In situ FT-IR reflective absorption spectroscopy for characterization of SiO 2 thin films deposited using sputtering-type electron cyclotron resonance microwave plasma

Abstract

Plasma conditions for depositing high quality SiO 2 thin films using a sputtering-type ECR (electron cyclotron resonance) method have been investigated. Film properties have been studied as a function of an oxygen flow rate, F O 2 , in the range 2–8 sccm with a constant Ar flow rate of 16 sccm. Dielectric breakdown characteristics have been investigated by ramp I- V measurements, indicating that the film prepared with F O 2 = 8 sccm to the thickness of 412 Å have a good dielectric breakdown field of 8–10 MV/cm. The deposited films were characterized in terms of refractive index and IR (infra-red) properties using FT-IRRAS (Fourier transform infrared reflective absorption spectroscopy) and ellipsometry. The refractive index of films deposited with more than F O 2 = 3 sccm is close to 1.46 which indicates that the films prepared in this range are approximately stoichiometric. In addition, quantitative analysis of the dominant IR (infra-red) mode shows that the peak frequency and FWHM (full width at half-maximum) of a TO (transverse optical phonon) mode for films prepared with more than F O 2 = 6 sccm are comparable with thermally grown SiO 2, i.e. v = 1075 cm −1 and FWHM = 70 cm −1. These observations indicate the optimum operating condition of the sputtering-type ECR apparatus, at which it can produce high quality films for MOS (metal-oxide semiconductor) device manufacture without the need for substrate heating.