NbN/AlN/NbN超导隧道结的制备工艺

The research of the fabrication of NbN/AlN/NbN superconductor tunnel junctions

研究了在MgO基片上制备NbN/AlN/NbN结的工艺,NbN和AlN的制备分别采用直流磁控溅射和交流磁控溅射。为了得到良好特性的隧道结,首先要在高真空反应室里沉积三层膜结构,经过光刻和反应离子刻蚀,得到底电极和桥区的三层结构图形。再经过第二步光刻和刻蚀,仅保留底电极最下层的NbN,得到结区的三层结构图形,并覆盖AlN绝缘层。经过Lift-off工艺,洗去结区上的光刻胶,最后沉积上电极。使用四端子方法对制备的隧道结进行了一系列测量,特别是在高频(THz)下的响应。

We present our process for fabricating NbN/AlN/NbN tunnel junctions on MgO substrates, in which NbN layers and AlN layers were prepared by DC and RF magnetron sputtering. In order to fabricate tunnel junctions with high qualities, all the three layers should be prepared once in our high vacuum chamber. Then we got the pattern of the junctions in the method of photolithography and reactive ion etching, followed with the insulated layer （AlN） and the upper probe layer （NbN）. The current -voltage （I -V） characteristics of junctions were measured with four terminal probes in iow temperature, and together with the other characteristics in high frequency, especially in the terahertz band.