Fabrication process and noise properties of antenna-coupled microbolometers based on superconducting YBCO films

An analysis of how the detectivity and lifetime depend on the fabrication p rocess of superconducting antenna-coupled microbolometers has been carried out. The temperature dependences of responsivity and noise equivalent power (NEP) have been estimated in terms of the thermal model. To reveal the mai n degradation mechanism, 1/f-noise characterization has been used, Monte-Ca rlo simulation of the annealing procedure of YBa2Cu3O7 (YBCO) films for the operating ranges of frequency and temperature has shown that prevailing so urces of flicker noise in superconducting microstrips are associated with t ransitions of oxygen atoms situated close to low-angle boundaries of the fi lm blocks. The magnetron sputtering technique has been optimized to reduce the Hooge parameter for flicker noise to a record-breaking low value for YB CO films of about 10(-4) at 93 K. Comparative analysis of chemical, ion and laser etching techniques by low-temperature scanning electron microscopy a nd magneto-optics allowed the fabrication of microstrips with uniform curre nt distribution characterized by critical current density higher than 10(6) A cm(-2) at 77 K and long-time stability. The process of low-energy ion mi lling of YBCO films with an Arf beam generated in a duopigatron ion source was used to reach a width resolution at the topology edge better than 0.2 m u m. The antenna-coupled bolometers fabricated from the superconducting mic rostrips were used to register microwave radiation at a frequency of 70.3 G Hz and temperature of 93 K. It is demonstrated that the developed technolog y makes possible the fabrication of long-lived YBCO-based antenna microbolo meters with electrical NEPe = 1.5 x 10(-12) W Hz(-1/2). The calculated resp onse time of the antenna is about 30-150 ns. Further development is associa ted with fabrication of coupling microbolometers with immersed lens, with p redicted optical detectivity D* = (4 x 10(9)-4 x 10(10)) cm Hz(1/2) W-1 in the wavelength range 100-1000 mu m.