CN113639921B - MEMS pressure sensor based on topological photon high Q cavity - Google Patents

Abstract

The invention relates to an MEMS pressure sensor based on a topological photon high Q cavity, and belongs to the technical field of MEMS pressure sensors. The pressure sensor is a sensitive element and a bagSi sheet beams containing 1 sequential photonic crystal slab; the photonic crystal plate is a regular polygon, the thickness range is 0.5 um-0.6 um, and the side length range is 20 um-250 um; the photonic crystal plate is provided with a circular hole array with the period of 519.25nm, and the radius of the circular hole is 175nm; the Si sheet beam works: the light emitted by the laser is coupled to the Si sheet beam through the optical circulator, and the Si sheet beam is deformed by the change of the environmental pressure, so that the return value of the signal light is influenced, and the wavelength value of the light on the spectrometer is changed. The sensor effectively reduces the influence of out-of-plane scattering, so that the Q value is very high, up to 1×10 ⁶ The detection sensitivity is as high as 2.17×10 ⁶ pm/kPa; has the advantages of simple structure, small volume, low cost and mass production.

Description

A MEMS pressure sensor based on topological photonic high-Q cavity

technical field

The invention specifically relates to a MEMS pressure sensor based on a topological photon high-Q cavity, and belongs to the technical field of MEMS pressure sensors.

Background technique

MEMS pressure sensor is a classic research direction in the field of MEMS, which can be mass-produced with high precision and low cost by using similar integrated circuit design technology and manufacturing process. The traditional mechanical quantity pressure sensor is based on the force deformation of the metal elastic body, which is measured by the elastic deformation of the mechanical quantity to the electric power conversion output. Compared with traditional pressure sensors, MEMS pressure sensors have the characteristics of small size, high stability, low power consumption, batch production and integration, and are widely used in aviation, aerospace, petrochemical, geological exploration and other fields. Among them, the silicon micro pressure sensor has become a research hotspot and focus in the field of pressure detection under the background of the rapid development of MEMS technology due to its advantages in material performance, process reliability, and superior performance parameters.

At present, according to the structure division, the common silicon micro pressure sensors on the market mainly have four structures: piezoresistive, capacitive, resonant and optical fiber. Among them, compared with other types of sensors, the silicon resonant pressure sensor has the characteristics of high precision, high stability and high anti-interference ability.

The piezoresistive silicon micro pressure sensor uses the piezoresistive effect of single crystal silicon to inject a semiconductor resistor connected to a Wheatstone bridge in a specific direction of the silicon diaphragm to form a pressure sensing element, and then combines the electric-force conversion device to realize micro-pressure detection. . This structure has a simple manufacturing process, low cost, and a good linear relationship between input and output, but the sensitivity of the sensor is affected by the temperature drift of the silicon material, and temperature compensation must be performed. Establishing a complete set of temperature compensation technology will not only increase the cost, but also increase the cost. At the same time, human resources are increased, and in a sense, the wide application of silicon piezoresistive pressure sensors is greatly limited.

There are two types of capacitive silicon micro-pressure sensors: pole distance change type and area change type. The working principle is to use the change of pole distance or area to reflect the change of pressure, and convert it into the change of capacitance for measurement. This type of sensor has good temperature stability and good dynamic response. Among them, the variable distance pressure sensor can realize non-contact measurement and has an average effect, but it has a large linear error. The area change pressure sensor has the advantage of linearity, but the sensitivity is not enough, and the process preparation is relatively complicated.

The optical fiber silicon pressure sensor is that the light emitted by the light source is transmitted through the optical fiber and projected on the inner surface of the diaphragm, then reflected, received by the receiving optical fiber and transmitted back to the photosensitive element, so that the output signal changes accordingly. This method is easy to implement and low cost, but the sensitivity is generally low.

The resonant silicon pressure sensor uses a silicon resonator and a frequency-selective amplifier to form a positive feedback oscillation system. When the system is subjected to pressure, its inherent oscillation frequency changes. Therefore, the pressure can be measured according to the change of its frequency. size. The performance of the resonant silicon micro pressure sensor mainly depends on the mechanical quality of the resonator, and its accuracy, stability and resolution have orders of magnitude advantages over piezoresistive and capacitive. However, the resonant structure is too complex, which causes great difficulty in processing.

