US-12622174-B2 - Methods of forming group III piezoelectric thin films via removal of portions of first sputtered material

US12622174B2US 12622174 B2US12622174 B2US 12622174B2US-12622174-B2

Abstract

A method of forming a piezoelectric thin film includes sputtering a first surface of a substrate to provide a piezoelectric thin film comprising AlN, AlScN, AlCrN, HfMgAlN, or ZrMgAlN thereon, processing a second surface of the substrate that is opposite the first surface of the substrate to provide an exposed surface of the piezoelectric thin film from beneath the second surface of the substrate, wherein the exposed surface of the piezoelectric thin film includes a first crystalline quality portion, removing a portion of the exposed surface of the piezoelectric thin film to access a second crystalline quality portion that is covered by the first crystalline quality portion, wherein the second crystalline quality portion has a higher quality than the first crystalline quality portion and processing the second crystalline quality portion to provide an acoustic resonator device on the second crystalline quality portion.

Inventors

Craig Moe
Jeffrey B. Shealy
Mary Winters
Dae Ho Kim
Abhay Saranswarup Kochhar

Assignees

AKOUSTIS TECHNOLOGIES CORP.

Dates

Publication Date: 20260505
Application Date: 20240119

Claims (7)

1 . A method of forming a piezoelectric thin film, the method comprising: providing an inert gas and a nitrogen process gas to a process chamber including a substrate and a target comprising one or more Group III elements; sputtering the one or more Group III elements from the target onto a first surface of the substrate to provide the piezoelectric thin film including a nitride of the one or more Group III elements on the first surface of the substrate; forming a first electrode on the piezoelectric thin film; forming a sacrificial layer on the first electrode; processing a second surface of the substrate that is opposite the first surface of the substrate to provide an exposed surface of the piezoelectric thin film from beneath the second surface of the substrate, wherein the exposed surface of the piezoelectric thin film comprises a first crystalline quality portion of the piezoelectric thin film; and removing a portion of the exposed surface of the piezoelectric thin film to access a second crystalline quality portion of the piezoelectric thin film that is covered by the first crystalline quality portion of the piezoelectric thin film, wherein the second crystalline quality portion of the piezoelectric thin film has a higher quality than the first crystalline quality portion of the piezoelectric thin film; wherein the second crystalline quality portion of the piezoelectric thin film has a crystallinity in a range from 1.0 degree at Full Width Half Maximum (FWHM) to 10 arcseconds at FWHM, inclusively, measured using X-ray diffraction (XRD); and wherein sputtering the one or more Group III elements from the target onto the first surface of the substrate comprises heating the substrate to a temperature in a range between 350 degrees Centigrade to 850 degrees Centigrade, inclusively.
2 . The method of claim 1 , the piezoelectric thin film comprises AlN, AlScN, AlCrN, HfMgAlN, or ZrMgAlN.
3 . The method of claim 2 , wherein removing the portion of the exposed surface of the piezoelectric thin film comprises removing at least 500 Angstroms of the piezoelectric thin film to expose the second crystalline quality portion of the piezoelectric thin film.
4 . The method of claim 2 , wherein sputtering the one or more Group III elements from the target onto the first surface of the substrate comprises heating the substrate to a temperature in a range between 400 degrees Centigrade to 600 degrees Centigrade, inclusively.
5 . The method of claim 2 , wherein sputtering the one or more Group III elements from the target onto the first surface of the substrate comprises sputtering a seed layer directly including the one or more Group III elements onto the first surface of the substrate to form a nucleation layer prior to formation of the piezoelectric thin film.
6 . The method of claim 5 , further comprising: sputtering the one or more Group III elements onto the nucleation layer to form the piezoelectric thin film.
