Lithium niobate SAW device hetero-transferred onto silicon integrated circuit using elastic and sticky bumps

In this study, a new process to temporarily integrate two components via an elastic and sticky silicone layer was developed. The developed integration process is as easy as contact photolithography and even reworkable, and thus will be useful for the quick test of hetro-integrated devices made of different materials of wafer. It was applied to integrated SAW oscillators with resonance frequencies of 400-600 MHz. LiNbO₃-based SAW resonators supported by a glass wafer were transferred onto an IC wafer with CMOS sustaining amplifiers. A transfer yield of 96% was obtained, while electrical interconnection was failed for two thirds of samples optimized process conditions to be optimized. The measured phase noise was comparable with that of the SAW oscillator integrated by Au-to-Au bonding.