CN106549649B - N-type heavily doped oven controlled oscillator and oven control method thereof - Google Patents

Abstract

The invention provides an N-type heavily doped constant temperature control oscillator and a constant temperature control method thereof, wherein the constant temperature control oscillator comprises: the device comprises a resonance structure, an anchor point, a heating beam and a temperature sensor; the resonance structure comprises an N-type heavily-doped longitudinal vibration beam and a first electrode; the N-type heavily doped longitudinal vibration beam and the first electrode are distributed along the direction of a monocrystalline silicon <100> crystal orientation family; the anchor points are positioned at two sides of the resonance structure; the heating beam penetrates through the N-type heavily doped longitudinal vibration beam; the temperature sensor is located at the anchor point surface. In the invention, a zero crossing point exists along the frequency temperature coefficient of the N-type heavily doped structure of the <100> crystal orientation family, and the temperature of the zero crossing point of the frequency temperature coefficient is determined by doping concentration; by adjusting the N-type doping concentration, the zero crossing point of the temperature coefficient of the <100> crystal orientation group resonant frequency is slightly higher than the upper limit of the working temperature zone of the oscillator; the heating beam penetrating through the resonance structure is arranged, and constant temperature control can be realized by electrifying the heating beam, so that the N-type heavily-doped constant temperature control oscillator has better performance stability and better temperature characteristic.

Description

N-type heavily doped oven controlled oscillator and oven control method thereof

technical field

The invention relates to the field of sensors, in particular to an N-type heavily doped constant temperature controlled oscillator and a constant temperature control method thereof.

Background technique

Oscillators are the basic components that provide clock frequency in digital electronic systems, and are required in almost all electronic systems. In modern communication systems, due to the limited frequency resources and many users, extremely high requirements are placed on the stability of the oscillator. The GSM mobile phone requires the oscillator's full-temperature frequency stability to be within ±2.5ppm, while the mobile base station requires the oscillator's stability to be within ±0.05ppm.

For a long time, the quartz crystal resonator has been the main component that provides the clock frequency signal in the electronic system, and its performance is stable and the temperature characteristic is good. However, quartz oscillators are difficult to integrate, and it is difficult to manufacture high-frequency oscillators due to the limitation of mechanical processing methods, and the anti-vibration performance is poor, making it difficult to meet the needs of future mobile smart devices.

Silicon-based oscillators are a new generation of oscillators made with micro-electromechanical technology (MEMS) technology. They have excellent resonant characteristics, are easy to integrate with integrated circuits, can achieve GHz-level oscillation frequency output, and can withstand high shock environments.

A major issue that silicon-based oscillators must address is temperature compensation of frequency. The frequency stability of the oscillator is extremely required. For example, the long-term stability of the 3rd-level clock is required to be better than 4.6ppm in the range of -40 to 85°C. But on the other hand, the temperature coefficient of Young's modulus of single crystal silicon is as high as -56ppm/°C, resulting in a temperature coefficient of frequency as high as -30ppm/°C. As a comparison, the uncompensated AC-cut quartz resonant structure has a frequency temperature coefficient of about 26 ppm in the range of -40 to 85 °C. The temperature coefficient of frequency in the full temperature range of silicon is more than two orders of magnitude larger than that of quartz. The frequency temperature coefficient as high as -30ppm/°C greatly increases the difficulty of temperature compensation. In 2010, Kenny et al. of Stanford University developed a thermostatically controlled MEMS oscillator. Taking advantage of the low heat capacity of the MEMS resonant structure, the resonant structure can be kept at a constant temperature of 90°C with only a power consumption of the order of mW, which is expected to achieve low power consumption. temperature compensation for consumption. However, since the temperature coefficient of silicon frequency is as high as -30ppm/°C, in order to achieve a temperature stability of 1ppm (3E-class clock), it is necessary to ensure that the constant temperature fluctuation of the resonant structure within the full temperature range is less than 0.033°C, which is extremely difficult to achieve.

In recent years, the heavily doped passive compensation technology can directly reduce the temperature coefficient of silicon Young's modulus, thereby reducing the frequency temperature coefficient of the resonant structure. It is an important method to realize low power consumption and high stability of silicon oscillator.

Heavily doped passive compensation is a technology that directly changes the temperature coefficient of Young's modulus of single crystal silicon through P-type or N-type heavy doping. Experiments show that this method has little effect on the Q value of the resonant structure, and is currently the most promising. Passive compensation technology.

