Fabrication of high-quality superconductor-insulator-superconductor junctions on thin SiN membranes

Abstract

We have successfully fabricated high-quality and high-current density (Jc≊4 000 A/cm2) superconductor-insulator-superconductor (SIS) junctions on freestanding thin (∼1 μm) silicon nitride (SiN) membranes. These devices can be used in a novel millimeter-wave and THz receiver system which is made using micromachining. The SIS junctions with planar antennas were fabricated first on a silicon wafer covered with a SiN membrane, the Si wafer underneath was then etched away using an anisotropic KOH etchant. The current-voltage characteristics of the SIS junctions remained unchanged after the whole process, and the junctions and the membrane survived thermal cycling.

Micromachined room-temperature microbolometers for millimeter-wave detection

“…Recently, silicon micromachining technology has been used to fabricate horn antennas for millimeter and submillimeter wave detectors. [1][2][3] In this letter, we report fabrication and characterization of a micromachined millimeterwave antenna-coupled uncooled microbolometer using a Nb film as the radiation absorber and temperature sensing element. Bismuth has been the material of choice for metallicfilm microbolometers because it has a low electrical conductivity, and therefore, Bi microbolometers can be easily impedance matched with planar antennas.…”