AFM characterization of patterned sapphire substrate with dense cone arrays: Image artifacts and tip-cone convolution effect

Abstract

Abstract Reliable AFM topography characterization of patterned sapphire substrate (PSS) is essential for deriving accurate dimensions and revealing structure-performance relationship of LED devices with PSS as substrates. Here we systematically and quantitatively studied AFM image artifacts of PSS with dense cone arrays (diameter: 2.93 μm, pitch: 3.23 μm, and height: 1.64 μm) and the tip-cone convolution effect for three types of AFM tips—two different pyramidal tips and one tetrahedral tip. We found that AFM artifacts of single cone protrusion and dense cone arrays, i.e., broaden planes, merged topography of patterns, or tails, are caused by the obstructive effects from the working tip’s planes/edges and adjacent cone arrays. Tetrahedral tips of high aspect ratio with steep edges could be used to avoid artifacts and obtain artifact-free topography of dense cone arrays. The findings reported in this paper will contribute to reliable AFM characterization of PSS with arrays of micron/submicron size, and along with our study on the tip-cylinder convolution effect ( Appl. Surf. Sci. , 422 (2017) 482–491), will also help gain a deeper understanding about AFM image artifacts and the tip-sample convolution effect.