The effect of heavy doping on changing the temperature coefficient of Young's modulus of semiconductors is a carrier redistribution effect. As early as the 1960s, Keyes et al. made a detailed study on the theory of this effect and established a model based on the energy band theory. The model of Keyes et al. shows that strain along some specific crystallographic directions changes the relative positions of the band boundaries of degenerate semiconductors, resulting in a redistribution of charge carriers in different energy bands, while the redistribution of charge carriers decreases Strain-induced elastic potential energy, which affects Young's modulus. The generation mechanism of this effect is similar to the piezoresistive effect, which is closely related to the crystal orientation and doping type, but has little to do with the specific impurity ions. In semiconductors, the relative position of the energy band boundary will change due to the strain in some crystallographic orientations, so there is a piezoresistive effect in these crystallographic orientations, and doping also has a significant effect on the Young's modulus of these crystallographic orientations. However, the strain on some crystal directions will only cause the overall shift of each energy band without changing the relative position of the energy band boundary, and the carriers will not be redistributed, so there is no obvious piezoresistive effect in these crystal directions. The Young's modulus of the crystal orientation also has no significant effect. In 1967, Hall et al. obtained the variation of the stiffness coefficient of N-type silicon with a doping concentration of 2×10 ¹⁹ /cm ³ with the doping concentration by measuring the speed of sound in a semiconductor. The Young’s modulus can be directly calculated from the stiffness coefficient tensor. . For a long time, because the doping effect of Young's modulus of silicon has no specific application, the related research has not been further developed.

SUMMARY OF THE INVENTION

In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide an N-type heavily doped oven-controlled oscillator and an oven-controlled control method thereof, which are used to solve the problems in the prior art because the silicon-based oscillator has up to -30ppm/ The temperature compensation of the frequency caused by the frequency temperature coefficient of ℃ is more difficult.

In order to achieve the above object and other related objects, the present invention provides an N-type heavily doped oven-controlled oscillator, the N-type heavily doped oven-controlled oscillator includes: a resonance structure, an anchor point, a heating beam and a temperature sensor;

The resonant structure includes an N-type heavily doped longitudinal vibration beam and a first electrode; the first electrodes are located at both ends of the N-type heavily doped longitudinal vibration beam; the N-type heavily doped longitudinal vibration beam and the The first electrodes are all distributed along the direction of the monocrystalline silicon <100> crystal orientation group;

The anchor points are located on both sides of the resonant structure and are spaced apart from the resonant structure by a certain distance;

the heating beam penetrates the N-type heavily doped longitudinal vibration beam, and two ends of the heating beam are respectively located in the anchor point;

The temperature sensor is located on the anchor surface.

As a preferred solution of the N-type heavily doped oven-controlled oscillator of the present invention, the number of the N-type heavily doped longitudinal vibration beams is two, and the two N-type heavily doped longitudinal vibration beams are arranged in parallel and spaced apart. cloth; the first electrode connects the two N-type heavily doped longitudinal vibration beams.

As a preferred solution of the N-type heavily doped oven-controlled oscillator of the present invention, the N-type heavily doped concentration in the N-type heavily doped vertical vibration beam is greater than 10 ¹⁹ /cm ³ .

As a preferred solution of the N-type heavily doped oven-controlled oscillator of the present invention, the midpoint of the heating beam coincides with the midpoint of the resonant structure.

As a preferred solution of the N-type heavily doped oven controlled oscillator of the present invention, the heating beam includes a single crystal silicon layer, a first insulating layer, a heating resistor and a second electrode; the single crystal silicon layer, the The first insulating layer and the heating resistor are stacked sequentially from bottom to top, and the second electrodes are located on the surfaces of both ends of the heating resistor.

As a preferred solution of the N-type heavily doped oven-controlled oscillator of the present invention, the single crystal silicon layer, the anchor point and the first electrode are all N-type heavily doped structures, and the single crystal silicon layer, the anchor point and the first electrode are all N-type heavily doped structures, and the single crystal silicon layer The silicon layer, the anchor point, the N-type heavily doped longitudinal vibration beam and the first electrode are an integrated structure.

As a preferred solution of the N-type heavily doped oven-controlled oscillator of the present invention, the N-type heavily doped oven-controlled oscillator further includes a third electrode, the third electrode is located in the anchor point, and the The resonant structure is electrically extracted through the third electrode.

