Ex-situ Tunnel Junction Process Technique Characterized by Coulomb Blockade Thermometry
Abstract
We investigate a wafer scale tunnel junction fabrication method, where a plasma etched via through a dielectric layer covering bottom Al electrode defines the tunnel junction area. The ex-situ tunnel barrier is formed by oxidation of the bottom electrode in the junction area. Room temperature resistance mapping over a 150 mm wafer give local deviation values of the tunnel junction resistance that fall below 7.5 % with an average of 1.3 %. The deviation is further investigated by sub-1 K measurements of a device, which has one tunnel junction connected to four arrays consisting of N junctions (N = 41, junction diameter 700 nm). The differential conductance is measured in single-junction and array Coulomb blockade thermometer operation modes. By fitting the experimental data to the theoretical models we found an upper limit for the local tunnel junction resistance deviation of ~5 % for the array of 2N+1 junctions. This value is of the same order as the minimum detectable deviation defined by the accuracy of our experimental setup.
Keywords
Cite
@article{arxiv.1006.2436,
title = {Ex-situ Tunnel Junction Process Technique Characterized by Coulomb Blockade Thermometry},
author = {M. Prunnila and M. Meschke and D. Gunnarsson and S. Enouz-Vedrenne and J. M. Kivioja and J. P. Pekola},
journal= {arXiv preprint arXiv:1006.2436},
year = {2015}
}