High-resistivity Zr resistors with Ti barrier layer for Nb Josephson circuits

Abstract

We apply Zr resistors to Josephson integrated circuits in place of MO because a Zr thin film has about five times the resistivity of MO. Zr resistors do not need to be protected during etching, unlike conventional MO resistors, because Zr has much smaller etching rate than Nb. Zr resistors occupy only 25% of a unit cell area. Using Zr resistors reduces the area of the Josephson gate and allows increased circuit integration. We found increased contact resistance between Zr and Nb films after annealing about 350°C but suppressed it with a Ti barrier. We were able to fabricate resistors with a resistance variation throughout a wafer of within 2.8%.