CN211504500U

CN211504500U - Micro-pressure sensor

Info

Publication number: CN211504500U
Application number: CN202020199875.XU
Authority: CN
Inventors: 赵晓锋; 武静; 刘义波; 温殿忠
Original assignee: Heilongjiang University
Current assignee: Heilongjiang University
Priority date: 2020-02-19
Filing date: 2020-02-19
Publication date: 2020-09-15
Anticipated expiration: 2030-02-19

Abstract

The utility model discloses a micro-pressure sensor, which comprises an SOI substrate, wherein an elastic element and a sensitive element are arranged on the SOI substrate to realize the measurement of externally-applied micro-pressure; the sensing element is a Wheatstone bridge structure formed by four piezoresistors on the ladder-shaped beam structure. The utility model discloses a microelectronic machining technique makes elasticity silicon membrane, four trapezoidal beam structures and four piezo-resistor on the SOI wafer, has the characteristics that integrate and miniaturize, and the micro-pressure sensor of constitution can realize external pressure's detection and can realize the micro-pressure and measure.

Description

Micro-pressure sensor

Technical Field

The utility model relates to a sensor technical field, concretely relates to micro-pressure sensor.

Background

A micro-pressure sensor, also called a micro-pressure sensor, is a sensor for measuring micro-pressure. Such sensors require high sensitivity, i.e. a large electrical signal output under a small pressure. Such sensors are in urgent need in medical (intraocular pressure, intracranial pressure, etc.), automotive, smart home, process control, etc.

At present, in order to realize micro-pressure measurement, the adopted structure mainly comprises a square silicon film structure, a rectangular beam film structure and the like, when the measuring range of the sensor is small to a certain degree, the square silicon film is required to be very thin so as to ensure enough high sensitivity, and at the moment, the large deflection effect of the square silicon film structure becomes a prominent contradiction, so that the nonlinearity of the sensor is increased, and the measurement accuracy is rapidly reduced. The rectangular beam in the rectangular beam membrane structure can realize stress concentration, so that the sensitivity of the sensor is improved, the defect of poor linearity when the membrane is very thin is effectively overcome, but the sensitivity cannot meet the special requirements of some micro-pressure measurement, such as medical treatment and the like.

Therefore, a technical problem to be solved is to provide a micro-pressure sensor with high sensitivity, good linearity and high integration degree.

SUMMERY OF THE UTILITY MODEL

In order to overcome the above problems, the present inventors have conducted intensive studies to design a micro-pressure sensor, which utilizes an insulating layer Silicon (SOI) wafer device layer to form an elastic silicon film, and make four isosceles trapezoidal beams on the silicon film, and make four piezoresistors on the four trapezoidal beams respectively to constitute a wheatstone bridge structure, thereby realizing the detection of micro-pressure, and thus completed the present invention.

Particularly, the utility model aims at providing following aspect:

in a first aspect, a micro-pressure sensor is provided, wherein the micro-pressure sensor includes an SOI substrate, and an elastic element and a sensing element are disposed on the SOI substrate to implement measurement of externally applied micro-pressure.

In a second aspect, a manufacturing process of the micro-pressure sensor according to the first aspect is provided, where the manufacturing process includes the following steps:

step 1, zero-time photoetching and dry etching are carried out on an SOI wafer register mark;

step 2, cleaning the SOI wafer;

step 3, primary oxidation is carried out, and a thin oxygen layer with the thickness of 30 nm-50 nm grows on the device layer 3;

step 4, carrying out primary photoetching to etch P^-Injecting boron ions into the area window to form a P-type piezoresistor;

step 5, removing the photoresist, and cleaning the SOI wafer;

step 6, secondary photoetching and etching P⁺Forming a window, implanting boron ions to form P⁺A region serving as an ohmic contact;

step 7, carrying out high-temperature annealing after the ion implantation process;

step 8, removing the thin oxygen layer by BOE, and cleaning the SOI wafer;

step 9, secondary oxidation, growing a second insulating layer on the device layer 3 by a PECVD method, wherein the thickness of the second insulating layer is 300-500 nm;

step 10, etching the second insulating layer 4 by three times of photoetching to form a lead hole of the piezoresistor;

step 11, cleaning the SOI wafer, and evaporating metal aluminum on the second insulating layer 4;

step 12, performing four times of photoetching, and etching the metal aluminum to form a metal aluminum interconnection line and an aluminum electrode;

