Microelectromechanical resonator
A moveable micromachined member of a microelectromechanical system (MEMS) device includes an insulating layer disposed between first and second electrically conductive layers. First and second mechanical structures secure the moveable micromachined member to a substrate of the MEMS device and include respective first and second electrical interconnect layers coupled in series, with the first electrically conductive layer of the moveable micromachined member and each other, between first and second electrical terminals to enable conduction of a first joule-heating current from the first electrical terminal to the second electrical terminal through the first electrically conductive layer of the moveable micromachined member.
1 . A method comprising:
receiving an integrated circuit device having a microelectromechanical systems (MEMS) vibrating structure, a first external pin or contact, a second external pin or contact, a heating element, and circuitry, the MEMS vibrating structure characterized by a resonance frequency, the first external pin or contact to output a timing signal dependent on the resonance frequency, the integrated circuit device further having at least one structure having a material property that is changed under application of the heat, the resonance frequency being dependent on the material property, the second external pin or contact being adapted to cause the heating element to heat the at least one structure; and
as part of a calibration operation for the integrated circuit device, measuring the timing signal to identify a deviation between the timing signal and a target value and, responsive to identification of the deviation, applying one or more electronic signals to the second external pin or contact to cause the heating element to heat the at least one structure in a manner that reduces the deviation such that, during run-time of the integrated circuit device, the at least one timing signal will be produced with the reduced deviation.
2 . The method of claim 1 wherein the integrated circuit device is a packaged device having one or more dies, wherein each of the first external pin or contact are on an external surface of the packaged device, and wherein the MEMS vibrating structure is on a first die of the one or more dies.
3 . The method of claim 1 wherein the at least one structure comprises one or more layers of the vibrating structure and wherein the heating element is adapted to heat the one or more layers via joule heating.
4 . The method of claim 1 wherein the target value comprises a frequency of the timing signal at a predetermined operating temperature, and wherein measuring further comprises performing the measuring at the predetermined operating temperature.
5 . The method of claim 4 wherein the integrated circuit device further comprises electronic storage and wherein the method further comprises:
identifying a temperature-dependent variation associated with the timing signal; and
the method further comprises:
also measuring the frequency of the timing signal at a plurality of other temperatures, which are different than the predetermined temperature, and identifying respective deviations between the frequency of the timing signal and a predetermined resonance frequency at the other temperatures of the plurality;
calculating a correction polynomial dependent on the respective deviations; and
programming into the electronic storage parameters which define the correction polynomial, such that the integrated circuit device thereby stores the correction polynomial, for application during run-time of the integrated circuit device.
6 . The method of claim 5 wherein the integrated circuit device further comprises a temperature sensor and signal conditioning circuitry, the signal conditioning circuitry to, during run-time of the integrated circuit device, receive a sensed signal dependent on motion of the MEMS vibrating structure and to generate the timing signal dependent on the sensed signal, wherein the signal conditioning circuitry is configured to electronically correct the frequency of the timing signal on a basis that is internal to the integrated circuit device during run-time of the integrated circuit device, within an operating temperature range of the integrated circuit device, dependent on temperature sensed by the temperature sensor and dependent on the correction polynomial.
7 . The method of claim 6 wherein the MEMS vibrating structure is part of a first MEMS resonator, wherein the temperature-dependent behavior is a first temperature-dependent behavior, wherein the temperature sensor comprises the first MEMS resonator and a second MEMS resonator, the second MEMS resonator having a second temperature-dependent behavior, and wherein the integrated circuit comprises circuitry operable to identify temperature sensed by the temperature sensor as a function of divergence in the second temperature-dependent behavior from the first temperature dependent behavior.
8 . The method of claim 1 wherein the MEMS vibrating structure is a resonating structure which comprises at least a layer of crystal silicon, a conductive layer, and a piezoelectric layer, and wherein the method further comprises causing application of a drive signal to the conductive layer during the calibration operation, to cause the MEMS vibrating structure to vibrate dependent on the piezoelectric layer.
9 . The method of claim 1 wherein the integrated circuit device is encapsulated, wherein the integrated circuit device further comprises the temperature sensor and third external pin or contact, wherein the method further comprises, during the calibration operation, receiving an indication of sensed temperature from within the encapsulated integrated circuit device, via the third external pin or contact, and wherein applying the one or more electronic signals includes selecting a signal dependent on the indication of sensed temperature and applying the selected signal.
10 . The method of claim 1 wherein the one or more electronic signals comprise a pulsed signal having a frequency of at least one kilohertz.
