Light-Mediated Contact Printing of Phosphorus Species onto Silicon Using Carbene-Based Molecular Layers

Abstract

The ability to deposit pattern-specific molecular layers onto silicon with either regional p-/n-doping properties or that act as chemoselective resists for area-selective deposition is highly sought after in the bottom-up manufacturing of microelectronics. In this study, we demonstrate a simple protocol for the covalent attachment and patterning of a phosphorus-based dopant precursor onto silicon(100) functionalized with reactive carbene species. This method relies on selective surface reactions, which provide terminal functionalities that can be photochemically modified via ultraviolet-assisted contact printing between the carbene-functionalized substrate and an elastomeric stamp inked with the inorganic dopant precursor. X-ray photoelectron spectroscopy (XPS) analysis combined with scanning electron microscopy (SEM) imaging was used to characterize the molecule attachment and patterning ability of this technique. XPS spectra are indicative of the covalent bonding between phosphorus-containing molecules and the functionalized surface after both bulk solution-phase reaction and photochemical printing. SEM analysis of the corresponding printed features demonstrates the effective transfer of the phosphorus species in a patterned orientation matching that of the stamp pattern. This simple approach to patterning dopant precursors has the potential to inform the continued refinement of thin-film electronic, photonic, and quantum device manufacturing.

Figure 1

(Top) Illustration of carbene-based functionalization, (middle) C 1s, N 1s, F 1s, and P 2p XPS region spectra measured from the following surfaces: NH₂–Si, Diaz–Si, PPh₂–Si (no UV), and PPh₂–Si represented by the green, pink, blue, and purple profiles, respectively, and (bottom) histograms showing the quantitative XPS characterization of region scans (C 1s, N 1s, F 1s, and Si 2p) for each surface, all normalized by the Si 2p peak intensity.

Figure 2

(Left) XPS P 2s core-level XPS spectra for (top) PPh₂–Si surface with electron detection carried out at an angle of 30° and (bottom) PPh₂–Si surface with electron detection carried out perpendicular from the surface and (right) histograms showing the integrated area (in arbitrary units) of each respective P 2s and Si plasmon peak.

Figure 3

SEM images of the (a) PUA stamp mold bearing 8 μm squares, (b) corresponding P-doped Si(100) surface post-printing, (c) Diaz–Si surface post-printing with DPP-inked stamp and no UV exposure, and (d) Diaz–Si surface post-printing with an inkless stamp and UV exposure and (bottom right) histogram showing XPS ratios of C 1s, N 1s, F 1s, and P 2p over Si 2p electron signals (corrected by the atomic sensitivity factors) on PPh₂–Si, stamped PPh₂–Si, and stamped PPh₂–Si (no UV) substrates.