CN102811022A - Micro-electromechanical system (MEMS) oscillator apparatus for controlling baking oven - Google Patents

Abstract

Disclosed is MEMS oscillator apparatus for controlling a baking oven. A system based on the invention comprises an MEMS oscillator which is configured to perform oscillation with a predetermined frequency at a predetermined temperature, wherein the predetermined frequency is based on temperature dependence and at least one predetermined attribute. The system further comprises an excitation mechanism which is configured to excite the MEMS oscillator toe oscillate with a predetermined frequency, and a temperature control loop which is configured to use resistance sensing to detect the temperature of the MEMS oscillator, and to determine whether the temperature of the MEMS oscillator is in a predetermined range of the predetermined temperature on the basis of temperature dependence and the at least one predetermined attribute, so as to minimize frequency drift, and adapt to the temperature of the MEMS oscillator to remain in the predetermined range. The system further comprises a frequency output which is configured to output the predetermined frequency of the MEMS oscillator.

Description

Baking oven control MEMS oscillator arrangement

Technical field

The disclosure is usually directed to system, and this system comprises baking oven control MEMS (MEMS) oscillator.

Background technology

Known MEM system and especially the MEMS resonator have high quality factor (Q), and can be used for making up oscillator, this makes it can be used as frequency reference unit, and is of Fig. 1.Yet traditionally, because quartz crystal has better temperature stability, working frequency benchmark therefore commonly used.When higher stable of needs,, for example, usually use the oven controlled crystal oscillator as in the broadcast transmitter system.Yet this quartz devices is very big and use the system of quartzy benchmark that the low shortcoming of integrated level is arranged.The MEMS oscillator is very little on the other hand, and can be integrated, thereby greatly reduces cost.Yet; Not with the MEMS resonator of compensation demonstrate produce frequency drift with variations in temperature hypersensitivity (for example; On 100 ℃ of ambient temperature ranges, have+-frequency drift of 5000ppm); Thereby and compare quartz crystal and have the more unsettled frequency characteristic that changes with variations in temperature, of Fig. 2.

The temperature that depends on measurement, through sense ambient temperature, and (for example, electrically), the MEMS resonator can carry out stable better on wide in range ambient temperature range (for example, 100 degrees centigrade of ambient temperature ranges) to pass through compensation MEMS resonator.Fig. 3 has described a kind of like this prior art solution.Ambient temperature is by the external temperature sensor sensing that contacts with MEMS device good thermal, and the MEMS oscilator system based on the temperature of measuring by the frequency control apparatus electrical compensation.In other words, environment temperature sensor drives the frequency compensation knob of resonator system.Like this, the MEMS resonator typically can 100 ℃ of ambient temperature ranges (for example, from-20 ℃ to+80 ℃ ambient temperature) go up controlled reaching+-precision of 100ppm.

Yet the problem of these mechanisms is precision and temperature stabilities of temperature sensor itself.The drift that they self produce with variations in temperature has limited the accessible temperature stability of MEMS resonator, and this is the reason that usually needs reliable (and expensive) temperature reference in this system.Another restriction is restricted thermo-contact between resonator and the temperature sensor, and this has limited possible attainable correction.

Publication number is that 2009/0243747 U.S. Patent application has used two resonators in a kind of oscillator configuration to produce a stabilized frequency, and is as shown in Figure 4.Two resonators that have different frequency-temperature coefficients through use; (TCF=Δ f/f.1/ Δ T; This is the frequency change of each variations in temperature), and, realize temperature stability through to because the frequency difference between the resonator that temperature drift produces compensates.Predetermined temperature T _SetBe present in two places (if not applying compensation) that frequency is identical.Control loop compensates variations in temperature and guarantees for other temperature also holding frequency identical.Therefore, realized the stable of resonant frequency.Yet this theory has weak point: need have two resonators of different TCF, thereby need a large amount of device area.And two resonators should be configured to oscillator, need extra circuit.And in order to reach desired frequency, the temperature at two resonator bar places should be identical, should design through coupling, and this possibly be easy in theory, but in fact the utmost point cannot say for sure to demonstrate,prove.At last, the parasitic couplings between two devices causes so unjust clock output.

Summary of the invention

Disclose a kind of system, be used for producing the output signal, utilized this basicly stable frequency can reach the frequency drift of reduction with basicly stable frequency based on MEMS.

According to the disclosure, utilize the system of the technical characterictic that comprises first claim to realize this target.

Especially; According to finding; Frequency drift for minimization system; Need ratio measuring temperature control loop; Ratio measuring temperature control loop be associated with said micromechanics oscillator and comprise be used to utilize the impedance sensing according to ratio measure that principle is surveyed, the assembly of assessment and adapt trickle mechnical oscillator, and ratio measuring temperature control loop also is provided to temperature with the micromechanics oscillator and remains in the said predetermined predetermined temperature range that is provided with around the temperature, said predetermined temperature range is confirmed based on the said attribute of said micromechanics oscillator and the said temperature dependency of said frequency.

System of the present disclosure has the advantage of benchmark voluntarily, thereby makes that not having the outside reference source of temperature or frequency need be used for its operation perhaps needs the limit frequency drift.Because only relative temperature error need detect (that is, whether actual temperature is greater than or less than preferred temperature), so the absolute measurement of the amplitude of error need not detect.Thereby, not needing amplifier or analog-digital converter, this typically requires the accurate and stability characteristic (quality) of temperature variant height.This has simplified system greatly, makes it more feasible.Gain error in the detected temperatures error is for reaching expectation T _SetBe incoherent, because measurement of correlation only is " too high " perhaps " too low ", rather than Tai Gao or too low what measurement.

