SINIS fabrication process for realizing integrated circuits in RSFQ impulse logic

Abstract

At PTB, a new type of fabrication process has been developed to verify rapid single flux quantum (RSFQ) integrated circuits based on intrinsically shunted two-tunnel Josephson junctions (JJs). The process has been realized in LTS implementation using SINIS technology. A variety of single JJs, junction arrays and test circuits have been fabricated and experimentally investigated. The critical current densities of the junctions were set to a nominal value of j C = 500 A cm −2 , with values of the characteristic voltage V C equal to or larger than 160 µV. The JJs show nearly hysteresis-free behaviour (less than 10%); the intrawafer parameter spread is smaller than ±10%. Various basic RSFQ circuits have been realized with operation margins of bias currents of larger than ±20%.

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.…”

Stationary properties of SINIS double-barrier Josephson junctions

“…In the last few years, in the field of low-temperature superconducting (LTS) electronics, increasing activities aimed at producing superconductor-insulator-normal metalinsulator-superconductor (SINIS) multilayer structures for use as active circuit elements have been reported [1][2][3][4][5][6][7][8][9][10][11][12]. This type of junction combines advantageous properties of weak links and tunnel junctions [1,2].…”

“…for Josephson voltage standards, for rapid single flux quantum (RSFQ) circuits, for SQUID devices and for the generation of sub-mm wavelength radiation in oscillators based on discrete Josephson junction arrays. Beyond this, with regard to the requirements placed on future technological developments, SINIS junctions are very promising candidates for implementation in highly integrated LTS circuit architectures [2,[7][8][9][10].…”

Harmonic current-phase relation in Nb–Al-based superconductor/insulator/normal conductor/insulator/superconductor-type Josephson junctions between 4.2 K and the critical temperature

“…In particular, the SINIS concept considerably facilitates the realization of moderately damped Josephson junctions without external shunt; first promising applications in the fields of Josephson voltage standards 2 and rapid single flux quantum logics have been presented. 3 Although the shape of the current-voltage characteristic ͑IVC͒ of such junctions was found to be close to that given by the resistively shunted junction model ͑see, e.g., Ref. 4͒, the properties of the supercurrent were not studied in detail.…”