step 13, cleaning the SOI wafer, and growing Si on the device layer 3 by PECVD₃N₄A passivation layer with a thickness of 100nm to 200 nm;

step 14, performing photoetching for five times, and etching the passivation layer to form a pressure welding point;

step 15, cleaning the SOI wafer, and carrying out an alloying process at 350-450 ℃, preferably 420 ℃ for 20-40 min to form ohmic contact;

step 16, performing six times of photoetching, and etching the device layer 3 to form a ladder-shaped beam structure;

step 17, carrying out seven times of photoetching, etching the support substrate 1 of the SOI wafer to the first insulating layer 2 to form an elastic silicon film;

and step 18, cleaning the SOI wafer, and bonding the SOI wafer support substrate 1 with borosilicate glass.

Step 19, spin-coating scribing protective glue on the surface of the SOI wafer, and removing the chip surface protective glue by adopting an acetone solution after the SOI wafer is scribed;

and 20, cleaning, packaging the chip and finishing the process manufacturing of the micro-pressure sensor.

In a third aspect, a micro-pressure sensor manufactured by the manufacturing method of the second aspect is provided.

The utility model discloses the beneficial effect who has includes:

(1) the micro-pressure sensor provided by the utility model realizes the effective combination of the elastic silicon film, the isosceles trapezoid beam and the piezoresistor on the Silicon On Insulator (SOI) wafer, has the characteristics of integration and miniaturization, and simultaneously utilizes the stress concentration effect of the isosceles trapezoid beam to complete the detection of external micro-pressure, and can realize the measurement of the pressure in the range of 0-3 kPa;

(2) the micro-pressure sensor provided by the utility model utilizes the Silicon On Insulator (SOI) wafer device layer as the elastic silicon film, the thickness of the Silicon On Insulator (SOI) wafer device layer is easy to control, and the micro-pressure sensor can have better sensitivity consistency;

(3) the utility model provides a manufacturing process method of micro-pressure sensor, it is compatible high with current silicon technology, easy operation, the condition is easily controlled, is suitable for the large-scale production.

Drawings

Fig. 1 is a schematic view showing the overall structure of a micro-pressure sensor according to a preferred embodiment of the present invention;

fig. 2 is a schematic top view of a micro-pressure sensor according to a preferred embodiment of the present invention;

fig. 3 is a schematic cross-sectional view of a micro-pressure sensor according to a preferred embodiment of the present invention, wherein a in fig. 3 shows a schematic cross-sectional view along AA 'direction, and b in fig. 3 shows a schematic cross-sectional view along BB' direction;

fig. 4 shows a circuit diagram of the micro-pressure sensor of fig. 1 according to the present invention, wherein a in fig. 4 shows an equivalent circuit diagram of fig. 1, and b in fig. 4 shows a schematic circuit diagram of the present invention;

FIGS. 5-1 to 5-9 show a flow chart of the manufacturing process of the micro-pressure sensor of the present invention;

fig. 6 shows a simulated stress distribution diagram of a pressure sensor of different structures in experimental example 1 of the present invention; wherein a in fig. 6 shows a stress profile of a sensor having a square silicon film structure, b in fig. 6 shows a stress profile of a sensor having a rectangular beam film structure, and c in fig. 6 shows a stress profile of a sensor having an isosceles trapezoid silicon film structure;

fig. 7 shows a change curve of output voltage and applied pressure of a pressure sensor of different structure in experimental example 2 of the present invention;

fig. 8 shows the output voltage and applied pressure variation curve of the isosceles trapezoid beam film structure micro-pressure sensor with different long edges and waist included angles in experimental example 3 of the present invention.

The reference numbers illustrate:

1-a support substrate;

2-a first insulating layer;

3-a device layer;

4-a second insulating layer;

5-P⁺a zone;

6-P^-a zone;

7-a lead hole;

8-an interconnect line;

9-a passivation layer;

10-a thin oxygen layer;

an L-ladder beam structure;

alpha-the angle between the long side and the waist;

L₁-a first ladder beam;

L₂-a second ladder beam;

L₃-a third ladder beam;

L₄-a fourth ladder beam;

R₁-a first varistor;

R₂-a second varistor;

R₃-a third varistor;

R₄-a fourth varistor;

Δ R-resistance change value;

V_DD-a power source;

GND-ground;

V_OUT1-a first output voltage;

V_OUT2-a second output voltage.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. The features and advantages of the present invention will become more apparent from the description.

