Abstract
Due to the flowability of benzocyclobutene (BCB) and the unavoidable shear components of the bonding force applied by bonding facilities, it is quite challenging to achieve void-free BCB adhesive bonding with simultaneous high post-bonding alignment accuracy. To solve this problem, this paper reports a compensation method for alignment errors to achieve simultaneous void-free and accurate wafer bonding using soft-baked BCB. By characterizing the wafer shift induced bonding force, it is found that the wafer shift is a systematic error associate with the bonders but independent of the wafers. Upon this investigation, a compensation method presetting a pre-bonding alignment shift opposite to the post-bonding shift is proposed to compensate the bonding induced wafer shift. Using this method, void-free bonding with soft-baked BCB has been achieved, and the alignment errors are improved significantly from around 35–40 μm to around 3 μm. Test results show that the average bonding strength of soft-baked BCB is about 26.4 % higher than that of partially-cured BCB. The preliminary results demonstrate the efficacy of the proposed compensation method, which has potential to improve the alignment accuracy of BCB bonding for three-dimensional integration, MEMS, and microsensors.
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Song, Z., Tan, Z., Liu, L. et al. Void-free BCB adhesive wafer bonding with high alignment accuracy. Microsyst Technol 21, 1633–1641 (2015). https://doi.org/10.1007/s00542-014-2242-4
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DOI: https://doi.org/10.1007/s00542-014-2242-4