CN105043603A - Capacitive pressure sensor provided with self-detection apparatus, and preparation method thereof - Google Patents

Abstract

The invention discloses a capacitive pressure sensor with a self-detection device, which includes a silicon substrate, a lower electrode, an insulating medium layer, a vacuum sealed cavity, an upper electrode, a passivation layer, and a metal lead; the silicon substrate is connected with a lower electrode; the insulating medium layer is located above the lower electrode; a vacuum-sealed cavity is provided above the insulating medium layer; the upper electrode of the sensor is located above the vacuum-sealed cavity; the passivation layer is grown above the upper electrode; the lower part of the metal lead extends into the passivation The electrode lead-out hole of the layer is in contact with the upper and lower electrodes. The capacitive pressure sensor uses electrostatic force to simulate the pressure value in actual detection, can quickly realize the change of the pressure value, and has higher efficiency when analyzing the performance of the sensor; at the same time, it also provides a preparation method of the pressure sensor, which is simple and easy.

Description

Capacitive pressure sensor with self-detection device and preparation method thereof

technical field

The invention relates to a pressure sensor, in particular to a capacitive pressure sensor with a self-detection device and a preparation method thereof.

Background technique

Among the products realized by silicon micromachining technology, the pressure sensor is a relatively mature category. At present, pressure sensors have been widely used in various industrial and biomedical fields. Capacitive pressure sensors have gradually become a hot spot for pressure sensors due to their high sensitivity, better temperature performance, low power consumption, no temperature drift, firm structure, and little influence from external stress. Before a sensor is formally put into industrial practice, a series of links such as testing and calibration must be carried out to study the performance of the sensor. The traditional detection method is to place the pressure sensor in the air box, and simulate the actual measurement environment by setting the pressure value. But there is a disadvantage in this traditional method. The set pressure value cannot be changed drastically. When it is necessary to change from one pressure value to another, it often takes a long time for the change. This is not conducive to simulating the actual measurement environment, and thus cannot accurately detect the performance of the pressure sensor.

Contents of the invention

Technical problem: The technical problem to be solved by the present invention is to provide a capacitive pressure sensor with a self-detection device, which uses electrostatic force to simulate the pressure value in the actual detection, and can quickly realize the change of the pressure value. When analyzing the performance of the sensor, with higher efficiency. At the same time, the preparation method of the sensor is provided, which is simple and easy.

Technical scheme: in order to solve the above technical problems, the technical scheme adopted in the present invention is:

A capacitive pressure sensor with a self-detection device, the pressure sensor includes a silicon substrate, a lower electrode, an insulating medium layer, an upper electrode, a passivation layer, and a metal lead; the lower electrode is fixedly connected to the top surface of the silicon substrate; the insulating The dielectric layer is fixedly connected to the top surface of the lower electrode; the upper electrode is located above the insulating dielectric layer, and a vacuum-sealed cavity is provided between the upper electrode and the insulating dielectric layer; the passivation layer is grown above the upper electrode; the metal lead extends into the passivation The electrodes of the layer are led out of the holes, and the two ends of the metal leads are in contact with the upper electrode and the lower electrode respectively.

Further, the lower electrode includes a first lower electrode and a second lower electrode, the top surface of the first lower electrode and the top surface of the second lower electrode are located in the same plane; the first lower electrode and the upper electrode constitute a self-detection device, The second lower electrode and the upper electrode constitute the upper and lower plates of the sensor.

Further, the first lower electrode is in the shape of a square, the second lower electrode is in the shape of a frame, and the first lower electrode is located in the second lower electrode.

Further, the first lower electrode and the second lower electrode are squares of equal size, the first lower electrode is two pieces, the second lower electrode is two pieces, and the first lower electrode and the second lower electrode are evenly arranged. And the two first lower electrodes are on a diagonal line, and the two second lower electrodes are on another diagonal line.

Further, the lower electrode is made of heavily doped single crystal silicon, polycrystalline silicon, or metal.

Further, the upper electrode is made of polysilicon.

Further, the insulating dielectric layer includes a first silicon dioxide layer and a first silicon nitride layer grown on the first silicon dioxide layer.

Further, the passivation layer includes a second silicon dioxide layer and a second silicon nitride layer located above the second silicon dioxide layer.

