NOVELTY - A silicon chip is sent into furnace tube of a diffusion furnace, nitrogen is supplied (15-25 L/minute) to furnace and temperature of diffusion furnace is controlled to 770-810 degrees C. The furnace door is closed, nitrogen (5-20 L/minute) is supplied to furnace, and temperature of the furnace is controlled to 770-810 degrees C for 10-15 minutes. Nitrogen mixed with PHOSPHORYL CHLORIDE (1.5-2 L/minute) is supplied into the furnace, and simultaneously oxygen (1.5-2 L/minute) and nitrogen (20-25 L/min) are supplied to the furnace. Thus, production of solar cell is carried out.    USE - Preparation of solar battery.    ADVANTAGE - The method efficiently and economically provides solar battery having improved in-chip resistance.    DETAILED DESCRIPTION - A silicon chip is sent into furnace tube of a diffusion furnace, nitrogen is supplied (15-25 L/minute) to furnace and temperature of diffusion furnace is controlled to 770-810 degrees C. The furnace door is closed, nitrogen (5-20 L/minute) is supplied to furnace, temperature of the furnace is controlled to 770-810 degrees C for 10-15 minutes. Nitrogen mixed with PHOSPHORYL CHLORIDE (1.5-2 L/minute) is supplied into the furnace; and simultaneously oxygen (1.5-2 L/minute) and nitrogen (20-25 L/min) are supplied to the furnace, and temperature of the diffusion furnace is adjusted to 810-830 degrees C for 3-5 minutes. Then, nitrogen (0.8-1.2 L/minute) mixed with phosphoryl chloride is supplied into the furnace; and simultaneously oxygen (0.5-1 L/minute) and nitrogen (15-20 L/min) are supplied, and the temperature of the diffusion furnace is adjusted to 850-870 degrees C for 8-12 minutes. Nitrogen mixed with PHOSPHORYL CHLORIDE (0.8-1.2 L/minute) is supplied into the furnace and simultaneously oxygen (0.5-1 L/minute) and nitrogen (15-20 L/minute) are supplied and temperature of diffusion furnace is adjusted to 850-870 degrees C for 10-12 minutes. Oxygen (2-2.5 L/minute) and nitrogen (15-20 L/minute) are supplied to furnace, temperature of the diffusion furnace is adjusted to 850-870 degrees C for 3-5 minutes. Then, oxygen (2-2.5 L/minute) and nitrogen (15-20 L/minute) are continuously fed to furnace, temperature of furnace is adjusted to 820-840 degrees C for 8-10 minutes, cooled to 770-810 degrees C for 10-15 minutes. The silicon chip is discharged after feeding 15-20 L/minute of nitrogen and temperature of the diffusion furnace is adjusted to 770-810 degrees C. Thus, production of solar cell is carried out.