In this work, the polarization-dependent loss (PDL) of a SiO₂/Si arrayed waveguide demultiplexer (AWG DEMUX) is optimized. The physical factors causing the polarization dependence of the AWG and the process methods and conditions required to eliminate this dependence are analyzed theoretically. AWG DEMUX chips are fabricated by semiconductor processes, such as chemical-vapor deposition, photolithography, and etching. The boron and phosphorus contents in the cladding material are optimized and adjusted according to theoretical analysis. The PDLs of the chips are successfully reduced to 0.12 dB so that the PDL parameters meet the chip's commercialization requirements.