The realization of a revolutionary generation of electronics based on high-temperature superconductors (HTS) crucially depends on the ability to make high-quality thin film microstructures. These will incorporate materials such as YBa2Cu3O7-δ (YBCO), TlBaCaCuO, or BiSrCaCuO in a fashion similar to the circuits and devices made of their low Tc counterparts Nb or NbN. Without exception, the most valuable structures will be composed of multiple layers of superconducting films and dielectrics, in some cases combined with normal metals, low-temperature superconductors, or a variety of semiconductors. Generically, these can be combined in two ways: in a hybrid design where specialized packages and bonding are used to attach dissimilar materials, or in a monolithic thin film structure such as the one seen in Figure 1.
The division between hybrid and monolithic multilayers results from the historical development of electronic circuits. Hybrid designs typically require linewidths and alignment accuracy somewhat less demanding than those used in fully integrated circuits. The advantage of hybrid construction is the separation of incompatible processing steps onto different substrates or die. The monolithic integrated circuit, whether microelectronic, millimeter wave, or radio frequency, can be made in large batches with concomitant economy of scale and can be fabricated with fewer parasitic constraints. Superconducting integrated circuits have followed the semiconductor pattern of being developed in a hybrid fashion, then transferred to a fully integrated process.