Acoustic wave device and method of fabricating the same
An acoustic wave device includes: a substrate; a pad formed on the substrate; a cap formed of an inorganic insulating material and located on the substrate, the cap including a cavity located in a surface of the cap at a substrate side and a penetration hole formed in a location overlapping with the pad; a terminal filling the penetration hole, coupled to the pad on the substrate, and formed of solder; and a functional element formed on an upper surface of the substrate and in the cavity, the functional element exciting an acoustic wave.
1. An acoustic wave device comprising:
a substrate;
a pad formed on the substrate;
a cap formed of an inorganic insulating material, located on the substrate and bonded to the substrate, the cap including a penetration hole formed in a location overlapping with the pad, and defining a cavity between the substrate and the cap;
a terminal filling the penetration hole, coupled to the pad on the substrate, formed of solder, and being surrounded by the cavity in a planar view; and
a functional element formed on an upper surface of the substrate and in the cavity, the functional element exciting an acoustic wave.
2. The acoustic wave device according to claim 1 , wherein
the penetration hole has a tapered shape to taper from an upper surface of the cap toward the cavity.
3. The acoustic wave device according to claim 1 , wherein
the pad includes a protrusion protruding upward from the upper surface of the substrate, and the terminal is bonded to the protrusion.
4. The acoustic wave device according to claim 3 , wherein
the protrusion extends from the upper surface of the substrate to an inside of the penetration hole.
5. The acoustic wave device according to claim 1 , wherein
the terminal protrudes upward from an upper surface of the cap.
6. The acoustic wave device according to claim 1 , further comprising:
a metal layer continuously formed from an upper surface of the cap to a lower surface of the cap through an inner wall of the penetration hole, wherein
the terminal is bonded to the metal layer.
7. The acoustic wave device according to claim 1 , further comprising:
a plated layer covering a surface of the terminal.
8. The acoustic wave device according to claim 1 , wherein
the substrate is a piezoelectric substrate, and
the functional element is an IDT.
9. The acoustic wave device according to claim 8 , wherein
the cap is formed of a piezoelectric substance or sapphire.
10. The acoustic wave device according to claim 1 , wherein
the functional element is a region in which an upper electrode, a piezoelectric thin film, and a lower electrode of a piezoelectric thin film resonator overlap with each other.
11. The acoustic wave device according to claim 10 , wherein
the substrate is formed of silicon; and
the cap is formed of silicon or glass.
12. The acoustic wave device according to claim 1 , wherein
the substrate and the cap are formed of a same material.