The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

The utility model discloses a first aspect provides a micro-pressure sensor, as shown in FIG. 1, the sensor includes the SOI substrate be provided with elastic element and sensing element on the SOI substrate to realize the measurement to external micro-pressure that adds.

The SOI is silicon on an insulating layer, and the dielectric isolation of a device layer and a substrate is realized through the insulating layer.

According to a preferred embodiment of the present invention, the SOI substrate includes a supporting substrate 1, a first insulating layer 2, and a device layer 3, which are sequentially arranged from bottom to top.

In a further preferred embodiment, the support substrate 1 is a monocrystalline silicon wafer of <100> crystal orientation.

The inventor finds that the silicon film process manufacturing of the sensor chip is improved by selecting the monocrystalline silicon wafer with the crystal orientation of <100> as the supporting substrate.

In a further preferred embodiment, the thickness of the support substrate 1 is 300 to 500 μm, preferably 350 to 450 μm, and more preferably 400 μm.

According to a preferred embodiment of the present invention, the first insulating layer 2 is a silicon dioxide layer having a thickness of 500 to 800 nm.

In a further preferred embodiment, the thickness of the first insulating layer 2 is 550 to 750nm, preferably 650 nm.

According to a preferred embodiment of the present invention, the device layer 3 is n-type single crystal silicon having a <100> crystal orientation and a resistivity of 1 to 10 Ω · cm, preferably 3 to 5 Ω · cm.

In a further preferred embodiment, the device layer 3 has a thickness of 30 to 40 μm.

In a further preferred embodiment, a second insulating layer 4, which is a silicon dioxide layer with a thickness of 300 to 500nm, preferably 400nm, is disposed on the upper surface of the device layer 3.

According to a preferred embodiment of the present invention, as shown in FIGS. 1 to 3, the elastic element comprises an elastic silicon film, which is located on the SOI wafer device layer, corresponds to the etch window on the lower surface of the support substrate 1, and has a certain thickness,

the thickness of the elastic silicon film is preferably 30-40 μm, and more preferably 35 μm.

The inventors have studied and found that forming an elastic silicon film using a device layer of a silicon-on-insulator (SOI) wafer facilitates control of the thickness of the elastic silicon film.

In a further preferred embodiment, the elastic silicon membrane has a rectangular, square or circular shape, preferably a square shape.

The inventor researches and discovers that when the diameter of the circular diaphragm is equal to the side length of the square diaphragm, the natural frequency of the circular diaphragm is larger than that of the square diaphragm under the condition that the thickness of the silicon film is equal, and the square diaphragm with the size can obtain larger diaphragm deformation and larger transverse and longitudinal strain difference, so that the sensitivity of the sensor is favorably improved. Meanwhile, in terms of processing technology, the square diaphragm is easy to form through a wet etching process, and the process is simple. Therefore, the square elastic silicon film is preferably provided in the present invention.

According to a preferred embodiment of the present invention, the elastic element further comprises four ladder beam structures L disposed on the upper surface of the elastic silicon membrane,

the ladder beam structure comprises a first ladder beam L₁A second ladder beam L₂And a third ladder beam L₃And a fourth ladder beam L₄And the four trapezoidal beams are arranged in the middle of the edge of the upper surface of the elastic silicon film.

The inventor finds that the beam structure is additionally arranged on the upper surface of the elastic silicon film, so that the stress concentration effect is favorably applied.

In a further preferred embodiment, as shown in fig. 2, said first ladder beam L₁And a third ladder beam L₃Along the sensor chip<011>The crystal directions are symmetrically arranged, and the crystal orientation is symmetrical,

the second ladder beam L₂And a fourth ladder beam L₄Along the sensor chip<01_1>The crystal orientation is symmetrically arranged.

In a further preferred embodiment, said first ladder beam L₁A second ladder beam L₂And a third ladder beam L₃And a fourth ladder beam L₄Are all isosceles trapezoidal beams,

preferably, the included angle between the long side and the waist of the isosceles trapezoid-shaped beam is alpha, and the range of alpha is 80-89 degrees, and is preferably 87 degrees.

Wherein, set up the roof beam into isosceles trapezoid roof beam, and set up the contained angle of long limit and waist as above-mentioned angle, be favorable to improving stress concentration effect.