At present, the relevant research on silicon resonant pressure sensors has entered a mature stage, and foreign countries started earlier. Japan's Yokogawa Electric Co., Ltd. designed a double-resonant strain gauge structure pressure sensor based on silicon materials. The Q value in vacuum is about 50,000. 0.01% FS was achieved. There are also many research teams in China that have carried out research on MEMS resonant pressure sensors. The Institute of Electronics, Chinese Academy of Sciences proposed a miniature resonant differential pressure sensor in 2020, with a Q value of 18,000.

In summary, it is necessary to find a new way to study higher sensitivity and miniaturized silicon micro-pressure sensors. The present invention provides a MEMS pressure sensor based on topological photonic high-Q cavities.

Contents of the invention

The object of the present invention is to propose a MEMS pressure sensor based on a topological photonic high-Q cavity, aiming at the problems of simple structure, miniaturization and high sensitivity existing in existing MEMS pressure sensors.

In order to achieve the above object, the present invention adopts the following technical solutions.

The MEMS pressure sensor based on the topological photonic high-Q cavity is a sensitive element, including a Si sheet beam;

Wherein, the Si sheet beam is an ordered photonic crystal plate;

The photonic crystal plate is a regular polygon, and the thickness of the regular polygon is in the range of 0.5um to 0.6um;

The number of side lengths of regular polygons of regular polygons is greater than or equal to 4, and the side length range is 20um to 250um;

The photonic crystal plate is provided with a periodic hole array, the period of the periodic hole array is 519.25nm, and the radius of the hole is 175nm;

The Si sheet beam is constrained in a cuboid base, an optical fiber is connected above the cuboid base, the optical fiber is connected to an optical circulator, and the optical circulator is connected to a spectrometer.

The test system of the MEMS pressure sensor comprises a laser, an optical circulator, a sensitive element and a spectrometer; the laser is connected with the optical circulator, and the optical circulator is respectively connected with the laser, the sensitive Components are connected to the spectrometer.

The connection and working process of the MEMS pressure sensor based on the topological photonic high-Q cavity are as follows:

Step 1, constraining the Si sheet beam of the MEMS pressure sensor in the cuboid abutment;

Step 2, connecting an optical fiber above the cuboid abutment;

Step 3, connecting the optical fiber to an optical circulator;

Step 4, connecting the optical circulator to a spectrometer;

Step 5. When the detected environmental pressure changes, the Si sheet beam is deformed;

Step 6, the spectrometer displays the pressure value corresponding to the deformation of the Si sheet beam;

So far, from step 1 to step 6, the pressure connection and testing process using a MEMS pressure sensor based on a topological photonic high-Q cavity is completed.

Beneficial effect

Compared with the existing MEMS pressure sensor, the MEMS pressure sensor based on topological photon high-Q cavity according to the present invention has the following beneficial effects:

1. The MEMS pressure sensor is designed using mechanical effects and topological effects of photonic crystals. Since the main limiting factor of the Q value of photonic crystals is the scattering loss caused by manufacturing defects or disorder, the MEMS pressure sensor uses ordered photonic crystals plate, which effectively reduces the influence of out-of-plane scattering, so that the Q value is very high, so that the prepared MEMS pressure sensor has extremely high detection sensitivity;

2. The MEMS pressure sensor is processed on a silicon wafer through MEMS technology, which has the advantages of low cost and small volume, and is conducive to mass production.

Description of drawings

Fig. 1 is a kind of MEMS pressure sensor embodiment system schematic diagram based on topological photon high Q cavity of the present invention;

Fig. 2 is a kind of comsol simulation model figure of sensitive element in the MEMS pressure sensor embodiment based on topological photon high Q cavity of the present invention;

Fig. 3 is a comsol simulation result diagram of the deformation of the sensitive element in a MEMS pressure sensor example 1 based on a topological photonic high-Q cavity of the present invention;

Fig. 4 is a comsol simulation result figure of the deformation of the sensitive element in the MEMS pressure sensor example 2 based on the topological photonic high-Q cavity of the present invention;

Fig. 5 is a graph showing the relationship between the side length of the sensitive element and the lower limit of detection in Example 1 of a MEMS pressure sensor based on a topological photonic high-Q cavity of the present invention;