As a preferred solution of the N-type heavily doped oven-controlled oscillator of the present invention, the N-type heavily doped oven-controlled oscillator further includes a substrate and a second insulating layer, and the anchor point passes through the second insulating layer. The layer is fixed on the surface of the substrate; the surface of the substrate has a certain distance from the resonant structure and the lower surface of the heating beam.

As a preferred solution of the N-type heavily doped oven controlled oscillator of the present invention, the temperature sensor includes a temperature-sensitive resistor, a fourth electrode and a third insulating layer; the temperature-sensitive resistor is connected to the temperature-sensitive resistor through the third insulating layer. The anchor point is fixed, and electrical extraction is achieved through the fourth electrode.

As a preferred solution of the N-type heavily doped oven-controlled oscillator of the present invention, the temperature sensor includes a temperature-sensitive diode.

As a preferred solution of the N-type heavily doped oven-controlled oscillator of the present invention, the N-type heavily doped oven-controlled oscillator is packaged in a vacuum environment.

The present invention also provides a constant temperature control method for an N-type heavily doped constant temperature controlled oscillator, the constant temperature control method comprising:

The zero-crossing point of the frequency temperature coefficient of the resonant structure distributed along the <100> crystal direction group is adjusted to be slightly larger than the working temperature region by N-type heavy doping;

The operating temperature of the resonant structure distributed along the <100> crystal direction group direction is controlled at the zero-crossing point of the frequency temperature coefficient through constant temperature control, thereby realizing a silicon-based oscillator with high temperature stability.

As a preferred solution of the constant temperature control method of the N-type heavily doped constant temperature controlled oscillator of the present invention, the operating temperature of the resonant structure distributed along the <100> crystal direction group direction is controlled to a temperature over the frequency temperature coefficient through constant temperature control. The specific method of zero point is:

The resonant structure is supported by a heating beam; the midpoint of the resonant structure coincides with the midpoint of the heating beam;

Passing current on the heating beam makes the temperature at the midpoint of the heating beam reach the zero-crossing point of the frequency temperature coefficient of the <100> crystal orientation, so as to realize constant temperature control.

As a preferred solution of the constant temperature control method of the N-type heavily doped constant temperature controlled oscillator of the present invention, the heating beam includes a heating resistor, and both ends of the heating beam are provided with anchor points, and the anchor points are provided with Temperature sensor; the specific method of passing current on the heating beam to realize constant temperature control is:

The temperature T _a at the anchor point is measured by the temperature sensor, and the predetermined operating temperatures T _t and T _a pass the formula:

P=β(T _t −T _a )

Calculate the heating power; in the formula, β is a function of the size of the heating beam and the thermal conductivity;

The heating voltage V _{t is obtained from the average resistance value of the heating resistor, and the constant temperature control can be realized by applying the heating voltage V t on} the heating beam.

As a preferred solution of the constant temperature control method of the N-type heavily doped constant temperature controlled oscillator of the present invention, the heating beam includes a heating resistor, and both ends of the heating beam are provided with anchor points, and the anchor points are provided with Temperature sensor; the specific method of passing current on the heating beam to realize constant temperature control is:

The temperature Ta at the anchor point is measured by the temperature sensor, _a heating current is applied to the heating beam, and the resistance R _r of the heating beam is measured at the same time; the resistance R _r of the heating beam satisfies the formula:

R _r =R _r0 +R _r0 α((1-γ)T _m +γT _a +T _t )

In the formula, R _r0 is the resistance value of the heating beam at the working temperature, α is the first-order temperature coefficient of the heating beam, T _m is the actual temperature at the midpoint of the heating beam, and the value of γ is determined by the heating beam. Decide;

The above formula is used to obtain the difference ΔT between the temperature T _m at the midpoint of the heating beam and the temperature Ta at the anchor point, and the constant temperature control can be achieved by reducing ΔT to a minimum through _a feedback algorithm to achieve feedback control of the resonant structure temperature.

As mentioned above, the N-type heavily doped oven-controlled oscillator and the oven-controlled method thereof of the present invention have the following beneficial effects: the frequency temperature coefficient of the N-type heavily doped structure along the <100> crystal orientation family has a zero-crossing point, and the frequency The temperature of the zero-crossing point of the temperature coefficient is determined by the doping concentration; by adjusting the N-type doping concentration, the zero-crossing point of the temperature coefficient of the resonant frequency of the <100> crystal orientation family can be slightly higher than the upper limit of the operating temperature region of the oscillator; The heating beam can realize constant temperature control by passing a current on the heating beam, so that the N-type heavily doped constant temperature controlled oscillator has better performance stability and better temperature characteristics.