More preferably, the long sides of the four isosceles trapezoidal beams are close to the central position of the sensor.

In the present invention, it is preferable to use a square elastic silicon film and a first ladder beam L thereon₁A second ladder beam L₂And a third ladder beam L₃And a fourth ladder beam L₄The beam structure is used as an elastic element, and the isosceles trapezoid beam has good stress concentration effect at the root part, so that the micro-pressure can be measured, and the sensitivity is improved.

According to a preferred embodiment of the present invention, the sensitive element comprises a first varistor R arranged in series₁Second, secondVoltage dependent resistor R₂A third voltage dependent resistor R₃And a fourth varistor R₄Respectively arranged on the first trapezoidal beam L₁A second ladder beam L₂And a third ladder beam L₃And a fourth ladder beam L₄。

The four piezoresistors form a Wheatstone bridge structure so as to realize the detection of external pressure.

In a further preferred embodiment, the first varistor R₁A second voltage dependent resistor R₂A third voltage dependent resistor R₃And a fourth varistor R₄Respectively located in the stress areas of the corresponding isosceles trapezoid beams.

In a further preferred embodiment, the first varistor R₁And a third varistor R₃Along the sensor chip<011>The crystal directions are symmetrically arranged, and the crystal orientation is symmetrical,

the second piezoresistor R₂And a fourth varistor R₄Along the sensor chip<01_1>The crystal orientation is symmetrically arranged.

According to a preferred embodiment of the present invention, as shown in fig. 2 and 4, the first varistor R₁And a fourth varistor R₄Is connected with a power supply V at the connecting end_DDConnecting; the second piezoresistor R₂And a third varistor R₃Is connected with the ground wire GND.

In a further preferred embodiment, the first varistor R₁And the other end of the second voltage dependent resistor R₂Is connected with the other end of the first output voltage V_OUT1；

The third piezoresistor R₃And the other end of the fourth voltage dependent resistor R₄Is connected with the other end of the first output voltage, and the connecting end is a second output voltage V_OUT2。

In the utility model, by measuring the first output voltage V_OUT1And a second output voltage V_OUT2The difference in the values of (a) and (b) enables detection of the applied pressure. Specifically, under an applied pressure, the elastic silicon film springsThe resistance value of the piezoresistor is changed through the sexual deformation, the resistance change value is △ R, the output voltage is changed accordingly, and therefore the pressure detection is achieved.

The inventor researches and discovers that compared with the traditional silicon device layer, the utility model discloses in adopt the SOI wafer as the substrate to make piezo-resistor in the stress concentration region of isosceles trapezoid roof beam, can show improvement the sensitivity of minute-pressure sensor.

According to a preferred embodiment of the present invention, the interconnection line 8 is further formed on the upper surface of the second insulating layer 4, and is obtained by a vacuum evaporation technique.

The second aspect of the present invention provides a manufacturing process of the micro-pressure sensor of the first aspect, as shown in fig. 5-1 to 5-9, the manufacturing process includes the following steps:

step 1, photoetching the plate alignment mark (zero-time photoetching), and etching the plate alignment mark by adopting a dry method.

The dry etching refers to a process technology for etching away the exposed surface material on the silicon wafer by utilizing the plasma generated in the gas state to generate physical and chemical reactions with the silicon wafer exposed to the plasma.

And 2, cleaning the SOI wafer.

The utility model discloses in, adopt RCA standard cleaning method to wash the silicon substrate, wash as follows: the monocrystalline silicon substrate is boiled to be white smoke by concentrated sulfuric acid, is washed by a large amount of deionized water after being cooled, and is washed twice by electronic cleaning liquids No. 1 and No. 2 respectively (the main components and the volume ratio of the No. 1 liquid are ammonia water, hydrogen peroxide and water are 1:1:5, wherein the concentration of the ammonia water is 27 percent, and the concentration of the hydrogen peroxide is 30 percent, and the main components and the volume ratio of the No. 2 liquid are hydrochloric acid, hydrogen peroxide and water are 1:1:5, wherein the concentration of the hydrochloric acid is 37 percent, and the concentration of the hydrogen peroxide is 30 percent), and then is washed by a large amount of deionized water, and finally is put into a spin dryer for spin drying.

In a further preferred embodiment, the support substrate 1 is a monocrystalline silicon wafer of n-type <100> crystal orientation.

