Reactive ion beam etching of superconducting Bi2212 by Ta/PR and PR´/Ta/PR masks for the generation of THz waves

Generation of powerful THz radiation from intrinsic Josephson Junctions (IJJs) of Bi₂Sr₂CaCu₂O_8+¿ (Bi2212) may require mesas with large lateral dimension. However, there are difficulties in fabrication of perfect rectangular mesas. Mesa lateral angles should be close to 90 degrees to obtain IJJs with same planar dimensions for synchronization of IJJs. Since thick photoresist (PR) layer shades the lateral dimension of mesa during ion beam etching, we patterned Ta/PR and PR´/Ta/PR masks on Bi2212 and used selective ion etching to overcome this problem. The reactive ion beam etchings have done with ion beam of Ar, N₂ and O₂ and we have obtained mesas about 1 ¿m with lateral angle of approximately 50 to 75° which is better than the mesas fabricated with single layer mask.