11 . The method of claim 1 wherein the method further comprises a bidirectional frequency tuning process and wherein the applying of the one or more electronic signals comprises selectively applying one of:
a first electronic signal to the second external pin or contact, to cause the heating element to heat the at least one structure in a manner that reduces a first one of positive deviation or negative deviation; and
a second electronic signal to the second external pin or contact, to cause the heating element to heat the at least one structure in a manner that reduces a second one of positive deviation or negative deviation.
12 . The method of claim 1 wherein receiving the integrated circuit device further comprises fabricating the MEMS vibrating structure using a semiconductor fabrication process.
13 . A method comprising:
receiving an integrated circuit device having:
a first die having a microelectromechanical systems (MEMS) vibrating structure;
a second die having circuitry;
a first external pin or contact; and
a second external pin; and
wherein:
the integrated circuit device further has a heating element;
the MEMS vibrating structure is characterized by a resonance frequency;
the first external pin or contact is to output a timing signal dependent on the resonance frequency;
the integrated circuit device further has at least one structure having a material property that is changed under application of the heat;
the resonance frequency is dependent on the material property; and
the second external pin or contact is adapted to cause the heating element to heat the at least one structure; and
as part of a calibration operation for the integrated circuit device, measuring the timing signal to identify a deviation between the timing signal and a target value and, responsive to identification of the deviation, applying one or more electronic signals to the second external pin or contact to cause the heating element to heat the at least one structure in a manner that reduces the deviation such that, during run-time of the integrated circuit device, the at least one timing signal will be produced with the reduced deviation.
14 . The method of claim 13 wherein the integrated circuit device is an encapsulated device, wherein each of the first external pin or contact are on an external surface of the encapsulated device, and wherein measuring is performed by electrical coupling the first external pin or contact to a recipient device, the measuring thereby being performed notwithstanding the presence of the encapsulation.
15 . The method of claim 13 wherein the at least one structure comprises one or more layers of the vibrating structure and wherein applying comprises applying at least a one kilohertz signal to the second electrical contact to cause the heating element to heat the one or more layers via joule heating.
16 . The method of claim 13 wherein:
the target value comprises a frequency of the timing signal at a predetermined operating temperature, and wherein measuring further comprises performing the measuring at the predetermined operating temperature;
the integrated circuit device further comprises electronic storage; and
the method further comprises:
also measuring the frequency of the timing signal at a plurality of other temperatures, which are different than the predetermined temperature, and identifying respective deviations between the frequency of the timing signal and a predetermined resonance frequency at the other temperatures of the plurality;
calculating a correction polynomial dependent on the respective deviations; and
programming into the electronic storage parameters which define the correction polynomial, such that the integrated circuit device thereby stores the correction polynomial, for application during run-time of the integrated circuit device.
17 . The method of claim 16 wherein the integrated circuit device is configured such that the correction polynomial is internally applied by the integrate circuit device, and wherein the integrated circuit device is configured such that, during run-time, the first external pin or contact will output a temperature-corrected timing signal.
18 . The method of claim 13 wherein the MEMS vibrating structure is a resonating structure which comprises at least a layer of crystal silicon, a conductive layer, and a piezoelectric layer, and wherein the method further comprises causing application of a drive signal to the conductive layer during the calibration operation, to cause the MEMS vibrating structure to vibrate dependent on the piezoelectric layer.
19 . The method of claim 13 wherein the method further comprises a bidirectional frequency tuning process and wherein the applying of the one or more electronic signals comprises selectively applying one of:
a first electronic signal to the second external pin or contact, to cause the heating element to heat the at least one structure in a manner that reduces a first one of positive deviation or negative deviation; and
a second electronic signal to the second external pin or contact, to cause the heating element to heat the at least one structure in a manner that reduces a second one of positive deviation or negative deviation.
20 . A method comprising:
fabricating an integrated circuit device having a microelectromechanical systems (MEMS) structure, a storage device, a heating element and circuitry, the MEMS structure characterized by a temperature-dependent behavior, the circuitry being adapted to generate an electronic signal dependent on movement or deflection of the MEMS structure during run-time of the integrated circuit device;
as part of a calibration operation for the integrated circuit device, causing the heating element to heat the structure to a plurality of different temperatures and, for each of the different temperatures in the plurality, identifying deviation of a property conveyed the electronic signal from a desired value;
calculating a correction polynomial dependent on the identified deviations; and
programming into the storage device parameters which define the correction polynomial, such that the integrated circuit device thereby stores the correction polynomial, for application during run-time of the integrated circuit device, to electronically correct the electronic signal, within an operating temperature range of the integrated circuit device.