Superconducting Technology Assessment - nitrd
Superconducting Technology Assessment - nitrd
Superconducting Technology Assessment - nitrd
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Fig. 17. Photograph of the FLUX-1r1 microprocessor chip<br />
fabricated in NGST’s 4-kA/cm process. The chip is 1 cm on a<br />
side, contains $63 000 junctions, and dissipates 9 mW. The inset<br />
represents the potential reduction in chip size if the FLUX chip is<br />
redesigned in a 20-kA/cm process.<br />
Table 8<br />
Nb <strong>Technology</strong> Roadmap<br />
for petaFLOPS scale computing. Semiconductor technology<br />
has scaled by 0.7 in feature size and 2.5 in gate density for<br />
each generation, each of which has taken about three years<br />
and a substantial capital investment. Beyond the present 8- to<br />
10-kA/cm processes, continued evolutionary improvements<br />
in niobium technology will require only relatively modest investment<br />
in new process tools and facilities.<br />
IX. CONCLUSION<br />
Because of its extreme speed advantage and ultralow<br />
power dissipation, superconductor electronics based on<br />
RSFQ logic will eventually find widespread use in high-performance<br />
computing and in applications that need the fastest<br />
digital technology such as analog-to-digital converters and<br />
digital signal processing. To be a viable commercial digital<br />
technology, the superconductor electronics community must<br />
demonstrate systems that operate at higher speeds with lower<br />
power than any other technology. Process development efforts<br />
are pushing the boundaries of niobium technology in<br />
three key areas: increasing speed, increasing complexity,<br />
and increasing yields. Rapid progress has been achieved in<br />
the past few years, driven by the high-performance computing<br />
initiative. In addition to advancements in fabrication,<br />
the superconductor electronics community needs to focus<br />
attention on standardization of test and design tools. Finally,<br />
building complete systems or subsystems, which have taken<br />
into account I/O, magnetic shielding, cooling, and other<br />
packaging issues will be required to expand the customer<br />
base beyond a few specialty applications.<br />
ACKNOWLEDGMENT<br />
The authors would like to thank the NGST foundry team<br />
for their many years of fabrication support, particularly in<br />
establishing and maintaining stable fabrication processes,<br />
and the NGST test and packaging teams for their many<br />
years of timely support with parametric data, trend charting,<br />
and wafer preparation. The authors would also like to thank<br />
A. Kleinsasser and the e-beam lithography team at JPL for a<br />
very successful collaboration, and F. D. Bedard of DoD and<br />
D. Van Vechten of ONR for their continuing support of advanced<br />
process development, and John Spargo, Andy Smith,<br />
and Paul Bunyk of NGST and Professor Ted Van Duzer<br />
of University of California, Berkeley for their valuable<br />
discussions. We especially want to acknowledge the many<br />
individuals who contributed to Table 1: K. K. Berggren,<br />
Massachusetts Institute of <strong>Technology</strong>; F.-Im. Buchholz,<br />
Physikalisch-Technische Bundesanstalt; W. Chen, State University<br />
of New York, Stony Brook; P. Dresselhaus, National<br />
Institute of Standards and <strong>Technology</strong> (NIST); M. Hidaka,<br />
SRL; G. Hilton, NIST; Prof. W. Jutzi, Universität Karlsruhe;<br />
X. Meng, University of California, Berkeley; H.-G. Meyer,<br />
IPHT-Jena; A. Shoji, AIST; S. K. Tolpygo, HYPRES; and<br />
J.-C. Villégier, CAE-Grenoble.<br />
REFERENCES<br />
[1] K. K. Likharev and V. K. Semenov, “RSFQ logic/memory family:<br />
A new Josephson-junction technology for sub-terahertz-clock-frequency<br />
digital systems,” IEEE Trans. Appl. Superconduct., vol. 1,<br />
pp. 3–28, Mar. 1991.<br />
[2] W. Chen, A. V. Rylyakov, V. Patel, J. E. Lukens, and K. K. Likharev,<br />
“Rapid single flux quantum T-flip flop operating up to 770 GHz,”<br />
IEEE Trans. Appl. Superconduct., vol. 9, pp. 3212–3215, June 1999.<br />
[3] K. K. Likharev, “RSFQ: The fastest digital technology,” in Proc. 5th<br />
Eur. Workshop Low Temperature Electronics 2002, p. 155.<br />
[4] T. Sterling, “How to build a hypercomputer,” Sci. Amer., pp. 38–45,<br />
July 2001.<br />
[5] T. Sterling, G. Gao, K. K. Likharev, P. M. Kogge, and M. J. Mac-<br />
Donald, “Steps to petaflops computing: A hybrid technology multithreaded<br />
architecture,” in Proc. IEEE Aerospace Conf. 1997,vol.2,<br />
pp. 41–75.<br />
1530 PROCEEDINGS OF THE IEEE, VOL. 92, NO. 10, OCTOBER 2004