A preparation method of a capacitive pressure sensor with a self-detection device, the preparation method comprising the following steps:

The first step is to form a heavily doped region by ion implantation on one side of the double-sided polished silicon substrate as the lower electrode;

In the second step, the epitaxial first silicon dioxide layer and the first silicon nitride layer are used as an insulating dielectric layer on the lower electrode;

The third step is to epitaxially grow a layer of silicon dioxide on the insulating dielectric layer as a sacrificial layer;

The fourth step is to grow a layer of polysilicon layer above the sacrificial layer as the upper electrode of the sensor;

The fifth step is to photoetch the polysilicon layer to form a sacrificial layer release hole, and use hydrofluoric acid to release the sacrificial layer;

The sixth step is to epitaxially grow the vacuum chamber sealing material above the upper electrode to form a vacuum sealed chamber between the insulating medium layer and the upper electrode, and at the same time epitaxially grow a passivation layer above the vacuum chamber sealing material layer;

The seventh step is to photoetch the passivation layer, form electrode lead-out holes, and sputter metal aluminum to be used as metal leads.

Beneficial effects: Compared with the prior art, the present invention has the following beneficial effects: convenient testing, high efficiency, surface micromachining technology is adopted in the preparation process, the process is simple, and the feasibility is high. The electrostatic force generated by applying a voltage between the first lower electrode and the upper electrode is used to conveniently simulate the pressure value in actual detection, which has higher efficiency. The capacitive pressure sensor adopts a self-detection device. When a voltage is applied between the first lower electrode and the upper electrode, the electrostatic force generated between the two causes the movable sensitive film layer composed of the upper electrode and the passivation layer to bend. , the distance between the upper electrode and the lower electrode becomes shorter, thereby changing the output capacitance of the sensor, and detecting its change can realize pressure measurement. The invention conveniently uses the electrostatic force to simulate the pressure value in the actual detection, and has higher efficiency when analyzing the performance of the sensor. At the same time, the capacitive pressure sensor adopts surface micromachining technology, which effectively solves the problem of electrode lead-out of the capacitive pressure sensor, avoids the conventional MEMS bonding process for forming a pressure chamber, and simplifies the manufacturing process of the capacitive pressure sensor , so that the MEMS structure can be compatible with the CMOS process.

Description of drawings

Fig. 1 is a structural sectional view of the present invention.

Fig. 2 is a structural sectional view of the first step of the preparation method of the present invention.

Fig. 3 is a structural sectional view of the second step of the preparation method of the present invention.

Fig. 4 is a structural sectional view of the third step of the preparation method of the present invention.

Fig. 5 is a structural sectional view of the fourth step of the preparation method of the present invention.

Fig. 6 is a structural sectional view of the fifth step of the preparation method of the present invention.

Fig. 7 is a structural sectional view of the sixth step of the preparation method of the present invention.

Fig. 8 is a structural sectional view of the seventh step of the preparation method of the present invention.

Fig. 9 is a schematic diagram of a layout of the bottom electrode in the present invention.

FIG. 10 is a schematic diagram of another layout of the bottom electrode in the present invention.

In the figure, there are: silicon substrate 1, lower electrode 2, insulating medium layer 3, vacuum sealed chamber 4, upper electrode 5, passivation layer 6, metal leads 7, first lower electrode 201, second lower electrode 202, first A silicon dioxide layer 301 , a first silicon nitride layer 302 , a second silicon dioxide layer 601 , and a second silicon nitride layer 602 .

Detailed ways

The technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings.

As shown in FIG. 1 , a capacitive pressure sensor with a self-detection device of the present invention includes a silicon substrate 1 , a lower electrode 2 , an insulating medium layer 3 , an upper electrode 5 , a passivation layer 6 and metal leads 7 . The lower electrode 2 is fixedly connected to the top surface of the silicon substrate 1 . The insulating medium layer 3 is fixedly connected to the top surface of the lower electrode 2 . The upper electrode 5 is located above the insulating medium layer 3 , and a vacuum sealed cavity 4 is provided between the upper electrode 5 and the insulating medium layer 3 . A passivation layer 6 is grown over the upper electrode 5 . Electrode extraction holes are provided in the passivation layer 6 . The metal lead 7 extends into the electrode lead-out hole of the passivation layer 6 , and the two ends of the metal lead 7 are respectively in contact with the upper electrode 5 and the lower electrode 2 .

In the above capacitive pressure sensor, the lower electrode 2 includes a first lower electrode 201 and a second lower electrode 202 , and the top surface of the first lower electrode 201 and the top surface of the second lower electrode 202 are located in the same plane. The first lower electrode 201 and the upper electrode 5 constitute a self-detection device. The second lower electrode 202 and the upper electrode 5 constitute the upper and lower pole plates of the sensor.

