Fabrication of sub-wavelength anti-reflective light trapping structures by maskless interference lithography

Sub-wavelength gratings and pillars with tapered profile such as pyramidal and conical have been employed in solar cells to suppress the reflection over broader wavelengths. The hard mask of these structures is currently fabricated by high cost, low throughput electron beam lithography. We fabricated gratings and pillars with period of 300nm, 500nm & 1000nm on silicon by a maskless interference lithographic technique and subsequent very short reactive ion etching at room temperature. The profile and aspect ratio of as-fabricated structures was controlled by the SF₆/O₂ gas flow ratio in final etching step. We also fabricated nickel stamps of aforementioned structures using electroplating technique suitable for large area nanoimprint lithography. The SEM and AFM analysis of the samples fabricated from both methods were carried out.