Fig. 6 is a graph showing the relationship between the thickness of the sensitive element and the lower limit of detection in Example 1 of a MEMS pressure sensor based on a topological photonic high-Q cavity of the present invention;

Fig. 7 is a graph of the relationship between the side length of the sensitive element and the sensitivity in Example 2 of a MEMS pressure sensor based on a topological photonic high-Q cavity of the present invention;

Fig. 8 is a graph showing the relationship between the side length of the sensitive element and the lower limit of detection in Example 2 of a MEMS pressure sensor based on a topological photonic high-Q cavity of the present invention;

Fig. 9 is a graph of the relationship between the Q value of the sensitive element and the sensitivity in Example 2 of a MEMS pressure sensor based on a topological photonic high-Q cavity of the present invention;

Fig. 10 is a graph of the relationship between the Q value of the sensitive element and the lower limit of detection in Example 2 of a MEMS pressure sensor based on a topological photonic high-Q cavity of the present invention;

Fig. 11 is a structural schematic diagram of a wafer-shaped Si sheet beam connection base of a MEMS pressure sensor based on a topological photonic high-Q cavity of the present invention;

FIG. 12 is a schematic structural diagram of a square-shaped Si sheet beam connection base of a MEMS pressure sensor based on a topological photonic high-Q cavity according to the present invention.

Detailed ways

The embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, so as to define the protection scope of the present invention more clearly. The specific implementation of a MEMS pressure sensor based on a topological photonic high-Q cavity according to the present invention is described in detail with reference to the accompanying drawings and specific embodiments.

Example 1

The invention proposes a MEMS pressure sensor based on a topological photonic high-Q cavity, which belongs to the category of silicon resonant pressure sensors and is used to improve the sensitivity of pressure measurement. The MEMS pressure sensor uses a special photonic crystal plate, and the photonic crystal plate is distributed with a special circular hole array. This structure can effectively suppress the out-of-plane scattering loss caused by manufacturing defects, and greatly enhance the pressure of the MEMS. The Q value of the sensor. Through COMSOL simulation, we obtained a quality factor as high as 1×10 ⁶ and a sensitivity as high as 2.17×10 ⁶ pm/kPa. Compared with other known silicon resonant pressure sensors, the structure of the pressure sensor is simpler, and the Q value is the same as Greater sensitivity.

The MEMS pressure sensor based on the topological photonic high-Q cavity is a sensitive element comprising a Si sheet beam; the Si sheet beam is distributed with a circular hole array, and the circular hole radius of the circular hole array is 175nm, and the array period is 519.25nm; when the sensitive element is put into the detected environment, it will deform due to the change of environmental pressure. Preferably, when the size of the Si sheet beam is 250um×250um×0.5um, the lower detection limit is 7.14×10 ^-4 Pa, and the sensitivity is 2.17×10 ⁶ (pm/kPa).

The Si sheet beam is constrained in a cuboid base; an optical fiber is suspended above the base; the optical fiber is connected with an optical circulator; the optical circulator is connected with a spectrometer.

The principle of the present invention is as follows: the laser emits a signal light, the signal light is coupled to the Si sheet beam through the optical circulator, the change of the environmental pressure will cause the deformation of the Si sheet beam to change, thereby affecting the return value of the signal light, and finally reflected The result is that the wavelength value of the light output from the third end of the optical circulator changes.

Fig. 1 is described MEMS pressure sensor test system schematic diagram, comprises laser, optical circulator, sensitive element and spectrometer among the figure; Described laser is connected with described optical circulator, and described optical circulator is connected with described laser, described optical circulator respectively The sensitive element is connected to the spectrometer; the laser emits a signal laser to the optical circulator, the signal laser is coupled to the sensitive element through the optical circulator, and the signal light returned from the sensitive element is output to the spectrometer through the optical circulator again, so that the signal can be obtained The wavelength of light changes.

Fig. 2 is the comsol simulation structure diagram of the sensitive element, in the figure is a Si sheet with a length of 20um, a width of 20um, and a height of 0.5um, and an array of circular holes is distributed on the Si sheet, and the radius of the circular holes of the array of circular holes is 175nm , with an array period of 519.25 nm, thus constituting a photonic crystal plate whose on-chip photonic resonance is less susceptible to out-of-plane scattering losses than expected due to its unique topological properties.

