SiOx layer formation during plasma sputtering of Si and SiO2 targets

Deposition of SiO x layers of variable composition onto silicon wafers was performed by co-sputtering of spaced Si and SiO2 targets in argon plasma. Coordinate dependences of the thickness and refractive index of separately deposited Si and SiO2 layers and the SiO x layer grown during co-sputtering of targets were determined using optical techniques. It was shown that the SiO x layer composition is not equal to a simple sum of thicknesses of separately deposited Si and SiO2 layers. The coordinate dependences of the Si and SiO2 layer thicknesses were calculated. To fit the calculated and experimental data, it is necessary to assume that no less than 10% of silicon is converted to dioxide during co-sputtering. A comparison of the coordinate dependences of the IR absorbance in SiO2 and SiO x layers with experimental ellipsometric data confirmed the presence of excess oxygen in the SiO x layer. Taking into account such partial oxidation of sputtered silicon, composition isolines in the substrate plane were calculated. After annealing of the SiO x layer at 1200°C, photoluminescence was observed in a wafer area predicted by calculations, which was caused by the formation of quantum-size Si nanocrystallites. The photoluminescence intensity was maximum at x = 1.78 ± 0.3, which is close to the composition optimum for ion-beam synthesis of nanocrystals.