US 12,289,098 B2
Filter using transversely-excited film bulk acoustic resonators
Wei Yang, Goleta, CA (US); Andrew Guyette, San Mateo, CA (US); and Gregory Dyer, Santa Barbara, CA (US)
Assigned to Murata Manufacturing Co., Ltd., Nagaokakyo (JP)
Filed by Murata Manufacturing Co., Ltd.
Filed on Mar. 30, 2022, as Appl. No. 17/708,765.
Claims priority of provisional application 63/168,093, filed on Mar. 30, 2021.
Prior Publication US 2022/0321103 A1, Oct. 6, 2022
Int. Cl. H03H 9/56 (2006.01); H03H 9/02 (2006.01); H03H 9/205 (2006.01)
CPC H03H 9/568 (2013.01) [H03H 9/02228 (2013.01); H03H 9/205 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A bandpass filter comprising:
a ladder filter circuit comprising a series transversely-excited film bulk acoustic resonator (XBAR) and a shunt XBAR,
wherein the series XBAR comprises:
a lithium niobate (LN) piezoelectric layer;
a front-side dielectric layer of silicon oxide between interleaved fingers of an interdigital transducer disposed on the LN piezoelectric layer of the series XBAR,
wherein the series XBAR has an LN-equivalent thickness teqa less than or equal to 305 nanometers, and the LN-equivalent thickness tega of the series XBAR is given by the formula tp+ka*(tfsd), where tp is a thickness of the LN piezoelectric layer of the series XBAR, ka is a constant for the series XBAR and ka=0.45, and tfsd is a thickness of the front side dielectric layer of the series XBAR,
wherein the shunt XBAR comprises:
a LN piezoelectric layer;
a front-side dielectric layer of silicon oxide between interleaved fingers of an interdigital transducer disposed on the LN piezoelectric layer of the shunt XBAR, and
wherein the shunt XBAR has an LN-equivalent thickness teqr greater than or equal to 310 nanometers and the LN piezoelectric layer has a thickness that is less than 1500 nanometers, and the LN-equivalent thickness teqr of the shunt XBAR is given by the formula tp+kr*(tfsd), where tp is a thickness of the LN piezoelectric layer of the shunt XBAR, and kr is a constant for the shunt XBAR and kr=0.57, and tfsd is a thickness of the front-side dielectric layer of the shunt XBAR.