System of the present disclosure has lower powered advantage; Because the MEMS oscillator is arranged in baking oven; Thereby with environment shielding, and further because needing can to avoid the benchmark MEMS oscillator (being in the double resonator system of describing in 2009/0243747 the U.S. Patent application as publication number) in the baking oven.

In certain embodiments, predetermined temperature range can be chosen in 0.10 ℃ at most, and this ratio measuring temperature control loop of the present disclosure capable of using is realized, and can frequency drift be reduced to only several ppm perhaps still less.

The frequency of oscillation of micromechanics oscillator (oscillator can be designed to vibrate according to different mode or frequency) is confirmed by the attribute of micromechanics oscillator; Described attribute; Except that other business; It comprises material, its layout (for example, shape and layout) and the size thereof that makes up the micromechanics oscillator.

Preferred material is a SiGe, it has-and the TCF (frequency-temperature coefficient) of 40ppm/ ℃.Utilize control loop of the present disclosure and be limited to 0.05 ℃ predetermined temperature range, frequency drift can be limited to 2ppm.In addition, this design attributes can be optimized to reach better stability.Therefore, utilize the proportional quantities observing and controlling system loop that has resistance sensing to combine for example SiGe oscillator, can reach 1ppm or frequency drift still less.

Another kind of possible material is a silicon, it has-and the TCF of 30ppm/ ℃.In order to be limited to 2ppm to frequency drift, 0.067 ℃ temperature range can be set in control loop.Likewise, drift can further reduce through the relevant design of the attribute of oscillator.Notice that also available other the suitable material of MEMS oscillator makes up.

In certain embodiments, the MEMS oscillator can be a bulk acoustic wave resonator.Alternatively or additionally, the MEMS oscillator can be SAW resonator, crooked syntony device or other resonator arbitrarily.

In certain embodiments, the micromechanics oscillator can hang by means of two fixed ends beam (clamped-clamped beam), for example is suspended in the vacuum-packed encapsulation, and each beam comprises two supporting legs, and it has with the common of MEMS oscillator and is connected.This beam is had advantage as the support ground tackle of resonator: every leg through for example making beam about crooked wavelength (as the result of micromechanics oscillator vibration; Beam is with this bending wave progress row vibration) be long on acoustics; Can strengthen the thermal insulation (for example, through making every leg longer) of resonator than the several times of crooked wavelength.As another advantage, according to discovery, utilize this support anchor, the power consumption of single MEMS oscilator system can be lower than 1mW, thereby makes the power consumption of whole system can be reduced to 10mW perhaps still less.As an advantage again, the length of leg can be optimized, so that avoid influencing the quality factor of oscillator.

In certain embodiments, the one or more beams in these beams can be used as heating resistor, are used for heating the MEMS oscillator.In this manner, the one or more parts that can be used as control ring in these beams.

In other embodiments, the MEMS oscillator also can be by the support anchor suspension of other type.

The heating of oscillator as the part of control loop, can comprise radiation source, be used for through radiation or arbitrarily the mode of other heating arrangements heat micromechanical resonator.

The resistance sensing of ratio measuring temperature control loop can be through placing two sensing elements and the enough good thermo-contact of micromechanical resonator provides, thereby make these two sensing elements stand and the essentially identical temperature of resonator.Rely on characteristic because two sensing elements have different temperature, therefore provide ratio to measure principle, thus make when measuring curve with the predetermined set temperature T _SetCorresponding predetermined joining intersects.Whether the actual temperature that like this, can easily confirm the MEMS oscillator is greater than or less than or equals predetermined temperature T _Set, and thereby this loop of may command.In certain embodiments, first sensing element, first sensing signal capable of using carries out sensing, and second sensing element, second sensing signal capable of using carries out sensing.In certain embodiments, first and second sensing signals can have essentially identical amplitude.In certain embodiments, first and second sensing signals do not have identical symbol (positive and negative) or phase place or duration.

In one embodiment, the configurable one-tenth of control loop subtracts each other first and second sensing signals, thereby confirms differential signal.Control loop can further be configured to amplify this differential signal, thereby produces control signal.

In certain embodiments, control circuit can be connected to the post-compensation circuit, and this post-compensation circuit arrangement becomes to remove the residual error in the control signal, thereby produces the post-compensation signal.Linearity, quadratic equation or the polynomial transformation of post-compensation signal for example control signal capable of using are confirmed.Alternatively or additionally, post-compensation signal for example look-up table capable of using is confirmed.Also can adopt other example.

The post-compensation signal can offer control circuit as offset signal or shifted signal, so that reduce the temperature of integrated electronics and the difference between the predetermined temperature.

Through using this post-compensation circuit to remove residual error, can further reduce inaccuracy, heat lag and/or other unfavorable effect that skew causes.

Description of drawings

The disclosure has been done further explaination in the description of drawings of accompanying drawing and several kinds of example embodiment of explanation of the present disclosure.Notice that accompanying drawing is not to draw in proportion.Accompanying drawing is intended to describe principle of the present disclosure.Additional embodiments of the present disclosure can combine the different characteristic of different accompanying drawings and element to use.

Fig. 1 shows the typical MEMS resonator that is applied in oscillator and the filter.

The chart that Fig. 2 shows with baking oven control quartz crystal variations in temperature and is used for not compensating the typical frequencies drift of MEMS resonator.

Fig. 3 shows typical MEMS system.

Fig. 4 shows another kind of typical MEMS system.

Fig. 5 A-E shows according to the top view (5A-B) of the typical MEMS oscillator structure of embodiment and sectional view (5C-D), and comprises the Vacuum Package view (5E) according to the MEMS oscillator of embodiment.

According to embodiment, Fig. 6 shows example MEMS system.

According to embodiment, Fig. 7 A-B shows and the corresponding example measurement voltage signal of temperature-dependent resistor device value (7A), the difference between the example measurement voltage signal (7B), and the relatively output between the example measurement voltage signal.

