Selective deposition holds promise to simplify next-generation device fabrication and bring down economic cost. In this work, selectively depositing polymers on metal/dielectric patterns was achieved by spin dewetting, a phenomenon that refers to the dewetting of polymers during spin coating. Our strategy utilizes self-assembled monolayers (SAMs) to induce dewetting of polymers over some areas. Line patterns of Cu/SiO<sub>2</sub> were investigated. A hydrophobic SAM, octyltrichlorosilane (OTS, Cl<sub>3</sub>Si–C<sub>8</sub>H<sub>17</sub>), was selectively formed on SiO<sub>2</sub> in the presence of Cu to render SiO<sub>2</sub> non-wettable. During a subsequent spin coating step, polymers dewet from OTS-functionalized SiO<sub>2</sub> and coat Cu exclusively. The spin dewetting process is strongly dictated by the spin coating kinetics. A systematic study of the processing conditions revealed strong dependence of polymer film coverage on spin speed, solution concentration, polymer molecular weight, casting solvent, and SAM hydrophobicity.
Conventional doping of crystalline Si via ion implantation results in a stochastic distribution of doped regions in the x-y plane along with relatively poor control over penetration depth of dopant atoms. As the gate dimensions get to 10 nm, the related device parameters also need to be scaled down to maintain electrical activity. Thus highly doped abrupt, ultra-shallow junctions are imperative for source-drain contacts to realize sub-10 nm transistors. Uniform ultra-shallow junctions can be achieved via monolayer doping, wherein thermal diffusion of a self-limiting monolayer of dopant atomcontaining organic on Si surface yields sub-5 nm junctions. We have extended the use of organic dopant molecules in the monolayer doping technique to introduce a new class of spin-on polymer dopants. In effect, these new spin-on dopants offer a hybrid between the monolayer doping technique and traditional inorganic spin-on dopants. We have been able to uniformly introduce p- and n-type dopants with doping efficiencies comparable to the monolayer doping technique. Control over junction depth can be easily achieved via optimizing annealing temperature and time. Concurrently, sequestering the dopant precursors within the cores of block copolymer micelles allows us to achieve precise control over the spatial positions of dopant atoms in all three dimensions owing to the high periodicity of block copolymer domains on the 10-100 nm length scale.
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 3-dimensional wafer topography, for example, for shrinkage of the size of trench openings. 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. <p> </p>Furthermore, on acute 3-dimensional semiconductor topography, the creation of highly doped abrupt, ultra-shallow junctions with three-dimensional 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.