METHODS OF FORMING GROUP III-NITRIDE SINGLE CRYSTAL PIEZOELECTRIC THIN FILMS USING ORDERED DEPOSITION AND STRESS NEUTRAL TEMPLATE LAYERS
A method of forming a piezoelectric thin film can include depositing a material on a first surface of a Si substrate to provide a stress neutral template layer. A piezoelectric thin film including a Group III element and nitrogen can be sputtered onto the stress neutral template layer and a second surface of the Si substrate that is opposite the first surface can be processed to remove that Si substrate and the stress neutral template layer to provide a remaining portion of the piezoelectric thin film. A piezoelectric resonator can be formed on the remaining portion of the piezoelectric thin film.
1 . (canceled)
2 . An RF filter circuit, comprising:
a plurality of acoustic resonators arranged in the RF filter circuit, at least one of the plurality of acoustic resonators including:
a support layer having a support layer upper surface that includes a recess therein;
an electrode in the recess, the electrode including an electrode upper surface that is aligned to the support layer upper surface at an edge of the recess; and
a piezoelectric film overlying the support layer upper surface and the electrode upper surface, the piezoelectric film including a piezoelectric film lower surface conforming to the support layer upper surface and to the electrode upper surface at the edge of the recess.
3 . The RF filter circuit of claim 2 further comprising:
a reflector structure within the support layer beneath a lower surface of the electrode.
4 . The RF filter circuit of claim 2 further comprising:
a cavity within the support layer exposing a lower surface of the electrode.
5 . The RF filter circuit of claim 2 wherein the support layer comprises a substrate, the RF filter circuit further comprising:
a trench within the substrate exposing a lower surface of the electrode.
6 . The RF filter circuit of claim 2 wherein the electrode comprises a first electrode, the RF filter circuit further comprising:
a second electrode overlying an upper surface of the piezoelectric film opposite the first electrode, wherein a resonator area of the piezoelectric film is defined by an overlap of the second electrode and the first electrode projected onto the piezoelectric film; and
a second electrode cavity included in an upper surface of the second electrode, wherein the second electrode cavity is located within the resonator area.
7 . The RF filter circuit of claim 6 wherein a cross-sectional thickness of the second electrode cavity inside the resonator area is less than a cross-sectional thickness of the second electrode outside the resonator area.
8 . The RF filter circuit of claim 2 further comprising:
an electrode contact via passing completely through the piezoelectric film to expose the electrode upper surface; and
a metal in the electrode contact via connecting to the electrode.
9 . The RF filter circuit of claim 2 wherein the piezoelectric film includes Sc.
10 . The RF filter circuit of claim 2 wherein the electrode upper surface and the support layer upper surface are co-planar.
11 . The RF filter circuit of claim 2 wherein the electrode upper surface is aligned to the support layer upper surface at opposing edges of the recess.
12 . (canceled)
13 . (canceled)
14 . A method of forming a Bulk Acoustic Wave resonator, the method comprising:
forming a support layer having a support layer upper surface;
forming a piezoelectric film overlying the support layer upper surface, the piezoelectric film including a piezoelectric film lower surface conforming to the support layer upper surface;
forming a recess in the support layer to expose the piezoelectric film lower surface; and
forming an electrode in the recess, the electrode including an electrode outer surface at a bottom of the recess that is aligned to the support layer upper surface at an edge of the recess and conforms to the piezoelectric film lower surface.
15 . The method of forming of claim 14 , wherein forming the recess within the support layer to expose the piezoelectric film lower surface comprises:
removing a portion of the support layer opposite the piezoelectric film to form the recess;
forming the electrode in the recess; and
forming a cap on the support layer to seal the recess.
16 . The method of forming of claim 14 wherein forming the recess in the support layer further comprises:
forming an electrode contact via passing completely through the piezoelectric film and completely through the support layer; and
forming a metal in the electrode contact via and on the support layer upper surface to connect to the electrode.
17 . The method of claim 14 wherein forming the piezoelectric film comprises forming the piezoelectric film including Sc.
18 . The method of claim 14 wherein forming the electrode comprises forming an outer surface of the electrode at the bottom of the recess to be co-planar with the support layer upper surface.
19 . A method of forming a Bulk Acoustic Wave resonator, the method comprising:
forming a first electrode on an upper surface of a piezoelectric film so that the first electrode includes a first electrode lower surface that conforms to the upper surface of the piezoelectric film; and
forming a support layer overlying the first electrode and the upper surface of the piezoelectric film to provide a recess for the first electrode within a lower surface of the support layer, wherein the lower surface of the support layer is aligned to the first electrode lower surface.
20 . The method of claim 19 wherein forming the first electrode on the upper surface of the piezoelectric film is preceded by forming the piezoelectric film on a first surface of a growth substrate, the method further comprising:
coupling an upper surface of the support layer to a bond substrate;
processing a second surface of the growth substrate, opposite the first surface, to expose a lower surface of the piezoelectric film;
forming an electrode contact via passing completely through the piezoelectric film to expose the first electrode lower surface; and
forming a metal on the lower surface of the piezoelectric film and in the electrode contact via connecting to the first electrode.
21 . The method of claim 20 further comprising:
removing a portion of the metal from the lower surface of the piezoelectric film to form a second electrode on the lower surface of the piezoelectric film and separate the metal in the electrode contact via from the second electrode.
22 . The method of claim 21 further comprising:
removing a portion of an upper surface of the second electrode to form a second electrode cavity in the upper surface of the second electrode to reduce a thickness of a cross-section of the second electrode within the second electrode cavity relative to a thickness of the cross-section of the second electrode outside the second electrode cavity.