Ultra-thin Conformal Coating for Spin-on Doping Applications

As devices become ever smaller and more sophisticated, there is also a general need for creating high quality defect-free thin coatings of polymers on three-dimensional wafer topography. To address this challenge, we developed a spin-on polymer brush material, which comprises of a dopant moiety with a universal adhesive dopamine end group. We demonstrate that the polymer coating is highly conformal and free of pinhole defects, even when only a few nm thick, or when coated over high aspect ratio over 200 nm deep trench topography. Our investigations demonstrate that the dopamine end group enables stable sub-10 nm thick conformal coatings on three-dimensional surfaces. Furthermore, on acute three-dimensional semiconductor topography, the creation of highly doped abrupt, ultra-shallow junctions with lateral control are essential for successful source-drain contacts. In consideration of this need, we extended the above polymer brush concept further by incorporating a suitable implant dopant atom, such as boron, into the monomer structure. After conformal coating and a subsequent rapid thermal annealing process, the dopant atom is driven into the semiconductor substrate underneath the polymer film. This is potentially very useful for uniform all-around doping of 3-dimensional topography such as FinFETs or Nanowire-FETs. A high dopant dosage on silicon substrate with appropriate shallow implant characteristics was demonstrated for the end-functionalized dopant polymer brush, highlighting one of the promising applications of such conformal coatings.