| 摘要 |
Josephson junction devices are normally manufactured by the deposition of metal and insulator layers in vacuum, the layers being patterned as required by masking and etching. A pattern layer, such for example, as that providing the base electrode of a Josephson junction, forms a step causing the subsequently applied layers to have an undulating surface.
<??>To avoid this, the base electrode layer (31) of a Josephson junction device is deposited on a substrate (30), a pattern of resist (41) is built up on the layer (31), and this layer is then etched away to leave the required pattern, the etching method being such as to leave an undercut edge (43) to the metal pattern, and an overhanging ledge of resist (42). An insulating layer(33A) is then deposited on the substrate (30), and built up until it is of slightly less depth than the metal layer (31), leaving a small gap (44) under the overhanging ledge (42) of the resist. The resist mask (41) is then removed with the aid of a solvent, which is able to penetrate through the gap (44) to undermine and remove the resist layer with whatever insulating material will have been deposited on its top and edges, leaving an almost plane surface for further processing.
<??>Similar steps may be applied to other layers, in particular to those forming the counter electrodes of the Josephson junctions.
<??>The substrate may be at a small angle to the beam of material being deposited, and may be rotated to ensure that the layer (33A) is able to penetrate under the overhanging edge of the resist mask (41).
<??>In a modification of the method, the insulating layer is deposited first, the photoresist mask is applied to the insulating layer, and the exposed portions of the layer removed by plasma etching, the edges of the photoresist mask being slightly undercut. The metal layer is then deposited to a depth such as to leave a slight gap under the overhanging ledge of photoresist, and the resist is removed as before. |