Fig. 8 shows the example MEMS system that comprises heater according to embodiment.

First and second temperature that Fig. 9 shows according to embodiment relies on characteristic.

Figure 10 shows the example MEMS system that comprises heater and control loop according to embodiment.

Figure 11 has explained the stability of not controlling the example output signal of MEMS oscillator with the baking oven that dual sensor is controlled, the band dual sensor controls and be with dual sensor and post-compensation to control according to embodiment.

Figure 12 shows the example MEMS system that comprises heater and control system, and wherein the post-compensation signal is a bias voltage.

Figure 13 shows the example MEMS system that comprises heater and control system, and wherein the post-compensation signal plays the effect of phase-locked loop.

Figure 14 A-C shows the displacement according to the example of the vibration MEMS oscillator of embodiment.

Figure 15 shows the sketch map according to the bulk acoustic wave lengthwise oscillations device that passes through radiation heating of embodiment.

Figure 16 shows the measurement data according to 100 * 100 μ m SiGe oscillators of embodiment, and it shows the corresponding relation of the incident optical power on the frequency change resonator.

Figure 17 shows the example crooked syntony device according to embodiment.

Figure 18 shows the another kind of example crooked syntony device according to embodiment.

Figure 19 show according to embodiment via supporting the example MEMS oscillator that heats through joule.

Figure 20 shows the example MEMS oscillator according to embodiment, arranges on it that two resistors having 4 access lines measure the resistance at the top of MEMS oscillator, and no matter the resistance of access line and temperature how.

Embodiment

The disclosure will be described about embodiment and with reference to some accompanying drawing, but the disclosure is not limited thereto.The accompanying drawing of describing only is schematic but not circumscribed.In the accompanying drawings, for purposes of illustration, some size of component possibly exaggerated and not to scale (NTS) is drawn.Size and relative size needn't with put into practice of the present disclosure actual dwindle corresponding.

In addition, the term first, second, third in specification and claims etc. is used between similar components, distinguishing and needn't be used to describe rank order or age ordering.Term is not interchangeable under appropriate environments, embodiment of the present disclosure can according to except describe here or the order of explanation other operate in proper order.

In addition, the terms top in specification and claims, the end, on, under etc. be used for purpose of description and relative position needn't be described.The term that uses like this is interchangeable under adapt circumstance, and disclosed embodiment described herein can operate according to other orientation except the orientation of describing here or explaining.

The term that uses in claims " comprises ", should not be construed as the means of listing after being confined to; It does not get rid of other element or step.It need be interpreted as and specify mentioned regulation characteristic, integer, step or the assembly that occurs, and does not get rid of appearance or increase its one or more further features, integer, step or assembly or grouping.Thereby the scope of expressing " equipment comprises device A and B " should not be limited to the equipment that only is made up of element A and B.It means that about the disclosure only relevant apparatus assembly is A and B.

The disclosure provides a kind of and has been used for temperature stabilization with micro electronmechanical (MEMS) oscillator at predetermined temperature T _SetSystem.Fig. 1 shows the typical MEMS resonator that is applied in oscillator and the filter.Typical case MEMS oscillator 11 can be used for various application, in some cases as pressure sensor, oscillator and strain gauge.Because the MEMS structure is often less, so they can be integrated in many equipment, comprise for example complementary metal oxide semiconductors (CMOS) (CMOS) chip.

Yet, be that their characteristic can serious drift take place with temperature as a problem of the typical MEMS structure of MEMS oscillator 11.For example, in the MEMS oscillator, frequency can be at the interior drift of 100 ℃ of temperature ranges (for example, from-20 ℃ to+80 ℃) 5000ppm.For example, based on the MEMS oscillator of silicon about its resonance frequency f _Res(T) typically has sensitivity to temperature-30ppm/ ℃.In other words, the frequency-temperature coefficient (TCF) of this MEMS oscillator based on silicon is-30ppm/ ℃.

There are several kinds of technology that are used for stablizing the frequency of MEMS oscillator.In a kind of technology, use electronic compensating, the feedback signal of wherein revising pierce circuit is to keep stable frequency.In another kind of technology, the temperature T of MEMS oscillator _CompRemain on stable predetermined temperature T _SetFor this reason, the MEMS oscillator can place baking oven (oven), such as the baking oven shown in Fig. 12, and oven temperature, T _OvenCan maintain predetermined temperature.Yet this technological model ground needs certain mode to confirm whether the temperature in the baking oven is higher or lower than predetermined value T _SetIn publication number was 2009/0243747 U.S. Patent application, this confirmed to utilize two MEMS resonators with different TCF (for example, TCF1 and TCF2) to make, and control signal 88 produces based on mixing, and is as shown in Figure 4.

Fig. 5 A-E shows the view according to the typical MEMS oscillator structure of embodiment, top view of MEMS oscillator (5A-B) and cross section (5C-D) view and comprise the Vacuum Package (5E) according to the MEMS oscillator of embodiment.Shown in Fig. 5 B, MEMS oscillator 11 comprises first resistor 61, and it has the first resistance r1 and first temperature coefficient of resistance (TCR) TCR1.MEMS oscillator 11 further comprises the second resistor r2, and it has the second resistance r2 and the 2nd TCRTCR2.First resistor 61 and second resistor 62 are shown in the top of the resonator bar of MEMS oscillator 11 and handle.First resistor 61 still contacts with MEMS oscillator 11 good thermal with MEMS oscillator 11 electric insulations with second resistor 62, so that have the hot precision of expectation.In conjunction with at least the first sensing signal 81 (Ilin) and second sensing signal 82 (I2in), select resistance value.First sensing signal 81 can comprise for example first direct current (DC) signal, and this direct current signal flows through first resistor 61.Similarly, second sensing signal 82 can comprise the 2nd DC signal that flows through second resistor 62.Resistance value can be selected, thereby make to produce the voltage curve 83 shown in Fig. 7 A, the voltage curve 84, voltage curve with predetermined temperature T _SetCorresponding joining 85 intersects.Resistor 61,62 is formed for the embodiment according to the resistance sensing element in the proportional quantities observing and controlling system loop of system of the present disclosure.

