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. A method of forming a piezoelectric thin film, the method comprising:
performing Metal Organic Chemical Vapor Deposition (MOCVD) to deposit a layer of Al x Ga (1-x) N onto a first surface of a Si substrate to provide a stress neutral template layer wherein 1-x at a surface of the stress neutral template layer is in a range between 0.5 and 1.0;
sputtering Al and N onto the stress neutral template layer to provide an AlN piezoelectric thin film with a crystalline quality of less than 0.5 degrees to 0.4 degrees measured at FWHM using XRD;
processing a second surface of the Si substrate that is opposite the first surface, to remove the Si substrate and the stress neutral template layer to provide a remaining portion of the AlN piezoelectric thin film; and
forming a piezoelectric resonator on the remaining portion of the AlN piezoelectric thin film.
2. The method of claim 1 , wherein the sputtering is performed at a power level of 14 W to 25 W.
3. The method of claim 1 , wherein the sputtering comprises sputtering Al and Sc onto a surface of the stress neutral template layer to provide an AlScN piezoelectric thin film, and wherein the AlScN piezoelectric thin film has a concentration of Sc in a range between 9% and 20% Sc.
4. The method of claim 1 , wherein the sputtering is performed at a power level of 14 W to 25 W.
5. The method of claim 1 , wherein the Si substrate comprises a Si <111> substrate.
6. The method of claim 1 , wherein the AlN piezoelectric thin film is substantially free of abnormally oriented grains.
7. The method of claim 1 , wherein the stress neutral template layer has a stress in a range between −200 Mpa and +200 MPa.
8. A method of forming a piezoelectric thin film, the method comprising:
performing Metal Organic Chemical Vapor Deposition (MOCVD) to deposit a layer of Al x Ga (1-x) N onto a first surface of a Si substrate to provide a stress neutral template layer wherein 1-x at a surface of the stress neutral template layer is in a range between 0.5 and 1.0;
sputtering Al and Sc onto the surface of the stress neutral template layer to provide an AlScN piezoelectric thin film having a crystalline quality of less than 0.44 degrees to 0.25 degrees measured at FWHM using XRD;
processing a second surface of the Si substrate that is opposite the first surface, to remove the Si substrate and the stress neutral template layer to provide a remaining portion of the AlScN piezoelectric thin film; and
forming a piezoelectric resonator on the remaining portion of the AlScN piezoelectric thin film.
9. The method of claim 8 , wherein the stress neutral template layer has a stress in a range between −200 MPa and +200 MPa.
10. The method of claim 8 , wherein a concentration of Ga is in a range between 20% to 80% at a surface of the stress neutral template layer.
11. The method of claim 8 , wherein a thickness of the stress neutral template layer from the first surface of the Si substrate to the surface of the stress neutral template layer is in a range between 400 nm to 600 nm.
12. The method of claim 8 , wherein performing the MOCVD to deposit the layer of Al x Ga (1-x) N onto the first surface of the Si substrate comprises first forming a nucleation layer of AlN in contact with the first surface of the Si substrate.
13. The method of claim 8 , wherein the AlScN piezoelectric thin film has a concentration of Sc in a range between 9% and 20% Sc.
14. The method of claim 8 , wherein the sputtering is performed at a power level of 14 W to 25 W.
15. The method of claim 8 , wherein the Si substrate comprises a Si <111> substrate.
16. The method of claim 8 , wherein the AlN piezoelectric thin film is substantially free of abnormally oriented grains.