Description of drawings

FIG. 1 is a schematic three-dimensional structure diagram of an N-type heavily doped oven-controlled oscillator of the present invention.

FIG. 2 is a schematic top view of the structure of the N-type heavily doped oven controlled oscillator of the present invention.

FIG. 3 is a schematic diagram showing the working mode shape of the resonant structure in the N-type heavily doped oven controlled oscillator of the present invention.

FIG. 4 shows a flow chart of the constant temperature control method of the N-type heavily doped constant temperature controlled oscillator of the present invention.

Component label description

10 Resonant structure

101 N-type heavily doped longitudinal vibration beam

102 first electrode

11 Heated beam

111 Monocrystalline silicon layer

112 first insulating layer

113 Heating resistance

12 Anchors

13 Temperature sensor

131 Temperature sensitive resistor

132 Fourth electrode

133 Third insulating layer

14 Second electrode

15 Third electrode

16 Substrate

17 Second insulating layer

Detailed ways

The embodiments of the present invention are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

Please refer to FIG. 1 to FIG. 4. It should be noted that the diagrams provided in this embodiment are only for illustrating the basic concept of the present invention in a schematic way, although the diagrams only show the components related to the present invention rather than actual implementation. The number, shape and size of the components are drawn at the time, and the type, number and proportion of each component can be arbitrarily changed in actual implementation, and the layout of the components may also be more complicated.

Example 1

Please refer to FIG. 1 to FIG. 2 , the present invention provides an N-type heavily doped oven-controlled oscillator. The N-type heavily doped oven-controlled oscillator includes: a resonant structure 10 , an anchor point 12 , a heating beam 11 and a temperature sensor 13;

The resonant structure 10 includes an N-type heavily doped longitudinal vibration beam 101 and a first electrode 102; the first electrode 102 is located at both ends of the N-type heavily doped longitudinal vibration beam 101; the N-type heavily doped longitudinal vibration beam 101 The longitudinal vibration beam 101 and the first electrode 102 are distributed along the monocrystalline silicon <100> crystal direction; the anchor points 12 are located on both sides of the resonance structure 10 and are spaced from the resonance structure 10 by a certain distance. distance; the heating beam 11 runs through the N-type heavily doped longitudinal vibration beam 101 , and the two ends of the heating beam 11 are respectively located in the anchor point 12 ; the temperature sensor 13 is located on the surface of the anchor point 12 Specifically, the temperature sensor 13 is located on the anchor point 12 on either side of the N-type heavily doped longitudinal vibration beam 101 .

As an example, the N-type heavily doped longitudinal vibration beam 101 and the first electrode 102 are distributed along the monocrystalline silicon <100> crystal direction. Specifically, the resonant structure 10 may use a (100) silicon wafer. During manufacture, the N-type heavily doped vertical vibration beam 101 may be along the [100] crystallographic orientation on the (001) crystal plane, and the first electrode 102 may be along the [010] crystallographic orientation on the (100) crystallographic plane. The frequency temperature coefficient of the N-type heavily doped structure along the <100> crystal orientation family has a zero-crossing point, and the temperature of the frequency temperature coefficient zero-crossing point is determined by the doping concentration; by adjusting the N-type doping concentration, the <100> crystal orientation can be made. The zero-crossing point of the temperature coefficient of the resonant frequency is slightly higher than the upper limit of the operating temperature range of the oscillator.

As an example, as shown in FIG. 1 and FIG. 2 , the number of the N-type heavily doped longitudinal vibration beams 101 may be but not limited to two, and the two N-type heavily doped longitudinal vibration beams 101 are arranged in parallel and spaced apart ; The first electrode 102 connects the two N-type heavily doped longitudinal vibration beams 101 .

As an example, the concentration of N-type heavy doping in the N-type heavily doped vertical vibration beam 101 can be set according to actual needs. Preferably, the N-type heavily doped vertical vibration beam 101 in this embodiment The concentration of type heavy doping should be greater than 10 ¹⁹ /cm ³ .

