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A new through substrate via for millimeter-wave frequencies is proposed. The via is formed by copper nanowires connecting the bottom to the top surfaces of a porous alumina membrane. It is shown here that the nanowire-via is simple to fabricate using only six low-cost processing steps. Its dimensions and spacing are only limited by the photolithography process, reaching small sizes, important for high-density interconnections. The nanowire-vias were tested as CPW transitions and characterized up to 40 GHz. The results show low insertion loss of less than 0.035 dB per transitions at 40 GHz.
Pinheiro et al. (Sun,) studied this question.