US 12,088,271 B2
Structure and manufacturing method of surface acoustic wave filter with back electrode of piezoelectric layer
Guojun Weng, Shenzhen (CN); and Gongbin Tang, Shenzhen (CN)
Assigned to Shenzhen Newsonic Technologies Co., Ltd., Shenzhen (CN)
Filed by Shenzhen Newsonic Technologies Co., Ltd., Shenzhen (CN)
Filed on Sep. 16, 2022, as Appl. No. 17/933,075.
Prior Publication US 2023/0008048 A1, Jan. 12, 2023
Int. Cl. H01L 21/306 (2006.01); C23C 14/06 (2006.01); C23C 14/10 (2006.01); C23C 14/48 (2006.01); C23C 14/58 (2006.01); C23C 16/24 (2006.01); C23C 16/34 (2006.01); C23C 16/40 (2006.01); C23C 16/56 (2006.01); H03H 3/08 (2006.01)
CPC H03H 3/08 (2013.01) [C23C 14/0641 (2013.01); C23C 14/0652 (2013.01); C23C 14/10 (2013.01); C23C 14/48 (2013.01); C23C 14/5873 (2013.01); C23C 16/24 (2013.01); C23C 16/34 (2013.01); C23C 16/345 (2013.01); C23C 16/401 (2013.01); C23C 16/56 (2013.01)] 18 Claims
OG exemplary drawing
 
1. A fabrication method of a surface acoustic wave (SAW) filter, comprising:
obtaining a piezoelectric substrate;
forming a back electrode on a first portion of the piezoelectric substrate;
forming a first dielectric layer on the first portion of the piezoelectric substrate, covering the back electrode;
forming a trench in the first dielectric layer and exposing a portion of the back electrode, the trench surrounding a portion of the first dielectric layer;
forming a second dielectric layer on the first dielectric layer and covering sidewalls and a bottom of the trench;
forming a third dielectric layer on the second dielectric layer, the third dielectric layer filling in the trench;
bonding a bottom substrate to the third dielectric layer;
removing a second portion of the piezoelectric substrate and leaving the first portion of the piezoelectric substrate, the first portion of the piezoelectric substrate constituting a piezoelectric layer;
forming an interdigital transducer (IDT) on the piezoelectric layer; and
etching and releasing the portion of the first dielectric layer surrounded by the trench to form a cavity below the back electrode.
 
10. A fabrication method of a surface acoustic wave (SAW) filter, comprising:
obtaining a piezoelectric substrate;
forming an interdigital transducer (IDT) on a first portion of the piezoelectric substrate;
forming a first dielectric layer on the first portion of the piezoelectric substrate, covering the IDT;
forming a trench in the first dielectric layer and exposing a portion of the first portion of the piezoelectric substrate, the trench surrounding a portion of the first dielectric layer that covers an interdigital portion of the IDT;
forming a second dielectric layer on the first dielectric layer and covering sidewalls and a bottom of the trench;
forming a third dielectric layer on the second dielectric layer, the third dielectric layer filling in the trench;
bonding a bottom substrate to the third dielectric layer;
removing a second portion of the piezoelectric substrate and leaving the first portion of the piezoelectric substrate, the first portion of the piezoelectric substrate constituting a piezoelectric layer;
forming a back electrode on the piezoelectric layer; and
etching and releasing the portion of the first dielectric layer surrounded by the trench to form a cavity below the interdigital portion of the IDT.