As an example, the midpoint of the heating beam 11 coincides with the midpoint of the resonant structure 10 , that is, the connection point between the heating beam 11 and the N-type heavily doped longitudinal vibration beam 101 is the N-type heavily doped longitudinal vibration beam 101 . The midpoint of the doped longitudinal vibration beam 101 is taken as an example in FIG. 1 to FIG. 2 , at this time the center of the heating beam 11 is located at the center between the midpoints of the two N-type heavily doped longitudinal vibration beams 101 . The connection point between the heating beam 11 and the N-type heavily doped longitudinal vibration beam 101 is located at the point where the longitudinal tensile modal displacement of the N-type heavily doped longitudinal vibration beam 101 is the smallest, that is, at the N-type heavily doped longitudinal vibration beam 101 . The midpoint of the longitudinal vibration beam 101 is doped so that the influence of the heating beam 11 on the working mode shape of the resonant structure 10 is minimal.

As an example, the heating beam 11 includes a single crystal silicon layer 111 , a first insulating layer 112 and a heating resistor 113 ; the single crystal silicon layer 111 , the first insulating layer 112 and the heating resistor 113 are in order from bottom to top stacking; the single crystal silicon layer 111 is electrically connected to the two N-type heavily doped vertical vibration beams 101 . Two ends of the heating beam 11 are provided with second electrodes 14 , and a voltage is applied to the second electrodes 14 to heat the heating beam 11 and the resonant structure 10 . The heating resistor 113 is used for the constant temperature control of the heating beam 11, and the constant temperature heating power P and the midpoint temperature T _t and the anchor point temperature T _a of the two N-type heavily doped longitudinal vibration beams 101 satisfy the formula:

P=β(T _t −T _a )

In the formula, β is a function of the size and thermal conductivity of the heating beam; when the heating beam is a homogeneous rectangular section beam, β in the above formula satisfies the formula:

β=8kbh/L

In the formula, k is the thermal conductivity of the heating beam 11 , and b, h and L are the width, thickness and length of the heating beam 11 , respectively. In the actual structure, β is determined by actual experiments.

As an example, the single crystal silicon layer 111 , the anchor point 12 and the first electrode 102 are all N-type heavily doped structures, and the single crystal silicon layer 111 , the anchor point 12 , the N-type heavily doped structure The N-type heavily doped vertical vibration beam 101 and the first electrode 102 are an integrated structure, that is, the single crystal silicon layer 111 , the anchor point 12 , the N-type heavily doped vertical vibration beam 101 and the first electrode 102 . An electrode 102 can be obtained by etching the same single crystal silicon material layer.

As an example, the N-type heavily doped oven controlled oscillator further includes two third electrodes 15 , and the number of the third electrodes 15 is two, which are respectively located at the two anchor points 12 on both sides of the resonant structure 10 . Inside, the resonant structure 10 is electrically extracted through the third electrode 15 . It should be noted that the structure of the third electrodes 15 is not limited to those shown in FIG. 1 and FIG. 2 , and can be set according to actual structural needs. For example, for a capacitance detection oscillator, the two third electrodes 15 Can be used as an electrode by short circuit.

As an example, the N-type heavily doped oven-controlled oscillator further includes a substrate 16 and a second insulating layer 17 , and the anchor point 12 is fixed on the surface of the substrate 16 through the second insulating layer 17 . ; The surface of the substrate 16 and the lower surface of the resonant structure 10 and the heating beam 11 have a certain distance, that is, the heating beam 11 supports the resonant structure 10 and makes the resonant structure 10 It is in a floating state relative to the substrate 16 .

As an example, the temperature sensor 13 includes a temperature sensitive resistor 131 , a fourth electrode 132 and a third insulating layer 133 ; the temperature sensitive resistor 131 is fixed to the anchor point 12 through the third insulating layer 133 , and is connected to the anchor point 12 through the third insulating layer 133 . The fourth electrode 132 realizes electrical extraction; the temperature sensor 13 can measure the temperature of the anchor point 12 by externally connecting three resistors (not shown) to form a Wheatstone bridge.

As an example, the number of the fourth electrodes 132 may be set according to actual needs. Preferably, in this embodiment, the number of the fourth electrodes 132 is two, and the two fourth electrodes 132 are located in the On the temperature sensitive resistor 131 ; specifically, the two fourth electrodes 132 are located at both ends of the temperature sensitive resistor 132 .

As an example, the temperature sensor 13 is not limited to the structure shown in FIG. 1 , and the temperature sensor 13 can also adopt various methods such as a temperature-sensitive diode.

As an example, the N-type heavily doped oven-controlled oscillator is packaged in a vacuum environment.

