Method of fabricating acoustic resonator with planarization layer
View Patent ↗A method is provided for fabricating a bulk acoustic wave (BAW) resonator device. The method includes forming an etch stop layer over a bottom electrode and a substrate; forming a dielectric layer on the etch stop layer; forming a photomask over the dielectric layer defining an opening over the bottom electrode; etching a portion the dielectric layer through the opening of the photomask to the etch stop layer to create a corresponding opening in the dielectric layer; removing the photomask, leaving un-etched protruding portions of the dielectric layer around the opening in the dielectric layer; and removing the protruding portions of the dielectric layer, a portion of the etch stop layer located over the bottom electrode, and a minimal portion of the bottom electrode to provide a planarized surface including a top surface of the bottom electrode and an adjacent top surface of the dielectric layer deposited over the substrate.
1. A method of fabricating a bulk acoustic wave (BAW) resonator device, comprising:
forming a bottom electrode over a substrate;
forming an etch stop layer over the bottom electrode and the substrate;
forming a dielectric layer on the etch stop layer over the bottom electrode and the substrate;
forming a photomask over the dielectric layer, the photomask defining an opening over the bottom electrode, wherein the opening is slightly smaller than the bottom electrode;
etching a portion of the dielectric layer through the opening of the photomask to the etch stop layer to create a corresponding opening in the dielectric layer and un-etched protruding portions of the dielectric layer;
removing the photomask, leaving the un-etched protruding portions of the dielectric layer around the opening in the dielectric layer; and
removing at least the un-etched protruding portions of the dielectric layer and a portion of the etch stop layer located over the bottom electrode to provide a planarized surface comprising a top surface of the bottom electrode and an adjacent top surface of the dielectric layer deposited over the substrate.
2. The method of claim 1 , further comprising:
forming a piezoelectric layer on the planarized surface.
3. The method of claim 2 , wherein forming the piezoelectric layer on the planarized surface reduces cracks and voids in the piezoelectric layer.
4. The method of claim 3 , wherein forming the piezoelectric layer on the planarized surface increases a breakdown voltage of the piezoelectric layer.
5. The method of claim 4 , wherein forming the piezoelectric layer on the planarized surface enables the piezoelectric layer to withstand higher electro-static discharge (ESD).
6. The method of claim 2 , wherein the piezoelectric layer comprises aluminum nitride doped with one or more rare earth elements.
7. The method of claim 6 , wherein the one or more rare earth elements comprises scandium (Sc).
8. The method of claim 1 , wherein the un-etched protruding portions of the dielectric layer and the etch stop layer are removed by a polishing process.
9. The method of claim 8 , wherein the polishing process comprises chemical mechanical polishing (CMP) process using a silica slurry.
10. The method of claim 1 , wherein the bulk acoustic wave (BAW) resonator device comprises a thin film bulk acoustic resonator (FBAR), and the bottom electrode is formed over a cavity in the substrate initially containing a sacrificial material.
11. The method of claim 1 , wherein the bulk acoustic wave (BAW) resonator device comprises a solidly mounted resonator (SMR), and the bottom electrode is formed over a low acoustic impedance layer of an acoustic reflector.
12. The method of claim 1 , wherein the etch stop layer comprises one of aluminum nitride (AlN) and diamond-like carbon (DLC).
13. The method of claim 1 , wherein the dielectric layer comprises one of bow-silicate glass (BSG), silicon dioxide (SiO 2 ), and silicon nitride (SiN).
14. The method of claim 1 , wherein the dielectric layer comprises a polymeric material.
15. The method of claim 1 , wherein a thickness of the dielectric layer is at least about 10 percent greater than a first thickness of the bottom electrode.
16. A method of fabricating a resonator device, comprising:
forming an electrode over a base layer;
forming an etch stop layer over the electrode and the base layer;
forming a dielectric layer on the etch stop layer over the electrode and the base layer;
forming a photomask over the dielectric layer, the photomask defining an opening over the electrode, wherein the opening is slightly smaller than the electrode;
etching a portion of the dielectric layer through the opening of the photomask to the etch stop layer to create a corresponding opening in the dielectric layer and un-etched protruding portions of the dielectric layer;
removing the photomask, leaving the un-etched protruding portions of the dielectric layer around the opening in the dielectric layer; and
removing the un-etched protruding portions of the dielectric layer, a portion of the etch stop layer located over the electrode, and a minimal portion of the electrode to provide a planarized surface comprising a top surface of the electrode and an adjacent top surface of the dielectric layer deposited over the base layer.