Micro-electromechanical resonators having electrically-trimmed resonator bodies therein and methods of fabricating same using joule heating
A micro-electromechanical resonator includes an electrically-trimmed resonator body having at least one stiffness-enhanced semiconductor region therein containing metal-semiconductor lattice bonds. These metal-semiconductor lattice bonds may be gold-silicon lattice bonds and/or aluminum-silicon lattice bonds. A surface of the resonator body is mass-loaded with the metal, which may be provided by a plurality of spaced-apart metal islands. These metal islands may be aligned along a longitudinal axis of the resonator body. A size of the at least one stiffness-enhanced polycrystalline semiconductor region may be sufficient to yield an increase in resonant frequency of the resonator body relative to an otherwise equivalent resonator having a single crystal resonator body that is free of mass-loading by the metal.
1. A method of trimming a resonant frequency of a micro-electromechanical resonator, comprising: heating a semiconductor resonator body having at least one mass-loading metal layer thereon for a first duration sufficient to convert at least a portion of the semiconductor resonator body into a eutectic alloy comprising metal from the at least one mass-loading metal layer.
2. The method of claim 1 , wherein said heating comprises further heating the semiconductor resonator body to convert at least a portion of the semiconductor resonator body into a polycrystalline semiconductor region containing metal-semiconductor lattice bonds.
3. The method of claim 1 , wherein the semiconductor resonator body is anchored on opposite sides thereof to a substrate; and wherein said heating comprises passing current from the substrate to the semiconductor resonator body.
4. The method of claim 3 , wherein the semiconductor resonator body is anchored to the substrate by a pair of supports; and wherein said resistance heating comprises passing the current through the supports.
5. A method of fabricating a micro-electromechanical resonator, comprising: forming a resonator body opposite a recess in a semiconductor substrate, said resonator body having a plurality of spaced-apart metal islands on a surface thereof;
packaging the resonator body within a sealed chamber that shares an ambient with the recess in the semiconductor substrate; and resistance heating the packaged resonator body for a sufficient duration to convert at least a portion of the resonator body into a eutectic alloy comprising metal from the metal islands.
6. The method of claim 5 , wherein the metal islands comprise a metal selected from a group consisting of gold and aluminum; and wherein said resistance heating comprises heating the resonator body for a sufficient duration to convert at least a portion of the resonator body into a polycrystalline semiconductor region containing metal-semiconductor lattice bonds.
7. The method of claim 5 , wherein said forming comprises forming first and second resonator electrodes on the surface of the resonator body; and
wherein first and second portions of the first and second resonator electrodes, respectively, extend on opposite sides of the plurality of spaced-apart metal islands.
8. The method of claim 7 , wherein said forming comprises forming a resonator body having first and second supports that anchor opposing sides of the resonator body to the semiconductor substrate; and wherein said resistance heating comprises passing a current through the first and second supports.
9. The method of claim 5 , wherein said forming comprises forming a resonator body having first and second supports that anchor opposing sides of the resonator body to the semiconductor substrate; and wherein said resistance heating comprises passing a current through the first and second supports.