Method for fabricating an acoustic resonator device with perimeter structures
A method of manufacture for an acoustic resonator or filter device. In an example, the present method can include forming metal electrodes with different geometric areas and profile shapes coupled to a piezoelectric layer overlying a substrate. These metal electrodes can also be formed within cavities of the piezoelectric layer or the substrate with varying geometric areas. Combined with specific dimensional ratios and ion implantations, such techniques can increase device performance metrics. In an example, the present method can include forming various types of perimeter structures surrounding the metal electrodes, which can be on top or bottom of the piezoelectric layer. These perimeter structures can use various combinations of modifications to shape, material, and continuity. These perimeter structures can also be combined with sandbar structures, piezoelectric layer cavities, the geometric variations previously discussed to improve device performance metrics.
1. A method for fabricating an acoustic resonator device, the method comprising:
providing a substrate having a substrate surface region and a substrate backside cavity region characterized by a cavity geometric area;
forming a piezoelectric layer overlying the substrate surface region, the piezoelectric layer having a top piezoelectric surface region and a bottom piezoelectric surface region;
forming a backside energy confinement structure underlying the bottom piezoelectric surface region, the backside energy confinement structure being characterized by a backside structure geometric area and a backside structure perimeter, the backside energy confinement structure having at least one portion removed forming a backside structure break region; and
forming a backside metal electrode underlying the bottom piezoelectric surface region and within the backside energy confinement structure, the backside metal electrode being characterized by a backside electrode geometric area.
2. The method of claim 1 wherein the piezoelectric layer comprises an essentially single crystal material or polycrystalline material.
3. The method of claim 1 wherein the backside metal electrode is formed adjacent to the backside energy confinement structure.
4. The method of claim 1 further comprising forming a backside sandbar structure underlying the bottom piezoelectric surface region within a vicinity of the backside structure break region; wherein the backside sandbar structure is spatially configured outside the backside structure perimeter of the backside energy confinement structure.
5. The method of claim 4 wherein the backside sandbar structure is spatially configured with a gap having a distance of about 0.1 um to about 100 um to the backside metal electrode.
6. The method of claim 4 wherein the backside sandbar structure comprises a dielectric material, a metal material, or a combination of dielectric and metal materials.
7. The method of claim 4 wherein the backside sandbar structure comprises a straight sandbar structure, a curved sandbar structure, or an angled sandbar structure.
8. The method of claim 1 wherein the backside energy confinement structure comprises a dielectric material, a metal material, or a combination of dielectric and metal materials.
9. The method of claim 1 wherein the backside energy confinement structure comprises a castellation pattern characterized by a repeated castellation shape, wherein the castellation shape includes a square, a triangle, a polygon shape, or a non-polygon shape.
10. The method of claim 1 wherein each of the backside electrode geometric area, the backside structure geometric area, and the cavity geometric area includes a circle, an ellipses, skew non-polygonal shapes, irregular shapes, or a polygonal shape having n sides, where n is greater than or equal to three; wherein the backside electrode geometric area, the backside structure geometric area, and the cavity geometric area can be characterized by geometric areas having similar or dissimilar shapes.