Forming an xbar device with excess piezoelectric material removed

Abstract

A method of forming a filter device forms an adhesive layer on a substrate having at least one location for a first cavity and at least one location for a second cavity on a single die. A piezoelectric plate is adhered to the adhesive layer and spans the first cavity and the second cavity. Excess portions of the piezoelectric plate extending a length beyond a perimeter of the first cavity and the second cavity are removed. The excess portions can be piezoelectric material extending beyond the perimeter of the cavities 2% to 25% in length and width. An interdigital transducer (IDT) is located on a front side of the piezoelectric plate and has interleaved fingers over the first cavity.

Claims

1. A filter device, comprising: A substrate having at least one first cavity and at least one second cavity on a single die; An adhesive layer is formed on the substrate but does not at least partially cross the first cavity or the second cavity; A piezoelectric plate is bonded to the adhesive layer and spans the first cavity and the second cavity; The piezoelectric plate does not include any excess portion extending beyond the periphery of the first cavity and the second cavity; A first interdigital transducer has interlaced fingers on the front side of the piezoelectric plate and above the first cavity; A second interdigital transducer has interlaced fingers on the front side of the piezoelectric plate and above the second cavity; as well as At least one conductor connects the first interdigital transducer to the second interdigital transducer; Specifically, with respect to at least the first interdigital transducer, the second interdigital transducer, and the at least one conductor, the piezoelectric plate spans only the first cavity and the second cavity, is below the first interdigital transducer and the second interdigital transducer, and is below the at least one conductor.

2. The apparatus according to claim 1, characterized in that, The first cavity has a first periphery, the second cavity has a second periphery; and the excess portion is: The length and width of the periphery of the piezoelectric material of the piezoelectric plate spanning the first cavity and the second cavity, the length and width extending between 2% and 25% of the periphery of at least one of the first cavity and the second cavity.

3. The apparatus according to claim 1, characterized in that, The adhesive layer does not include any excess portion extending beyond the periphery of the first cavity and the second cavity.

4. The apparatus according to claim 1, characterized in that, The substrate is silicon, the adhesive layer is silicon dioxide, and the first interdigital transducer is metal.

5. The apparatus according to claim 4, characterized in that, The piezoelectric plate is either lithium niobate or lithium tantalate.

6. The apparatus according to claim 1, characterized in that, The corresponding radio frequency signals applied to the first interdigital transducer and the second interdigital transducer excite the corresponding main shear acoustic modes in the piezoelectric plates above the first cavity and the second cavity. The atomic motion of the electric field of the acoustic mod mainly moves laterally along the length of the piezoelectric plate, and the acoustic energy of the acoustic mod propagates in a direction substantially perpendicular to the atomic motion of the electric field. The acoustic energy of the acoustic modulus propagates in a direction substantially perpendicular to the surface of the piezoelectric plate.

7. The apparatus according to claim 6, characterized in that, The thickness of the piezoelectric plate is selected to adjust the primary shear acoustic mode in the piezoelectric plate.

8. The apparatus according to claim 1, characterized in that, It also includes connections to the first interdigital transducer and the second interdigital transducer, wherein the first interdigital transducer and the second interdigital transducer form the input and output of the radio frequency filter.

9. The apparatus according to claim 1, characterized in that, The piezoelectric plate has an opening in its surface located between the first interdigital transducer and the second interdigital transducer.

10. A method of forming a filter device, comprising: An adhesive layer is formed on a substrate having at least one location for a first cavity and at least one location for a second cavity on a single die. The piezoelectric plate is bonded to the adhesive layer; Remove the excess portion of the piezoelectric plate that extends beyond the periphery of the first cavity and the periphery of the second cavity; A first interdigital transducer is formed on the front side of the piezoelectric plate, with the interlaced fingers of the first interdigital transducer positioned above the first cavity. A second interdigital transducer is formed on the front side of the piezoelectric plate, and the second interdigital transducer has interlaced fingers above the position of the second cavity; as well as Form at least one conductor that connects the first interdigital transducer to the second interdigital transducer; Specifically, with respect to at least the first interdigital transducer, the second interdigital transducer, and the at least one conductor, the piezoelectric plate spans only the first cavity and the second cavity, is below the first interdigital transducer and the second interdigital transducer, and is below the at least one conductor.

11. The method according to claim 10, characterized in that, The first cavity has a first periphery, and the second cavity has a second periphery; And the removal of redundant parts includes: Remove the length and width of the periphery of the piezoelectric material of the piezoelectric plate across the positions of the first cavity and the second cavity, the length and width extending beyond at least 2% and 25% of the periphery of the positions of the first cavity and the second cavity, respectively.

12. The method according to claim 10, characterized in that, Removing excess parts from the piezoelectric plate includes: Patterning of the bonded piezoelectric plate; and The patterned piezoelectric plate is etched to remove excess portions of the piezoelectric plate.

13. The method according to claim 12, characterized in that, Removing excess parts from the piezoelectric plate includes: The adhesive layer is etched to remove excess portions of the adhesive layer that extend beyond the periphery of the locations of the first cavity and the second cavity.

14. The method according to claim 10, characterized in that, The substrate is silicon, the adhesive layer is silicon dioxide, and the first interdigital transducer is metal; wherein the piezoelectric plate is either lithium niobate or lithium tantalate.

15. The method according to claim 10, characterized in that, Removing excess portions of the piezoelectric plate includes removing excess portions of the piezoelectric plate before or after forming the first interdigital transducer. and Further, it includes forming the first cavity and the second cavity before bonding the plate to the substrate or after forming the first interdigital transducer.

16. The method according to claim 15, characterized in that, The piezoelectric plate, the first interdigital transducer, and the second interdigital transducer are configured such that radio frequency signals applied to the first interdigital transducer and the second interdigital transducer excite the main shear acoustic mode in the piezoelectric plate above the first cavity and the second cavity. The atomic motion of the electric field of the acoustic mod mainly moves laterally along the length of the piezoelectric plate, and the acoustic energy of the acoustic mod propagates in a direction substantially perpendicular to the atomic motion of the electric field. The acoustic energy of the acoustic modulus propagates in a direction substantially perpendicular to the surface of the piezoelectric plate.

17. The method according to claim 16, characterized in that, The thickness of the piezoelectric plate is selected to adjust the primary shear acoustic mode in the piezoelectric plate.

18. The method according to claim 15, characterized in that, It also includes forming connections to the first interdigital transducer and the second interdigital transducer, wherein the first interdigital transducer and the second interdigital transducer form the input and output of the radio frequency filter.

19. The method according to claim 10, characterized in that, It also includes forming an opening in the surface of the piezoelectric plate located between the first interdigital transducer and the second interdigital transducer.

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