Studies on the high-temperature superconductor (HTS)/metal/polymer dielectric interconnect structure for packaging applications

A HTS/metal/low dielectric constant polymer dielectric hybrid interconnect structure was fabricated using high density interconnect (HDI) copper/polyimide processing techniques. Nondegraded superconducting properties, J/sub c/ of over 1 MAcm/sup -2/ and T/sub c/ of 88 K, were obtained using optimum processing conditions. A 0.6 /spl mu/m-thick YBCO film was coevaporated on LaAlO/sub 3/ substrate, annealed, patterned, and Au contact pads were deposited. A Kapton polyimide film was laminated on HTS parts in an oxygen environment. Using a siloxane polyimide (SPI) base adhesive at 170-210/spl deg/C or a polyester base adhesive at 150/spl deg/C vias were drilled on the polymer layer using a 351 nm Ar laser followed by subsequent via cleaning with O/sub 2/+CF/sub 4/ plasma. To complete test parts Ti/Cu/Ti metallization and patterning with a laser adaptive lithography were followed. It was found that the laminated polymer film on the HTS protected HTS film properties from heating and water exposure. The polyimide laminated HTS film maintains its superconductivity up to 210/spl deg/C of lamination temperature. The hybrid structure also showed excellent reliability performances: 6% J/sub c/ decrease at 150/spl deg/C/65 h thermal bake, 12% J/sub c/ decrease after 100 thermal cycles from -96 to 150/spl deg/C, and maintain superconductivity in water immersion up to more than 10 h. T/sub c/ of samples remained always the same 88 K. Coplanar HTS lines, microstrip HTS/metal lines, and HTS power strip line structures were demonstrated on a 2-in-diameter HTS wafer coupon.<
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