In one embodiment, two sensing signals 81,82 can be basic identical.For example, each in the sensing signal 81,82 can be the DC signal that is produced by current mirror.In another kind of embodiment; Each sensing signal (for example; First sensing signal 81) for example switch capable of using is selectively used for a sensing element (for example, first sensing element 62), and measuring-signal (for example; First measuring-signal 83) can be stored in the storage device, such as the Measurement of capacitor (not shown).After sensing, the measuring-signal 83,84 (for example, voltage) that is stored on the storage device can compare or subtract each other, and is used for producing control signal 88.Like this, can avoid first and second sensing signals 81, any difference between 82.

Other resistive element except first and second resistors 61,62 also can use, and can obtain at the working temperature place as long as the temperature that intersects relies on characteristic 63,64, promptly as long as control loop keeps " ratio measurement ".Intersect can be through individual characteristics simple scalability or other operate and create.For example, the resistance of known diode has the dependence to cardinal index's property of temperature, and the dependence of resistor is linear basically, thereby temperature relies on extremely different.In order to simplify, principle of the present disclosure will be done further to resistor and describe, and also be fine although be appreciated that other element.

Get back to Fig. 5 B, in an embodiment, first and second sensing signals 81,82 are produced by electric equipment 7.In certain embodiments, first and second sensing signals 81,82 can produce in same chip, and this chip comprises MEMS equipment 11.In another kind of embodiment, sensing signal 81,82 can for example be supplied power outside baking oven 2 from electric equipment 7 externally feds.Expectation joining 65 (shown in Fig. 7 A) and corresponding preferred temperature T _SetCan be fixing or variable.In certain embodiments, expectation joining 65 and corresponding preferred temperature T _SetCan regulate through changing sensing signal 81,82.Allowing to supply with outside sensing signal 81,82 also can allow to proofread and correct and/or calibration.

Through placing two resistors 61,62 and 11 thermo-contacts of MEMS structure,, can guarantee during operation electric equipment 7 (for example chip) temperature T of resonator bar especially with the thermo-contact of resonator bar _CompAs far as possible near coupling predetermined temperature T _SetThereby, stablize the resonant frequency of this MEMS structure 11 as far as possible, because resonant frequency is the most responsive to the local temperature of resonator bar.Note, during operation electric equipment 7, in the temperature T of oven interior _OvenAnd there is temperature gap between the temperature of MEMS structure 11.Therefore, can expect sensing element 61,62 is positioned near MEMS structure 11 parts.

Fig. 5 C shows the cross section of the structure of Fig. 5 B, and wherein sense resistor 61,62 is positioned on the Electric insulator, and this Electric insulator is positioned over the top of resonator.Like this, realized the not thermo-contact of charged insulation.Fig. 5 D shows according to another kind of embodiment of the present disclosure.It will be apparent to those skilled in the art that and to use many other layouts.

In an embodiment, baking oven is a Vacuum Package 22, and it comprises MEMS oscillator 11 and heater 21.Encapsulation 22 provides the heat between the outside ambient temperature of MEMS equipment 11 and Vacuum Package to isolate, and forms baking oven 2 or dry by the fire formula system 1 with heater 21.In a preferred embodiment, MEMS element 11 can through guide current through its supporting leg, heat MEMS equipment 11 through joule and heat (referring to Figure 19).Can use the heater 21 of any other types, contact with temperature- sensing device 61,62 good thermal, that is to say to have essentially identical temperature up to MEMS element 11.

A kind of other example is a radiation heating, referring to Figure 15 and 16.In this embodiment, heater comprises adjustable infrared source 100, and provides MEM resonant element 101 to absorb the thermal radiation that is produced by this adjustable infrared source.In other words; MEM resonant element 101 is arranged to receive the thermal radiation by these adjustable infrared source 100 radiation; And control circuit is arranged in this with the variations in temperature by means of resistance sensing element (not shown) monitoring MEM resonant element; For example at the top of resonant element, in other embodiment described herein.The temperature translation is monitored by control circuit, and this control circuit makes its output signal adaptation in this adjustable infrared source, is used to be relevant to the parameter value translation of being monitored and changes the thermal exposure of being radiated.This can through change the thermal-radiating intensity radiated, through switching this source ON/OFF discontinuously or otherwise carrying out.Through with the thermal radiation form heat energy being provided, heat energy can be concentrated towards MEM resonant element 101, thereby even reduce avoid directly heating the MEM resonant element around.Because heat energy can more directly be absorbed by the MEM resonant element, can realize the higher reaction speed of equipment of the present disclosure to variations in temperature.Light source 100 can for example be an integrated LED, and its intensity can be supplied to the LED electric current of LED to adjust through control.

Preferably, resistance sensing element 61,62 above the MEMS element 11, below or near MEMS element 11 parts, be placed with each other be close, or stack each other, resistance sensing element and MEMS element are by electric insulation but the layer separation of heat conduction.Also can using arbitrarily, other provides the implementation of good thermal contact and not serious damage MEMS element function 11.

Ratio measures principle and can realize through using different TCR values, and different TCR values can realize through two kinds of different materials that use the required resistor 61,62 of dual sensor loop.Fig. 7 A shows the relative resistance r=Δ R/R of first and second resistor 61,62 and the relativeness example of temperature T, perhaps is that the temperature of first and second sensing element 61,62 relies on characteristic 63,64 in short.

