In this paper, we investigate the fabrication of high aspect ratio photonic crystal air holes in AlGaAs materials using general inductively coupled plasma (ICP) dry etching system. We propose dividing the long etching process into multiple short-time etching segments during the ICP etching process, so that there is enough time to exhaust the etch products out from the bottom of the holes before the next etching segment, which is beneficial for deep air hole etching. Simultaneously, a novel method to suppress lateral penetration of holes by in-situ sidewall passivation is proposed, which can be realized by inserting one oxygen plasma treatment between two etching segments. This method also allows the optimization of etch rate to be achieved independent of sidewall passivation. Our experiment results show that the sidewall passivation has a crucial influence on the etched morphology of air holes. Without sidewall passivation, the air holes are lateral penetrated in the middle. While with appropriate oxidation for sidewall passivation, deep air holes with high verticality are obtained. Finally, high-aspect-ratio air holes with a diameter of 130 nm and a depth of over 1.5 μm are successfully manufactured.
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