Superconductor-insulator-normal- conductor-insulator-superconductor process development for integrated circuit applications

Abstract

The paper reports on recent developments in a new technology process in LTS implementation to fabricate intrinsically shunted tunnel junctions. The process has been realized in SINIS multilayer thin-film technology. In various test series, circuits containing a large variety of single junctions and junction arrays of different contact areas and sizes were fabricated and measured. By variation of the oxidation parameters the fabrication process has been optimized for application in integrated circuits operating in RSFQ impulse logic. The junction parameter values realized for the critical current density range to up to about , those for the characteristic voltage to up to about . The junctions show nearly non-hysteretic current-voltage characteristics; the intra-wafer parameter spread is below 10%. The junctions realized fulfil the requirements imposed for digital RSFQ circuit operation at clock frequencies in the lower GHz frequency range.

The current-phase relation in Josephson junctions

“…2001;Hagedorn et al, 2001Hagedorn et al, , 2002Kaul and van Duzer, 2001;Ohta et al, 2001;Schubert et al, 2001; van Duzer et al, 2002. 5 See Amin et al, 1992;Nevirkovets, 1995Nevirkovets, , 1997Capogna and Blamire, 1996;Nevirkovets et al, 1996Capogna et al, 1997;Maezawa and Shoji, 1997;Sugiyama et al, 1997Sugiyama et al, , 1999Balashov et al, 1998Balashov et al, , 1999Balashov et al, , 2001Schulze et al, 1998Behr et al, 1999;Buchholz and Kessel, 1999;Brinkman et al, 1999Brinkman et al, , 2001Khabipov et al, 1999Khabipov et al, , 2002aKhabipov et al, , 2002bKupriyanov et al, 1999;Buchholz et al, 2001;Cassel et al, 2001;Kohlmann et al, 2001Kohlmann et al, , 2002Nevirkovets, Ketterson, and Rowell, 2001;Nevirkovets, Ketterson, and Siegel, 2001;Shaternik et al, 2001;Kieler et al, 2002;Nevirkovets and Ketterson, 2002;Yamamori et al, 2002;Tolpygo, Brinkman, et al, 2003. between the S electrodes. Until now, only a planar geometry has been realized in experiments by…”

“…At TϾT c Ј Al is in the normal state, and I S () is close to sin if ␥ eff is large. At TϽT c Ј Al is in 10 See Maezawa and Shoji, 1997;Sugiyama et al, 1997Sugiyama et al, , 1999Balashov et al, 1998Balashov et al, , 1999Balashov et al, , 2001Schulze et al, 1998Behr et al, 1999;Buchholz and Kessel, 1999;Khabipov et al, 1999Khabipov et al, , 2002aKhabipov et al, , 2002bBuchholz et al, 2001;Cassel et al, 2001;Kohlmann et al, 2001Kohlmann et al, , 2002Kieler et al, 2002. FIG.…”

Properties of planar Nb/α-Si/Nb Josephson junctions with various degrees of doping of the α-Si layer

“…4-7, the shape of CVC changes substantially with the impurity concentration in the α Si layer: as the tungsten con centration decreases, it transforms from the CVC of a classical SNS junction to the curves typical of two barrier Josephson structures [9][10][11][12]44]. This change can only be explained by another current transport mechanism, which dominates over both the mecha nism of direct current passage through the N layer and direct electron tunneling through the layer.…”

“…The barriers in all materials were formed by the oxidation of aluminum. The substantial difference in the mor phologies of an Al film on an S electrode and the film located between dielectric layers makes it possible to achieve the required symmetry only in the case of low transparency barriers [10][11][12][13][14].…”

Boundary conditions for the order parameter and the proximity influenced internal phase differences in double superconducting junctions

“…When a normal metal is placed between the superconductors, the Josephson coupling emerges as a consequence of superconducting correlations generated by proximity effects in the normal metal region [22][23][24][25][26]. A number of hybrid systems with proximity-induced Josephson coupling through normal metal electrodes, have recently been the focus of scientific scrutiny [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41].…”