Thin Si wafer substrate bonding and de-bonding below 250 °C for the monolithic 3D integration

We studied low temperature (<250 °C) transfer of 8 in. full sized thin Si wafer layer on the SiO2/Si substrate without any wafer flip up/down and subsequent high temperature process. This method includes temporary bonding of carrier wafer with bonding material at 200 °C, grinding or etching substrate, and transfer layer at 250 °C. Thickness values of transferred thin Si layer using bulk Si and silicon-on-insulator (SOI) wafer substrates are 87 μm and 216 nm on the SiO2/Si substrate, respectively. Plasma treatment under N2 and O2 mixture ambient assisting to form hydrophilic surface was carried out during bonding process and enhanced bonding strength was confirmed by contact angle measurement. Our wafer bonding process can be feasible to form various monolithic 3D devices due to thin Si layer transfer and low temperature process.