According to a preferred embodiment of the present invention, the first insulating layer 2 is a silicon dioxide layer, and the thickness thereof is 500 to 800nm, preferably 550 to 750nm, and more preferably 650 nm.

According to a preferred embodiment of the present invention, the device layer 3 is n-type <100> crystal orientation single crystal silicon, and has a resistivity of 1 to 10 Ω · cm, preferably 3 to 5 Ω · cm.

In a further preferred embodiment, the device layer 3 has a thickness of 30 to 50 μm.

And 3, carrying out primary oxidation, and growing a thin oxygen layer 10 with the thickness of 30-50 nm (shown in figure 5-1) on the device layer 3.

The thin oxygen layer is grown by a thermal oxidation method, namely, the cleaned SOI wafer is put into a high-temperature oxidation furnace to be oxidized, and the thin oxygen layer (namely, a silicon dioxide layer) is grown by oxidation by taking oxygen as a gas source.

According to a preferred embodiment of the present invention, the thickness of the thin oxygen layer is 30 to 50nm, preferably 40 nm.

Step 4, carrying out primary photoetching to etch P^-And (4) implanting boron ions into the area window 6 to form the P-type piezoresistor (shown in figure 5-2).

Wherein the boron B ion implantation is performed by an ion implanter.

According to a preferred embodiment of the present invention, the implantation energy of the boron ions is 40 to 80keV, preferably 50 to 70keV, such as 60 keV.

In a further preferred embodiment, the implantation dose of the boron ions is 1 × 10¹²cm^-2～1.5×10¹⁴cm^-2Preferably 1 × 10¹³cm^-2～1×10¹⁴cm^-2。

In the present invention, the photolithography process is a common method in the prior art, and includes spin coating, prebaking, exposing, developing, hardening, etching, and removing photoresist.

The type of the primer adopted in the glue homogenizing process is preferably LOR10B, and the type of the positive photoresist adopted is preferably AZ 1500.

And 5, removing the photoresist and cleaning the SOI wafer.

Step 6, secondary photoetching and etching P⁺ A region window 5, implanting boron ions to form P⁺And (4) forming ohmic contacts (as shown in fig. 5-3).

In a further preferred embodiment, the implantation dose of the boron ions is 1 × 10¹⁵cm^-2～8×10¹⁵cm^-2Preferably 5 × 10¹⁵cm^-2。

Wherein, four piezoresistors are formed by the process.

And 7, performing high-temperature annealing after the ion implantation process.

Wherein the annealing temperature is 800-1200 ℃, preferably 900 ℃, and the annealing time is 15-40 min, preferably 30 min.

And 8, removing the thin oxygen layer by BOE, and cleaning the SOI wafer.

In the present invention, it is preferable to adopt BOE (buffered Oxide etch) solution to remove the thin oxygen layer, wherein BOE is buffered Oxide etching solution, and the volume ratio of hydrofluoric acid with a concentration of 49% to water is 1: 6, mixing the components.

Step 9, secondary oxidation, and growing a second insulating layer 4 on the device layer 3 by a PECVD method (as shown in FIGS. 5-4).

Wherein, a second insulating layer is grown by a Plasma Enhanced Chemical Vapor Deposition (PECVD) method, is a silicon dioxide insulating layer, and has a thickness of 300-500 nm, preferably 400 nm.

And 10, etching the second insulating layer 4 by three times of photoetching to form a lead hole (7) of the piezoresistor (shown in figures 5-5).

And 11, cleaning the SOI wafer, and evaporating metal aluminum on the second insulating layer 4 by adopting a vacuum evaporation technology.

Wherein the thickness of the evaporated metal aluminum is 0.5-1.0 μm.

And step 12, four times of photoetching is carried out, and the metal aluminum is etched to form a metal aluminum interconnection line 8 and an aluminum electrode (shown in figures 5-6).

Step 13, cleaning the SOI wafer, and growing a passivation layer 9 on the device layer 3 by PECVD (as shown in FIGS. 5-7);

wherein the passivation layer is Si₃N₄The thickness is 100 to 200nm, preferably 150 nm.

step 15, cleaning the SOI wafer, and forming ohmic contact by an alloying process;

according to the utility model relates to a preferred embodiment, alloying is handled and is gone on under the vacuum environment, and the processing temperature is 350 ~ 450 ℃, preferably 420 ℃.

In a further preferred embodiment, the time of the alloying treatment is 20 to 40min, preferably 30 min.

