Direct Imprinting of Liquid Silicon

Abstract

A polymeric precursor solution for semiconducting silicon called "liquid silicon" was synthesized and directly imprinted to form well-defined and fine amorphous silicon patterns. The spin-coated film was cured and imprinted followed by annealing at 380 °C to complete the polymer-to-silicon conversion. A pattern with dimensions of several hundreds of nanometers or less was obtained on a substrate. We demonstrated that the curing step before imprinting is particularly important in the imprinting process. A curing temperature of 140-180 °C was found to be optimal in terms of the film's deformability and molding properties. Fourier transform infrared spectroscopy and thermal analysis clarified that the cross-linking of the polymer due to the 1,2-hydrogen shift reaction was induced exponentially with the release of a large amount of SiH4/H2 gases at temperatures between 140 and 220 °C, leading to the solidification of the film. Consequently, the film completely lost its deformability at higher temperatures. Despite a volume shrinkage as large as 53-56% during the polymer-to-silicon conversion, well-defined angular patterns were preserved. Fine silicon patterns were formed via the direct imprinting of liquid silicon with high resolution and high throughput, demonstrating the usefulness of this technique for the future manufacturing of silicon electronics.

Silicon deposition in nanopores using a liquid precursor

“…5(c)). Because the cross-linking temperature (>120 °C)20 overlaps with the temperature at the point of capillary condensation (120 °C), the condensed CPS would turn into gel before capillary evaporation. Finally, the cross-linked CPS transforms into solid silicon at 400 °C14 (Fig.…”

“…The chamber temperature was subsequently increased to 150 °C, and this temperature was maintained for 10 min to solidify adsorbed CPS on the MMCS. Cross-linking due to the 1,2-hydrogen shift reaction led to solidification of CPS; this cross-linking process is known to occur in silicon hydride compounds when the temperature exceeds 120 °C20. Finally, the chamber was heated at 400 °C for 30 min to complete the transformation from CPS to solid silicon.…”

Fabrication of n-type Si nanostructures by direct nanoimprinting with liquid-Si ink

“…11,12 However, the nanostructures we fabricated in that study only contained pure Si as we had not included a dopant in the liquid-Si ink. Silicon can function as an n-type or p-type semiconductor depending on the dopant used, and semiconductor devices are fabricated from the combination of n-and p-type materials.…”

“…As reported in previous studies, the SiH 4 and H 2 desorbed from the liquid-Si ink (without P 4 ) during heating and the volumeshrinkage ratio reached 62%-85%. 11,12 The shrinkage ratio depends on the shape of the mold. The volume-shrinkage ratio of 69%-72% that was observed in the nanoimprinted Si film from P-doped liquid-Si ink is lower than that of conventionally produced Si nanostructures from non-doped liquid-Si ink with the same mold (84%).…”

Approaching Solar‐Grade a‐Si:H for Photovoltaic Applications via Atmospheric Pressure CVD Using a Trisilane‐Derived Liquid Precursor

“…Solution‐processed a‐Si:H layers have been deposition via inkjet printing, spin coating, slot die coating, atmospheric pressure chemical vapor deposition (APCVD), and aerosol‐assisted APCVD (AA‐APCVD) . The functional optoelectronic applications of such layers include thin‐film transistors, thin‐film solar cells, c‐Si surface passivation layers, and patterned films via imprinting . Much progress has been made with regard to ink preparation, coating techniques, and film quality, which has greatly improved the prospects for solution‐processed silicon optoelectronics.…”