A study on deep-reactive ion etching (DRIE) of silicon nanowire arrays at cryogenic temperatures is presented. The research investigates the fabrication of vertically aligned silicon nanowires (Si-NWs) with diameters ranging from micrometers down to 30 nm using cryo-DRIE combined with various lithography techniques. The study finds high selectivity (100–120 for resists and 700 for chromium hard masks) enabling the successful transfer of patterned geometries while preserving spatial resolution. The work demonstrates the ability to achieve high aspect ratios (up to 100) and sub-μm trenches with a 200 nm diameter Si-NW at an etch rate of ~4 μm/min without collapse. Surface roughness values of ~0.3, ~13, and ~2 nm were maintained on the top, sidewall, and bottom surfaces of the nanowires, respectively. The study establishes the foundation for the controlled development of Si nanoarchitectures, particularly for applications in energy harvesting, optoelectronics, quantum devices, photovoltaics, and biomedical devices. The study also explores the challenges of etching Si-NWs compared to etching Si fins and trenches, due to the loading effect, which influences the etch rate based on the exposed surface area. The cryo-DRIE process is shown to overcome these challenges by enabling high-aspect-ratio Si-NWAs with minimal undercut and high selectivity. The study presents various cryo-DRIE recipes for different mask materials and lithography techniques, including photolithography, nanosphere lithography, nanoimprint lithography, and electron-beam lithography. The results show that cryo-DRIE offers a versatile and reproducible method for fabricating Si-NWAs with high uniformity and fidelity, making it suitable for large-scale manufacturing. The study highlights the importance of optimizing process parameters to achieve the desired dimensions, aspect ratios, and surface roughness of the nanowires. The results demonstrate the potential of cryo-DRIE for the fabrication of high-quality Si-NWAs with applications in various fields, including energy harvesting, optoelectronics, and biomedical devices.A study on deep-reactive ion etching (DRIE) of silicon nanowire arrays at cryogenic temperatures is presented. The research investigates the fabrication of vertically aligned silicon nanowires (Si-NWs) with diameters ranging from micrometers down to 30 nm using cryo-DRIE combined with various lithography techniques. The study finds high selectivity (100–120 for resists and 700 for chromium hard masks) enabling the successful transfer of patterned geometries while preserving spatial resolution. The work demonstrates the ability to achieve high aspect ratios (up to 100) and sub-μm trenches with a 200 nm diameter Si-NW at an etch rate of ~4 μm/min without collapse. Surface roughness values of ~0.3, ~13, and ~2 nm were maintained on the top, sidewall, and bottom surfaces of the nanowires, respectively. The study establishes the foundation for the controlled development of Si nanoarchitectures, particularly for applications in energy harvesting, optoelectronics, quantum devices, photovoltaics, and biomedical devices. The study also explores the challenges of etching Si-NWs compared to etching Si fins and trenches, due to the loading effect, which influences the etch rate based on the exposed surface area. The cryo-DRIE process is shown to overcome these challenges by enabling high-aspect-ratio Si-NWAs with minimal undercut and high selectivity. The study presents various cryo-DRIE recipes for different mask materials and lithography techniques, including photolithography, nanosphere lithography, nanoimprint lithography, and electron-beam lithography. The results show that cryo-DRIE offers a versatile and reproducible method for fabricating Si-NWAs with high uniformity and fidelity, making it suitable for large-scale manufacturing. The study highlights the importance of optimizing process parameters to achieve the desired dimensions, aspect ratios, and surface roughness of the nanowires. The results demonstrate the potential of cryo-DRIE for the fabrication of high-quality Si-NWAs with applications in various fields, including energy harvesting, optoelectronics, and biomedical devices.