The temperature and time of the alloying treatment can enhance the adhesive force of the aluminum electrode, eliminate the Schottky barrier and form ohmic contact.

Step 16, performing six times of photoetching, and etching the device layer 3 to form a ladder-shaped beam structure L (shown in FIGS. 5-8);

according to a preferred embodiment of the present invention, the first ladder beam L₁A second ladder beam L₂And a third ladder beam L₃And a fourth ladder beam L₄Are formed by etching by adopting an ICP (inductively coupled plasma) technology.

The ICP refers to an inductively coupled plasma technology, which is one of the key technologies in the processing of mems devices.

In a further preferred embodiment, the etching thickness is 3 to 7 μm, and preferably 5 μm.

Wherein, the ICP technology is adopted to etch the front surface of the chip to form a first ladder-shaped beam L₁A second ladder beam L₂And a third ladder beam L₃And a fourth ladder beam L₄Are all isosceles trapezoidal beams,

preferably, the included angle between the long side and the waist of the isosceles trapezoid-shaped beam is alpha, and the range of alpha is 85-89 degrees, and is preferably 87 degrees.

Step 17, etching the support substrate 1 of the SOI wafer by seven times of photoetching until the first insulating layer 2 is etched to form an elastic silicon film (shown in FIGS. 5-9);

the support substrate 1 of the SOI wafer is etched by adopting an ICP etching technology through a double-sided photoetching alignment process to a first insulating layer 2, so that an elastic silicon film is formed.

The utility model discloses in, utilize SOI device layer formation elasticity silicon membrane, have the characteristics of integrating and miniaturizing, easily control the thickness of elasticity silicon membrane moreover, can show the sensitivity that improves the micro-pressure sensor.

According to a preferred embodiment of the present invention, the thickness of the elastic silicon film is preferably 30 to 40 μm, and more preferably 35 μm.

The utility model discloses a micro-electronic mechanical processing technique (MEMS), processing produces elasticity silicon membrane, four isosceles trapezoid roof beams and four piezo-resistor on the SOI wafer, has the characteristics of integrating and miniaturizing, because the existence of isosceles trapezoid roof beam makes isosceles trapezoid roof beam root produce fine stress concentration effect simultaneously, based on the piezoresistive effect, can realize the measurement to plus minute-pressure.

The third aspect of the present invention provides a micro-pressure sensor manufactured by the manufacturing method of the second aspect.

Examples of the experiments

Experimental example 1

Adopt ANSYS15.0 software respectively to have square silicon membrane's pressure sensor, have the pressure sensor of rectangle roof beam membrane structure and micropressure sensor with isosceles trapezoid roof beam membrane structure carry out the characteristic simulation.

And (3) carrying out stress analysis on the sensor according to the following steps:

(1) constructing entity models of three structural sensors by ANSYS15.0 software, wherein the chip sizes of the three sensors are 5000 micrometers multiplied by 5000 micrometers, and the sizes of the elastic silicon films are 4000 micrometers multiplied by 4000 micrometers;

the thickness of the film in the square silicon film structure is 35 mu m, the thickness of the film in the rectangular beam film structure and the isosceles trapezoid beam film structure is 30 mu m, the thickness of the beam in the rectangular beam film structure is 5 mu m, the length of the beam in the rectangular beam film structure is 580 mu m, the width of the beam in the rectangular beam film structure is 340 mu m, the length of the long side of the beam in the isosceles trapezoid beam film structure is 340 mu m, the height of the long side of the beam in the isosceles trapezoid beam film structure is 580 mu m.

(2) The material parameters were set, and the Young's modulus of Si was set to 1.33 × 10⁵MPa, coefficient of expansion set to 2.8 × 10^-6K^-1The poisson's ratio is set to 0.35.

(3) Dicing with a dicing die (for uniform meshing), then performing a full-body combination, and performing meshing, wherein the mesh size is 80 μm in the meshing, boundary conditions are set, the degrees of freedom of all the side surfaces of the chip (i.e., x, y, and z directions) are set to be 0, pressure is applied, and the pressure applied to the surface of the chip is 3kPa, and stress simulation is performed.

