Study On Preparation And Preferential Orientations Growth Of Polycrystalline AIN Thin Films

Aluminum nitride (AlN) thin films with different preferential orientations were deposited on (111) Silicon (Si) substrate by Radio Frequency reactive magnetron sputtering. The high pure Alunminum (99.99%) was used as sputtering target material, high pure argon (99.99%) and nitrogen (99.99%) were used as sputtering and reactive gas respectively. AlN thin films were characterized by FT-IR, step profiler and XRD. The process parameters were optimized according to the experimental results. The effect of working pressure, subtrste temperature, N2 flow rate percentage and target-substrate distance on film desposition rate, crystalline and chemical structure were investigated. The preferential orientations of AlN thin films were analyzed quantitatively by FT-IR absorbtion spectrum. Experimental results showed as followed:It was found that process parameters have a significant influence on the film deposition rate, crystalline and chemical structure. Lowering working pressure is positive to raising the depositing species'energy when they arrive at substrate surface; lowering the target substrate distance leads to more bombardment to substrate surface and makes a higher nucleation density; raising substrate temperature enhances the diffusion and mobility of adatoms, the crystal quality of films were improved; increasing N2 flow rate percentage reduces the film deposition rate and makes it has surface diffusing time for lattice rearrangement before next atomes layer's coming. Therefore, lowering working pressure, N2 flow rate percentage and target substrate distance, raising substrate temperature benefits the highly preferential orientation of (002) orientation. On the contrary, rising working pressure, N2 flow rate percentage and target substrate distance, reducing substrate temperature leads to (100) preferential oriention. The mechanism of the influence of process parameters on the preferential orientation of AlN thin films were discussed.The deconvolution of Al-N FTIR absorption peak at around 678 cm-1 resulted in two vibration mode:the A1(TO) mode at 612cm-1 and E1(TO) mode at 672 cm-1. The ratio of the integrated areas of A1(TO) and E1 (TO) absorption mode has a strong correlation with the preferential orientation of AlN thin films, suggesting that FTIR absorption spectrum can be used as a supplementary characterization technique of XRD to evaluate the preferential orientation of polycrystalline AlN films.