Introduction of Sub-2-micron Cu traces to EnCoRe enhanced copper redistribution layers for heterogeneous chip integration

The fabrication of a 2.5D glass interposer was demonstrated, and its electrical performance, including signal transmission, was characterized. Single-sided multi-level enhanced copper redistribution layers were fabricated on a glass substrate with through glass via. This structure will enable heterogeneous chip integration requiring both high-speed signal processing and high-density signal lines. The 3D-simulated insertion loss (Sdd
₂₁
) of the high-speed signal lines (5 mm in length), which were fabricated using a semi-additive process, was as low as -0.86 dB at a frequency of 16 GHz due to low conductor loss. The insertion loss was 1/12 that of a damascene-based signal line. The 4-μm-pitch Cu traces used as high-density signal lines were electrically isolated by using optimized barrier metal etching chemistry. The lower insertion loss and reliable electrical isolation make this interposer advantageous compared to competitive packaging technologies such as 2.5D silicon and 2.1D organic interposers.