The simulation results are respectively shown as a, b and c in fig. 6, and it can be seen from the stress distribution diagrams of the three structures that the stress extreme value of the silicon film in the square silicon film structure pressure sensor is 9.4MPa and is distributed at the centers of the four edges of the silicon film and is distributed symmetrically; the stress extreme value of an elastic element in the pressure sensor with the rectangular beam film structure is 14.8MPa, and the elastic element is distributed at the tail ends of the four short beams and is symmetrically distributed; the utility model discloses in isosceles trapezoid roof beam membrane structure minute-pressure sensor in elastic element's stress extreme value be 15.6MPa and distribute at four isosceles trapezoid roof beam end and symmetric distribution.

Obviously, compare with square silicon membrane structure and rectangle roof beam membrane structure, micropressure sensor elastic element who is provided with isosceles trapezoid roof beam membrane structure have better stress concentration.

Experimental example 2

Adopt ANSYS15.0 software respectively to have square silicon membrane's pressure sensor, have the pressure sensor of rectangle roof beam membrane structure and the pressure sensitive characteristic of the micro-pressure sensor with isosceles trapezoid roof beam membrane structure simulate, go on according to following step:

(1) the chip size of the three sensors is 5000 micrometers multiplied by 5000 micrometers, the size of the silicon film is 4000 micrometers multiplied by 4000 micrometers, and the film thickness in the square silicon film structure is 35 micrometers; the film thickness in the rectangular beam film structure and the isosceles trapezoid beam film structure is 30 micrometers, the beam thickness is 5 micrometers, the beam length in the rectangular beam film structure is 580 micrometers, and the beam width in the rectangular beam film structure is 340 micrometers; the length of the long side of the beam in the isosceles trapezoid beam film structure is 340 micrometers, the height of the long side of the beam is 580 micrometers, and the included angle between the long side and the waist is 87 degrees; the resistive track size is 100 μm by 20 μm.

(2) And cutting a slicing module, meshing, defining boundary conditions, and finally applying a power supply voltage of 5V, an external pressure of 0kPa-3kPa and a step length of 0.5 kPa.

The relationship curve of the output voltage and the applied pressure is simulated, and the simulation result is shown in fig. 7.

From the simulation results of fig. 7, it can be seen that the output voltages of the three types of structure sensors increase with the increase of the applied pressure, wherein the square silicon film structure pressure sensor has the maximum output voltage at the applied pressure of 3kPa, and the maximum output voltage is 15.9 mV; the rectangular beam membrane structure pressure sensor has the maximum output voltage when the external pressure is 3kPa, and the maximum output voltage is 33.8 mV; be provided with micropressure sensor of isosceles trapezoid beam membrane structure have the maximum output voltage when external pressure is 3kPa, the maximum output voltage is 69.1 mV.

According to the aforesaid, among three kinds of structure pressure sensor, square silicon membrane structure pressure sensor's full scale output voltage is minimum, be provided with isosceles trapezoid beam film structure's minute-pressure sensor's full scale output voltage maximum, for square silicon membrane structure pressure sensor's full scale output voltage's 2 times. Therefore, compare with square silicon membrane structure, rectangle beam membrane structure pressure sensor, the micropressure sensor who is provided with isosceles trapezoid beam membrane structure have the highest sensitivity.

Experimental example 3

Adopting ANSYS15.0 software to simulate the voltage output characteristics of the micro-pressure sensor provided with an isosceles trapezoid beam film structure (the included angle between the long edge and the waist is different), and carrying out the following steps:

(1) the method comprises the following steps of constructing an entity model, wherein the chip size of a pressure sensor with an isosceles trapezoid beam film structure is 5000 micrometers multiplied by 5000 micrometers, the size of a silicon film is 4000 micrometers multiplied by 4000 micrometers, the film thickness is 30 micrometers, the beam thickness is 5 micrometers, the long side of a beam in the isosceles trapezoid beam film structure is 340 micrometers long and 580 micrometers high, the included angles alpha between the long side and the waist are respectively 87 degrees, 88 degrees, 89 degrees and 90 degrees, and the size of a resistor strip is 100 micrometers multiplied by 20 micrometers.

The relationship curve between the output voltage of the sensor and the applied pressure is simulated, and the simulation result is shown in fig. 8.

