Decomposition of amorphous Si2C by thermal annealing

Abstract

In the present paper, the decomposition and the crystallization behaviour of amorphous Si2C films, which were deposited by r.f. magnetron co-sputtering on Si wafer substrates, are investigated. For analysis, the following methods were used: x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), grazing incidence x-ray diffractometry (GIXRD), atomic force microscopy and scanning electron microscopy. After deposition, the films exhibited a homogenous amorphous structure with a variety of bonding states reaching from homonuclear silicon-like Si-Si bonds over mixed Si-Si-C bonds to heteronuclear Si-C bonds. Annealing at 1200°C for 2h leads to the crystallization of silicon and silicon carbide with grain diameters of several nanometers within the amorphous matrix, as evidenced by GIXRD and TEM. With XPS also a distinct change of the bonding states is detected. After 2h of annealing, only Si-Si and Si-C bonds are detectable. After prolonged annealing at 1200°C for 20h, XPS shows only Si-C bonding states but no more Si-Si bonding. In addition, GIXRD verifies the absence of any polycrystalline silicon in the film. The microstructure of the film changed dramatically towards a jagged and porous structure. The vanishing of silicon during isothermal annealing is explained on base of in situ and ex situ TEM measurements, and a possible model for decomposition is suggested.