The growth of ZnO film on (0001) sapphire substrates was studied using the high density helicon wave oxygen plasma (>1011/cm2) assisted evaporation process. The addition of Ar into oxygen plasma (Ar/O2=1/2) enhanced the production of excited atomic oxygen (O*). The effect of a grounded grid installed at the exit of the plasma source on the crystallinity and optical properties of film is discussed. The full width at half maximum (FWHM) of θ rocking curve for (0002) plane is 0.53° under grid installation while 0.63° without the grid, indicating slightly improved crystallinity when adopting a grounded grid. The AFM image for the film deposited with grid installation shows a smoother surface morphology than in the case of no grid. PL spectra for the film deposited with the aid of a grid show a strong near-band edge emission at 3.36 eV at 10K, but those without a grid show prominent deep-level emissions. The deep level emission is attributed to the impurities and native defects in the film. The optical properties were greatly improved by a grounded grid, which effectively eliminated the ionic species and selectively extracted the excited neutrals.