ITO films were deposited on the Corning 1737 glass by the RF-magnetron sputtering method with and without external heating as a function of deposition time. The as-grown ITO film, deposited on room temperature substrate without external heating for 10 min, was amorphous in nature. Continuous deposition over 20 min resulted in the development of crystallization of the films. The crystallization by prolonged deposition was initiated from the top surface of the film where energetic ions bombard. When the films were deposited with external heating, the crystallization was initiated from the beginning of the deposition at the surface of the substrate.