The capacitive pressure sensor of the present invention is a capacitive pressure sensor with a self-detection device compatible with the CMOS (Chinese: Complementary Metal Oxide Semiconductor) process.

The first lower electrode 201 and the upper electrode 5 of the lower electrodes 2 constitute a self-detection device. The second lower electrode 202 and the upper electrode 5 in the lower electrode 2 constitute the upper and lower pole plates of the capacitive pressure sensor. The first lower electrode 201 in the self-detection device is used to apply a voltage to generate an electrostatic force with the upper electrode 5 to bend the movable sensitive film layer composed of the upper electrode 5 and the passivation layer 6 . The second lower electrode 202 and the upper electrode 5 of the capacitive pressure sensor form a capacitor for detecting changes in reaction pressure.

The working process of the capacitive pressure sensor with the above structure is: when a voltage is applied to the first lower electrode 201 and the upper electrode 5, the electrostatic force generated between the two makes the movable part formed by the upper electrode 5 and the passivation layer 6 The bending of the sensitive film layer causes the distance between the second lower electrode 202 and the upper electrode 5 to become shorter, thereby changing the output capacitance of the pressure sensor, and detecting the change can realize pressure measurement.

The capacitance of a capacitive pressure sensor can be approximated as a plate capacitance, according to the definition of plate capacitance:

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}\mathrm{<span\; class="notranslate">\; A</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}$

In the formula: C is the capacitance of the plate capacitor, ε ₀ is the vacuum dielectric constant, ε _r is the relative dielectric constant of the dielectric layer, A is the area of the plate, and d is the distance between the two plates.

A voltage U is applied between the first lower electrode 201 and the upper electrode 5, and the electric energy between the plates is:

According to the principle of virtual work, the electrostatic force F between the first lower electrode 201 and the upper electrode 5 is:

$\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; W</span>}}{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}{\mathrm{<span\; class="notranslate">\; AU</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; d</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

During detection and calibration, the sensor is subjected to electrostatic force F, but in practical applications, the sensor is usually subjected to pressure P from the outside world.

P=F/A

Under the action of the pressure P, the movable sensitive film layer of the pressure sensor bends ω(x, y), which causes the output capacitance of the sensor to change.

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; \&Integral;</span><span\; class="notranslate">\; \&Integral;</span>\frac{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}{\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>}\mathrm{<span\; class="notranslate">\; dxdy</span>}$

Among them, ω(x,y) is the deflection surface equation related to the pressure P. For thin film layers of different shapes, the relationship between ω(x,y) and P is different.

For a pressure sensor with a square movable sensitive film layer, the deflection surface equation is:

$\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; cos</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{\mathrm{<span\; class="notranslate">\; \&pi;x</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; a</span>}}{\mathrm{<span\; class="notranslate">\; cos</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{\mathrm{<span\; class="notranslate">\; \&pi;y</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; a</span>}}$

Among them, ω ₀ can be obtained by the minimum energy principle:

${\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; a</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; P</span>}}{{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; D.</span>}}$

in, $\mathrm{D.}=\frac{{\mathrm{Eh}}^3}{12(1-v^2)}$

In the formula, ω is the film deflection of the coordinates (x, y), the coordinate system is based on the center of the movable sensitive film layer as the origin, the horizontal direction is the X axis, and the vertical direction is the Y axis; a is the edge of the movable sensitive film layer P is the pressure on the movable sensitive film layer, D is the bending stiffness of the movable sensitive film layer material, E is the Young’s modulus of the movable sensitive film layer material, v is the movable sensitive film layer material Poisson's ratio, h is the thickness of the movable sensitive film layer.

For a pressure sensor with a circular movable sensitive film layer, the deflection function is:

$\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; P</span>}}{\mathrm{<span\; class="notranslate">\; 64</span>}\mathrm{<span\; class="notranslate">\; D.</span>}}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

In the formula, ω(r) is the deflection of the film at a distance r from the center of the circular film, P is the pressure on the movable sensitive film layer, D is the bending stiffness of the material of the movable sensitive film layer, and r is the The distance from the center of the film circle, R is the radius of the movable sensitive film layer.

Through the sensed output capacitance, pressure measurement can be realized.