Existence and production with resistor of predetermined TCR value are known in the prior art.For example, according to known formula, the temperature coefficient of resistance TCR of n-or p-type silicon depends on doping content.A.Razborsek and F Schwager have described and how to have produced a kind of resistor at " membrane system (Thin film systems for low RCR resistors) that is used for low RCR resistor "; This resistor comprises the TaN that is coated with Nipad, its have-150ppm/ ℃ and+adjusted TCR between the 500ppm/ ℃.The patent No. is resistor and the manufacturing approach thereof that 7659176 United States Patent (USP) has been described the adjustable resistance temperature coefficient.The TCR value of resistor can change through using different materials, and comprise same material but have the crystals with different structure or crystal orientation, or the resistor of different doping ranks or impurity levels also can have different TCR values.

Centering on T _SetLittle, predetermined temperature range in, temperature relies on the curve of characteristic 63,64 can ask approximate through formula:

R(T)＝R ₀(1+αΔT) (1)

Wherein α is a material characteristics, is called temperature coefficient of resistance, is known as TCR.When using a technical term " resistor ", be appreciated that the parallel connection or the tandem compound that also can use two or more independent resistors, to obtain to have the composition resistor of combined electrical resistance r1 and combination TCR1 value.

In using the disclosure embodiment of resistor as sensing element, one of them of TCR-value is 0 basically, and another TCR value is for just.In another kind of embodiment, one of them of TCR-value is 0 basically, and another TCR value is for negative.In another embodiment, one of them of TCR value be for negative, and another TCR value is for just.In another embodiment, two TCR-values are negative but have different values.In another embodiment, two TCR-values just are being but are having different values.Other TCR value also is fine.

In embodiment of the present disclosure, first sensing signal 81 is AC electric currents, and second sensing signal 82 is AC electric currents, and first measuring-signal 83 is that the AC voltage and second measuring-signal 84 are AC voltage.In another kind of embodiment, first sensing signal 81 is DC electric currents, and second sensing signal 82 is DC electric currents, and first measuring-signal 83 is that the dc voltage and second measuring-signal 84 are dc voltages.In another embodiment, first sensing signal 81 is an AC voltage, and second sensing signal 82 is an AC voltage, and first measuring-signal 83 is that the AC electric current and second measuring-signal 84 are AC electric currents.In another embodiment, first sensing signal 81 is dc voltages, and second sensing signal 82 is dc voltages, and first measuring-signal 83 is that the DC electric current and second measuring-signal 84 are DC electric currents.Sensing signal 81,82 can be continuous signal or the signal that is interrupted.Sensing and measuring-signal also can adopt other form.

In the embodiment of control circuit 71; The measuring-signal 83,84 (for example voltage) that is produced by sensing element 61,62 (for example resistor) is subtracted each other and is amplified alternatively; Produce that for example the differential signal shown in Fig. 7 B 85 is (perhaps opposite; Depend on whether first measuring-signal deducts, and vice versa from second measuring-signal).Randomly, one of them of measuring- signal 83,84 can be carried out convergent-divergent before subtract each other.When differential signal 85 is correct time, the temperature T of MEMS oscillator 11 _CompBe higher than T _Set, and baking oven 2 should cool off, and under the situation of passive cooling, can not realize through not giving heater 21 power supplies.When differential signal 85 when negative, the temperature T of MEMS equipment 11 _CompBe lower than T _Set, and baking oven 2 need heat.In the reality, T _SetMay be selected to be and be higher than 10 ℃ of ambient temperatures at least, thereby can adopt passive cooling.

In certain embodiments, power supply can be proportional with the amplitude of differential signal 85 to the actual heating power of heater 21, perhaps can be quadratic equation, index or another kind of relation.In other words, control loop can, for example, the temperature profile (for example, resistance) through a temperature sensor 61 relatively and the temperature profile (for example resistance) of second temperature sensor 62 are assessed the temperature T of MEMS oscillator 11 _CompVia the temperature control loop road, oven temperature, T _OvenBe driven to temperature T _Set, wherein characteristic intersects (difference of comparative result is 0), thereby makes the output of MEMS oscillator 11 be adjusted to the basicly stable output signal of generation.Temperature T _OvenBe controlled in T _SetNear predetermined temperature range has been confirmed the possible frequency drift of output signal.The ratio that has resistance sensing through use measures loop, and temperature range can for example be limited in T _SetNeighbouring 0.10 ℃, cause several ppm or drift still less.Temperature range can be through considering MEMS oscillator 11 attribute and the temperature of operating frequency rely on, towards for example 2 or the target peak frequency drift of 1ppm be optimized (restriction).

In another kind of embodiment, measuring- signal 83,84 for example utilizes that the comparator (not shown) comes to compare each other, produces the for example comparison signal shown in Fig. 7 C 86.When the signal 86 of Fig. 7 C is correct time, the temperature T of MEMS equipment 11 is lower than T _Set, and baking oven 2 should heat.Depend on comparator arrangement, can produce other comparison signal 86, for example be cut to plus or minus voltage, those skilled in the art can be easily like heater 21,100 adaptive requiredly sort signals.

Fig. 6 shows the example MEMS system according to embodiment.Oven temperature, T _OvenControl be based on two elements 61, the characteristic rate between 62 or difference.System 1 comprises baking oven 2; Wherein placed the electric equipment that comprises MEMS equipment; Electric equipment 7 comprises MEMS structure 11 and two temperature sensors 61,62; This temperature sensor has aforesaid different temperatures and relies on characteristic 63,64, for example has two resistor R 1 and the R2 of TCR1 and TCR2 respectively.System further comprises control circuit 71, and this control circuit is realized control loop, is used for the temperature T comp of MEMS structure 11, especially its element 11 is controlled or be arranged to fixing or preferred temperature T _SetControl circuit 71 can be the part of electric equipment 7 or the part of baking oven 2.System turns round as follows.

