Impact of circuit metallization on dielectric permittivity measurement by scanning microwave microscopy

This study demonstrates a dielectric permittivity measurement technique using scanning microwave microscopy (SMM). The proposed technique can be used to evaluate the local dielectric permittivity of a circuit substrate with circuit metallization. The impact of the circuit metallization was reduced by analyzing the positional dependence of the resonance frequencies. Although the evaluated dielectric permittivity of the alumina substrate was in the range of 18-25 without the modification, the values were modified to 9.3. The modified dielectric permittivity was compared to those of other local dielectric measurement techniques, a probe-backside reflection (PBR) method. Dielectric permittivity was evaluated as 9.5 0.35 using the PBR method. Therefore, the SMM result corresponded to the accuracy range. This validated the reliability of the proposed measurement technique using the SMM method.