A Double thick-polymer technology to realize low signal pad capacitance suitable for high-speed data transmission

A Pad-on-Stacked-Polymer (PASPO) technology, based on low cost packaging process, has been developed by utilizing 13-mum-thick double polymer layers and modified signal land design. The bottom photosensitive polymer shows higher via-hole resolution and higher chemical tolerance than conventional passivation polymer. The highly-reliable top polymer is planarized by CMP. For the 20-mum-square signal land, the PASPO technology drastically reduces the signal pad capacitance from 173 fF to 11 fF, and a clear eye opening for 40 Gbps signal transmission has been achieved for the low-k test chip.