The variation of the resistance r of each resistor R 1, R2 is described in Fig. 7 A and is remembered and make function r1 (T) and r2 (T).Two resistance all are functions of temperature T.In the temperature range of being considered, there is (and only one a) point, wherein r1 (T) and r2 (T) equate.This point is by predetermined temperature T _SetDefine.For this temperature: r1 (T _Set)=r2 (T _Set).This equality is only at target oven temperature, T _SetThe place effectively.Control loop control oven temperature,, thus r1 (T made _Set)=r2 (T _Set).When realizing this point, oven temperature, is T _SetAnd remain on T _SetIn fact, T _SetBe positioned at the intersection of measuring curve 83,84, the intersection of indicatrix was identical when this intersection equated with sensing signal 61,62, and curve is the factor m of translation in addition, and m is the ratio of the amplitude of sensing signal 61,62.

In steady state operation, the temperature of MEMS equipment 11 remains on T _Set, and removed temperature drift in fact.If control loop has unlimited gain (integrating circuit) at the DC place, then this control loop can obtain absolute mean temperature precision in fact under the situation that does not have the undesirable item of other circuit (such as the temperature in the sensing circuit relies on skew)

Utilize any particular algorithms well known by persons skilled in the art, control loop 71 can be realized according to the analog or digital form.Additionally, control loop 71 can provide a kind of circuit, is used for controlling and monitoring the MEMS structure 11 of baking oven 2.Control loop can comprise effective operating system 7 usually or regulate required any element or the mechanism of output signal 87 (for example, the frequency of the resonator of the MEMS structure among Fig. 6) as required.Especially, control loop will guarantee that the temperature of MEMS structure 11 remains on T _SetThe signal quality factor of MEMS structure 11 and parameter also can be write down and/or monitored by control loop.Such as thermal change, noise, elasticity, stress, pressure, add strain and comprise the electrical bias of voltage, electric field and electric current and the output that the factor resonator material, attribute and the structure can influence MEMS structure 11.Monitor the relation between the output signal characteristic of contribution factor resonator of output signal that these factors can be used for deriving resonator.Understanding these relations allows people that the output signal 87 that is produced is carried out more control.

Fig. 8 shows the example MEMS system that comprises heater according to embodiment.The purpose of first and second sensing element 61,62 and control circuit 71 is the temperature stabilizations that will keep in the baking oven 2, equals T _Set, and no matter ambient temperature.Therefore, component parameter changes minimum.The temperature of two temperature sensor 61,62 sensing MEMS assemblies 11. Transducer 61,62 has different temperature and relies on.They export two temperature dependence value S1 and S2, for example above-mentioned measuring voltage V1 and V2.Control loop 71 drives heater 21, the temperature T comp of this heater control MEMS assembly 11.Control loop control oven temperature,, thus m*S2=S1 made, and wherein m is the constant real number of being scheduled to.This equality is only at a separate temperature T _SetThe place sets up.Therefore, when loop stability, the temperature of assembly 11 is T _Set, and thereby its temperature to rely on parameter be stable.This is shown in Fig. 9, and first and second temperature that Fig. 9 shows according to embodiment rely on characteristic.

Can be observed, heater control signal 88 can be ambient temperature T _AmbFunction.Certainly, suppose that ambient temperature descends, then owing to the ambient temperature around the baking oven 2, the assembly temperature in then little baking oven 2 also descends.Therefore, S1 and m.S2 the two also will change (they can increase or reduce, and depend on the symbol that temperature relies on).This will trigger control loop and come once more heated oven 2 to target temperature T with compensating heater control signal 88 _SetCertainly, this loop will force m.S2 to get back to equal S1.Can find out that from this example control signal 74 is ambient temperature T _AmbFunction.Thereby dual sensor temperature stabilization loop 71 can be used as temperature sensor.

Although the dual sensor control loop 71 shown in Fig. 8 is desirable, dual sensor control loop 71 possibly run into non-ideal conditions in the real world applications.This possibly cause the residual temperature of the component parameter that is heated (for example, frequency) to rely on.In other words, though T _SetShould be along with variation of ambient temperature be fixing, T _SetPossibly have slight remnants with variation of ambient temperature changes; Shown in figure 11, it shows the stability (by " only dual sensor control " indicated curve) of not controlling the example output signal of MEMS oscillator with the baking oven that dual sensor is controlled, the band dual sensor controls and be with dual sensor and post-compensation to control according to embodiment.As shown in, component parameter still possibly change with temperature, this is not expectation.

According to another aspect of the present disclosure, residual temperature rely on can be further mode through post-compensation reduce, like Figure 10 explanation, it shows the example MEMS system that comprises heater and control loop according to embodiment.In this method, ambient temperature T _AmbNeed carry out sensing.T _AmbMeasurement then guide compensation scheme, it proofreaies and correct the imperfect assembly of this loop.Because the original residual temperature drift that non-ideality causes is less, so T _AmbMeasurement needn't be very accurate.The post-compensation scheme can be any independent kind, and it influences parameters of interest (for example, resonant frequency) rather than temperature.For example, expression environment temperature T _AmbControl signal 88, can guide the bias voltage of MEMS assembly 11, shown in figure 12, it shows a kind of example MEMS system that comprises heater and control system, wherein the post-compensation signal is a bias voltage.

