Yiu-Huen Wong

RF measurement technique for characterizing thin dielectric films

We have developed a novel technique for measuring the dielectric constant and loss tangent of a thin film dielectric material up to 5 GHz. The dielectric film needs to be deposited on a metal layer and capped with a metal electrode layer. The bottom metal layer does not have to be very conductive, as long as its sheet resistance is uniform and known. Only one step lithography on the top metal layer is required. No dc electrical contact to the bottom metal layer is necessary. The measurement is taken with a Vector Network Analyzer and a coplanar-wave-guide miniature wafer probe.

Measurements of the bulk, C-axis electromechanical coupling constant as a function of AlN film quality

Piezoelectric thin film AlN has great potential for on-chip devices such as thin-film resonator (TFR)-based bandpass filters. The AlN electromechanical coupling constant, K/sup 2/, is an important material parameter that determines the maximum possible bandwidth for bandpass filters. Using a previously published extraction technique, the bulk c-axis electromechanical coupling constant was measured as a function of the AlN X-ray diffraction rocking curve [full width at half maximum (FWHM)]. For FWHM values of less than approximately 4/spl deg/, K/sup 2/ saturates at approximately 6.5%, equivalent to the value for epitaxial AlN. For FWHM values >4/spl deg/, K/sup 2/ gradually decreases to approximately 2.5% at a FWHM of 7.5/spl deg/. These results indicate that the maximum possible bandwidth for TFR-based bandpass filters using polycrystalline AlN is approximately 80 MHz and that, for 60-MHz bandwidth PCS applications, an AlN film quality of >5.5/spl deg/ FWHM is required.