In the first embodiment of the MEMS pressure sensor based on topological photonic high-Q cavity, we restrict the four sides of the Si sheet beam, and discuss the Si sheet beam from the two dimensions of the size and thickness of the Si sheet beam. Influencing factors of detection limit and sensitivity.

FIG. 3 is a comsol simulation result diagram of the deformation of the Si sheet beam described in Embodiment 1 of the MEMS pressure sensor based on the topological photonic high-Q cavity. When the detected environmental pressure changes, the Si sheet beam will be deformed accordingly. The amount of deformation is expressed as the total displacement on the surface. In the figure, the four sides of the Si sheet beam are constrained, the length is 20um, the width is 20um, the height is 0.5um, the surface load is 80N/m^2, the distance from the center of the beam to the edge is 10um, and the relative deformation is about 1×10 ^-5 um, reaching a micron The deformation of one millionth of the magnitude.

FIG. 5 is a curve diagram of the detection lower limit corresponding to Si sheet beams of different sizes in Embodiment 1 of the MEMS pressure sensor based on a topological photonic high-Q cavity. It can be seen from the figure that the larger the size, the lower the detection limit and the higher the detection accuracy. Taking the side length of the Si sheet beam as the X axis and the lower detection limit as the Y axis, the formula of the fitting curve can be obtained as Y=816163X ^−3.002 . The optimal size of the Si sheet beam selected by the sensor is 250um×250um. Preferably, the side length and thickness of the Si sheet beam are selected to be 250um and 0.5um, respectively.

Fig. 6 is a curve diagram of the detection lower limit corresponding to Si sheet beams with different thicknesses in Embodiment 1 of the MEMS pressure sensor based on the topological photonic high-Q cavity. It can be seen from the figure that the thinner the thickness, the lower the detection limit and the higher the detection accuracy. Taking the thickness of the Si sheet beam as the X axis and the lower detection limit as the Y axis, the formula of the fitting curve can be obtained as Y=0.5625X ² −0.2457X+0.0348. The optimum thickness of the Si sheet beam selected in the present invention is 0.5um. When a Si sheet beam with a length of 250um, a width of 250um and a thickness of 0.5um is selected, the lower detection limit of the sensitive element is 0.0364Pa, and the sensitivity is 4.25×10 ⁴ pm/kPa.

Example 2

In the second embodiment of the MEMS pressure sensor based on topological photonic high-Q cavity, the Si sheet beam is unilaterally constrained, and the side length, detection limit, sensitivity and Q value of the Si sheet beam are discussed respectively. the relationship between the four.

Fig. 4 is the comsol simulation result diagram of the deformation variable of the Si sheet beam described in the embodiment 2 of the MEMS pressure sensor based on the topological photonic high-Q cavity, the surface load is 1.6N/m^2, and the edge to the constraint with the highest degree of deformation The distance between the sides is 20um, and the relative deformation is about 2×10 ^-5 um, which also reaches a deformation of one millionth of a micron level.

Fig. 7 is a graph showing the sensitivity relationship curves corresponding to different sizes of unilaterally constrained Si sheet beams in Embodiment 2 of the MEMS pressure sensor based on the topological photonic high-Q cavity, wherein the dotted line represents the situation where the Q value is 10 ⁶ , and the solid line represents The case where the Q value is 10 ⁵ ; it can be seen from the figure that the sensitivity of the Si sheet beam has nothing to do with the Q value, and the larger the size, the higher the sensitivity. Fig. 8 is the curve diagram of the lower limit of detection corresponding to different sizes of unilaterally constrained Si sheet beams in Example 2, wherein the dotted line represents the situation where the Q value is 10 ⁶ , and the solid line represents the situation where the Q value is 10 ⁵ ; it can be seen from the figure It can be seen that the detection limit of the Si sheet beam is related to the Q value, the larger the size, the smaller the detection limit and the higher the detection accuracy. Fig. 9 is the sensitivity relation graph corresponding to the different Q values of the Si sheet beam of unilateral restraint in embodiment two, wherein the dotted line represents the situation that the side length is 50um, and the solid line represents the situation that the side length is 20um; As can be seen from the figure It is shown that the sensitivity of the Si sheet beam has nothing to do with the Q value, and the larger the size, the higher the sensitivity. Fig. 10 is the detection lower limit relationship graph corresponding to the different Q values of the Si sheet beam of unilateral constraint in embodiment two, wherein the dotted line represents the situation that the side length is 50um, and the solid line represents the situation that the side length is 20um; As can be seen from the figure It is found that the detection limit of the Si sheet beam is related to the Q value, and the larger the size, the smaller the detection limit. When a Si sheet beam with a length of 250um, a width of 250um, and a thickness of 0.5um is selected, the lower detection limit of the sensitive element is 7.14×10 ^{- 4} Pa, the sensitivity is 2.17×10 ⁶ pm/kPa. From Fig. 7, Fig. 8, Fig. 9, the following conclusions can be summed up in the four pictures of Fig. 10: the sensitivity of the Si sheet beam has nothing to do with the Q value, the larger the size, the higher the sensitivity, the detection limit is related to the Q value (inversely proportional), and the size The larger the value, the smaller the detection limit. The higher the Q value and the larger the size, the better the performance of the sensitive element.

