Electro-acoustic resonator and method for manufacturing the same
Electro-acoustic resonator and method for manufacturing the same An electro-acoustic resonator comprises an acoustic mirror ( 120 ) disposed on a carrier substrate ( 110 ), a bottom electrode ( 130 ) and a piezoelectric layer ( 140 ). A structured silicon dioxide flap layer ( 150 ) is disposed on the piezoelectric layer ( 140 ), both layers having a common contact surface. Direct disposal of the silicon dioxide ( 150 ) on the piezoelectric layer ( 140 ) increases the quality factor of the resonator and leads to enhanced RF filter performance.
1. An electro-acoustic resonator, comprising:
a carrier substrate;
an acoustic mirror disposed on the carrier substrate;
a bottom electrode disposed on the acoustic mirror;
a piezoelectric layer, disposed on the bottom electrode;
a top electrode disposed on the piezoelectric layer; and
a structured silicon dioxide layer disposed on portions of the piezoelectric layer surrounding a region in which the top electrode is disposed, the portions of the piezoelectric layer and the structured silicon dioxide layer having a common contact surface.
2. The electro-acoustic resonator of claim 1 , wherein the piezoelectric layer and the structured silicon dioxide layer have a common contact surface without a seed layer disposed therebetween.
3. The electro-acoustic resonator of claim 1 , wherein the piezoelectric layer and the structured silicon dioxide layer have a direct mechanical contact with each other.
4. The electro-acoustic resonator of claim 1 , wherein the structured silicon dioxide layer is structured to have a portion removed in which the top electrode ( 170 ) is disposed.
5. The electro-acoustic resonator of claim 1 , wherein the top electrode comprises a layer stack comprising a bottom layer of tungsten, an intermediate layer of a composition of aluminum and copper and a top layer of a metal nitride.
6. The electro-acoustic resonator of claim 1 , further comprising a metal overlap layer disposed on the structured silicon dioxide layer and extending underneath a portion of the top electrode layer, wherein the metal overlap layer is disposed between the top electrode ( 170 ) and the piezoelectric layer at said portion.
7. The electro-acoustic resonator of claim 6 , wherein the metal overlap layer comprises a layer stack of titanium and tungsten.
8. The electro-acoustic resonator of claim 1 , wherein the piezoelectric layer comprises one of aluminum nitride and aluminum scandium nitride.
9. A method for manufacturing an electro-acoustic resonator, comprising:
providing a carrier substrate and an acoustic mirror disposed on the carrier substrate;
forming a structured bottom electrode on the acoustic mirror;
forming a piezoelectric layer on the bottom electrode;
forming a layer of silicon dioxide on the piezoelectric layer thereby forming a common contact surface between the layer of silicon dioxide and the piezoelectric layer;
removing a portion of the silicon dioxide layer in a region opposite the bottom electrode thereby exposing the piezoelectric layer; and
forming a top electrode on the piezoelectric layer in the region of the exposed piezoelectric layer.
10. The method of claim 9 , wherein the layer of silicon dioxide is formed on the piezoelectric layer without an intervening metal seed layer.
11. The method of claim 9 , wherein the step of forming a layer of silicon dioxide comprises depositing the layer of silicon dioxide by physical vapor deposition.
12. The method according of claim 9 , wherein the step of forming a piezoelectric layer and the step of forming a layer of silicon dioxide are performed without breaking a vacuum.
13. The method of claim 9 , after the step of removing a portion of the silicon dioxide layer and before the step of forming a top electrode, performing a step of forming an overlap layer made of metal and removing a portion of the overlap layer in a region opposite the bottom electrode so that the overlap layer is disposed between the top electrode and the piezoelectric substrate in a region where the portion of the silicon dioxide layer is removed.
14. A Radio frequency (RF) filter, comprising:
a first and a second port;
a series path coupled between the first and second ports, the series path comprising a serial connection of electro-acoustic resonators; and one or more shunt paths coupled to at least one of the resonators of the series path, the one or more shunt paths each including at least one electro-acoustic resonator comprising:
a carrier substrate;
an acoustic mirror disposed on the carrier substrate;
a bottom electrode disposed on the acoustic mirror;
a piezoelectric layer, disposed on the bottom electrode;
a top electrode disposed on the piezoelectric layer; and
a structured silicon dioxide layer disposed on portions of the piezoelectric layer surrounding a region in which the top electrode is disposed, the portions of the piezoelectric layer and the structured silicon dioxide layer having a common contact surface.