NOVELTY - A silicon sheet surface is placed in diffusion furnace, and subjected to diffusion (I) at 810-830 degrees C for 5-15 seconds under nitrogen concentration of 21000-23000 ml. Resultant product is subjected to diffusion (II) at furnace temperature of 830-850 degrees C for 60-800 seconds under nitrogen concentration of 27000-29000 ml, and further subjected to diffusion processes (IV)-(X) at specified temperatures for specified time under different concentration of nitrogen. Thus, phosphorus diffusion process of polycrystalline silicon chips is carried out.    USE - Phosphorus diffusion process of polycrystalline silicon chips used for solar battery.    ADVANTAGE - The solar battery using phosphorus-diffused polycrystalline silicon chips has excellent durability and conversion efficiency, and is economical.    DETAILED DESCRIPTION - A silicon sheet surface is placed in a diffusion furnace, and subjected to diffusion (I) at furnace opening temperature of 810-830 degrees C for 5-15 seconds under nitrogen concentration of 21000-23000 ml. The resultant product is subjected to diffusion (II) at furnace temperature of 830-850 degrees C for 60-800 seconds under nitrogen concentration of 27000-29000 ml, and further subjected to diffusion (III) at furnace temperature of 800-820 degrees C for 70-900 seconds under nitrogen concentration of 27000-29000 ml. The resultant product is subjected to diffusion (IV) at 800-820 degrees C under diffusion time of 50-700 seconds under nitrogen concentration of 8000-9000 ml or 800-1200 ml, and further subjected to diffusion (V) at furnace temperature at 810-830 degrees C for 80-1000 seconds under nitrogen concentration of 8000-9000 ml, phosphorus oxychloride concentration of 700-900 ml and oxygen concentration of 300-500 ml. The resultant product is subjected to diffusion (VI) at 840-850 degrees C for 60-800 seconds under nitrogen concentration of 700-900 ml, phosphorus concentration of 700-900 ml, and oxygen concentration of 400-500 ml. The obtained product is further subjected to diffusion (VII) at 830-850 degrees C for 1100-1300 seconds under nitrogen concentration of 700-900 ml and oxygen concentration of 1500-3000 ml, and further subjected to diffusion (VIII) at 800-820 degrees C for 110-130 seconds under nitrogen concentration of 21000-23000 ml. The obtained product is subjected to diffusion (IX) at 800-820 degrees C for 700-900 seconds under nitrogen concentration of 27000-29000 ml, and further subjected to diffusion (X) at 810-840 degrees C for 10-20 seconds under nitrogen concentration of 20000-22000 ml. Thus, phosphorus diffusion process of polycrystalline silicon chips is carried out.