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Abstract: We report on the fabrication of Josephson junction and superconducting bridges using a damascene CMP process applied for a first time to superconductors. The demonstrated industrial reliability of damascene CMP processes on large scale semiconductor circuits is a major incentive for our research that should allow large numbers of nanometric Josephson junctions to be fabricated in both Nb and Al, the two main material employed in superconducting quantum computing (qubit) and RSFQ electronics fabrication.We carried out a Chemical-Mechanical Polishing (CMP) process on Nb and Al films deposited on a SiO2 layer patterned with trenches of 100 to 300nm of nominal depth. The process formed long bridges, 1 to 4μm wide. The susceptibility and resistive transitions showed that CMP has no observable influence on superconductivity.We have also developed a hybrid technique that uses Al/Al2O3/Al shadow evaporation in the trenches before the damascene CMP process. This allows for high quality “in-situ” junction oxidation with the size reduction benefit provided by the damascene CMP process. We easily reach junctions sizes near 0.5μm2 which are difficult to fabricate by other methods.We describe these techniques and report on measurements on large bridges and junctions and on the fabrication and measurements of Al and Nb nanobridges. [Copyright &y& Elsevier]

In this paper, a design and optimization method for submillimeter-wave Schottky diode is proposed. Parasitic capacitance is significantly reduced to under 20% of the total capacitance of the diode. The parasitic capacitance value is measured to be 0.6 fF for 1 μm anode radius which increased the cut-off frequency to 1.5 THz. A corresponding microfabrication process that provides higher degrees of freedom for the anode diameter, air-bridge dimensions and distance to the substrate is introduced and implemented. The DC and RF measurements are provided and compared with the simulations. In order to provide a better understanding of the diode behavior, the limiting factors of the cut-off frequency for different applications are studied and compared. For the mixer/multiplier mode, an improved and expanded formulation for calculation of the cut-off frequency is introduced. It is shown that the usable voltage bias range (with acceptable cut-off frequency) is limited by the exponential reduction of junction resistance, R j , in mixer/multiplier mode. [ABSTRACT FROM AUTHOR]

In the fabrication of microelectronic devices, sputtering of thin films leads to isotropic rough surfaces described by (i) a Gaussian height distribution and (ii) a constant power spectral density (PSD) up to a roll-off frequency of q 0 from which it decays as a power law. This paper introduces a robust approach to estimate the topography parameters such as the density, the mean radius of curvature and the height distribution of summits for isotropic Gaussian rough micro-surfaces. The proposed approach consists of computing the PSD function from the atomic force microscopy measurements, approximating the value of q 0 and the magnitude P 0 of the plateau by curve fitting algorithms, and analytically deriving the topography parameters using the random process theory. The robustness of the proposed methodology is assessed on a sputtered gold micro-surface. The investigations show that the proposed PSD-based approach reduces the dependence of the topography parameters on the sampling length compared to the deterministic method. Moreover, the PSD-based estimated density of summits is in a good agreement with scanning electron microscopy analysis, in contrast to both deterministic and autocorrelation-based methods. The proposed approach is therefore more suitable to extract topography parameters from measurements of micro-surfaces for the development of contact asperity-based models. • Power spectral analysis of gold micro-surface. • Statistical estimation of the density, radius of curvature and height distribution of summits from sputtered gold. • Reduction of the sensitivity of the topography parameters to the measurement resolution. [ABSTRACT FROM AUTHOR]