As can be seen from fig. 8, the full-scale output voltage of the micro-pressure sensor with the isosceles trapezoid beam film structure (the included angle between the long side and the waist is different) increases with the increase of the applied pressure, and the full-scale output voltage value gradually increases with the decrease of the included angle α between the long side and the waist. When the included angle is alpha which is 90 degrees and the applied pressure is 3kPa, the full-scale output voltage of the sensor is 33.8 mV; when the included angle alpha is 89 degrees and the applied pressure is 3kPa, the full-scale output voltage of the sensor is 66.5 mV; when the included angle alpha is 88 degrees, the output voltage of the sensor is 64.2mV when the applied pressure is 3 kPa; when the included angle alpha is 87 degrees, and the applied pressure is 3kPa, the full-scale output voltage of the sensor is 69.1 mV.

Therefore, the pressure sensor with the isosceles trapezoid beam membrane structure has the maximum sensitivity of 23.0mV/kPa when the maximum full-scale output voltage is 69.1mV when the included angle alpha is 87 deg.

In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front", "rear", and the like indicate the position or positional relationship based on the operation state of the present invention, and are only for convenience of description and simplification of description, but do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; the connection may be direct or indirect via an intermediate medium, and may be a communication between the two elements. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art.

The present invention has been described above in connection with preferred embodiments, which are merely exemplary and illustrative. On this basis, can be right the utility model discloses carry out multiple replacement and improvement, these all fall into the utility model discloses a protection scope.

Claims

1. A micro-pressure sensor is characterized by comprising an SOI substrate, wherein an elastic element and a sensitive element are arranged on the SOI substrate to realize the measurement of externally-applied micro-pressure;

the SOI substrate comprises a supporting substrate (1), a first insulating layer (2) and a device layer (3) which are sequentially arranged from bottom to top;

the thickness of the device layer (3) is 30-50 mu m;

the elastic element comprises an elastic silicon film which is positioned on the device layer (3) and corresponds to the corrosion window on the lower surface of the supporting substrate (1),

the device layer thickness is the thickness of the elastic silicon film,

the thickness of the elastic silicon film is 30-40 mu m;

the elastic element also comprises four ladder-shaped beam structures (L) arranged on the upper surface of the elastic silicon film,

the ladder beam structure (L) comprises a first ladder beam (L)₁) A second ladder beam (L)₂) A third ladder beam (L)₃) And a fourth ladder beam (L)₄) The four trapezoidal beams are arranged in the middle of the edge of the upper surface of the elastic silicon film,

the first ladder beam (L)₁) A second ladder beam (L)₂) A third ladder beam (L)₃) And a fourth ladder beam (L)₄) Are all isosceles trapezoidal beams.

2. The micro-pressure sensor according to claim 1, wherein the isosceles trapezoidal beam has an angle α between the long side and the waist, the angle α is in the range of 80 ° to 89 °,

the long edges of the four isosceles trapezoidal beams are close to the center of the sensor.

3. Micro-pressure sensor according to claim 1, characterized in that the first ladder-shaped beam (L)₁) And a third ladder beam (L)₃) Along the sensor chip<011>The crystal directions are symmetrically arranged, and the crystal orientation is symmetrical,

the second ladder beam (L)₂) And a fourth ladder beam (L)₄) Along the sensor chip

The crystal orientation is symmetrically arranged.

4. Micro-pressure sensor according to claim 3, characterized in that the sensitive element comprises a first piezoresistor (R)₁) A second voltage dependent resistor (R)₂) A third voltage dependent resistor (R)₃) And a fourth varistor (R)₄) Are respectively arranged at the firstLadder beam (L)₁) A second ladder beam (L)₂) A third ladder beam (L)₃) And a fourth ladder beam (L)₄) The above.

5. Micro-pressure sensor according to claim 4, characterized in that the first piezoresistor (R)₁) And a third varistor (R)₃) Along the sensor chip<011>The crystal directions are symmetrically arranged, and the crystal orientation is symmetrical,

the second piezoresistor (R)₂) And a fourth varistor (R)₄) Along the sensor chip

The crystal orientation is symmetrically arranged.

6. Micro-pressure sensor according to claim 4, characterized in that the first piezoresistor (R)₁) And a fourth varistor (R)₄) Is connected with one end of the power supply (V) and the connection end of the power supply (V)_DD) Connecting;

the second piezoresistor (R)₂) And a third varistor (R)₃) Is connected with the ground wire (GND).

7. The micro-pressure sensor according to claim 1, wherein a second insulating layer (4) is provided on the upper surface of the device layer (3), and is a silicon dioxide layer with a thickness of 300-500 nm.

8. The micro-pressure sensor according to claim 7, characterized in that an interconnection line (8) is also made on the upper surface of the second insulating layer (4).