Figure 13 shows the example MEMS system that comprises heater and control system, and wherein the post-compensation signal plays the effect of phase-locked loop.Embodiment shown in Figure 13 regulates follow-up PLL, and this PLL adopts the MEMS oscillator as importing and provide the output frequency through regulating.This other compensation 90 can be any mathematical kind, and is for example linear, quadratic equation or polynomial, perhaps based on look-up table, perhaps based on other compensation arbitrarily well known by persons skilled in the art.The operation of post-compensation 90 and (for example to component parameter or output parameter 92; Frequency) influence explains that in Figure 11 Figure 11 has explained the stability of not controlling the example output signal of MEMS oscillator with the baking oven that dual sensor is controlled, the band dual sensor controls and be with dual sensor and post-compensation to control according to embodiment.As shown in, dual sensor control and post-compensation curve 92 are than corresponding to the curve 87 with the system of post-compensation 90 is more not flat.

Mention like preamble, dual sensor loop 71 can be embodied as analogue loop or digital loop.Therefore, ambient temperature output T _AmbCan be analog or digital, and post-compensation scheme 90 also can be an analog or digital.

Although post-compensation 90 may command independence control signals (for example, the bias voltage of MEMS assembly 11), it also can be to temperature loop assembly generation effect.Post-compensation scheme 90 also can be to not being the external parameter generation effect of the part of this system.For example, ambient temperature measurement component parameter capable of using plays the effect of the post-compensation in the external system.For example, post-compensation externally carries out among the PLL, and this outside PLL uses the oscillator of baking formula based on MEMS.

Below, be used for embodiment according to the MEMS resonator device of system of the present disclosure with being used to provide the maximum support anchor of frequency and the electromechanical stability and the high Q-factor to describe.Fig. 5, the MEMS resonator device shown in 15 and 19 includes rectangle main resonator body, but other shape also is fine (for example, square, circular, parallelepiped, cube etc.).Excitation reaches by means of (promptly at the transducing gap location to the main resonator body 101) electrode 111,112 that is positioned over short range.Body supports 121,122 by means of the T-type and is suspended on the substrate, and this support is used for the main resonator body is anchored to substrate.

The T-type supports or T-supports and comprises two fixed ends beam (clamped-clamped beam), and this two fixed ends beam comprises the two legs that is attached to substrate by means of anchor, and public and that be positioned at the center in some cases, to the connection of main resonance body 101.MEMS resonator structure 11 is configured at least with preassigned pattern resonance, for example breathing pattern.The main resonator body is to be relevant to the resonance frequency (f of its natural response _Res) carry out resonance.The length of selecting two fixed ends beam or support is used to provide the frequency stability and the high Q factor with relevant with crooked wavelength (type of wavelength depends on the most important stress assembly that will support).The T-supported design of using rigidity two fixed ends beam to support provides the electromechanical stability along transmission direction.More particularly, the length L of each beam _TsupThe half the multiple that is chosen as crooked wavelength adds shift term.

In these embodiment, each beam is used for by adaptive, as the result of the said vibration of said resonator body, with given crooked wavelength according to beam mode with said operating frequency (f _Res) vibrate.This means the attribute of selecting beam, thereby beam is vibrated according to beam mode (that is, showing soft for this vibration) as the result of the target vibration of resonator body.According to finding that the ability that this beam vibrates with beam mode can strengthen or keep at least the electromechanical stability of resonator, should understand the beam design that beam mode can be used to optimize other parameter simultaneously.In addition, every leg is " long on the acoustics " about the said crooked wavelength of said beam vibration, means that this leg has long relatively length about prior art equipment, and this has strengthened the thermal insulation of resonator body.Therefore, resonator can be heated to working temperature, and is basicly stable with the maintenance operating frequency, and do not face the great thermal loss of substrate.Consider that from the stability of electromechanical convenience center connects preferably selects or be designed with minimum length.Minimum length is confirmed by design parameter and manufacture process.

Preferably, every leg has length (L _{Tsup, opt}), it equals said crooked wavelength divided by the prearranged multiple after 2, adds predetermined migration, considers that the thermal resistance of optimizing this leg selects said prearranged multiple, and considers that the quality factor of optimizing this resonator selects said predetermined migration.One of them of these length through selecting this supporting leg, the impedance at the tie point place of resonator and the impedance at anchor place are mated.Thereby, can minimize via the energy loss of anchor, and the resonator device that has through the Q-factor of optimizing can be provided substrate.Preferably, predetermined migration equals to have the length (L of the two fixed ends beam of the first crooked syntony frequency basically _{Cl-cl, l}) half the, the said first crooked syntony frequency equals operating frequency (f _Res).According to finding that the Q-factor is the periodic function of the supporting leg length of resonator, and this predetermined migration corresponds essentially to the maximum of periodic function.

In a preferred embodiment, the resonator body is applicable to according to breathing pattern and carries out resonance, and it has symmetry axis, wherein displacement be minimum and wherein the public connection of two fixed ends beam be positioned at said symmetry axis place.This means that said beam is connected with the resonator body at the some place of least displacement, this can strengthen the electromechanical stability of resonator.Figure 14 A-C shows the displacement that is applicable to according to the vibration MEMS resonator among the embodiment of the present disclosure.Resonator vibrates according to breathing pattern, i.e. body expansion and contraction.Figure 14 A shows the main body with its initial, flat shape, does not promptly have displacement.Figure 14 B shows the displacement at the some place of the largest extension of the vibration of main body: do not have displacement basically at vertical (center) of body axle and along maximum displacement place of the longitudinal edge of body.Figure 14 C shows the displacement at the some place of the maximum collapse of the vibration of main body: at the longitudinal axis place of body and along maximum displacement place of the longitudinal edge of body, do not have displacement equally basically.This shows this longitudinal axis is the optimum position that connects the support that is used for this oscillator according to this breathing pattern.

Can apply big voltage according to stable high-level further permission of electromechanical that the disclosure reaches, and not have to introduce the danger of (pull-in), thereby reach the lower movement resistance of MEMS resonator, this causes being easier to integrated.

