Oxidation and bonding a porous silicon (PSi) thin film onto an active device wafer

Wafer bonding is the process by which two mirror-polished wafers adhere to each other at room temperature. The bonding is enabled through the van der Waals force. Because bonding enables stacking of integrated circuits, it adds a third dimension to a traditional 2D circuit so more circuits features can be packed in the same small footprint without the need to shrink the features of the circuit. For this project, we explored oxidizing a porous silicon (PSi) thin film and bonding the resulting porous silica (PSiO2) thin film to a silicon wafer. The silicon wafer may contain active devices, such as modulators and photodetectors. Wafer bonding is a promising approach toward the production of Volumetric Photonic Integrated Circuits (VPICs) because the PSiO2 can be used as low-loss transparent scaffold for photoresist in a direct laser write (DLW) process to make graded index (GRIN) optics. However, currently the bonding process has relatively low yield because the intermediate substrate cannot tolerate the high temperature and high pressure when the PSi is oxidized, bonded, and processed. Therefore, we investigated whether the process can be optimized by using a suitable sacrificial substrate or sacrificial layer that can tolerate the high temperature, high pressure process. Once the PSiO2 film can be intactly transferred and bonded, we can make VPICs with greater yield and functionality. This PSiO2 transfer and bonding process can also give a hint to other electronic integration applications that require an intermediate high temperature process.LimitedSenior thesis has possible patentable material and a form was submitted from ECE requesting access be closed until further notice