This study investigates the deep-reactive ion etching (DRIE) of silicon nanowires (Si-NWs) at cryogenic temperatures to fabricate arrays of vertically aligned Si-NWs with dimensions ranging from micrometers to 30 nm in diameter. The research employs various lithography techniques, including optical, electron-beam, nanoimprint, and nanosphere/colloidal masking, to achieve large selectivity ratios of ~100 to 120 and ~700 with resists and chromium hard masks, respectively. The high aspect ratios of up to 100 and sub-μm trenches were achieved without collapse, maintaining low surface roughness values of ~0.3, ~13, and ~2 nm for the top, sidewall, and bottom surfaces, respectively. The work demonstrates the potential of cryo-DRIE for controllably developing Si nanoarchitectures, particularly for applications in energy harvesting, storage, optoelectronics, quantum devices, photovoltaics, and biomedical devices. The study also explores the impact of different lithography methods and mask materials on the uniformity and fidelity of the Si-NW arrays, using techniques such as atomic force microscopy, scanning electron microscopy, angle-resolved Mueller matrix polarimetry, and angle-resolved Fourier microscopy.This study investigates the deep-reactive ion etching (DRIE) of silicon nanowires (Si-NWs) at cryogenic temperatures to fabricate arrays of vertically aligned Si-NWs with dimensions ranging from micrometers to 30 nm in diameter. The research employs various lithography techniques, including optical, electron-beam, nanoimprint, and nanosphere/colloidal masking, to achieve large selectivity ratios of ~100 to 120 and ~700 with resists and chromium hard masks, respectively. The high aspect ratios of up to 100 and sub-μm trenches were achieved without collapse, maintaining low surface roughness values of ~0.3, ~13, and ~2 nm for the top, sidewall, and bottom surfaces, respectively. The work demonstrates the potential of cryo-DRIE for controllably developing Si nanoarchitectures, particularly for applications in energy harvesting, storage, optoelectronics, quantum devices, photovoltaics, and biomedical devices. The study also explores the impact of different lithography methods and mask materials on the uniformity and fidelity of the Si-NW arrays, using techniques such as atomic force microscopy, scanning electron microscopy, angle-resolved Mueller matrix polarimetry, and angle-resolved Fourier microscopy.