SAW Filters With Excellent Temperature Stability and High Power Handling Using LiTaO3/SiC Bonded Wafers

The development of 5G has put forward a higher demand for filters, and the purpose of this work is fabricating surface acoustic wave (SAW) filters with excellent temperature stability and high power handling using LiTaO ₃ /SiC bonded wafers. SAW resonators with different wavelengths are fabricated on LiTaO ₃ /SiC, and LiTaO ₃ /Si, bulk LiTaO ₃ as well. We evaluate these resonators, concluding that the bilayer substrates can enhance the performance. Subsequently, SAW filters are designed and fabricated. For the filters based on LiTaO ₃ /SiC, the center frequency is around 2.62 GHz and the minimum insertion loss is 1.90 dB. The whole passband is flat and larger than 200 MHz, and the return loss is larger than 10 dB. SiC is more effective than Si in the enhancements of temperature stability and power handling. SiC reduces the temperature coefficient of the frequency at the left side of the passband to about half of that on LiTaO ₃ /Si and one-sixth of that on bulk LiTaO ₃ , and enlarges the peak power handling to 35.7 dBm. The time-to-failure of the filters on LiTaO ₃ /SiC is 3.8 times as long as LiTaO ₃ /Si and 11.3 times the level of bulk LiTaO ₃ , when an input power of 30 dBm is applied ceaselessly. This work demonstrates the potential of SAW filters based on LiTaO ₃ /SiC for RF filters in 5G. [2021-0233]