The present invention uses electrostatic force to simulate the pressure value in actual detection, and has higher efficiency when analyzing the performance of the sensor, especially the voltage applied between the first lower electrode 201 and the upper electrode 5 in the self-detection device can be changed at any time size. At the same time, the change of the voltage can quickly change the shape of the movable sensitive film layer composed of the upper electrode and the passivation layer. Compared with the traditional detection method of setting pressure, the detection of the capacitive pressure sensor of the present invention is faster and more efficient.

There are many ways to arrange the first bottom electrode 201 and the second bottom electrode 202 , and two ways are selected in this embodiment. The first way: as shown in FIG. 10 , the first lower electrode 201 is in the shape of a square, the second lower electrode 202 is in the shape of a frame, and the first lower electrode 201 is located in the second lower electrode 202 . Of course, it is also possible that the second lower electrode 202 is in the shape of a square, the first lower electrode 201 is in the shape of a frame, and the second lower electrode 202 is located in the first lower electrode 201 .

The second method: as shown in Figure 9, the first lower electrode 201 and the second lower electrode 202 are square shapes of equal size, the first lower electrode 201 is two pieces, and the second lower electrode 202 is two pieces , the first lower electrodes 201 and the second lower electrodes 202 are evenly arranged, and the two first lower electrodes 201 are on a diagonal line, and the two second lower electrodes 202 are on the other diagonal line.

Further, the lower electrode 2 is made of conductive material, such as heavily doped single crystal silicon, polycrystalline silicon, metal and other conductive materials. The upper electrode 5 is made of polysilicon. The lower electrode 2 is used as a fixed electrode, and the material only needs to be conductive. The upper electrode, as a movable electrode, needs to have good mechanical properties.

Further, the insulating dielectric layer 3 includes a first silicon dioxide layer 301 and a first silicon nitride layer 302 grown on the first silicon dioxide layer 301 . At the same time, the silicon dioxide layer and the silicon nitride layer are used as the insulating dielectric layer 3, so that the insulating performance is better. The insulating medium layer 3 is used to prevent the phenomenon of short circuit caused by contact between the second lower electrode 202 and the upper electrode 5 when the electrostatic force generated between the first lower electrode 201 and the upper electrode 5 is too large.

Further, the passivation layer 6 includes a second silicon dioxide layer 601 and a second silicon nitride layer 602 above the second silicon dioxide layer 601 . The passivation layer above the upper electrode 5 is used to protect the pressure sensor and improve the stability and reliability of the device.

The manufacturing process of the capacitive pressure sensor with the self-detection device of the above structure is as follows:

The first step, as shown in Figure 2, is to form a heavily doped region as the lower electrode 2 by ion implantation on one side of the double-sided polished silicon substrate 1;

In the second step, as shown in FIG. 3 , the first silicon dioxide layer 301 and the first silicon nitride layer 302 are epitaxially formed on the lower electrode 2 as the insulating dielectric layer 3;

In the third step, as shown in FIG. 4 , epitaxially grow a layer of silicon dioxide on the insulating dielectric layer 3 as the sacrificial layer 8 ;

The fourth step, as shown in FIG. 5 , is to grow a layer of polysilicon layer above the sacrificial layer 8 as the upper electrode 5 of the sensor;

In the fifth step, as shown in FIG. 6, the polysilicon layer is photolithographically formed to form release holes in the sacrificial layer 8, and the sacrificial layer 8 is released by hydrofluoric acid;

In the sixth step, as shown in FIG. 7 , epitaxially grow the vacuum chamber sealing material above the upper electrode 5 to form a vacuum sealed chamber 4 between the insulating medium layer 3 and the upper electrode 5 , and at the same time epitaxially grow the vacuum chamber sealing material layer passivation layer 6;

In the seventh step, as shown in FIG. 8 , the passivation layer 6 is photolithographically formed to form electrode extraction holes, and metal aluminum is sputtered to be used as metal leads 7 .

In the pressure sensor with the above structure, the vacuum sealed cavity 4 corrodes the sacrificial layer, and then seals the vacuum cavity by an epitaxy process, which avoids the conventional MEMS bonding process for forming the pressure cavity, and simplifies the manufacturing process of the capacitive pressure sensor. The material used to seal the vacuum sealed cavity 4 may be silicon dioxide or polysilicon.

