We have developed high-density packaging technologies with Cu/photosensitive benzocyclobutene (BCB) multi-layer on a silicon substrate. We have adopted stacked via structure as multi-layer and a silicone as a core substrate. The core substrate is composed of silicon using metal through plugs. The interconnects consist of stacked via with 20μm via and 30μm land, and the via is filled by electroplating. The conductor layer was formed by semi-additive process using copper sputtering layer as seed metal. The width of the patterned line is 5μm and the space between them is also 5μm. The through-hole was 10μm in diameter and 170μm deep, which was formed deep-RJE etching. The holes have been filled with electroplating Cu and Cu/Ag conductive paste, which makes it possible to form the via on via and via on through plug. Since such stack structure makes connection length short between LSI and a board, the reduction of delaying time for signal propagation could be improved. We have evaluated electrical performances of the Cu/BCB substrate with fine conductive line. The width of the line is from 6μm to 11 μm, and the length is from 5.0mm to 15.0mm to study the dependence of signal attenuation behavior on the line length and width. S-parameter of micro strip line structure was measured by network analyzer. The transmission power loss of 6|im width, 15mm length line was less than -3dB in the range of up to 16GHz frequency.
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