Method of manufacture for single crystal acoustic resonator devices using micro-vias
A method of manufacture for an acoustic resonator device. The method includes forming a nucleation layer characterized by nucleation growth parameters overlying a substrate and forming a strained piezoelectric layer overlying the nucleation layer. The strained piezoelectric layer is characterized by a strain condition and piezoelectric layer parameters. The process of forming the strained piezoelectric layer can include an epitaxial growth process configured by nucleation growth parameters and piezoelectric layer parameters to modulate the strain condition in the strained piezoelectric layer. By modulating the strain condition, the piezoelectric properties of the resulting piezoelectric layer can be adjusted and improved for specific applications.
1. A method for fabricating an acoustic resonator device, the method comprising:
providing a seed substrate having a substrate crystallographic orientation;
placing the seed substrate within a processing chamber having a controlled environment;
heating the seed substrate to a first desired temperature within the processing chamber;
cooling the seed substrate to a second desired temperature within the processing chamber;
after cooling the seed substrate to the second desired temperature, initiating a film growth process having film growth conditions by introducing reactants to the controlled environment of the processing chamber to form a nucleation layer overlying the seed substrate;
modifying the film growth conditions by adjusting the controlled environment of the processing chamber, the film growth conditions including piezoelectric film growth conditions;
forming on the nucleation layer a strained piezoelectric film having an acoustic velocity range of ±1000 m/s by modifying the strain of the piezoelectric film using the modified film growth conditions thereby changing the piezoelectric properties of the strained piezoelectric film and improving fabrication flexibility such that acoustic properties of a device or devices subsequently fabricated using the strained piezoelectric film can be tuned to correspond with a particular application of the device or each device;
after forming the strained piezoelectric film, turning off the reactants; and
reducing the temperature of the processing chamber to room temperature.
2. The method of claim 1 wherein the seed substrate is selected from one of the following: a silicon substrate, a sapphire substrate, silicon carbide substrate, a GaN bulk substrate, a GaN template, an AlN bulk, an AlN template, and an Al x Ga 1-x N template; and
wherein the substrate crystallographic orientation includes a polar, non-polar, or semi-polar crystallographic orientation.
3. The method of claim 1 wherein heating the seed substrate to the first desired temperature includes introducing a purified hydrogen gas to the processing chamber and heating the seed substrate in the range of 1100 to 1350 degrees Celsius at a reduced pressure between 5-800 mbar.
4. The method of claim 3 wherein the purified hydrogen gas is introduced in the range of 5-30 slpm and the purity of the hydrogen gas is greater than 99.9995%.
5. The method of claim 1 wherein cooling the seed substrate includes cooling the seed substrate by 100-200 degrees Celsius.
6. The method of claim 1 wherein introducing the reactants includes introducing Group III and Group V reactants.
7. The method of claim 1 wherein the piezoelectric film growth process includes a direct growth upon a nucleation layer, growth upon a super lattice nucleation layer, or a growth upon graded transition nucleation layers; wherein the super lattice nucleation layer includes alternating pairs of nucleation layers; and wherein the nucleation layer, each layer of the graded transition nucleation layers, and each nucleation layer within the super lattice nucleation layer includes materials or alloys having at least one of the following: AlN, AlGaN, GaN, AlScN, InN, InGaN, AlInN, AlInGaN, and BN.
8. The method of claim 1 wherein the modulating of the strain state includes introducing one or more impurities into the piezoelectric film; wherein the one or more impurity species can include the following: silicon (Si), magnesium (Mg), carbon (C), oxygen (O), erbium (Er), rubidium (Rb), strontium (Sr), scandium (Sc), beryllium (Be), molybdenum (Mo), zirconium (Zr), Hafnium (Hf), and vanadium (Va); wherein the one or more impurity species has impurity concentrations ranging from 1E+10 to 1E+21 per cubic centimeter; and wherein introducing one or more impurities includes using a gas source to directly deliver the one or more impurity species or using an organometallic source to derive the source gas to deliver the one or more impurity species.
9. The method of claim 1 wherein the modulating of the strain state includes introducing one or more alloying elements into the piezoelectric film; wherein the alloying elements include the following: magnesium (Mg), erbium (Er), rubidium (Rb), strontium (Sr), scandium (Sc), titanium (Ti), zirconium (Zr), Hafnium (Hf), vanadium (Va), Niobium (Nb), and tantalum (Ta); wherein the alloying element (ternary alloys) or elements (in the case of quaternary alloys) has concentrations ranging from about 0.01% to about 50%; and wherein introducing one or more alloying elements includes using a gas source to directly deliver the one or more alloying elements or using an organometallic source to derive the source gas to deliver the one or more alloying elements.
10. The method of claim 1 wherein modifying the film growth conditions by adjusting the controlled environment of the processing chamber includes modifying nucleation growth conditions.