Fabrication Of Suspended Shadow Mask By Electron Beam Lithography & Deep UV Lithography

Quantum computation research is become an international hot subject in recent years, superconducting Josephson Junction is the basic unit of superconducting qubits. As one of the only two pioneer national institutes in superconducting qubits research, we've done lots of work on the research of Al/Al2O3/Al tunnel junctions. We have certain experience in fabrication of high-performance Al/Al2O3/Al tunnel junction technology, and begin to design and fabricate the multi-junction system circuit of superconducting quantum bits. The fabrication of Al/Al2O3/AI tunnel junction using the method of the combination of angled evaporation based on a suspended shadow mask. The fabricated tunnel junctions have a low level of dissipation. By the control of specific parameters we can fabricate high-quality Al/Al2O3/Al tunnel junctions of required design area. The total work in this thesis will be introduced in three aspects below:1. The fabrication of suspended shadow mask by electron beam lithographyAfter stabling the conditions of fabrication and summarizing the basic control parameters, we can fabricate high-quality Al/Al2O3/Al tunnel junctions of required design area, by the control of specific parameters with the double angle evaporation technique and the thickness of the photo resist and other parameters. We can fabricate the suspended shadow mask by electron beam lithography, and the size of suspended area is 1μm and even 0.5μm.2. Reducing the dissipation by the design of asymmetric electrode structureThere is some positive correlation between the proportion of leakage current to superconducting current and the proportion of effective circumference to the area of junction. The means of reduce effective perimeter by the design of asymmetric electrode structure can lower the level of dissipation.3. The fabrication of suspended shadow mask by deep UV lithography (DUV)Based on the fabrication of single junction, we use DUV to fabricate the multi-junction system circuit of superconducting quantum bit. By means of optimizing the design of graphics and the exposure process, we can fabricate the suspended shadow mask by DUV. It laid a good foundation for preparation the multi-junction system circuit of superconducting quantum bits.The I-V characteristics of the AI/Al2O3/AI tunnel junction were measured at low temperature, T≈300mK. The successful fabrication of Al tunnel junction makes it promising for research in quantum bits. Simultaneously, we begin to fabricate the multi-junction system circuit of superconducting quantum bits, and can fabricate the suspended shadow mask by deep DUV lithography on the basis of optimizing the mask design and controlling the parameters of exposure continuously. It laid a good foundation for preparation the multi-junction system circuit of superconducting quantum bits.