570-ps 13-mW Josephson 1-kbit NDRO RAM

Nagasawa, Shuichi; Wada, Y.; Hidaka, Mutsuo; Tsuge, H.; Ishida, I.; Tahara, S.

doi:10.1109/jssc.1989.572615

Cited by 33 publications

(6 citation statements)

References 13 publications

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“…In addition to the VT-based RAMs, it is appropriate to mention some other, less successful, solutions [11], [12], [13], review [14], and declared "intentions" to develop a superconductor RAM [15]. We will not discuss here many existing original proposals of single memory cells, which are either not ready yet for integration into RAM, e.g., [16], or such an integration appears to be very complicated to the authors, e.g., [17,18], [19], etc.…”

Section: Introductionmentioning

confidence: 99%

Very Large Scale Integration of Josephson-Junction-Based Superconductor Random Access Memories

Семенов

Polyakov

Tolpygo

2019

IEEE Trans. Appl. Supercond.

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Arrays of Vortex Transitional (VT) memory cells with functional density up to 1 Mbit/cm 2 have been designed, fabricated, and successfully demonstrated. This progress is due to recent advances in design optimization and in superconductor electronics fabrication achieved at MIT Lincoln Laboratory.As a starting point, we developed a demo array of VT cells for the 100-μA/μm 2 MIT LL fabrication process SFQ5ee with 8 niobium layers. The studied two-junction memory cell with a twojunction nondestructive readout occupied 168 μm 2 , resulting in an over 0.5 Mbit/cm 2 functional density. Then, we reduced the cell area down to 99 μm 2 (corresponding to over 0.9 Mbit/cm 2 functional density) by utilizing self-shunted Josephson Junctions (JJs) with critical current density, Jc of 600 µA/μm 2 and eliminating shunt resistors. The fabricated high-Jc memory cells were fully operational and possessed wide Read/Write current margins, quite close to the theoretically predicted values. We discuss approaches to further increasing the integration scale of superconductor memory and logic circuits: a) miniaturization of superconducting transformers by using soft magnetic materials; b) reduction of JJ area by using planar high-Jc junctions similar to variable thickness bridges.

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Section: Introductionmentioning

confidence: 99%

Very Large Scale Integration of Josephson-Junction-Based Superconductor Random Access Memories

Семенов

Polyakov

Tolpygo

2019

IEEE Trans. Appl. Supercond.

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“…Josephson junction devices have the advantages of highspeed switching and low power dissipation. Using these superior characteristics, many research works have been conducted to realize high-speed computing systems, signal processing systems and so on [1][2][3][4][5][6][7][8]. In Japan, the MITI (Ministry of Trade and Industry) promoted the research of Josephson junction high-speed electronics as a part of the Large-Scale Project on Scientific Computing Systems [1,2].…”

Section: Introductionmentioning

confidence: 99%

“…In Japan, the MITI (Ministry of Trade and Industry) promoted the research of Josephson junction high-speed electronics as a part of the Large-Scale Project on Scientific Computing Systems [1,2]. In the project, the process technology for Nb Josephson junction LSIs, Josephson logic circuits, Josephson memories and prototypes for a Josephson computer system had been developed [1][2][3][4][5][6][7][8]. Since the completion of the former MITI project, research institutes, including universities, in Japan have been making steady improvement on their chip fabrication technology and circuit technology.…”

Section: Introductionmentioning

confidence: 99%

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Progress in Nb-based low-temperature superconductive electronics for high-speed digital applications in Japan

Nishino¹

1997

Supercond. Sci. Technol.

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Recent progress in Nb Josephson junction LSI technology in Japan is described. Improvements in fabrication processes of the Nb/AlOx/Nb junction have brought high junction-current densities and sub-micrometre junction sizes. Research efforts on logic LSIs have mainly focused on applications to high-speed switches for broad-band communication and high-performance parallel computing. The highest achieved clock frequency of the logic LSIs is beyond 3 GHz. Josephson memory technology has also progressed realizing an access time of 380 ps for a 4 kbit LSI. In a new approach toward logic circuits for future information systems, basic research on a hybrid circuit technology, composed of superconductive and semiconductor devices, has also been started in Japan. The present status of these research efforts in Japan is reviewed.

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“…Josephson devices have the advantages of high-speed operation and low power requirements. Recently, several kinds of Josephson memories have been developed, and their access times indicate potential for gigahertz clock operation [1][2][3][4]. However, functional tests at gigahertz clock frequencies have not yet performed because there is currently no memory tester that can test at gigahertz clock frequencies.…”

Section: Introductionmentioning

confidence: 99%

A Josephson built-in self-testing (JBIST) system for gigahertz functional tests of Josephson RAMs

Hashimoto

Tahara

Nagasawa

et al. 1996

Supercond. Sci. Technol.

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We propose a Josephson built-in self-testing (JBIST) system. The aim of the JBIST system is to perform functional tests for Josephson RAMs at more than 1 GHz. The prototype JBIST circuit is designed for a 256 bit Josephson RAM, and consists of an instruction ROM and a processing circuit. A MARCHING test program is written into the instruction ROM, and the processing circuit executes the program on the instruction ROM. Total power consumption of the JBIST circuit is designed to be 4.2 mW. Estimated delays for the critical paths suggest the potential of a gigahertz clock testing. We fabricated the JBIST circuit chips by using Nb-AlO x -Nb Josephson junctions. The component circuits in the JBIST circuit (sequence controller, comparator, and instruction ROM) are successfully operated.

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570-ps 13-mW Josephson 1-kbit NDRO RAM

Cited by 33 publications

References 13 publications

Very Large Scale Integration of Josephson-Junction-Based Superconductor Random Access Memories

Very Large Scale Integration of Josephson-Junction-Based Superconductor Random Access Memories

Progress in Nb-based low-temperature superconductive electronics for high-speed digital applications in Japan

A Josephson built-in self-testing (JBIST) system for gigahertz functional tests of Josephson RAMs

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