Examination of 3D-matrix superconducting micro-strip lines and its application to filters

由微带线制作的超导滤波器功率处理能力较小，不能用于发射滤波器。微带线外边缘的电流集中导致了滤波器功率处理能力的极限。因此，降低微带线外边缘的电流集中是非常重要的。在这个项目中，我们研究了用3D矩阵微带线制作的滤波器功率处理能力的提高。采用以下工艺制作了3D矩阵微带线滤光片。首先，我们用反应直流磁控溅射法制备了NbN-AlN-NbN三层膜。然后使用传统的光刻技术对滤光片进行图案化处理。采用干法刻蚀的方法对微带线进行刻蚀，将微带线分成窄线。对该滤波器的功率处理能力进行了测试，与传统的微带线滤波器相比，功率处理能力提高了约3.1分贝。这意味着沿3D-Marix微带线(3D-SMSL)外缘流动的电流比传统微带线中的电流集中程度低。3D-SMSL对于提高滤波器的功率处理能力是有用的。

The power handling capability of superconducting filters made by micro-strip lines is small, therefore, the filters cannot be used to the transmitting filters. The limit of power handling capability of filters is caused by the current concentration at the outer edge of a micro-strip line. Therefore, it is very important to reduce the current concentration on the outer edge of a micro-strip line. In this project, we examined the improvement of power handling capability of the filters made by the 3D-matrix micro-strip lines. The 3D-matrix micro-strip line filters were made by following process. First, we made a three-layered film, NbN-AlN-NbN by reactive dc magnetron sputtering. Then the filters were patterned using a conventional photolithography technique. The micro-strip lines were etched by dry etching to divide into the narrow lines. We measured a power handling capability of the filters, and found that the value increased by about 3.1 dB compared with that of the conventional micro-strip line filter. This means that current flowing along the outer edge of the 3D-marix micro-strip line(3D-SMSL) is less concentrated than in the conventional micro-strip line. The 3D-SMSL is useful to increase a power handling capability of a filter.