7 . The method of claim 1 , wherein the second crystalline quality portion of the piezoelectric thin film has a crystallinity in a range between 1.0 degree at FWHM to 0.5 degrees at FWHM, inclusively, measured using XRD.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM FOR PRIORITY Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are incorporated by reference under 37 CFR 1.57 and made a part of this specification. The present application hereby incorporates by reference, for all purposes, the following patent applications, all commonly owned: U.S. patent application Ser. No. Title Filing Date U.S. Pat. No.14/298,057 Resonance Circuit With A 6 Jun. 2014 9,673,384 Single Crystal Capacitor Dielectric Material 14/298,076 Acoustic Resonator Device 6 Jun. 2014 9,537,465 With Single Crystal Piezo Material And Capacitor On A Bulk Substrate 14/298,100 Integrated Circuit Configured 6 Jun. 2014 9,571,061 With Two Or More Single Crystal Acoustic Resonator Devices 14/341,314 Wafer Scale Packaging 25 Jul. 2014 9,805,866 14/449,001 Mobile Communication Device 31 Jul. 2014 9,716,581 Configured With A Single Crystal Piezo Resonator Structure 14/469,503 Membrane Substrate Structure 26 Aug. 2014 9,917,568 For Single Crystal Acoustic Resonator Device BACKGROUND The present invention relates generally to electronic devices. More particularly, the present invention provides techniques related to a method of manufacture and a structure for bulk acoustic wave resonator devices, single crystal bulk acoustic wave resonator devices, single crystal filter and resonator devices, and the like. Merely by way of example, the invention has been applied to a single crystal resonator device for a communication device, mobile device, computing device, among others. Wireless data communications can utilize RF filters operating at frequencies around 5 GHz and higher. It is known to use Bulk acoustic Wave Resonators (BAWR) incorporating polycrystalline piezoelectric thin films for some applications. While some polycrystalline based piezoelectric thin film BAWRs may be adequate for filters operating at frequencies from about 1 to 3 GHz, applications at frequencies around 5 GHz and above may present obstacles due to the reduced crystallinity associated with such thin poly-based films. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a simplified diagram illustrating an acoustic resonator device having topside interconnections according to an example of the present invention. FIG. 1B is a simplified diagram illustrating an acoustic resonator device having bottom-side interconnections according to an example of the present invention. FIG. 1C is a simplified diagram illustrating an acoustic resonator device having interposer/cap-free structure interconnections according to an example of the present invention. FIG. 1D is a simplified diagram illustrating an acoustic resonator device having interposer/cap-free structure interconnections with a shared backside trench according to an example of the present invention. FIGS. 2 and 3 are simplified diagrams illustrating steps for a method of manufacture for an acoustic resonator device according to an example of the present invention. FIG. 4A is a simplified diagram illustrating a step for a method creating a topside micro-trench according to an example of the present invention. FIGS. 4B and 4C are simplified diagrams illustrating alternative methods for conducting the method step of forming a topside micro-trench as described in FIG. 4A. FIGS. 4D and 4E are simplified diagrams illustrating an alternative method for conducting the method step of forming a topside micro-trench as described in FIG. 4A. FIGS. 5 to 8 are simplified diagrams illustrating steps for a method of manufacture for an acoustic resonator device according to an example of the present invention. FIG. 9A is a simplified diagram illustrating a method step for forming backside trenches according to an example of the present invention. FIGS. 9B and 9C are simplified diagrams illustrating an alternative method for conducting the method step of forming backside trenches, as described in FIG. 9A, and simultaneously singulating a seed substrate according to an embodiment of the present invention. FIG. 10 is a simplified diagram illustrating a method step forming backside metallization and electrical interconnections between top and bottom sides of a resonator according to an example of the present invention. FIGS. 11A and 11B are simplified diagrams illustrating alternative steps for a method of manufacture for an acoustic resonator device according to an example of the present invention. FIGS. 12A to 12E are simplified diagrams illustrating steps for a method of manufacture for an acoustic resonator device using a blind via interposer according to an example of the present invention. FIG. 13 is a simplified diagram illustrating a step for a method of manufacture for an acoustic resonator device according to an example of the present invention. FIGS. 14A to 14G are simplified diagrams illustrating method steps for a cap wafer process for an acoustic resonator de