Patterning issues in superconducting nanowire single photon detector fabrication
NEB22A2 CD SEM variation according to the stack differences for the same exposure doses, i.e., . (a) Right CD, patterned on stack 2 (PL1). (b) Under exposed pattern on stack 3 showing a linewidth of instead of expected.
Radial energy distribution at the resist/material interface at short range. Dotted lines shows RED for stack 1 (, rhombus) and stack 2 (PL1, square), and very similar and a continuous line for stack 3 (, triangle) with a RED twice less.
AFM images of SSPDs prepared from (a) NbN-a layer, after a moderate stripping (vertical full scale ), (b) NbN-a, using the passivating layer PL2 on top, and after an O2 stripping as in Table I (vertical full scale ).
Critical current of SSPDs at , patterned as described in text from the NbN-a sample, as a function of the meander width. The straight line corresponds to a critical current density of . Insert: typical curve obtained for meander width.
Summary of stripping experiments conditions and results. RIEs in various plasma atmospheres have been conducted sometimes followed by a wet clean of the sample. is the initial (final) resistance of samples at , and is their normal-superconductive transition temperature after treatment. NbN layer-B samples are size, cut from the same wafer.
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