Development of Novel Fine Line 2.1 D Package with Organic Interposer Using Advanced Substrate-Based Process

Development of 2.1D package with organic interposer in panel size based on the high resolution dry film photoresist and the ultra-thin electro-less copper seed layer will be reported in this paper. The aim of 2.1D technology is focus on the reducing of production cost and increase I/O counts simultaneously. Compare to the wafer level lithography process, substrate-based process leads to the benefit in cost reduction and risk elusion form chip first process. The high resolution photolithography semi-additive processes (SAP) can achieve 3 µm copper line width and 25 µm laser drilled vias in panel size (510*408mm). On the other hand, the sputtered metal seed layer can be replaced by electro-less copper plating seed layer (approximately 0.1 µm). When it comes to cost, dry film photoresist and electro-less copper seed layer processes can significantly save the equipment and material cost compared to the wafer patterning process. These high density interconnection lines, micro-bump pads and vias are integrated and demonstrated on an organic film in the thickness of 25 µm. Micro-bump pads designed for the copper pillar bond are with a 25 µm diameter and a 40 µm pitch. Flip chip bond alignment is verified by the x-ray examination. The embedded trace substrate (ETS) by using plating nickel thin layer for etching resistance, copper trace with 3 µm width and spacing embedded in the organic film can be formed with very good flatness performance. Moreover, this designed 2.1D organic interposer substrate has passed the MSL3 (Moisture Soaking Level 3) standard and the TCT (Thermal Cycling Test) reliability test with 1000 cycles. In terms of electrical property study, kinds of dielectric materials and high resolution photoresists are employed in this study. The electrical measurement including DC resistance and S-parameter is performed to tell apart the different performance of dielectric and photoresist materials, and the result show agreement with the formed appearance of copper traces.