Lamb wave type frequency device and method thereof

Abstract

A Lamb wave type high frequency device comprises: a piezoelectric substrate; an interdigital transducer (IDT) electrode formed on a first main surface of the piezoelectric substrate; a reinforcing substrate connected to a second main surface of the piezoelectric substrate; a space portion formed in one of the piezoelectric substrate and the reinforcing substrate, an area of the space portion being larger than a region in which a Lamb wave is propagated; and a connecting surface formed in a periphery of the space portion.

1 . A method for manufacturing a Lamb wave type high frequency device that includes, a piezoelectric substrate, an interdigital transducer (IDT) electrode formed on a first main surface of the piezoelectric substrate, a reinforcing substrate connected to a second main surface of the piezoelectric substrate, a space portion formed in one of the piezoelectric substrate and the reinforcing substrate, an area of the space portion being larger than a region in which a Lamb wave is propagated, and a connecting surface formed in a periphery of the space portion, the method comprising:
 forming a groove-like recess corresponding to the space portion provided in one of a thick plate of the piezoelectric substrate and the reinforcing substrate;   forming a sacrificed layer in the recess;   connecting the thick plate with the reinforcing substrate;   polishing the thick plate to a given thickness after the connection; and   forming the IDT electrode and removing the sacrificed layer after the polishing.   
   
   
       2 . A method for manufacturing a Lamb wave type high frequency device that includes, a piezoelectric substrate, an interdigital transducer (IDT) electrode formed on a first main surface of the piezoelectric substrate; a reinforcing substrate connected to a second main surface of the piezoelectric substrate, a space portion formed in one of the piezoelectric substrate and the reinforcing substrate, an area of the space portion being larger than a region in which a Lamb wave is propagated, and a connecting surface formed in a periphery of the space portion, the method comprising:
 forming a boxlike recess corresponding to the space portion in the reinforcing substrate;   forming a penetration hole in a bottom of the recess;   forming a sacrificed layer in the recess;   connecting a thick plate of the piezoelectric substrate with the reinforcing substrate;   polishing the thick plate to a given thickness after the connection; and   forming the IDT electrode and removing the sacrificed layer after the polishing.   
   
   
       3 . The method for manufacturing a Lamb wave type high frequency device according to  claim 1 , wherein the piezoelectric substrate is made of a quartz substrate, and the scarified layer is made of a material etched by an etchant that is different from another etchant etching the piezoelectric substrate. 
   
   
       4 . The method for manufacturing a Lamb wave type high frequency device according to  claim 1  further comprising:
 forming a protection layer against etching on the second main surface of the piezoelectric substrate made of a quartz substrate;   forming the scarified layer with SiO 2 ; and   removing the protection layer in a range that is lager than an area of the Lamb wave propagated after removing the sacrificed layer.   
   
   
       5 . A method for manufacturing a Lamb wave type high frequency device that includes, a piezoelectric substrate, an interdigital transducer (IDT) electrode formed on a first main surface of the piezoelectric substrate, a reinforcing substrate connected to a second main surface of the piezoelectric substrate, a space portion formed in one of the piezoelectric substrate and the reinforcing substrate, an area of the space portion being larger than a region in which a Lamb wave is propagated, and a connecting surface formed in a periphery of the space portion, the method comprising:
 forming a recess corresponding to the space portion provided in one of a thick plate of the piezoelectric substrate and the reinforcing substrate;   connecting the thick plate with the reinforcing substrate;   filling a thermosetting resin in the space portion to be a sacrificed layer and curing the thermosetting resin after the connection;   polishing the thick plate to a given thickness after the curing; and   forming the IDT electrode and removing the sacrificed layer after the polishing.