Modelling and Optimization for Deposition of SiO_xN_y Films by Radio-Frequency Reactive Sputtering

SiO_xN_y films are deposited by reactive sputtering from a Si target in Ar/O₂/N₂ atmospheres. In order to achieve the control of film composition and to keep a high deposition rate at the same time, a new sputtering model based on Berg's work is provided for the condition of double reactive gases. Analysis based on this model shows that the deposition process can easily enter the
target-poisoning mode when the preset gas flow (N₂ in this work) is too high, and the film composition will change from nitrogen-rich to SiO₂-like with the increase of oxygen supply while keeping the N₂ supply constant. The modelling results are confirmed in the deposition process of SiO_xN_y. Target self-bias voltages during sputtering are measured to characterize the different sputtering modes. FTIR-spectra and dielectric measurements are used to testify the model prediction of composition. Finally, an optimized sputtering condition is selected with the O₂/N₂ flow ratio varying from 0 to 1 and N₂ supply fixed at 1 sccm. Average deposition rate of 17nm/min is obtained under this selected condition, which has suggested the model validity and potential for industry applications.