Silicon oxide nanolayers for soft X-ray optics produced by plasma enhanced CVD

Abstract
We have studied the suitability of Plasma Enhanced Chemical Vapor Deposition (PECVD) to produce ultrasmooth silicon oxide layers ranging in thickness from some nanometers to some 10 nm. A tight process control of the layer thickness, layer density and microroughness of the growing film is required. We deposited silicon oxide on silicon wafers, float glass and superpolished quartz substrates. In a remote plasma enhanced CVD process, we used tetraethylorthosilicate (TEOS, Si(OC₂H₅)₄) as precursor. Films with a thickness of some 10 nm were produced at different deposition parameters and characterized by in-situ soft X-ray reflectivity, hard X-ray diffraction and auger electron spectroscopy. Best results could be found for the deposition using TEOS in oxygen plasma. In case of SiO₂ layers deposited on standard glass substrates signifcant roughness smoothing was obtained.