Title :
All refractory NbN integrated circuit process
Author :
Thomasson, S.L. ; Moopenn, A.W. ; Elmadjian, R. ; Murduck, J.M. ; Spargo, J.W. ; Abelson, L.A. ; Chan, H.W.
Author_Institution :
TRW Space & Technol. Group, Redondo Beach, CA, USA
fDate :
3/1/1993 12:00:00 AM
Abstract :
The authors describe the fabrication and electrical performance of an eight mask step, 2.5- mu m*2.5- mu m minimum junction size, all refractory NbN integrated circuit process. NbN/MgO/NbN trilayers sputtered in situ are patterned by reactive ion etching to form Josephson tunnel junctions. A two-level dielectric process has been developed to ensure low defect densities. Sputtered molybdenum films form a resistor layer. NbN wire J/sub c/ enhancement and improved step coverage have been achieved. This process has been used to successfully fabricate SQUID amplifier circuits, digital modified variable threshold logic circuits, arrays of 256 SQUIDs, SFQ counters, and 4000 junction strings. NbN logic circuit operation above 10 K was demonstrated.<>
Keywords :
Josephson effect; SQUIDs; critical current density (superconductivity); logic gates; niobium compounds; shift registers; sputter etching; superconducting integrated circuits; superconducting logic circuits; type II superconductors; Josephson tunnel junctions; Mo film resistor layer; NbN integrated circuit process; NbN-MgO-NbN trilayers; SFQ counters; SQUID amplifier circuits; SQUID arrays; all refractory; critical current density; digital modified variable threshold logic circuits; eight mask step; electrical performance; fabrication; junction strings; low defect densities; reactive ion etching; shift register array; two-level dielectric process; Counting circuits; Dielectrics; Fabrication; Logic arrays; Logic circuits; Optical films; Resistors; SQUIDs; Sputter etching; Wire;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
