Fabrication of Second-Level TriDelta Interconnects using Negative Dry-Film Photoresist

Chen, W., Song, Y., Liang, J., and Sitaraman, S. K.,“Fabrication of Second-Level TriDelta Interconnects using Negative Dry-Film Photoresist”, Proceedings of the ASME 2014 International Mechanical Engineering Congress & Exposition (IMECE2014), November 2014, Montreal, Quebec, Canada, IMECE2014-40154.
Compliant off-chip interconnects can accommodate the differential displacement between dissimilar materials such as a silicon substrate and an organic board, and can decrease stresses in a microelectronic system. In this paper, we present the fabrication of an area-array of TriDelta compliant interconnects on a 6-inch silicon wafer using sequential processes. The design consists of about 2000 compliant interconnects at a 400-µm pitch on each 18mm×18mm silicon substrate, and there are 32 substrates on a 6-inch wafer. The three arcuate beams of the compliant interconnects are the main parts that provide both the in-plane and out-of-plane compliance, and thus the arcuate beam width and thickness are the most important factor to be considered. DupontTM Riston® FX920 (thickness = 20μm) negative dry film photoresist is used in our study and the arcuate beam thickness is uniform throughout the pattern. However, by designing the arcuate beam width to be 10µm, 15µm, and 20µm, different compliance values can be achieved in the same or different substrates. The use of the dry film photoresist makes the fabrication process cost effective compared to the use of liquid film photoresist. The mechanical compliance of such fabricated compliant interconnects, intended as second-level interconnects, is presented in this work.