Fabricating Flux Qubits With Electron Beam Lithography

We will present work on fabricating an Al/AlO$_{x}$/Al flux qubit on a sapphire substrate. The device consists of a rectangle SQUID loop with an area of 5 $\mu $m x 10 $\mu $m, where one third of the loop area has been sectioned off by a line with four sub-micron Josephson tunnel junctions. Two thirds of the loop forms a SQUID with two larger area junctions. The area of each of its large junctions is 0.4 ($\mu $m)$^{2}$ with a desired critical current of 1-10 $\mu $A. Three of the other four sub-micron junctions have an area of 0.056 ($\mu $m)$^{2}$, where as the fourth junction has an area of 0.028 ($\mu $m)$^{2}$. Device fabrication on an insulating substrate (sapphire) requires some unconventional electron-beam lithography fabrication techniques. We will discuss the design, the fabrication process and our progress towards measuring the properties of the device at millikelvin temperatures.