We have investigated the chopping effect on the crystallinity of the ZnO films prepared by using a modified r.f. planar magnetron sputtering method, where the sputtering process is periodically chopped. In the experiment we have found that if the deposition and pause time is chosen optimally for the renucleation of ZnO grains, a highly c-axis-oriented ZnO film with a large crystallite size can be grown on the SiO2/Si(100) substrate.