Back to results
US 9,705,470 B1Granted
Temperature-engineered MEMS resonator
AssigneeSiTime Corporation
InventorsJoseph C. Doll, Paul M. Hagelin, Ginel C. Hill, Nicholas Miller, Charles I. Grosjean
Life of this patent
Estimating the term…
Abstract
Degenerately doped semiconductor materials are deployed within resonant structures to control the first and higher order temperature coefficients of frequency, thereby enabling temperature dependence to be engineered without need for cumulative material layers which tend to drive up cost and compromise resonator performance.
Claims15
A microelectromechanical system (MEMS) resonator comprising:
- a single-crystal silicon layer doped with an impurity concentration that renders the single-crystal silicon layer sufficiently conductive to serve as a first electrode;
- a conductive layer to serve as a second electrode;
- an aluminum nitride piezoelectric layer disposed between the conductive layer and the single-crystal silicon layer;
- wherein a resonator axis along which the MEMS resonator exhibits a predominant motion during resonant oscillation is offset from a dominant crystallographic axis of the single-crystal silicon layer by an angle that substantially reduces at least one of first-order or second-order temperature coefficients of frequency (TCFs) of the MEMS resonator relative to first- and/or second-order TCFs that would result without angular offset between the resonator axis and the dominant crystallographic axis;
- and
- wherein the impurity concentration and angular offset are jointly controlled to substantially attenuate the first-order and second-order TCFs.
3 more elements
A method of fabricating microelectromechanical system (MEMS) resonator, the method comprising:
- doping a single-crystal silicon layer with an impurity concentration that renders the single-crystal silicon layer sufficiently conductive to serve as a first electrode;
- disposing an aluminum nitride piezoelectric layer on the single-crystal silicon layer;
- disposing a conductive layer on the aluminum nitride piezoelectric layer to serve as a second electrode;
- offsetting a resonator axis along which the MEMS resonator exhibits a predominant motion during resonant oscillation from a dominant crystallographic axis of the single-crystal silicon layer by an angle that substantially reduces at least one of first-order or second-order temperature coefficients of frequency (TCFs) of the MEMS resonator relative to first- and/or second-order TCFs that would result without angular offset between the resonator axis and the dominant crystallographic axis;
- and
- jointly controlling the impurity concentration and angular offset to substantially attenuate the first-order and second-order TCFs.
3 more elements
A microelectromechanical system (MEMS) resonator comprising:
- a single-crystal silicon layer doped with an impurity concentration that renders the single-crystal silicon layer sufficiently conductive to serve as a first electrode;
- a conductive layer to serve as a second electrode;
- an aluminum nitride piezoelectric layer disposed between the conductive layer and the single-crystal silicon layer;
- and
- wherein first-order and second-order temperature coefficients of frequency (TCFs) of the MEMS resonator and at least one TCF of the MEMS resonator beyond second-order are substantially attenuated by virtue of (i) angular offset between a dominant crystallographic axis of the single-crystal silicon layer and a resonator axis along which the MEMS resonator exhibits a predominant motion during resonant oscillation, (ii) a chosen impurity concentration of the single-crystal silicon layer and (iii) chosen relative thicknesses of the single-crystal silicon layer and aluminum nitride piezoelectric layer.
2 more elements
A method of fabricating microelectromechanical system (MEMS) resonator, the method comprising:
- doping a single-crystal silicon layer with an impurity concentration that renders the single-crystal silicon layer sufficiently conductive to serve as a first electrode;
- disposing an aluminum nitride piezoelectric layer on the single-crystal silicon layer;
- disposing a conductive layer on the aluminum nitride piezoelectric layer to serve as a second electrode;
- and
- wherein the method further comprises (i) offsetting a dominant crystallographic axis of the single-crystal silicon layer from a resonator axis along which the MEMS resonator exhibits a predominant motion during resonant oscillation by a predetermined angle, (ii) doping the single-crystal silicon layer with a predetermined impurity concentration and (iii) forming the single-crystal silicon layer and aluminum nitride piezoelectric layer with relative thicknesses to collectively and substantially attenuate first-order and second-order temperature coefficients of frequency (TCFs) of the MEMS resonator and at least one TCF of the MEMS resonator beyond second-order.
2 more elements
Dependencies are inferred from the claim text.