The working mode shape of the resonant structure 10 is shown in FIG. 3 , the two N-type heavily doped longitudinal vibration beams 101 are in a longitudinal extensional mode (Length Extensional Mode, LE mode), and the first electrode 102 is Parasitic third-order bending vibration mode; the resonant frequency of the working mode of the resonant structure 10 is uniquely determined by the Young's modulus of the silicon <100> crystal direction.

In the present invention, the frequency temperature coefficient of the N-type heavily doped structure along the <100> crystal orientation family has a zero-crossing point, and the temperature at the zero-crossing point of the frequency temperature coefficient is determined by the doping concentration; by adjusting the N-type doping concentration, < 100>The zero-crossing point of the resonant frequency temperature coefficient of the crystal orientation family is slightly higher than the upper limit of the working temperature range of the oscillator; a heating beam running through the resonant structure is set, and constant temperature control can be realized by passing a current on the heating beam, so that the N-type heavily doped OTC oscillators have better performance stability and better temperature characteristics.

Embodiment 2

Referring to FIG. 4 , the present invention also provides a constant temperature control method for an N-type heavily doped constant temperature controlled oscillator. The constant temperature control method includes:

S1: Use N-type heavy doping to adjust the zero-crossing point of the frequency temperature coefficient of the resonant structure distributed along the <100> crystal direction to be slightly larger than the working temperature region;

S2: The operating temperature of the resonant structure distributed along the <100> crystal direction group direction is controlled at the zero-crossing point of the frequency temperature coefficient through constant temperature control, so as to realize a silicon-based oscillator with high temperature stability.

The S1 step is performed, please refer to the S1 step in FIG. 4 , and the zero-crossing point of the frequency temperature coefficient of the resonant structure distributed along the <100> crystal direction group direction is adjusted to be slightly larger than the operating temperature region by using N-type heavy doping.

As an example, the resonant structure includes two N-type heavily doped longitudinal vibration beams and a first electrode; the two N-type heavily doped longitudinal vibration beams are arranged in parallel and spaced apart, and the first electrodes are located on the two N-type heavily doped longitudinal vibration beams Both ends of the N-type heavily doped longitudinal vibration beams are connected, and the two N-type heavily doped longitudinal vibration beams are connected.

As an example, when the operating temperature of the N-type heavily doped oven controlled oscillator is -40° C. to -85° C., the resonant structure distributed along the <100> crystal direction group is made through N-type heavy doping. The zero-crossing point of the frequency temperature coefficient is around 90°C.

As an example, the doping concentration of the N-type heavy doping should be greater than 10 ¹⁹ /cm ³ ; the atomic types of the N-type heavy doping include conventional N-type doping such as phosphorus and arsenic; the doping process is commonly used in integrated circuits process.

Step S2 is performed, and the operating temperature of the resonant structure distributed along the <100> crystal direction group direction is controlled at the zero-crossing point of the frequency temperature coefficient through constant temperature control, so as to realize a silicon-based oscillator with high temperature stability.

As an example, in step S2, the specific method for controlling the operating temperature of the resonant structure distributed along the <100> crystal direction family direction at the zero-crossing point of the frequency temperature coefficient by constant temperature control is as follows:

S21: Use a heating beam to support the resonance structure; the heating beam runs through the two N-type heavily doped longitudinal vibration beams, and the heating beam is connected to the two N-type heavily doped longitudinal vibration beams The point is located at the midpoint of the two N-type heavily doped longitudinal vibration beams, and the center of the heating beam is located at the center between the midpoints of the two N-type heavily doped longitudinal vibration beams;

S22: Pass current on the heating beam to make the temperature at the midpoint of the heating beam reach the zero-crossing point of the frequency temperature coefficient of the <100> crystal orientation, so as to realize constant temperature control. The operation of constant temperature control is realized by a dedicated circuit.

As an example, the heating beam includes a heating resistor, two ends of the heating beam are provided with anchor points, and temperature sensors are provided on the anchor points; in step S22, a current is applied to the heating beam to make the two N-type heavyweights The temperature at the midpoint of the doped longitudinal vibration beam reaches the zero-crossing point of the frequency temperature coefficient of the <100> crystal orientation, and the specific method to achieve constant temperature control is as follows:

S221: Measure the temperature Ta at the anchor point by the temperature sensor, and use the predetermined working temperature Tt and Ta to pass the formula:

P=β(T _t −T _a )

Calculate the heating power; in the formula, β is a function of the size of the heating beam and the thermal conductivity;

S222: Obtain the heating voltage V _{t from the average resistance value of the heating resistor, and apply the heating voltage V t on} the heating beam to realize constant temperature control.

