HBAR Resonator with a High Level of Integration

A method for manufacturing a HBAR resonator comprising the following steps:

• providing (102) a piezoelectric transducer (6) made up of a layer of a first thickness of a first material oriented along an angle φ defined by the nomenclature (YXw)/φ of the IEEE Std-176 (1949 revision) standard equal to zero, cut along a first cutting angle θ1 defined by the nomenclature (YXl)/θ of the IEEE Std-176 (1949 revision) standard, such that the electroacoustic coupling of the shear waves within that material alone is greater than 5%, the transducer (6) having a temperature coefficient of the frequency CTFA as a function of the first cutting angle θ1, and
• providing (104) an acoustic substrate formed by a first layer with a second thickness of a second material having a working frequency acoustic quality coefficient product at least equal to 5.1012, oriented along an angle φ defined by the nomenclature (YXw)/φ of the IEEE Std-176 (1949 revision) standard equal to zero, cut along a second cutting angle θ2 defined by the nomenclature (YXl)/θ of the IEEE Std-176 (1949 revision) standard, having a polarization direction {right arrow over (P)}B1 corresponding to a first shearing mode of vibration, the acoustic substrate (10) having a temperature coefficient of the frequency of the first order CTFB1 corresponding to the at least one shearing mode and depending on the second cutting angle θ2,
• metalizing (106) one face of the substrate (10) and a first face of the transducer (6) using a thermo-compressible metal,
• assembling (108) the transducer (6) and the substrate (10),
• adhering, by compression (110), the respective faces of the substrate (10) and the transducer (6) metalized in the step (106),
• metalizing (114) an electrode (4) on a second face of the transducer (6),
• characterized in that
• during the assembly step (108), the transducer (6) is arranged in relation to the substrate (10) such that the relative arrangement of the transducer (6) and the substrate (10) is such that the polarization direction {right arrow over (P)}A of the shearing mode of the transducer (6) and the polarization direction {right arrow over (P)}B1of the at least one shearing mode of the substrate (10) corresponding to the second cutting angle θ2 are aligned, and
• in that in the step (104) for providing the substrate (10), the second cutting angle θ2 of the substrate (10) is chosen such that the temperature coefficient of the frequency of the first corresponding order CTFB1 is a local extremum with an absolute value of less than 20 ppm·K−1 and the variation of CTFB1 from said value of θ2 is slight with an absolute value of less than 2 ppm·K−1/degree.