Youngs modulus evaluation by SAWs for porous silica low-k film with cesium doping
Youngs moduli of porous silica low-k films with cesium (Cs) doping are determined by surface acoustic waves (SAWs) in this study. Four low-k samples doped with 030ppmwt% Cs in the precursor solution are investigated to check the mechanical promotion of the porous silica films. The SAW determination process is performed on these ultra-thin porous films. The detected signals with the signal-to-noise ratio of 50:1 are achieved in our measurements. The signal process with combination of wavelet and FIR filter is proposed to effectively restrain the high and low frequency noises and the Gibbs effect of the detected signals. The smooth experimental dispersive curves with frequency range from 20 to 150MHz, which is qualified for the data fitting process with the theoretical dispersion curves, are obtained for these detected thin low-k films. The determination results show that the mechanical property is improved with the pretreatment of cesium doping, which confirms that the degree of siloxane cross-linkage of the porous silica film is promoted by cesium doping.
youngs modulus porous silica low-k film cesium doping surface acoustic waves