As an example, the heating beam includes a heating resistor, two ends of the heating beam are provided with anchor points, and temperature sensors are provided on the anchor points; in step S22, a current is applied to the heating beam to make the middle point of the heating beam The temperature reaches <100> crystal orientation frequency temperature coefficient zero-crossing point, the specific method to achieve constant temperature control is:

S221: Measure the temperature Ta at the anchor point by the temperature sensor, apply _a heating current to the heating beam, and measure the resistance R _r of the heating beam at the same time; the resistance R _r of the heating beam satisfies the formula:

R _r =R _r0 +R _r0 α((1-γ)T _m +γT _a +T _t )

In the formula, R _r0 is the resistance value of the heating beam at the working temperature, α is the first-order temperature coefficient of the heating beam, and T _m is the actual temperature at the midpoint of the heating beam. When the heating beam is homogeneous γ is equal to 1/3 when the beam is rectangular, and γ is determined by experiments in the actual structure;

S222: Use the above formula to obtain the difference ΔT between the temperature T _m at the midpoint of the heating beam and the temperature T _a at the anchor point, and reduce ΔT to a minimum through a feedback algorithm to realize feedback control of the temperature of the resonant structure to achieve constant temperature Control; the specific feedback algorithm can be adopted but not limited to the PID algorithm. The operation of constant temperature control is realized by a dedicated circuit.

To sum up, the present invention provides an N-type heavily doped constant temperature controlled oscillator and a constant temperature control method thereof. The N-type heavily doped constant temperature controlled oscillator of the present invention includes: a resonant structure, an anchor point, a heating beam and a temperature sensor ; The resonant structure includes an N-type heavily doped longitudinal vibration beam and a first electrode; the first electrode is located at both ends of the N-type heavily doped longitudinal vibration beam; the N-type heavily doped longitudinal vibration beam and The first electrodes are distributed along the monocrystalline silicon <100> crystal direction group direction; the anchor points are located on both sides of the resonant structure and are spaced apart from the resonant structure by a certain distance; the heating beam runs through the resonant structure N-type heavily doped longitudinal vibration beam, and two ends of the heating beam are respectively located in the anchor point; the temperature sensor is located on the surface of the anchor point. In the present invention, the frequency temperature coefficient of the N-type heavily doped structure along the <100> crystal orientation family has a zero-crossing point, and the temperature at the zero-crossing point of the frequency temperature coefficient is determined by the doping concentration; by adjusting the N-type doping concentration, the <100 >The zero-crossing point of the temperature coefficient of the resonant frequency of the crystal orientation family is slightly higher than the upper limit of the operating temperature range of the oscillator; a heating beam is set through the resonant structure, and constant temperature control can be realized by passing a current on the heating beam, so that the N-type heavily doped constant temperature The controlled oscillator has better performance stability and better temperature characteristics.

The above-mentioned embodiments merely illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed in the present invention should still be covered by the claims of the present invention.

Claims (13)