In a preferred embodiment, the two fixed ends beam is the T-type, and the center is connected to the resonator body.In alternate embodiment, the two fixed ends beam also can for example be the beam that tilts.

In a preferred embodiment, the two fixed ends beam has the rigidity direction, and said exciting bank is positioned to the rigidity direction excitation resonator body along said beam.For example, under the situation of T-type beam, the rigidity direction is that the vertical and any direction that said beam edge is rectangular with it of supporting leg has soft.

Yet the disclosure is not restricted to and is designed to the micromechanics oscillator that vibrates according to breathing pattern.Other mode of operation also is fine.

Figure 17 shows the example that can be used for according to the crooked syntony device of embodiment of the present disclosure.Resonator is included between two exciting electrodes and extends and be applicable to the two fixed ends beam 130 according to beam mode resonance.Support 131,132 two fixed ends beams that also have like leg long on the acoustics described here.At the resonator top, two resistance sensing elements are to provide with same way as that the top Fig. 5 of combination describes.

Figure 18 shows the another kind of example that can be used for according to the crooked syntony device of embodiment of the present disclosure.Resonator comprises cantilever beam 140, and it extends between two exciting electrodes and is used for beam mode resonance by adaptive.Support 140 two fixed ends beams that also have leg long on the acoustics described here.At the top of resonator, two resistance sensing elements with provide with reference to figure 5 described identical modes.

In another preferred embodiment, shown in Figure 20, two resistors being made up of the material that has different TCR are sensing elements.Be connected the resistance that allows on the measuring equipment with the Kelvin (4-point) of resistor.In possible installation, electric current A is conducted through resistor, and voltage V is monitored.Then resistance is V/A, no matter the resistance of access line and temperature are how.Also can use other sensing configuration.

Claims (20)

1. system comprises:

Baking oven;

The micromechanics oscillator, it is arranged in said baking oven and is configured to and under predetermined temperature, vibrates with preset frequency, and wherein said preset frequency part at least relies on and at least one predetermined attribute based on temperature;

Excitation mechanism, it is configured to encourage said micromechanics oscillator to vibrate with said preset frequency;

The temperature control loop road, it is configured to:

Utilize resistance sensing to detect the temperature of said micromechanics oscillator;

Within the preset range of predetermined temperature, wherein said preset range part at least relies on and said at least one predetermined attribute based on temperature the temperature of confirming said micromechanics oscillator, drifts about with minimum frequency; And

The temperature of adaptive said micromechanics oscillator is to remain within the said preset range;

Frequency output, it is configured to export the preset frequency of said micromechanics oscillator.

2. the system of claim 1, wherein said at least one predetermined attribute comprises at least one size of the topological structure and the said micromechanics oscillator of the material of said micromechanics oscillator, said micromechanics oscillator.

3. the system of claim 1, wherein said predetermined temperature range is included in the temperature within maximum 0.10 ℃ of said predetermined temperature.

4. the system of claim 1, wherein said micromechanics oscillator comprises SiGe.

5. the system of claim 1, wherein said micromechanics oscillator comprises bulk acoustic wave resonator.

6. the system of claim 1, wherein said micromechanics oscillator comprises the crooked syntony device.

7. the system of claim 1, wherein said micromechanics oscillator comprises SAW resonator.

8. the system of claim 1, wherein said micromechanics oscillator utilizes the two fixed ends beam to hang, and wherein each beam comprises two supporting legs, and these two adjustable braces have the common connection to said micromechanics oscillator.

9. the system of claim 8, wherein:

Each beam is configured to vibrate according to beam mode with crooked wavelength, and said bending wave grows to few part based on said preset frequency; And

Every leg is long on acoustics about said crooked wavelength.

10. the system of claim 9, wherein every leg is long comprising on acoustics about crooked wavelength: every leg is longer than the multiple of crooked wavelength.

11. the system of claim 8, wherein at least one beam forms the heating resistor assembly of said control loop, and said heating resistor arrangement of components becomes the said micromechanics oscillator of heating.

12. the system of claim 1, wherein said control loop comprises radiation source, and said radiation source is configured to heat said micromechanics oscillator.

13. the system of claim 1, wherein said predetermined temperature is on the ambient temperature of system between the normal operating period at least 10 ℃.

14. the system of claim 1, wherein said excitation mechanism is included in the bias electrode within the said baking oven, and said bias electrode is in said micromechanics oscillator short range and be connected to bias voltage source.

15. the system of claim 1, wherein said frequency output is included in the sensing electrode within the said baking oven, and said sensing electrode is in said micromechanics oscillator short range.

16. the system of claim 1, wherein said control loop comprises:

The first resistance sensing element is with the thermo-contact of said micromechanics oscillator and have first resistance temperature and rely on; And

The second resistance sensing element; With the thermo-contact of said micromechanics oscillator and have second resistance temperature and rely on; Second resistance temperature relies on and is different from the dependence of first resistance temperature, and wherein each in first resistive element and second resistive element stands and the essentially identical temperature of micromechanics oscillator.

17. the system of claim 1, wherein:

The topological structure of said micromechanics oscillator has the axle of duration of oscillation minimum movement; And

The said first and second resistance sensing elements provide along said axle.

18. the system of claim 1 further comprises:

Be used to remove the post-compensation circuit of residual error, said post-compensation circuit arrangement becomes:

Receive control signal from said control loop; And

Change said control signal to produce the post-compensation signal.

19. the system of claim 1 further comprises:

Generator output signal, it is connected to said frequency output and is configured to produce the output signal based on said preset frequency.

20. the system of claim 1, wherein said baking oven comprises vacuum-packed encapsulation, and said encapsulation only comprises said micromechanics oscillator.

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