CPW在铁电薄膜介电常数测量中的结构优化

Optimize the CPW Structure Used for Permittivity Measurement of Ferroelectric Thin Films

共面波导线(CPW)被广泛用于测量铁电薄膜的复介电常数。共面波导电路通常被制作在沉淀了薄膜的铝制基片上,该文分析了薄膜的复介电常数与共面波导(CPW)的尺寸与谐振频率、品质因数之间的关系。由于铁电薄膜通常是中低损耗材料,并且厚度很薄,所以周边环境对介电常数的测量结果准确度有较大的影响。为了获得更高的测试灵敏度的同时获得更高的准确度,该文对共面波导谐振器(CPW)在不同尺寸条件下,谐振频率的改变,品质因数的变化和高次模抑制进行了分析,结果显示最优结构尺寸是共面波导的缝隙宽度(g)等于共面波导的厚度(h),同时,缝隙的宽度(g)不能超过共面波导微带线宽度的两倍(2s)。

Coplanar waveguide （CPW） lines are employed to measure the complex permittivity of ferroelec-tric thin films.The CPW circuit is made on the alumina substrate,with the thin film deposited on.The relation- ships among the complex permittivity of the thin films and the size of the CPW,the resonance frequency and the quality factor are analyzed.Since the ferroelectric thin films,usually are low or middle loss materials with small thickness,the environment has a great effect on the accuracy of measurement results.In order to get high measurement sensitivity and accuracy simultaneously,the changes in the resonance frequency,the quality factor and high-order mode of the different sizes of CPW resonator structure are analyzed.The re-sults show that it is optimal size that the gap of CFW（g）is equal to the thickness of CPW（h）, meanwhite,＂g＂ is no more than twice of the width of CPW conductor（2s）.