Catalytic amplification of the soft lithographic patterning of Si. Nonelectrochemical orthogonal fabrication of photoluminescent porous Si pixel arrays

Photoluminescent, porous silicon pixel arrays were fabricated via a Pt-promoted wet etching of p-type Si(100) using a 1:1:1 EtOH/HF/H₂O₂ solution. The pixels were fabricated with micrometer-scale design rules on a silicon substrate that had been modified with an octadecyltrichlorosilane (OTS) monolayer patterned using microcontact printing. The printed OTS layer serves as an orthogonal resist template for the deposition of a Pt(0) complex, which preferentially deposits metal species in areas not covered with OTS. The Pt centers generate a localized oxidative dissolution process that pits the Si in the Pt-coated regions, resulting in the formation of a porous silicon microstructure that luminesces around 580 nm upon illumination with a UV source. Scanning electron microscopy and fluorescence microscopy images of the fabricated porous silicon structures showed that features in the size range of ∼ 10-150/μm, and possibly smaller, can be generated by this catalytically amplified soft lithographic patterning method. Importantly, the OTS acts as an etch mask, so that, even with significant hole transport, etching is confined to areas coated with the Pt(0) complex.