Fabrication of High-Aspect-Ratio Macro-Mesopore Arrays Via Electrochemical Etching with Tunable Mode Transition

We demonstrate that backside-illuminated photoelectrochemical (PEC) etching enables deterministic control over mode transitions in silicon pore arrays, extending wet etching beyond conventional high-aspectratio formation. By combining photoelectrochemical dissolution with coordinated modulation of bias voltage, illumination, and HF concentration, we achieve stable macropore growth with aspect ratios up to $\sim 35$ within 80 minutes etching. This approach further allows in situ engineering of mesoporous domains and controlled undulations within pore structures. Such tunability establishes backside-illuminated PEC as a scalable platform for precision pore morphology control, with broad implications for through-silicon vias (TSVs), MEMS, and advanced 3D integration.