Patterning of pyramidal recesses in (1 0 0)InP substrate

Symmetrical pyramidal recesses were etched into (1 0 0)InP substrate in 3HCl:1H₃PO₄ at (16 ± 0.05) °C via 20 μm × 20 μm square windows opened in InGaAs. The windows had sides aligned in 〈0 0 1〉 and corners tapered along [0 1 1] and [0-11]. The recesses had each of the four sides at the square edges composed of a large ordinary facet (called pyramidal) and a small re-entrant facet. The pairs were identified to be initially close to {1 1 0}/{-110} (pyramidal pairs), i.e. the ordinary pyramidal facets were initially close to (1 1 0), (1 0 1),(1-10), and (10-1). However, they deviated towards planes with higher Miller indices with etching duration. The recesses were also confined to etch-stop ∼{0 1 1} and fast-etching ∼{1 1 1}B facets at the [0 1 1] taper edges and etch-stop ∼{2 1 1}A ones at the [0-11] taper edges. The recesses evolved into sharp inverted pyramids with sub-100 nm extremities at the bottom if etched at least 30 min. The sharpening is possible thanks to the elimination of the etch-stop ∼{2 1 1}A facets via a self-limited etching of the pyramidal pairs.

Source: Microelectronic Engineering

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