Methods for fabricating acoustic structure with inclined c-axis piezoelectric bulk and crystalline seed layers
Systems and methods for growing hexagonal crystal structure piezoelectric material with a c-axis that is tilted (e.g., 25 to 50 degrees) relative to normal of a face of a substrate are provided. A deposition system includes a linear sputtering apparatus, a translatable multi-aperture collimator, and a translatable substrate table arranged to hold multiple substrates, with the substrate table and/or the collimator being electrically biased to a nonzero potential. An enclosure includes first and second deposition stations each including a linear sputtering apparatus, a collimator, and a deposition aperture.
1. A method for fabricating at least one bulk acoustic wave resonator structure, the method comprising:
a first growth step including deposition of a crystalline seed layer over at least one resonator device complex, wherein each resonator device complex of the at least one resonator device complex includes a substrate and at least one first electrode structure arranged over at least a portion of the substrate, and wherein the first growth step is configured to yield at least 50% of the crystalline seed layer comprising a c-axis having an orientation distribution predominantly in a range of from 0 degrees to 35 degrees relative to normal of a face of the substrate; and
a second growth step including deposition of a hexagonal crystal structure piezoelectric material bulk layer over the crystalline seed layer that is arranged over the at least one resonator device complex, and being configured to yield at least 50% of the hexagonal crystal structure piezoelectric material bulk layer comprising a c-axis having an orientation distribution predominantly in a range of from 25 degrees to 50 degrees relative to normal of a face of the substrate;
wherein at least one of the first growth step or the second growth step comprises ejection of metal atoms from a target surface of a linear sputtering apparatus to (i) transit through a collimator comprising multiple collimator apertures and through a deposition aperture, and (ii) react with a gas species and be received by the at least one resonator device complex, wherein the target surface is arranged non-parallel to a face of the substrate.
2. The method of claim 1 , wherein the crystalline seed layer is compositionally matched to the hexagonal crystal structure piezoelectric material bulk layer.
3. The method of claim 1 , further comprising forming at least one second electrode structure over at least one portion of the hexagonal crystal structure piezoelectric material bulk layer.
4. The method of claim 3 , further comprising roughening a backside of the substrate after said forming of the at least one second electrode structure.
5. The method of claim 1 , wherein the second growth step is configured to yield at least 90% of the hexagonal crystal structure piezoelectric material bulk layer comprising a c-axis having an orientation distribution predominantly in a range of from 25 degrees to 50 degrees relative to normal of a face of the substrate.
6. The method of claim 1 , wherein the first growth step is performed at a deposition pressure in a range of from about 5 mT to about 50 mT.
7. The method of claim 1 , wherein the first growth step is performed at a first deposition pressure, the second growth step is performed at a second deposition pressure, and the first deposition pressure is greater than the second deposition pressure.
8. The method of claim 1 , wherein the target surface is oriented 15 to 55 degrees apart from a face of the substrate.
9. The method of claim 1 , wherein for each resonator device complex of the at least one resonator device complex, the substrate comprises a diameter of at least about 50 mm.
10. The method of claim 1 , wherein the at least one resonator device complex comprises a plurality of resonator device complexes.
11. The method of claim 1 , wherein at least one of the first growth step or the second growth step further comprises translating the collimator.
12. The method of claim 1 , wherein each resonator device complex of the at least one resonator device complex further comprises an acoustic reflector structure arranged between the substrate and the at least one first electrode structure.
13. The method of claim 1 , wherein the at least one resonator device complex is supported by a substrate table, and the method further comprises translating the substrate table during the first growth step and during the second growth step.
14. The method of claim 13 , wherein the target surface is oriented 15 to 55 degrees apart from the substrate table.
15. The method of claim 13 , further comprising electrically biasing at least one of the substrate table or the collimator to a potential other than ground during at least one of the first growth step or the second growth step.
16. The method of claim 13 , further comprising translating the collimator and translating the substrate table during operation of the linear sputtering apparatus during at least one of the first growth step or the second growth step, wherein a direction of translation of the collimator is substantially perpendicular to a direction of translation of the substrate table.
17. The method of claim 1 , further comprising dicing the at least one resonator device complex, over which the hexagonal crystal structure piezoelectric material bulk layer and the crystalline seed layer are deposited, into a plurality of chips.