Wafer scale fabrication of silicon nitride MEMS phase shifters with XeF2 dry vapor release etch process

McNulty, Karl; Niekerk, Matthew van; Deenadayalan, Venkatesh; Errando-Herranz, Carlos; Pruessner, Marcel W.; Fanto, Michael L.; Preble, Stefan F.

doi:10.1117/12.2606849

Cited by 2 publications

(1 citation statement)

References 18 publications

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“…Next, 500 nm of a sacrificial layer of LPCVD amorphous silicon is deposited at 580 °C. Amorphous silicon can be removed with a vapor xenon difluoride etch without attacking the photonic or MEMS layers or exerting destructive capillary forces like a wet etchant [33,35]. The high selectivity also eliminates the need for a timed isotropic etch often used in single-layer MEMS photonic designs [24,36,37].…”

Section: Fabricationmentioning

confidence: 99%

Coupled Mode Design of Low-Loss Electromechanical Phase Shifters

Abebe,

Pai,

Hwang

et al. 2024

Micro

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Micro-electromechanical systems (MEMS) have the potential to provide low-power phase shifting in silicon photonics, but techniques for designing low-loss devices are necessary for adoption of the technology. Based on coupled mode theory (CMT), we derive analytical expressions relating the loss and, in particular, the phase-dependent loss, to the geometry of the MEMS phase shifters. The analytical model explains the loss mechanisms of MEMS phase shifters and enables simple optimization procedures. Based on that insight, we propose phase shifter geometries that minimize coupling power out of the waveguide. Minimization of the loss is based on mode orthogonality of a waveguide and phase shifter modes. We numerically model such geometries for a silicon nitride MEMS phase shifter over a silicon nitride waveguide, predicting less than −1.08 dB loss over a 2π range and −0.026 dB loss when optimized for a π range. We demonstrate this design framework with a custom silicon nitride process and achieve −0.48 dB insertion loss and less than 0.05 dB transmission variation over a π phase shift. Our work demonstrates the strength of the coupled mode approach for the design and optimization of MEMS phase shifters.

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