Phosphorus Oxychloride (POCl₃) is a clear, volatile liquid used as a phosphorus source for N-type diffusion in semiconductor wafer fabrication. Stable below 300°C and highly reactive, it hydrolyzes in moisture to form phosphoric and hydrochloric acids. Widely applied in IC manufacturing, solar cells, optical fiber preforms, and discrete devices, POCl₃ also serves as a key raw material for high-purity phosphate esters.