The preparation method of the capacitive pressure sensor of the present invention adopts surface micro-machining technology, and effectively solves the problem of lead-out of the electrodes of the capacitive pressure sensor. The vacuum seal of traditional pressure sensors is formed by silicon-silicon bonding or silicon-glass bonding. The lower electrode is made on the substrate, and the lower electrode is drawn out from the back through a hole in the glass or silicon substrate. The process is cumbersome. The invention adopts the surface micromachining technology, the lower electrode is led out from the front of the sensor, and the process is simple. In addition, the vacuum sealed cavity 4 is sealed by an epitaxy process by etching the sacrificial layer. The invention does not adopt the conventional MEMS bonding process to make a vacuum-sealed cavity, simplifies the manufacturing process of the capacitive pressure sensor, and makes the MEMS structure compatible with the CMOS process. The MEMS bonding process needs to be carried out at a high temperature (about 400°C). Since the metal operation is involved in the CMOS process, it cannot be carried out at a high temperature.

Claims (9)

1. A capacitance type pressure sensor with a self-detection device is characterized by comprising a silicon substrate (1), a lower electrode (2), an insulating medium layer (3), an upper electrode (5), a passivation layer (6) and a metal lead (7);

the lower electrode (2) is fixedly connected with the top surface of the silicon substrate (1); the insulating medium layer (3) is fixedly connected with the top surface of the lower electrode (2); the upper electrode (5) is positioned above the insulating medium layer (3), and a vacuum sealing cavity (4) is arranged between the upper electrode (5) and the insulating medium layer (3); a passivation layer (6) is grown above the upper electrode (5); the metal lead (7) extends into the electrode leading-out hole of the passivation layer (6), and two ends of the metal lead (7) are respectively contacted with the upper electrode (5) and the lower electrode (2).

2. The capacitive pressure sensor with self-test device according to claim 1, wherein said lower electrode (2) comprises a first lower electrode (201) and a second lower electrode (202), the top surface of the first lower electrode (201) and the top surface of the second lower electrode (202) being located in the same plane; the first lower electrode (201) and the upper electrode (5) form a self-detection device, and the second lower electrode (202) and the upper electrode (5) form upper and lower electrode plates of the sensor.

3. The capacitive pressure sensor with self-test device according to claim 1, wherein the first lower electrode (201) is in the shape of a block, the second lower electrode (202) is in the shape of a frame, and the first lower electrode (201) is located in the second lower electrode (202).

4. The capacitive pressure sensor with self-test device according to claim 1, wherein the first lower electrode (201) and the second lower electrode (202) are both in the shape of a square block with equal size, the first lower electrode (201) is two, the second lower electrode (202) is two, the first lower electrode (201) and the second lower electrode (202) are uniformly arranged, the two first lower electrodes (201) are located on one diagonal, and the two second lower electrodes (202) are located on the other diagonal.

5. Capacitive pressure sensor with self-detection means according to claim 1, characterized in that the lower electrode (2) is made of heavily doped monocrystalline silicon, polycrystalline silicon, or metal.

6. Capacitive pressure sensor with self-detection means according to claim 1, characterized in that the upper electrode (5) is made of polysilicon.

7. Capacitive pressure sensor with self-detection means according to claim 1, characterized in that said insulating dielectric layer (3) comprises a first layer of silicon dioxide (301) and a first layer of silicon nitride (302) grown on top of the first layer of silicon dioxide (301).

8. Capacitive pressure sensor with self-detection means according to claim 1, characterized in that the passivation layer (6) comprises a second silicon dioxide layer (601) and a second silicon nitride layer (602) located above the second silicon dioxide layer (601).

9. A method for preparing a capacitive pressure sensor with a self-test device according to claim 1, comprising the steps of:

firstly, forming a heavily doped region serving as a lower electrode (2) on one surface of a silicon substrate (1) with two polished surfaces through ion implantation;

secondly, extending a first silicon dioxide layer (301) and a first silicon nitride layer (302) on the lower electrode (2) as an insulating medium layer (3);

step three, epitaxially growing a silicon dioxide layer above the insulating dielectric layer (3) to be used as a sacrificial layer (8);

fourthly, growing a polysilicon layer above the sacrificial layer (8) to be used as an upper electrode (5) of the sensor;

fifthly, photoetching the polysilicon layer to form sacrificial layer (8) release holes, and releasing the sacrificial layer (8) by using hydrofluoric acid;

sixthly, epitaxially growing a vacuum cavity sealing material above the upper electrode (5), forming a vacuum sealing cavity (4) between the insulating medium layer (3) and the upper electrode (5), and epitaxially growing a passivation layer (6) above the vacuum cavity sealing material layer;

and seventhly, photoetching the passivation layer (6), forming an electrode lead-out hole, and sputtering metal aluminum to be used as a metal lead (7).