For the Si sheet beam sensitive element with a circular hole array of the sensor, two connection structures are proposed here: Figure 11 is a schematic structural diagram of a disc-shaped Si sheet beam connection abutment, and the material of the cuboid abutment in the figure is two Silicon oxide, the size is 20um×20um×5um, there is a cylindrical hole with a radius of 5um and a height of 5um in the center of the cuboid abutment; the disc-shaped Si sheet beam has a radius of 5um and a thickness of 0.5um, and is horizontally embedded in the cylindrical hole , the upper surface of the disc-shaped Si sheet beam is 2.25um away from the upper surface of the cuboid base.

Figure 12 is a schematic diagram of the structure of a square-shaped Si beam-connected abutment. In the figure, the cuboid abutment is made of silicon dioxide, and its size is 20um×20um×5um. There is a 10um long, 10um wide, and high A cuboid hole of 5um; the square sheet-shaped Si sheet beam is 10um long, 10um wide, and 0.5um thick, and is horizontally embedded in the rectangular parallelepiped hole, and the upper surface of the square sheet-shaped Si sheet beam is separated from the upper surface of the cuboid abutment 2.25um.

The above description is only an embodiment of the present invention, and is not limited to the content disclosed in the embodiment and the accompanying drawings. The description of this implementation is only used to help understand the method of the present invention and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation and scope of application. The contents of the description should not be construed as limiting the present invention. Various obvious changes made to it without departing from the spirit of the method described in the present invention and the scope of the claims are within the protection scope of the present invention.

Claims (1)

1. A MEMS pressure sensor based on a topological photon high-Q cavity, comprising 1 Si sheet beam, and the Si sheet beam is connected with a base, it is characterized in that: the material of the base is silicon dioxide; wherein the The Si sheet beam is an ordered photonic crystal plate; the photonic crystal plate is provided with a periodic array of circular holes; The period of the periodic circular hole array is 519.25nm, and the circular hole radius is 175nm; The photonic crystal plate is a regular polygon and the thickness of the regular polygon is 0.5um; The regular polygon of the regular polygon has a side length of 4 and a side length range of 20um to 250um; The Si-sheet beam is a square sheet and its constraints are four-sided constraints; The relationship between the thickness Z of the Si sheet beam and the lower limit of detection Y is: Y＝0.5625Z ² -0.2457Z+0.0348; And the unit of Z is um, and the unit of Y is Pa; The relationship between the side length X of the Si sheet beam and the lower detection limit Y is: Y=816163X ^-3.002 ; the unit of X is um, and the unit of the lower detection limit Y is Pa; There is a cuboid hole in the middle of the abutment; the square-shaped Si-sheet beam is horizontally embedded in the cuboid hole; The connection and working process of the MEMS pressure sensor based on the topological photonic high-Q cavity are as follows: Step 1, constraining the Si sheet beam of the MEMS pressure sensor in the cuboid abutment; Step 2, connecting an optical fiber above the cuboid abutment; Step 3, connecting the optical fiber to an optical circulator; Step 4, connecting the optical circulator to a spectrometer; Step 5. When the detected environmental pressure changes, the Si sheet beam is deformed; Step 6, the pressure value corresponding to the deformation of the Si sheet beam is displayed on the spectrometer; So far, from step 1 to step 6, the pressure connection and testing process using a MEMS pressure sensor based on a topological photonic high-Q cavity is completed.

Images