Design and Verification of Benzocyclobutene (BCB) Templates for Chip-to-Wafer Alignment in 3D Integration

We report on designs of Benzocyclobutene (BCB) templates for chip-to-wafer (C2W) alignment in 3D integration, in order to effectively reduce the wafer bow and improve the alignment accuracy and wafer-level uniformity. The BCB template enables well-controlled alignment, few thermal cycles and high throughput of 3D system fabrication. In this paper, we evaluated the changes of wafer bow during the C2W 3D fabrication processes and proposed several solutions to reduce the wafer bow, including partial etch of backside oxide, use of a thinner BCB template, use of a partial cure of BCB, or removal of the template corner. Among these options, removing BCB template corner can release the wafer level stress, while improving the alignment accuracy and BCB etch uniformity.