Optical emission spectroscopy study on depositionprocess of microcrystalline silicon

This paper reports that the optical emission spectroscopy (OES) is used to monitor the plasma during the deposition process of hydrogenated microcrystalline silicon films in a very high frequency plasma enhanced chemical vapour deposition system. The OES intensities (SiH^*, H_\alpha^* and H_\beta^*) are investigated by varying the deposition parameters. The result shows that the discharge power, silane concentrations and substrate temperature affect the OES intensities. When the discharge power at silane concentration of 4% increases, the OES intensities increase first and then are constant, the intensities increase with the discharge power monotonously at silane concentration of 6%. The SiH^* intensity increases with silane concentration, while the intensities of H_\alpha^* and H_\beta^* increase first and then decrease. When the substrate temperature increases, the SiH^* intensity decreases and the intensities of H_\alpha^* and H_\beta^* are constant. The correlation between the intensity ratio of I_\rm H_\alpha^*/I_\rm SiH^* and the crystalline volume fraction (X_\rm c) of films is confirmed.