monolayer reaction can successfully address the limitations of conventional ion implantation, but lacks control over the concentration, and the 3D spatial positions of the dopants to within a few nanometers. Consequently, controlling the dopant distribution in all three dimensions represents a fundamental design challenge, especially as the feature size approaches the nanometer regime.
Block copolymers for spatially-defined doping
We have developed a modular approach relying on the self-assembly of block copolymers to confine dopants in all three dimensions. Briefly, an organic dopant precursor small molecule is encapsulated via hydrogen bonding into the interior of the polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) micellar aggregates in solution. Incorporation of the dopants via hydrogen bonding eliminates the need for tailored synthesis, thereby making the approach highly modular. Thin films cast from these solutions show a periodic hexagonally close packed array of micelles on Si substrates. Rapid thermal annealing effectively drives the encapsulated dopants into the underlying Si thereby confining them to within 30–100 nm in the x and y dimensions enabling discretely doped shallow junctions (< 10 nm in z-direction). Due to the modular nature of this approach, the size, pitch, dopant dosage and the junction depth can be independently varied and tuned for a wide range of dopant atoms (B, P, Sb, As, etc.).