Quality factor and frequency bandwidth of 2D self-inductors in 3D integration stacks

Effects due to 3D level stack on high frequency (HF) properties of 2D self-inductors integrated in the back end of line (BEOL) are investigated. Different stacking processes as Back to Face and Face to Face using a molecular SiO"2 bonding or a copper direct bonding are studied in order to determine silicon substrate stack influence on quality factor and frequency bandwidth of 2D self-inductors. Face to Face process with a molecular SiO"2 bonding allows improvements of self-inductor performances, better than Back to Face process with a molecular SiO"2 bonding and better than Face to Face process using a copper direct bonding.