1. an N-type heavily doped oven-controlled oscillator, wherein the N-type heavily doped oven-controlled oscillator comprises: a resonance structure, an anchor point, a heating beam and a temperature sensor; The resonant structure includes an N-type heavily doped longitudinal vibration beam and a first electrode; the first electrodes are located at both ends of the N-type heavily doped longitudinal vibration beam; the N-type heavily doped longitudinal vibration beam and the The first electrodes are all distributed along the direction of the monocrystalline silicon <100> crystal direction group, the concentration of N-type doping in the N-type heavily doped vertical vibration beam is greater than 10 ¹⁹ /cm ³ ; the anchor point is located at the resonance two sides of the structure, and there is a preset distance from the resonant structure; the heating beam penetrates the N-type heavily doped longitudinal vibration beam, and two ends of the heating beam are respectively located in the anchor point; The temperature sensor is located on the anchor surface. 2 . The N-type heavily doped oven-controlled oscillator according to claim 1 , wherein the number of the N-type heavily doped longitudinal vibration beams is two, and the two N-type heavily doped longitudinal vibration beams are 2. 3 . The beams are arranged in parallel and spaced apart; the first electrodes connect the two N-type heavily doped longitudinal vibration beams. 3 . The N-type heavily doped oven controlled oscillator according to claim 1 , wherein the midpoint of the heating beam coincides with the midpoint of the resonance structure. 4 . 4 . The N-type heavily doped oven controlled oscillator according to claim 1 , wherein the heating beam comprises a single crystal silicon layer, a first insulating layer, a heating resistor and a second electrode; the single crystal silicon The layers, the first insulating layer and the heating resistor are sequentially stacked from bottom to top, and the second electrodes are located on the surfaces of both ends of the heating resistor. 5 . The N-type heavily doped oven controlled oscillator according to claim 4 , wherein the single crystal silicon layer, the anchor point and the first electrode are all N-type heavily doped structures, and The single crystal silicon layer, the anchor point, the N-type heavily doped vertical vibration beam and the first electrode are an integrated structure. 6 . The N-type heavily doped oven-controlled oscillator according to claim 1 , wherein the N-type heavily doped oven-controlled oscillator further comprises a third electrode, and the third electrode is located at the anchor point. 7 . Inside, the resonant structure is electrically extracted through the third electrode. 7 . The N-type heavily doped oven-controlled oscillator according to claim 1 , wherein the N-type heavily doped oven-controlled oscillator further comprises a substrate and a second insulating layer, and the anchor point passes through the the second insulating layer is fixed on the surface of the substrate; the surface of the substrate and the lower surface of the resonant structure have a preset distance, and the surface of the substrate and the lower surface of the heating beam Has preset spacing. 8 . The N-type heavily doped oven controlled oscillator according to claim 1 , wherein the temperature sensor comprises a temperature sensitive resistor, a fourth electrode and a third insulating layer; the temperature sensitive resistor passes through the first The three insulating layers are fixedly connected to the anchor point, and are electrically drawn out through the fourth electrode. 9 . The N-type heavily doped oven controlled oscillator according to claim 1 , wherein the temperature sensor comprises a temperature-sensitive diode. 10 . 10 . The N-type heavily doped oven-controlled oscillator according to claim 1 , wherein the N-type heavily doped oven-controlled oscillator is packaged in a vacuum environment. 11 . 11. A constant temperature control method for an N-type heavily doped constant temperature controlled oscillator, wherein the constant temperature control method comprises: The zero-crossing point of the frequency temperature coefficient of the resonant structure distributed along the <100> crystal direction group direction is adjusted to be slightly larger than the working temperature region by using N-type heavy doping, the doping concentration of the N-type heavy doping is greater than 10 ¹⁹ /cm ³ ; The resonant structure is supported by a heating beam; the midpoint of the resonant structure coincides with the midpoint of the heating beam; Passing current on the heating beam makes the temperature at the midpoint of the heating beam reach the zero-crossing point of the frequency temperature coefficient of the <100> crystal orientation, so as to realize constant temperature control and realize a silicon-based oscillator with high temperature stability. 12 . The constant temperature control method for an N-type heavily doped constant temperature controlled oscillator according to claim 11 , wherein the heating beam comprises a heating resistor, and both ends of the heating beam are provided with anchor points, and the anchor There is a temperature sensor on the point; the specific method of passing current on the heating beam to realize constant temperature control is: The temperature T _a at the anchor point is measured by the temperature sensor, and the predetermined operating temperatures T _t and T _a pass the formula: P=β(T _t −T _a ) Calculate the heating power; in the formula, β is a function of the size of the heating beam and the thermal conductivity; The heating voltage V _{t is obtained from the average resistance value of the heating resistor, and the constant temperature control can be realized by applying the heating voltage V t on} the heating beam. 13 . The constant temperature control method of an N-type heavily doped constant temperature controlled oscillator according to claim 11 , wherein the heating beam comprises a heating resistor, and both ends of the heating beam are provided with anchor points, and the anchor There is a temperature sensor on the point; the specific method of passing current on the heating beam to realize constant temperature control is: The temperature Ta at the anchor point is measured by the temperature sensor, _a heating current is applied to the heating beam, and the resistance R _r of the heating beam is measured at the same time; the resistance R _r of the heating beam satisfies the formula: R _r =R _r0 +R _r0 α((1-γ)T _m +γT _a +T _t ) In the formula, R _r0 is the resistance value of the heating beam at the working temperature, α is the first-order temperature coefficient of the heating beam, T _m is the actual temperature at the midpoint of the heating beam, and the value of γ is determined by the heating beam. decision, T _t is the predetermined working temperature; The above formula is used to obtain the difference ΔT between the temperature T _m at the midpoint of the heating beam and the temperature Ta at the anchor point, and the constant temperature control can be achieved by reducing ΔT to a minimum through _a feedback algorithm to achieve feedback control of the resonant structure temperature.