An Intrinsically Switchable Ladder-Type Ferroelectric BST-on-Si Composite FBAR Filter

作者：Lee Seungku^*; Mortazawi Amir^*

来源：IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 2016, 63(3): 456-462.

DOI：10.1109/TUFFC.2016.2517643

• Barium strontium titanate (BST)
• bulk acoustic wave (BAW)
• electrostriction
• ferroelectric devices
• film bulk acoustic resonators (FBARs)
• intrinsically switchable
• ladder-type filters
• reconfigurable filters

This paper presents a ladder-type bulk acoustic wave (BAW) intrinsically switchable filter based on ferroelectric thin-film bulk acoustic resonators (FBARs). The switchable filter can be turned ON and OFF by the application of an external bias voltage due to the electrostrictive effect in thin-film ferroelectrics. In this paper, Barium Strontium Titanate (BST) is used as the ferroelectric material. A systematic design approach for switchable ladder-type ferroelectric filters is provided based on required filter specifications. A switchable filter is implemented in the form of a BST-on-Si composite structure to control the effective electromechanical coupling coefficient of FBARs. As an experimental verification, a 2.5-stage intrinsically switchable BST-on-Si composite FBAR filter is designed, fabricated, and measured. Measurement results for a typical BST-on-Si composite FBAR show a resonator mechanical quality factor (Q(m)) of 971, as well as a Q(m) x f of 2423 GHz. The filter presented here provides a measured insertion loss of 7.8 dB, out-of-band rejection of 26 dB, and fractional bandwidth of 0.33% at 2.5827 GHz when the filter is in the ON state at a dc bias of 40 V. In its OFF state, the filter exhibits an isolation of 31 dB.

• 出版日期2016-3